CN1691741A - Image processing device, printing control device, image processing method - Google Patents

Abstract

When image data is converted into an expression format based on the dot on-off state, such conversion is performed in a unit of a raster group comprising a predetermined number of adjacent rasters. When this is done, the binarization errors occurring in each pixel of the last raster located in the last position of such raster group are diffused into surrounding pixels and stored in a first storage unit. The errors are read out from the first storage unit for dot on-off state determination regarding the first raster of the raster group adjacent to the above-mentioned last raster, and binarization errors occurring in connection with this determination are stored in a second storage unit that permits faster reading and writing of data than the first storage unit. The remaining rasters following the first raster are converted into dot rows by conducting dot on-off state determination for each pixel therein in parallel with the process to convert the first raster into a dot row while taking into account the binarization errors that occurred in the first raster. Consequently, the errors that are taken into account by the pixels of the same raster are stored in the second storage unit that permits faster high-speed reading and writing of data, and the image data for the raster group can be converted at a high speed.

Description

Image processing device, printing control device, image processing method

This application is a divisional application of:

Title of Invention: Image processing device, printing control device, image processing method and recording medium

Application date: October 5, 2001

Application number: 01803036.X (PCT/JP01/08837)

                      

The present invention relates to a technique for converting image data represented by tone values of a plurality of pixels constituting an image, and specifically relates to converting the image data into image data in an expression form based on whether or not dots are formed for each pixel. technology.

Background technique

An image display device that expresses an image by forming dots on a display medium such as a printing medium or a liquid crystal screen is widely used as an output device of various image devices. Such an image display device can only partially express a certain state of whether or not dots are formed, but by appropriately controlling the formation density of dots according to the tone value of the image, an image with continuously changing tone can be expressed.

In such an image display device, in order to form dots at an appropriate density according to the tone value of the image, methods for judging the presence or absence of dot formation for each pixel include, for example, a method called the error diffusion method and a mathematically equivalent method. A method called the method of minimizing the average error, etc.

The method called the error diffusion method diffuses and stores the color tone expression error caused by the formation or non-formation of dots on the target pixel to unjudged pixels around the target pixel in advance, and when judging whether or not to form dots on unjudged pixels , to judge whether there is dot formation, to eliminate the error diffused from surrounding pixels. In addition, the method called the method of minimum average error does not diffuse the color tone expression error generated by the judgment of the presence or absence of dots to the surrounding pixels in advance and store it in the target pixel, but replaces it with the dot of the non-judged pixel in the judgment of the presence or absence of the dot. When forming, read out the errors stored in the surrounding pixels, and judge whether there is dot formation for the target pixel, so as to offset these errors.

In these methods, since an image is composed of a large number of pixels, it is impossible to judge whether or not dots are formed for all pixels at the same time. On the other hand, image data is supplied in the order of columns of pixels obtained by scanning (referred to as a raster) based on a relationship generated by scanning an original image. For these reasons, whether or not dots are formed is judged along the rasters constituting the image. That is, the presence or absence of dot formation is judged sequentially from the pixels located at the ends of the raster, and when the judgment of the presence or absence of all pixels on the raster is completed, the processing of the adjacent raster is started. In such a method, even if the pixels are adjacent to each other on the image, the pixels belonging to different rasters cannot be processed consecutively. Therefore, the error in tone expression generated by the dot formation judgment is stored in the error buffer in advance. , read from the error buffer for use when needed. In this way, by reflecting the error in tone expression that occurs in peripheral pixels, and judging whether there is dot formation to eliminate the error, it is possible to form dots at an appropriate density corresponding to the tone value of the image. As a result, it can be displayed on the image display device Displays high-quality images.

However, in such a method, it is necessary to frequently read and write an error in color tone expression that occurs every time the presence or absence of dots is determined, and thus cannot quickly determine the presence or absence of dots. That is, in the error diffusion method, the diffusion error that should be diffused to the surrounding pixels must be written into the error buffer every time it is judged whether or not a dot is formed, or in the average error minimum method, it must be read every time whether or not a dot is formed. In any case, errors in color tone expression generated in peripheral pixels are read out from the error buffer. In any case, reading and writing to the error buffer is frequently performed, and it takes a certain amount of time to determine whether or not dots are formed. If it takes a certain amount of time to judge whether or not dots are formed, it is difficult to quickly display an image.

Contents of the invention

The present invention is proposed to solve the above-mentioned problems in the prior art, and an object thereof is to provide a technology capable of rapidly displaying a high-quality image by shortening the time required for judging the presence or absence of dot formation without degrading the image quality.

In order to solve at least part of the above problems, the image processing apparatus of the present invention adopts the following configuration. That is, the present invention is a method of receiving image data representing the tone value of each pixel and converting the image data into dot presence or absence by judging whether or not dots are formed in each pixel constituting the raster through a raster along the column of the pixels. The image processing device of the form of expression formed is characterized in that: it has a grating group generation unit, a last grating transformation unit, a first error diffusion unit, a beginning raster transformation unit, a second error diffusion unit and the remaining grating transformation units, the grating group The generating unit assembles a plurality of adjacent gratings to generate a grating group; the last grating transformation unit selects the last grating located at the end of the above-mentioned grating group and determines whether or not dots are formed on each pixel constituting the last grating. The last raster is converted into a dot sequence indicating whether or not dots are formed; the first error diffusion unit calculates the color tone error that occurs in each pixel by judging the presence or absence of dots for each pixel constituting the last raster, and transfers it to the A plurality of undetermined pixels in the periphery of each pixel spread; the head raster conversion unit selects the head grating at the head position in the grating group adjacent to the above-mentioned last grating and considers the positions from the last grating to the first grating. The above-mentioned hue error of pixel diffusion is used to determine whether dots are formed in each pixel constituting the head raster, and the head raster is converted into a dot row indicating whether dots are formed; The above-mentioned color tone error that occurs in the above-mentioned raster group is diffused to the undetermined pixels located in the periphery of each pixel; the rest of the raster conversion unit considers that the rest of the raster group except the above-mentioned head raster belongs to the same grating group as the rest of the raster group and Having judged the above-mentioned hue error of pixel diffusion with or without dot formation and judging the presence or absence of dot formation in each pixel of the remaining rasters and converting the remaining rasters into dot columns in parallel with the process of converting the first raster into the above-mentioned dot columns, The above-mentioned first error diffusion unit and the above-mentioned second error diffusion unit store the error diffused to the pixels of the raster group different from the pixel for judging the presence or absence of the dot formation in the first error storage part, and then transfer the errors to and to judge whether or not the dot is formed. The pixel diffusion error of the formed grating group with the same pixel is stored in the cell of the second error storage unit.

In addition, the first image processing method of the present invention corresponding to the above-mentioned first image processing device is to receive image data representing the tone value of each pixel, and judge whether each pixel constituting the raster has An image processing method for converting the image data into a form of expression with or without dot formation in the presence or absence of dots, characterized in that it comprises the following steps, namely

(A) the step of combining a plurality of gratings adjacent to each other to generate a grating group;

(B) selecting the last grating located at the end of the grating group, and converting the last grating into a dot column indicating whether or not dots are formed by judging whether or not dots are formed on each pixel constituting the last grating;

(C) calculating, for each pixel constituting the last raster, a color tone error generated in each pixel by judging the presence or absence of dot formation, and spreading to a plurality of unjudged pixels located around the respective pixels;

(D) Select the head grating located at the head position of the grating group adjacent to the last grating, and calculate the color difference for each pixel constituting the head grating by considering the above-mentioned hue error diffused from the last grating to each pixel of the head grating. A step of judging whether dots are formed, and transforming the beginning raster into a dot column indicating whether dots are formed;

(E) a step of diffusing the color tone error occurring in each pixel constituting the first raster to undetermined pixels located around the respective pixels;

(F) By considering the above-mentioned tone error of the diffusion of pixels belonging to the same grating group as the remaining grating group and judging whether or not the dots are formed, and judging each of the remaining gratings except the first grating the step of converting the remaining rasters into dot trains in parallel with the process of converting the beginning raster into dot trains with or without dot formation in pixels;

The above-mentioned step (C) and the above-mentioned step (E) store the error diffused to the pixel of the grating group different from the pixel for judging the presence or absence of the dot formation in the first error storage part, and store the error for judging whether or not the dot is formed. The step of storing the pixel diffusion error of the raster group with the same pixel in the second error storage unit.

In such a first image processing device and image processing method, in units of a grating group constituted by a specified number of adjacent gratings, it is determined whether or not dots of each pixel are formed by each grating constituting the grating group. Instead, each raster is transformed into a point column. Here, when the color tone error generated by the judgment of the presence or absence of dot formation is diffused to the surrounding unjudged pixels, the sum of the error diffused to the pixels belonging to the same raster group as the judging pixel in which the color tone error occurred is distributed to the pixels related to the judging pixel. The errors of the pixel spread of different raster groups of pixels are stored differently. For the first raster, the color tone error diffused from the pixels of the adjacent raster group and stored is read out, and the first raster is converted into a dot row by judging whether or not dots are formed. On the other hand, for the above-mentioned remaining gratings, considering the color tone error diffused from the pixels belonging to the same grating group as the grating and for which the presence or absence of dot formation has been judged and stored, by judging the presence or absence of dot formation, and the The process of transforming the first raster into the above-mentioned point sequence parallelizes the transformation of the remaining rasters into the point sequence.

In this way, the image data of the raster group can be rapidly converted by performing the processing of converting the remaining rasters into dot rows in parallel with the processing of converting the first raster into dot rows. In addition, since image data is converted in units of raster groups, errors spreading to pixels belonging to the same raster group can be read earlier than errors spreading to pixels belonging to different raster groups. Therefore, as long as errors diffused to pixels belonging to the same grating group are stored differently from errors diffused to pixels belonging to different grating groups, errors can be quickly read out, and the processing by grating group unit can be executed more quickly. Transform image data processing.

In such an image processing device, errors spreading to pixels of the same grating group can be stored so that at least one of data storage or reading can be performed more quickly than errors spreading to pixels of a different grating group. .

When image data is converted in units of raster groups, color tone errors generated by judging the presence or absence of dot formation tend to spread more to pixels belonging to the same raster group than to pixels of different raster groups. Therefore, as long as at least one of data storage and readout can be performed more quickly than the error spreading to pixels belonging to the same grating group, the error spreading to the pixels belonging to the same grating group can be stored efficiently and efficiently. Promptly perform diffusion error processing.

In such an image processing device, for errors diffused to pixels of different grating groups, at least the same number of pixels as the number of pixels constituting the first grating can be simultaneously stored, and at the same time, pixels of the same grating group can be simultaneously stored. Diffused errors can simultaneously store a number of pixels smaller than the number of pixels constituting the head raster.

When image data is converted in units of raster groups, the error diffused to the pixels of the same raster group is used in the conversion to convert the image data of the raster group, and there is no need to store it later. Therefore, the storage unit that stores the error can store An error diffused to other pixels belonging to the raster group. Therefore, as long as only a number of pixels smaller than the number of pixels constituting the first raster can be stored for errors diffused to pixels of the same raster group, the storage unit can be effectively used.

In the image processing device that uses a computer to perform the conversion of the above-mentioned image data, the error diffused to the pixels of the same grating group can be stored in a storage element that can directly execute data writing or reading by the computing device of the computer, and can be transferred to Errors in the pixel diffusion of different grating groups can be stored in the memory element through which the computing device indirectly performs data writing or reading.

The storage element that can directly write or read data from the computing device of the computer can quickly write or read, so by storing in such a storage element, it is possible to quickly store or read data to the same grating group. Pixel Diffusion Error. Such a storage element is not limited to a storage element that can directly write or read data from the above-mentioned computing device, and may be a storage element that can directly write and read data from the computing device.

In such an image processing device, when the hue error generated in each pixel of the last raster is diffused to unjudged pixels belonging to a different raster group around the pixel whose presence or absence of dot formation is judged, Diffusion may be performed only to pixels of the first raster adjacent to the last raster.

In this way, the color tone error diffuses from the pixels of different raster groups only to the pixels of the first raster, and does not spread to the pixels of the remaining rasters. Therefore, only when judging whether each pixel of the above-mentioned head raster has dot formation or not, the error stored in the above-mentioned first error storage unit is read out to determine whether there is dot formation, and for the remaining rasters, the error stored in the second error storage unit can be read out, Determine whether a point is formed or not. As a result, the overall process is simplified, so that the process of judging the presence or absence of dot formation can be performed quickly.

In addition, in such an image processing device, the image data of each of the two rasters is sequentially converted into a dot sequence, and the first raster located in the front and the last raster located in the rear of the two rasters can be converted as follows Convert to a column of points. That is, a color tone error generated by determining the presence or absence of dot formation in each pixel of the last raster is diffused to the pixel of the last raster and the pixel of the first raster of the group adjacent to the last raster. In addition, the hue error generated by determining the presence or absence of dot formation in each pixel of the first raster is diffused to the pixel of the first raster and the pixel of the last raster after the first raster. It is possible to determine the presence or absence of dot formation for each pixel at the end of each raster group in consideration of the hue error caused by such diffusion.

In this way, only two rasters are sequentially converted into dot arrays, and a plurality of rasters can be converted into dot arrays in parallel with simple processing.

In such an image processing device, when the color tone error generated by judging the presence or absence of dot formation for each pixel is diffused from the pixel where the color tone error occurs to the unjudged pixel located at a distance greater than or equal to a specified value, it can The presence or absence of pixel spread of a grating group different from the grating group formed by the dot was judged.

When the color tone error generated by judging the presence or absence of dot formation is diffused to distant unjudged pixels, even if the positions of the diffused pixels are shifted to some extent, the image quality will not be greatly affected. Therefore, when diffusing to distant undetermined pixels, it is only necessary to collectively diffuse to pixels of a grating group different from the grating group for which presence or absence of dot formation has been judged, and the diffusion error can be easily processed.

In addition, in order to solve at least part of the above-mentioned problems, the second image processing device of the present invention adopts the following configuration. That is, the present invention is a method of receiving image data representing the tone value of each pixel and converting the image data into dot presence or absence by judging whether or not dots are formed in each pixel constituting the raster through a raster along the column of the pixels. The image processing device of the expression form formed is characterized in that: it has a grating group generation unit, a selection grating conversion unit, a first color tone error storage unit, a beginning raster conversion unit, a second color tone error storage unit and the rest of the grating conversion units, and the grating The group generation unit assembles a plurality of adjacent gratings to generate a grating group; the selection grating transformation unit includes at least the last grating located at the end of the above-mentioned grating group to select a grating from the grating group, and the selected gratings are selected. Each pixel judges whether dots are formed or not, and converts the selected grating into a dot row representing whether dots are formed; the first color tone error storage unit calculates each pixel constituting the selected grating by judging whether the above-mentioned dots are formed. The color tone error that occurs in the pixel is made to correspond to each pixel for which the determination has been made, and stored in the first storage unit; the head raster conversion unit selects the head of the head position in the raster group adjacent to the last raster For the raster, in the periphery of each pixel constituting the head raster, consider the above-mentioned hue error stored in the surrounding pixels that have been judged to have dot formation or not, and convert the head raster into a dot row by judging whether the dots are formed in each pixel; 2. The color tone error storage unit associates the above-mentioned color tone error that occurs in each pixel constituting the above-mentioned head raster with each pixel that has performed the above-mentioned judgment, and stores it in the second storage unit; The remaining gratings of the above-mentioned first grating consider the above-mentioned tone error occurring in the pixels belonging to the same grating group as the remaining gratings and the presence or absence of dot formation has been judged, and by judging whether or not dots are formed in each pixel of the remaining gratings, they are compared with the remaining gratings. The process of converting the first raster into the dot train described above converts the rest of the rasters into the dot train in parallel.

In the second image processing method of the present invention corresponding to such a second image processing device, image data representing the tone value of each pixel is received, and a raster along the column of the pixel is used to determine whether the pixel in each pixel constituting the raster is An image processing method for converting the image data into an expression form of dot formation with or without dot formation is characterized by including the following steps. Right now,

(A) the step of combining a plurality of gratings adjacent to each other to generate a grating group;

(B) Selecting a grating from the grating group including at least the last grating located at the end of the grating group, and determining the presence or absence of dots in each pixel constituting the selected grating, and converting the selected grating into an expression indicating presence or absence The steps of point columns formed by points;

(C) calculating, for each pixel constituting the selected raster, a color tone error generated in each pixel by judging the presence or absence of dot formation, and storing it in association with each pixel for which the judgment has been made;

(D) Select the head raster located at the head position of the grating group adjacent to the last raster, and consider the above-mentioned tone error stored in the peripheral pixels that have been judged to have dot formation around each pixel constituting the head raster , the step of transforming the beginning raster into a dot row by judging whether each pixel has a dot formation;

(E) A step of distinguishing the above-mentioned color tone error occurring in each pixel constituting the above-mentioned head raster from the color tone error stored in the step C, and storing it in correspondence with each pixel for which the above-mentioned determination is performed;

(F) For the rest of the grating group except the first grating, the color tone error occurred in the pixel belonging to the same grating group as the remaining grating and the presence or absence of dot formation has been judged, and by judging the remaining grating In parallel with the process of converting the first raster into the above-mentioned dot sequence, the step of converting the remaining rasters into the dot sequence is carried out in parallel.

In such a second image processing device and image processing method, as in the above-mentioned first image processing device and image processing method, a grating group composed of a specified number of adjacent gratings is used as a unit to configure Each grating of the grating group is converted into a dot row by judging whether or not dots are formed in each pixel. In this case, in the second image processing apparatus and image processing method, the color tone error generated in each pixel of the last raster is associated with each pixel for which the determination is made and stored, and the pixel of the first raster is judged to have When there is no dot formation, the color tone error stored in each pixel of the above-mentioned last raster around the pixel is read out, and whether or not dots are formed is judged. In this way, the color tone error occurring in each pixel of the first raster and the color tone error occurring in each pixel of the above-mentioned last raster are differentiated and stored in advance. For the rest of the above-mentioned rasters, considering the hue error occurring in pixels belonging to the same grating group as the rest of the rasters and for which the presence or absence of dot formation has been judged, by judging whether or not dots are formed, the conversion of the head raster into the above-mentioned dot array is performed. Processing transforms this remaining raster into a column of points in parallel.

In this way, the image data can be quickly converted by simply converting the image data into a dot row in parallel with the first raster and the remaining rasters in raster group units. In addition, since the image data is converted in raster group units, the color tone error that occurs in the last raster of the raster group being processed is different from the color tone error that occurs in other rasters. read out. Therefore, if the color tone error occurring in the last raster of the group of rasters is stored differently from the tone errors occurring in other rasters, the error can be quickly read and the image data can be quickly converted.

In such an image processing apparatus, at least one of storage and readout of data can be performed more quickly than color tone errors occurring in the last raster by storing color tone errors occurring in rasters other than the last raster. processing.

When converting image data in units of raster groups, there is only one last raster in one raster group, and there are more than one other raster. Hue errors occurring in the raster will be read out more frequently than those occurring in the last raster. Therefore, as long as at least one of data storage or readout can be performed more quickly than the color tone error occurring in the last raster, the hue error occurring in the raster other than the last raster can be efficiently and quickly Performs conversion in units of raster groups.

In such an image processing device, for the hue error occurring in each pixel of the last raster, at least the same number of pixels as the pixels constituting the last raster can be simultaneously stored, The color tone error occurring in each pixel of each pixel can be stored only by the number of pixels less than the pixels constituting the head raster.

When image data is converted in raster group units, the color tone error generated by judging the presence or absence of dot formation is used when judging the presence or absence of dot formation for the pixels of the same raster group, and does not need to be stored later. Therefore, the color tone error is stored. The storage unit may be used to store hue errors occurring in other pixels belonging to the same raster group. Therefore, it is possible to store the hue error generated in each pixel of the first raster by only a number of pixels less than the number of pixels constituting the first raster, so that the storage unit can be effectively used.

In the image processing device that uses a computer to convert the above-mentioned image data, the color tone error that occurs in each pixel of the above-mentioned head raster can be stored in a storage element that can directly write or read data by the computing device of the computer. A color tone error occurring in each pixel of the last raster can be stored in a storage element in which the computing means indirectly writes or reads data.

The storage element that can directly write or read data from the computing device of the computer can perform rapid writing or reading. Therefore, as long as the color tone error that occurs in the pixel of the first raster is stored in such a storage element, The image data of the raster group can be changed rapidly. Such a storage element may be a storage element capable of writing or reading data from the computing device.

In such an image processing device, only for the last raster in the raster group, the color tone error that occurs in each pixel constituting the raster is stored in each pixel, which can be used as the basis for determining the presence or absence of the first raster. The hue error of each pixel of the last raster is considered in consideration of the hue error in dot formation, and the first raster is converted into the dot sequence.

In this way, it is possible to read the color tone error occurring in the pixels of the last raster belonging to different raster groups only when judging whether or not dots are formed in each pixel of the first raster, and to judge whether or not dots are formed in each pixel of the remaining rasters. Since color tone errors occurring in pixels of different raster groups are read out at any time, the image data of the raster group can be changed rapidly.

In addition, in such an image processing device, the image data of each of the two rasters is sequentially converted into a dot sequence, and the first raster located in the front and the last raster located in the rear of the two rasters can be converted as follows Convert to a column of points. That is, only the tone error generated in the last raster is stored in the first storage unit, and when it is judged whether or not dots are formed in each pixel constituting the first raster, the tone error stored in each pixel of the last raster is read out and performed. It is judged that the color tone error generated in each pixel is stored in the second storage unit. The last raster following the first raster is converted into a dot sequence in parallel with the process of converting the first raster into a dot sequence in consideration of the hue error occurring in each pixel of the first raster.

In this way, only two rasters are sequentially converted into dot arrays, and the process of converting a plurality of rasters into dot arrays can be performed in parallel with simple processing.

In such a first image processing device or a second image processing device, in order to reflect the hue error occurring in each pixel of the above-mentioned head raster and convert the above-mentioned remaining rasters into a dot sequence, it is possible to consider The diffusion error diffused by each pixel of the remaining raster is judged whether or not dots are formed, and the remaining raster is converted into a dot row. Alternatively, the rest of the rasters may be converted into dot columns by determining whether or not dots are formed in consideration of color tone errors occurring in each pixel of the first raster.

Using these methods, it is possible to reflect the hue error occurring in each pixel of the above-mentioned head raster, and to convert the above-mentioned remaining rasters into dot columns.

In addition, by outputting printing data for controlling the formation of inkjet dots to a printing section that forms inkjet dots on a printing medium to print an image, the above-mentioned first aspect of the present invention can be used in a printing control device that controls the printing section. 1 image processing device or a 2nd image processing device.

That is, in the first image processing device or the second image processing device, image data representing the tone value of each pixel can be received, and the image data can be converted into image data determined by the presence or absence of dot formation. Therefore, if such a first image processing device or a second image processing device is applied to the above-mentioned print control device, image data can be quickly converted into print data. By outputting the print data obtained in this way to the printing unit, a high-quality image can be quickly printed by the printing unit.

In addition, the present invention can also be realized by using a computer by reading a program for realizing the first image processing method or the second image processing method described above into the computer. Therefore, the present invention also includes the following as forms of recording media. That is, the recording medium corresponding to the first image processing method described above receives image data representing the tone value of each pixel and judges whether or not dots are formed in each pixel constituting the raster by receiving image data representing the tone value of each pixel and forming a raster according to the column of the pixel. A program for converting the image data into a form of expression formed by the presence or absence of dots is recorded on a recording medium that can be read by a computer, and it is characterized in that a program for realizing the following functions is recorded, that is,

(A) The function of combining multiple gratings adjacent to each other to generate a grating group;

(B) A function of selecting the last grating located at the end of the above-mentioned grating group and converting the last grating into a dot row indicating whether or not dots are formed by judging the presence or absence of dots for each pixel constituting the last grating;

(C) A function of calculating, for each pixel constituting the last raster, a color tone error generated in each pixel by judging the presence or absence of dot formation, and diffusing it to a plurality of unjudged pixels located around the respective pixel;

(D) Select the head grating located at the head position of the grating group adjacent to the last grating, and calculate the color difference for each pixel constituting the head grating by considering the above-mentioned hue error diffused from the last grating to each pixel of the head grating. The function of judging whether dots are formed, and transforming the beginning raster into a dot column indicating whether dots are formed;

(E) a function of diffusing the color tone error that occurs in each pixel constituting the first raster to undetermined pixels located around the respective pixels;

(F) By considering the above-mentioned tone error of the diffusion of pixels belonging to the same grating group as the remaining grating group and judging whether or not the dots are formed, and judging each of the remaining gratings except the first grating The function of transforming the remaining rasters into dot trains in parallel with the process of transforming the beginning raster into dot trains with or without dot formation in pixels;

Simultaneously, record as above-mentioned function (C) and above-mentioned function (E) realize the difference between the error that diffuses to the pixel of the same grating group as the pixel that judged the above-mentioned presence or absence of dot formation and the error that diffuses to the pixel of different grating group A program that performs storage functions differently.

In addition, the recording medium corresponding to the above-mentioned second image processing method is to realize by receiving the image data representing the tone value of each pixel and judging whether each pixel constituting the raster has dots formed by the raster formed according to the column of the pixel. A program for converting the image data into a form of expression formed by the presence or absence of dots is recorded on a recording medium that can be read by a computer, and it is characterized in that a program for realizing the following functions is recorded, that is,

(A) The function of combining multiple gratings adjacent to each other to generate a grating group;

(B) Selecting a grating from the grating group including at least the last grating located at the end of the grating group, and determining the presence or absence of dots in each pixel constituting the selected grating, and converting the selected grating into an expression indicating presence or absence function of the column of points formed by the points;

(C) A function of calculating, for each pixel constituting the selected raster, a color tone error generated in each pixel by judging the presence or absence of dot formation, and storing it in association with each pixel for which the judgment has been made;

(D) Select the head raster located at the head position of the grating group adjacent to the last raster, and consider the above-mentioned tone error stored in the peripheral pixels that have been judged to have dot formation around each pixel constituting the head raster , the function of transforming the beginning raster into a dot row by judging whether each pixel has a dot formation;

(E) The function of distinguishing the above-mentioned color tone error generated in each pixel constituting the above-mentioned head raster from the color tone error stored in the step C, and simultaneously storing it in correspondence with each pixel for which the above-mentioned judgment is performed;

(F) For the rest of the grating group except the first grating, the color tone error occurred in the pixel belonging to the same grating group as the remaining grating and the presence or absence of dot formation has been judged, and by judging the remaining grating In parallel with the process of converting the first raster into the above-mentioned dot sequence, the function of converting the rest of the rasters into the dot sequence is performed.

By reading the programs recorded on these recording media into a computer and using the computer to realize the various functions described above, image data representing the tone value of each pixel can be quickly converted into image data in a form of dot presence or absence.

Description of drawings

FIG. 1 is a schematic configuration diagram of a printing system of this embodiment.

FIG. 2 is an explanatory diagram showing the configuration of a computer as the image processing apparatus of the present embodiment.

FIG. 3 is a schematic configuration diagram of a printer as the image display device of the present embodiment.

FIG. 4 is a flowchart showing the flow of image data conversion processing performed by the image processing apparatus of this embodiment.

FIG. 5 is an explanatory diagram conceptually showing the state of determining the presence or absence of dot formation using the error diffusion method.

FIG. 6 is an explanatory diagram showing a case where an error diffusion coefficient is set for each pixel.

FIG. 7 is an explanatory diagram showing the principle of shortening the processing time by performing processing of a plurality of rasters in parallel in the tone coefficient conversion processing of the first embodiment.

8 is a flowchart showing the flow of tone coefficient conversion processing in the first embodiment.

FIG. 9 is an explanatory view schematically showing a case where a plurality of rasters are processed in parallel in Modification 1 of the tone coefficient conversion processing of Embodiment 1. FIG.

FIG. 10 is an explanatory diagram conceptually showing a case where a plurality of rasters are processed in parallel in Modification 2 of the tone coefficient conversion processing of Embodiment 1. FIG.

11 is an explanatory diagram conceptually showing a case where a plurality of rasters are processed in parallel in Modification 3 of the tone coefficient conversion processing of the first embodiment.

12 is an explanatory diagram conceptually showing an error diffusion matrix in which an error diffused far away is diffused to a certain pixel of the error buffer in Modification 4 of the tone coefficient conversion process of the first embodiment.

13 is an explanatory diagram conceptually showing the principle of reducing processing time by performing processing on a plurality of rasters in parallel in the tone coefficient conversion processing of the second embodiment.

FIG. 14 is an explanatory diagram showing a state in which a weight coefficient is set for each pixel in tone coefficient conversion processing in a modified example of the second embodiment.

15 is a flowchart showing the flow of tone coefficient conversion processing in the second embodiment.

FIG. 16 is an explanatory diagram conceptually showing a case where a plurality of rasters are processed in parallel in Modification 1 of tone coefficient conversion processing of Embodiment 2. FIG.

Detailed ways

The best form for carrying out the invention

In order to more clearly describe the actions and effects of the present invention, examples of the present invention will be described in the following order.

A. Example

B. Example 1

B-1. Device structure

B-2. Outline of image data conversion processing

B-3. Tone coefficient conversion processing of Embodiment 1

B-4. Modifications

C. Example 2

C-1. Tone coefficient conversion processing of Embodiment 2

C-2. Variations

A. Example

Next, an embodiment of the present invention will be described with reference to FIG. 1 . FIG. 1 is an explanatory diagram for explaining an embodiment of the present invention by taking a printing system as an example. This printing system is composed of a computer 10 as an image processing device, a color printer 20, and the like. When the computer 10 receives tone image data of a color image from an imaging device such as a digital camera or a color scanner, it converts the image data into print data expressed by the presence or absence of dots of each color that can be printed by the color printer 20 . Such conversion of image data is performed using a dedicated program called printer driver 12.

OK. The tone image data of a color image can also be created by the computer 10 using various application programs.

The printer driver 12 is composed of a resolution conversion module, a color conversion module, a tone number conversion module, and a plurality of modules called an interleave module. The tone number conversion module is a module that performs processing for converting tone image data into an expression format with or without dot formation. The tone number conversion module of the present embodiment considers the tone error occurring in surrounding pixels when determining the presence or absence of dots in the target pixel, and determines whether the target pixel has dots in order to eliminate the error. The processing performed by other modules will be described later. The color printer 20 forms color images on a printing medium by forming ink dots of each color on the basis of the printing data converted by these modules.

The image data supplied to the printer driver 12 has a data structure in which the tone values of the pixels constituting the document image are sequentially output raster by raster from one end of the image as shown in the conceptual formula in FIG. 1 . The resolution conversion module and the color conversion module in the printer driver 12 perform their processing one raster by one raster according to the data structure of the supplied image data. In the tone number conversion module of the printing system of the present invention, the method described later is used. The specified number of rasters adjacent to each other are processed in parallel. FIG. 1 conceptually shows a case where three rasters are processed in parallel as an example. The details will be described later, but if a plurality of rasters can be processed in parallel in this way, then between the plurality of rasters processed in parallel, the dot formation can be judged in consideration of the hue error occurring in each raster, Therefore, it is not necessary to store hue errors or diffusion errors one by one into the error buffer. That is, in the tone number conversion module of this embodiment, it is not necessary to frequently read and write to the error buffer, so it is possible to quickly determine whether or not dots are formed.

In this way, there are various specific methods for judging the presence or absence of dot formation in parallel in consideration of color tone errors occurring among a plurality of rasters, and these various methods will be described below using various embodiments.

B. Example 1

B-1. Device structure

FIG. 2 is an explanatory diagram showing the configuration of a computer 100 as the image processing apparatus of the first embodiment. The computer 100 is a well-known computer including a CPU 102 as a center, and a ROM 104 , a RAM 106 , and the like are connected to each other via a bus 116 . The CPU 102 is composed of an arithmetic unit that actually performs processing, and a plurality of registers that temporarily hold data being processed. The data held by the registers can be processed at a much higher speed than the data stored in the RAM 106 .

Disk controller DDC109 for reading data from floppy disk 124 or mini-disk 126, peripheral device interface P·I/F108 for transmitting and receiving data with peripheral devices, video interface V·I/F112 for driving CRT114, etc. Connect with computer 100. A color printer 200 , a hard disk 118 and the like to be described later are connected to the P·I/F 108 . In addition, if a digital camera 120 or a color scanner 122 is connected to the P·I/F 108, an image captured by the digital camera 1220 or the color scanner 122 can also be printed. Also, if the network interface card NIC110 is installed and the computer 100 is connected to the communication line 300, the data stored in the storage device 310 connected to the communication line can be acquired.

FIG. 3 is an explanatory diagram showing a schematic configuration of the color printer 200 of the first embodiment. The color printer 200 is an inkjet printer capable of forming dots of four ink colors, cyan, magenta, yellow, and black. Of course, an inkjet printer capable of forming ink dots of a total of six colors including cyan (light cyan) ink with low dye concentration and magenta (light magenta) ink with low dye concentration in addition to these four color inks may be used. In addition, an inkjet printer capable of forming ink dots of a total of seven colors including low lightness (dark) yellow (dark yellow) ink may also be used. Below, depending on the situation, the cyan ink, magenta ink, yellow ink, black ink, light cyan ink, light magenta ink, and dark yellow ink are referred to as C ink, M ink, Y ink, K ink, LC ink, and LM ink respectively. ink and DY ink.

As shown in the figure, the color printer 200 has a mechanism for driving a printing head 241 mounted on a carriage 240 to eject ink and form dots, and a carriage motor 230 to drive the carriage 240 along the direction of the platen 236. The axial reciprocating mechanism, the mechanism for conveying the printing paper P by the paper feeding motor 235 and the control circuit 260 for the formation of control points, the movement of the carriage 240 and the conveyance of the printing paper are constituted.

Mounted on the carriage 240 is an ink cartridge 242 containing K ink and an ink cartridge 243 containing various inks of C ink, M ink, and Y ink. When the ink cartridges 242 and 243 are mounted on the carriage 240, the inks in the cartridges are supplied to the ink jet heads 242 to 247 of the respective colors provided on the lower side of the print head 241 through guide tubes not shown in the figure. In the ink jet head 244 for the K ink, as shown in the figure, a plurality of nozzles Nz are arranged in two rows alternately at a constant nozzle pitch k. The same applies to the ink jet heads 245 to 247 of other colors, each having a set of nozzle rows arranged in a staggered manner at a nozzle pitch k.

The control circuit 260 is composed of CPU261, ROM262, RAM263, etc., and controls the main scanning and sub-scanning of the carriage 240 by controlling the operation of the carriage motor 230 and the paper feeding motor 235. Ink droplets are ejected from each nozzle at all times. In this way, under the control of the control circuit 260, the color printer 200 can print a color image by forming ink dots of each color at an appropriate position on the printing medium.

Various methods can be applied to the method of ejecting ink droplets from the ink heads of each color. That is, a method of ejecting ink using a piezoelectric element, or a method of ejecting ink droplets by generating air bubbles in the ink passage using a heater disposed on the ink passage may be used. In addition, instead of ejecting ink, a printer of a method of forming ink dots on printing paper using a phenomenon such as thermal transfer or a method of attaching toner powder of each color to a printing medium using static electricity may be used.

In addition, it is also possible to control the size of the ink droplets ejected from the inkjet head or to eject a plurality of fine ink droplets at a time to control the number of ink droplets ejected, thereby controlling the size of the ink dots formed on the printing paper. small and large printers, so-called variable dot printers.

B-2. Outline of image data conversion processing

4 is a flowchart showing a flow of converting image data into print data by performing predetermined image processing on image data received by the computer 100 as the image processing apparatus according to the first embodiment. Such processing is started when the operating system of the computer 100 activates the printer driver 12 . Next, the image data conversion processing of the first embodiment will be briefly described with reference to FIG. 4 .

When the printer driver 12 starts image data conversion processing, it first starts to read TGB color image data to be converted (step S100). Image data is read into the printer driver 12 one by one raster by one raster drop for each color of R (red), G (green), and B (basket).

Then, the resolution of the captured image data is converted into a resolution for printing by the color printer 200 (step S102). When the resolution of the color image data is lower than the printing resolution, new data is generated between adjacent image data by performing linear interpolation; Data to convert the resolution of the image data into the printing resolution.

When the resolution is converted in this way, color conversion processing of the color image data is performed (step S104). The so-called color conversion process is to convert the color image data expressed by the combination of R, G, and B tone values into the image data expressed by the combination of the tone values of each color used by the color printer 200 such as C, M, Y, and K. processing. Color conversion processing can be quickly performed by referring to a three-dimensional numerical table called a color conversion table (LUT). The above-described resolution conversion processing (step S102) and color conversion processing (step S104) are performed for each raster.

When the color conversion process ends, the tone number conversion process starts (step S106). The tone number conversion processing is the processing described below. The tone data converted by the color conversion process is expressed as data having a tone width of 256 for each color. On the contrary, in the color printer 200 of this embodiment, only one of "dot formation" and "dot formation non-formation" can be adopted. That is, the color printer 200 of this embodiment can only partially express two tones. Therefore, it is necessary to convert image data having 256 tones into image data expressed in 2 tones that can be expressed by the color printer 200 . The processing for performing such a conversion of the number of tones is the conversion of the number of tones. As described above, in the tone number conversion process of this embodiment, by judging whether or not dots are formed in a plurality of rasters in parallel, rapid processing can be performed. The tone number conversion processing will be described in detail later.

In this way, when the tone number conversion process is completed, the printer driver starts the interleaving process (step S108). The interleaving process is a process of sequentially converting image data converted into a format indicating whether or not dots are formed to be transmitted to the color printer 200 in consideration of the order in which dots are formed. The printer driver outputs the interleaved image data as print data to the color printer 200 (step S110 ). The color printer 200 forms ink dots of each color on a print medium according to print data. As a result, a color image corresponding to the image data is printed on the printing medium.

Next, in the tone number conversion process of the first embodiment, processing for quickly performing a determination of the presence or absence of dot formation by processing a plurality of rasters in parallel will be described.

B-3. Hue number conversion processing in Embodiment 1

(a) Outline of the tone number conversion process using the error diffusion method

Next, as a preparation for explaining the method of judging the presence or absence of dot formation in a plurality of rasters in parallel and the principle of shortening the time required for the tone number conversion process by doing it in parallel, a brief description will be given of judging along the lines in the so-called error diffusion method. There are methods of dot-free formation of gratings.

FIG. 5 is an explanatory diagram conceptually showing enlarged part of an image to be judged whether or not dot formation is present. The small squares of 1 and 1 represent pixels, and the pixels are arranged in a row to form a raster. For ease of explanation, the grating on the cutting board shown in Figure 5(a) is called "grating 0", the grating below it is called "grating 1", and the others are "grating 2" and "grating 3" in turn. In order to distinguish each pixel, each pixel is also marked with "Pmn". Pixel Pmn represents the nth pixel of raster m. The image data after the color conversion process shown in FIG. 4 is data in which the tone value of each color is associated with each pixel.

In the error diffusion method, the presence or absence of dot formation is judged pixel by pixel along the raster, as described below. FIG. 5( a ) is an explanatory diagram conceptually showing whether or not dots are formed on the pixel P11 . Like the pixel P11 , a pixel whose presence or absence of dot formation is to be determined is referred to as a target pixel in this specification. In the figure, the pixel of interest is indicated by framing the pixel P11 with a thick line. In addition, hatched areas in the figure indicate that the pixels in this area have already been judged as to whether or not dots are formed.

As shown in FIG. 5( a ), when the presence or absence of dot formation is determined for the target pixel P11 , as a result, a tone error E11 occurs in the target pixel P11 . That is, regardless of whether the pixel P11 forms a dot or not, the tone value expressed in the pixel P11 (hereinafter, such a tone value is referred to as a result value) usually does not match the tone value of the image data of the pixel. Therefore, the difference between the resultant value of the pixel P11 and the tone value of the image data of the pixel P11 causes a tone error in the target pixel. The error diffusion method adds a specified weight to the surrounding non-judged pixels of the target pixel, and diffuses the color tone error that occurs every time it is judged whether there is a dot formation. The weight coefficient used when spreading to surrounding undetermined pixels is called an error diffusion coefficient, and is determined in advance for each pixel centering on the target pixel.

FIG. 6 is an explanatory diagram of a case where an error diffusion coefficient is determined. The obliquely drawn pixels in FIG. 6 are target pixels, and the error diffusion coefficient of each pixel is determined according to the position to the target pixel. In this way, a matrix in which error diffusion coefficients are set to peripheral pixels centered on a target pixel is called an error diffusion matrix. For example, in the error diffusion matrix of FIG. 6( a ), for the pixel adjacent to the right of the target pixel, the error diffusion coefficient K01 is set to "1/4". Therefore, when the error diffusion matrix of FIG. 6( a ) is used, 1/4 of the hue error occurring in the target pixel is allocated to the pixel adjacent to the right. Similarly, the 1/4 error of the hue error generated in the target pixel is allocated to each of the lower left, right lower, and lower right pixels of the target pixel. The error diffusion matrix is not limited to the example shown in Figure 6. The range of the diffusion error and the error diffusion coefficient can be set to various values. In the actual error diffusion method, in order to obtain a good image quality, an appropriate error is used according to the situation diffusion matrix. In order to avoid complicating the description, in the following description, the error diffusion matrix in FIG. 6( a ), which is the matrix with the narrowest diffusion range among the exemplary error diffusion matrices, is used for description.

As the error diffusion matrix, if the matrix in FIG. 6(a) is used, as shown in FIG. A total of 4 pixels including the lower pixel P21 and the lower right pixel P22 are assigned 1/4 of the color tone error E00. Among the 4 peripheral pixels, 3 pixels, including the pixel P20, the pixel P21, and the pixel P22, are different from the target pixel P11. Pixels belonging to raster 2. As described above, the error diffused to each pixel around the target pixel (diffusion error) is used for dot formation determination of these pixels, and therefore, it is necessary to distinguish and store each pixel. Therefore, the diffusion error is stored in the large-capacity RAM 106 capable of storing diffusion errors of a large number of pixels (see FIG. 2 ).

When the color tone error of the pixel P11 is diffused to the surrounding pixels, the determination of the presence or absence of dot formation is started for the pixel P12 adjacent to the right. FIG. 5( b ) is an explanatory diagram conceptually showing the state of judging the presence or absence of dot formation in the target pixel P12 . When performing dot formation determination, first, the accumulated diffusion errors distributed from peripheral pixels to the target pixel P12 are read out, and the image data of the target pixel P12 is corrected using the read diffusion errors. As shown in Figure 5(b), on the target pixel P12, four pixels from the surrounding pixels that have been judged to form dots, that is, the pixel P01, the pixel P02, the pixel P03, and the pixel P11, are accumulated according to the above-mentioned error diffusion matrix. error. This diffusion error is read out from the RAM 106, the image data of the target pixel P12 is corrected, and the presence or absence of dot formation is determined by comparing the obtained correction value with a predetermined threshold value. FIG. 5( c ) shows a state in which it is determined whether or not dots are formed for a new target pixel P12 . As a result of judging the presence or absence of dot formation, the hue error E12 has occurred in the new target pixel P12. Therefore, as described with reference to FIG. 5(a), this hue error is diffused to surrounding pixels according to the error diffusion matrix.

When the color tone error generated in the pixel P12 spreads to the surrounding pixels, it starts to judge whether or not dots are formed in the pixel P13 adjacent to the right. A color tone error also occurs in the new target pixel P13, so the error is diffused to the surrounding pixels according to the error diffusion matrix, and it is judged whether there is dot formation in the pixel adjacent to the right. In this way, if the hue error is diffused to the surrounding pixels, the target pixel is moved to the right by 1 pixel one by one, and if it reaches the pixel at the right end of the image, it returns to the left end of the image temporarily, and begins to align the pixel at the next raster (in the next raster). In the example shown in FIG. 5 , it is the pixel P20) that determines whether or not dots are formed. Like raster 1, if raster 2 also reaches the pixel at the right end of the image, it returns to the left end of the image again and starts processing raster 3.

In this way, in the error diffusion method, the target pixel is shifted one by one along the raster, and the presence or absence of dot formation is determined in consideration of diffusion errors diffused from peripheral pixels. The color tone error generated in the target pixel by the judgment is diffused to and stored in surrounding unjudged pixels, and is used when judging whether or not dots are formed in these unjudged pixels.

Here, as described above, pixels on a raster different from the raster to which the target pixel belongs are also included in the peripheral pixels. The presence or absence of dot formation is determined along the raster, so even if a diffusion error has been allocated, it is necessary to store the allocated diffusion error before starting the processing of the raster to which the pixel belongs. Furthermore, since a large number of pixels are included in the raster, it is necessary to store the assigned diffusion error for a considerable number of pixels in a state that distinguishes each pixel. This is the reason for using the RAM 106 with a large storage capacity to store diffusion errors.

In addition, in order to spread the color tone error that occurs every time the presence or absence of dot formation is judged for the target pixel to surrounding unjudged pixels, it is necessary to frequently read and write data to the RAM 106 . If the data is frequently read and written to the RAM 106, the time for reading and writing increases, and the time required for judging whether or not dots are formed will be extended.

(b) Outline of tone number conversion processing in this embodiment

On the other hand, in the tone number conversion process of this embodiment, the presence or absence of dot formation is determined in parallel for a plurality of rasters as described below. In this way, the frequency of reading and writing data to the RAM 106 is reduced, so that the presence or absence of dot formation can be quickly judged. Next, the principle of quickly performing the determination of the presence or absence of dot formation by performing the processing of a plurality of rasters in parallel will be described.

FIG. 7 is an explanatory diagram showing, as the simplest example, the principle of judging the presence or absence of dot formation with respect to two gratings in parallel. Here, whether or not dots are formed is judged in parallel with two gratings, i.e., grating i and grating j below it.

First, determine the leftmost pixel Pi0 of raster i. Fig. 7(a) conceptual formula shows the situation of judging the presence or absence of dot formation in the pixel Pi0. The error is allocated from the pixel Ph0 and the pixel Ph1 of the raster h located directly above the raster i, and is stored in the pixel Pi0. Therefore, the diffusion error stored in the pixel Pi0 is read out from the RAM 106 of the computer 100, the tone value of the image data in the pixel Pi0 is corrected, and the presence or absence of dots is determined for the pixel Pi0 by comparing the obtained correction value with a specified threshold. In this way, when it is judged whether or not a dot is formed in the pixel Pi0, a tone error occurs in the pixel Pi0, and therefore, it is diffused to the surrounding pixels according to the error diffusion matrix. Here, in order to avoid complicating the description, a relatively simple error diffusion matrix shown in FIG. 6( a ) will be used for description. To facilitate understanding, the same matrix as the error diffusion matrix in FIG. 6( a ) is shown in FIG. 7( b ). The tone error generated in pixel Pi0 is distributed to three pixels including pixel Pi1, pixel Pj0, and pixel Pj1 according to the error diffusion matrix of FIG. In FIG. 7( a ), the case where the color tone error spreads from the pixel Pi0 to surrounding pixels is conceptually shown by thick arrows.

In this specification, the diffusion error between multiple rasters processed in parallel (in FIG. 7, for example, the diffusion error diffused from the pixel of raster i to the pixel of raster j) is stored in the register, not between the rasters processed in parallel. The diffusion error (in FIG. 7 , for example, the diffusion error diffused from the pixel of raster j to the pixel of raster k) is stored in RAM 106 . As mentioned above, the registers can be read and written at a higher speed than the RAM 106, so by utilizing the registers, the tone number conversion process can be performed more quickly. Errors between rasters processed in parallel do not necessarily have to be stored in registers, and may be stored in, for example, RAM 106 . Even if these diffusion errors to be used immediately are stored in the RAM 106, the values remaining in the cache memory of the CPU 102 can usually be used, so reading and writing can actually be performed at a high speed, thereby enabling rapid tone number conversion processing.

When the presence or absence of dot formation is determined for the pixel Pi0 and the generated tone error is diffused, the determination of the presence or absence of dot formation in the pixel Pi1 adjacent to the right begins. For the pixel Pi1, the color tone error generated in the pixel of the raster h located one row above it is diffused according to the error diffusion matrix of FIG. 7( b ), and stored in the RAM 106 in advance. Therefore, the error previously stored in the RAM 106 diffused from the pixel of the raster h is read out, and the tone value of the image data of the pixel Pi1 is corrected using the diffused error and the diffused error distributed from the pixel Pi0 to the pixel Pi1 and stored in the register. In this way, the image data of the pixel Pi1 is corrected by the error diffused from the pixel Ph0, the pixel Ph1, the pixel Ph2, and the pixel Pi0 located on the raster h, so that a correction value equal to that of the usual error diffusion method can be obtained.

The magnitude relationship between this correction value and a specified threshold is compared, and if the correction value is larger than the threshold, it is determined that a dot is formed in the pixel Pi1, otherwise it is determined that a dot is not formed. As a result of the judgment, a color tone error also occurs in pixel Pi1, so it is assigned to four surrounding pixels, namely, pixel Pi2, pixel Pj0, pixel Pj1, and pixel Pj2, according to the error diffusion matrix. The values of diffusion errors assigned to these four pixels are stored in registers of the CPU 102 for each pixel. In FIG. 7( a ), the state in which the color tone error generated in the pixel Pi1 spreads to surrounding pixels is conceptually shown by thin solid arrows. For the pixel Pj0, since the diffusion error diffused from the pixel Pi0 is already stored, the diffusion error diffused from the pixel Pi1 is added to this value and stored. In addition, when it is determined whether or not dots are formed in the pixel Pi1, there is no need for a register used to store the diffusion error diffused to the pixel Pi1, so this register can be used to store the diffusion error distributed from the pixel Pi1 to other pixels.

When the presence or absence of dot formation is determined for the pixels Pi0 and Pi1 located on the raster i, the determination of the presence or absence of dot formation is started for the pixel Pj0 located at the left end of the raster j. That is, here, the color tone error generated by the judgment of the presence or absence of dots is diffused to the surrounding pixels according to the error diffusion matrix of FIG. is to distribute all the diffusion errors. Therefore, after the determination of the dot formation of these two pixels is performed, the determination of the pixel Pj0 is performed.

FIG. 7( c ) is an explanatory diagram conceptually showing a state of judging the presence or absence of dot formation in the pixel Pj0 . According to the error diffusion matrix shown in FIG. 7( b ), the error is diffused from the pixel Pi0 and the pixel Pi1 to the pixel Pj0 , and the value of the error is not stored in the RAM 106 but in the register of the CPU 102 as described above. Therefore, the tone value of the image data in the pixel Pj0 is corrected using this value, and the presence or absence of dot formation is determined based on the magnitude relationship between the correction value and the threshold value. As a result of the determination, the color tone error generated in the pixel Pj0 is diffused to three surrounding pixels including the pixel Pj1 , the pixel Pk0 , and the pixel Pk1 according to the error diffusion matrix.

Here, in the example shown in FIG. 7 , whether or not dots are formed is determined in parallel for the pixels of the raster i and the pixels of the raster j. In this way, the determination of the presence or absence of dot formation in the two pixels of the pixel Pk0 and the pixel Pk1 is performed after the determination of all the pixels of the raster i and the raster j is completed. Therefore, the values of the diffusion error to the pixel Pk0 and the diffusion error to the pixel Pk1 are considered to be temporarily unused, and therefore these values are stored in the RAM 106 . On the other hand, the diffusion error to the pixel Pj1 will be used soon, so it is stored in the register of the CPU 102 . In this way, since the determination of whether or not dots are formed on the two rasters is performed in parallel for the raster i and the raster j, errors occurring in the raster above the raster i and spreading to the pixels of the raster i are stored in the RAM 106 . Similarly, errors that have occurred in raster j and spread to the pixels of raster k are also stored in RAM 106 . On the contrary, the error generated in the raster i and diffused to the pixel of the raster j is stored in the register of the CPU 102 . In FIG. 7 , oblique lines in raster i and raster k indicate that the diffusion errors diffused to the pixels of these rasters are stored in RAM 106 .

In FIG. 7( c ), the arrows pointing from pixel Pj0 to pixel Pk0 or from pixel Pj0 to pixel Pk1 use hollow arrows, indicating that the diffusion errors assigned to these pixels are stored in registers of the CPU 102 . Since the presence or absence of dot formation has been determined for the pixel Pj0, the register for storing the diffusion error for the pixel Pj0 can be used for other purposes, and the register for storing the diffusion error for the pixel Pj1 can be used.

In this way, if the color tone error generated in the pixel Pj0 is diffused to the surrounding pixels, the color tone error generated by judging the presence or absence of dot formation in the pixel Pi1 of the raster i is diffused to the surrounding pixels, and then the presence or absence of the pixel Pj1 of the raster j is judged. dots formed. FIG. 7( d ) is an explanatory diagram conceptually representing this situation. When judging whether the pixel Pi2 has a dot or not, the color tone value of the image data is corrected using the diffusion error stored in the RAM 106 diffused from the pixel of the raster h and the diffusion error stored in the register diffused from the pixel Pi1. With or without dots formed. The hue error generated by the judgment spreads to the surrounding pixels. As indicated by thick arrows in FIG. 7( d ), the diffusion error to the peripheral pixels is stored in a register. Then, when judging the presence or absence of dot formation in the pixel Pj1, the presence or absence of dot formation is judged based on the magnitude relationship with the specified threshold value using the tone value of the diffusion error correction image data stored in the register. The hue error generated by judging i and the diffusion error to the pixel of raster k are stored in RAM 106, and the diffusion error to the pixel of raster j is stored in the register. Through the above processing, when the processing of the pixel Pi2 and the pixel Pj1 is completed, the processing of the pixel Pi3 and the pixel Pj2 is performed in the same way.

The numbers marked with circles in the pixels of FIG. 7( d ) indicate the order of judging the presence or absence of dot formation for the pixels of raster i and raster j. As shown in the figure, the determination of the presence or absence of dot formation is alternately performed on the pixel of raster i and the pixel of raster j located on the lower left of the pixel. In this way, if raster i and raster j are processed in parallel, the diffusion error for the pixel of raster j can be stored in the register, and the diffusion error for the pixel of raster k can be stored in the RAM 106 . That is, it is possible to reduce the frequency of spreading errors in writing and reading to the RAM 106, so that it is possible to quickly determine the presence or absence of dot formation.

As shown in FIG. 7, for the pixel Pi0 at the left end of the raster i, there is no pixel of the raster j at the lower left of the pixel, so the processing of the pixel Pi1 located on the same raster i is performed after the pixel Pi0 . Assume an overhead pixel Pj-1 at the lower left of pixel Pi0, after the overhead pixel Pj-1 is processed immediately after pixel Pi0, such overhead pixel Pj-1 can be discarded without using the judgment result of dot formation . In this way, for the pixels at the left end, the usual processing can also be performed on the overhead pixels, so there is no need for flexible processing.

FIG. 8 is a flowchart showing the flow of processing for judging the presence or absence of dot formation for two rasters in parallel. This processing is performed by CPU 102 of computer 100 . As mentioned above, the color printer of this embodiment is a printer capable of forming ink dots of four colors, such as C, M, Y, and K, and the tone number conversion process shown in FIG. 8 is also performed for each color. However, to avoid description, To complicate matters, the color of the ink dot is not specified. Of course, in addition to the above 4 colors, LC ink and LM ink can also be added for 6-color printers.

In addition, as described above, the color printer of this embodiment may also be a variable dot printer capable of forming dots of varying sizes for each color. When using variable dot thulium, for example, when using a variable dot printer capable of forming large, medium, and small dots, the tone number conversion process described below is performed for dots of various sizes.

In this way, as the color of the ink used increases and dots of various sizes can be formed, the number of times to perform the tone number conversion process also increases, so the time required for these processes will also be extended. The tone number conversion processing used in this embodiment described below can be processed quickly, so it is very suitable for this case as well.

When the tone number conversion process of this embodiment is started, at first, the diffusion error that the image data of the pixel for which the presence or absence of dot formation is to be judged is diffused to the pixel is obtained from the first raster of the parallel processed rasters (step S200) . Here, it is assumed that the pixel to be processed is each n-th pixel Pin of the raster i. Both image data Cdin and diffusion error Edin are stored in RAM 106 .

Then, the correction data Cxin of the pixel Pin is calculated by adding the image data Cdin of the pixel Pin and the diffusion error Edin (step S202 ). Comparing the correction data Cxin obtained in this way with the specified threshold th (step S204), if the correction data is large, it is judged that a dot is formed in the pixel Pin, and the value "1" representing the formation of a dot is written into the variable Cr representing the judgment result ( Step S206). Otherwise, it is determined that no dot is formed in the pixel Pin, and a value "0" indicating that no dot is formed is written into the variable Cr (step S208).

When it is judged whether or not dots are formed in the pixel Pin of the raster i, the hue error resulting from the judgment is calculated (step S210). The color tone error Ein can be obtained by subtracting the tone value (result value) expressed in the pixel Pin from the correction data Cxin according to whether a dot is formed or not. The obtained hue error is multiplied by the error diffusion coefficient to calculate the diffusion error diffused to the surrounding pixels. The error diffusion coefficient is set for each pixel based on the error diffusion matrix. The diffusion error diffused to the pixel of raster i obtained in this way is also stored in the register as the diffusion error diffused to the pixel of raster j located directly below the raster i (step S212). Diffusion errors diffused to other pixels are stored in RAM 106 if, for example, diffusion errors are diffused to pixels of raster k.

In this way, when the determination of the presence or absence of dot formation in the pixel of raster i is completed and the diffusion of the error is completed, the determination of the presence or absence of dot formation in the pixel Pjn-1 of raster j is started. That is, the image data Cdin of the pixel Pjn-1 is read from the RAM 106 (step S214), and the diffusion error Edin-1 diffused to the pixel Pjn-1 is read from the register (step S216). The diffusion error Edin-1 read from the register also includes the diffusion error diffused from the pixel Pin for which the determination of whether or not dot formation has just been performed. When the pixel Pin of the raster i is the pixel Pi0 at the left end, such processing is performed on the overhead pixel Pj-1.

Next, add the image data Cdin-1 and the diffusion error Edin-1 to calculate the correction data Cxin-1 (step S218), compare the obtained correction data Cxin-1 with the specified threshold th (step S220), if the correction data is large When it is judged that a dot is formed, a value "1" indicating that a dot is formed is written into the variable Cr representing the judgment result (step S222). Otherwise, a value "0" indicating that no dot is formed is written (step S224). Then, the hue error Ejn-1 generated in the pixel Pjn-1 accompanying this determination is calculated (step S226). The hue error Ejn-1 can be obtained by subtracting the result value of the pixel Pjn-1 from the correction data Cxin-1. The color tone error obtained is multiplied by the error diffusion coefficient set according to the error diffusion matrix, and the diffusion error diffused to the surrounding pixels is calculated. Thus, when the diffusion error is obtained, the diffusion error diffused to the pixel of raster j is stored in the register, and the diffusion error diffused to the pixel of raster k is stored in the RAM 106 (step S228).

Through the above processing, if the dot formation judgment and error diffusion processing for the pixels of raster i and raster j are completed, it is judged whether the processing of all the pixels of raster i and raster j is completed (step S230). When there are still unprocessed pixels, the position of the pixel is moved to the right by 1 pixel, that is, "n" is replaced with the value of "n+1" (step S232), and then returns to step S200 to continue a series of processing. When there are no unprocessed pixels, it is determined that the processing of all rasters has ended (step S234). Substitute "i" (step S236), and return to step S200 to continue a series of processing. When there is no more unprocessed raster, the tone number conversion process shown in FIG. 8 is terminated, and the process returns to the image data conversion process shown in FIG. 4 .

As described above, in the tone number conversion process of the first embodiment, the presence or absence of dot formation is alternately determined in parallel with respect to the pixel of raster i and the pixel of raster j. In this way, for the pixel of raster j, it is judged immediately after the pixel of raster i or whether there is dot formation or not. Therefore, whether or not dots are formed in the pixel of raster j can be directly judged without temporarily storing the diffusion error from the pixel of raster i to the surrounding pixels in the error buffer, so that the frequency of writing to the error buffer can be reduced. Spend. As long as the frequency of writing to the error buffer can be reduced, the time required for judging the presence or absence of dot formation can be shortened, so that the tone number conversion process can be performed quickly.

Also, when it is necessary to save the storage capacity of the error buffer, a process of reusing the error buffer temporarily used for determining whether or not dots are formed is performed for the determination of another raster. In this case, in the tone number conversion process of the first embodiment above, an error buffer can be provided for each raster of two rasters, so the number of all rasters stored in the error buffer can be halved. As a result, it is possible to save the capacity of the error buffer without performing a process of reusing the error buffer used for forming the judgment point for judgment of another raster. Of course, if more than two rasters are processed in parallel, an error buffer can be provided for each of the plurality of rasters, so the capacity of the error buffer can be reduced.

B-4. Modifications

(1) Modification 1

In the above, as the simplest example, the case of judging the presence or absence of dot formation is performed on two gratings in parallel, however, the number of gratings to be processed in parallel is not limited to two, and three or more gratings may be processed in parallel. Raster processing. FIG. 9 is an explanatory diagram conceptually showing a state of judging the presence or absence of dot formation for three gratings in parallel. In FIG. 9 , whether or not dots are formed is determined in parallel for three gratings, namely, grating i, grating j, and grating k. In order to avoid complicating the description, the error diffusion matrix shown in FIG. 6( a ) is used here as in the case of FIG. 7 .

Oblique lines in raster i and raster L indicate that the diffusion errors of the pixels assigned to these rasters are stored in RAM 106 . The numbers in the circled symbols of the pixels of raster i, raster j, and raster k indicate the order of judging the presence or absence of dot formation in each pixel. As shown in the figure, for the first three pixels, the presence or absence of dot formation is determined in the same order as when the two rasters described in FIG. 7 are processed in parallel. Starting from the fourth pixel thereafter, three pixels of raster i, raster j, and raster k are regarded as a group, and the presence or absence of dot formation is judged in parallel in this order. Here, since the processing of three rasters of raster i to raster k is performed in parallel, the errors diffused to the pixels of these three rasters are quickly used, and therefore are stored in the registers of the CPU 102 . The error of pixel diffusion of raster L is used after the processing of three rasters of raster i to raster k is completed, so the error of pixel diffusion of raster L is stored in RAM 106 . By repeating such processing, it is possible to perform in parallel the determination of whether or not dots are formed on the three gratings.

In this way, if the judgment of whether the pixels of grating i ~ grating k have dot formation is performed in parallel, the same effect as that of processing two gratings in parallel can be obtained between adjacent grating i and grating j or between grating j and grating k .

In addition, if the processing of raster i to raster k is performed in parallel, for the pixel of raster k, it is judged whether or not dots are formed immediately after or shortly after the pixel of raster i. Therefore, even if the diffusion error diffused from the pixel of raster i to the surrounding pixels is not temporarily stored in the error buffer, it is possible to directly judge whether or not the pixel of raster k has dot formation, thereby reducing the frequency of reading and writing to the error buffer. Therefore, the time required for judging the presence or absence of dot formation can be shortened.

(2) Modification 2

In the various embodiments above, in order to avoid the complexity of the description, the error diffusion matrix uses a relatively small matrix as shown in FIG. 6( a ). Of course, when other error diffusion matrices are used, the presence or absence of dots can be judged in parallel for pixels of a plurality of gratings in the same way. As an example, using the error diffusion matrix of FIG. 6( b ), a process of judging whether or not dots are formed on two rasters in parallel will be described with reference to FIG. 10 .

For ease of understanding, the error diffusion matrix used is shown in FIG. 10( a ). This matrix is the same as that shown in Fig. 6(b). When such an error diffusion matrix is used, the hue error generated in the obliquely-lined target pixel is diffused not only to the pixels adjacent to the target pixel but also to the adjacent pixels. Comparing this with FIG. 10( b ), the hue error occurring in pixel Pj2 spreads to pixels Pi3 and Pi4 for raster i, and spreads to pixels Pj0 to Pj4 for raster j. In other words, for pixel Pj0 of raster j, a diffusion error from pixel Pi2 is assigned in addition to the diffusion error from pixel PiO of raster i and the diffusion error from pixel Pi1. Therefore, after the determination of the presence or absence of dot formation of the three pixels included in the raster i is completed, the determination of the presence or absence of dot formation of the pixel Pj0 located in the raster j is started. That is, when using the error diffusion matrix shown in FIG. 10( a ), the positional relationship between the pixels of raster i and the pixels of raster j is such that the pixels of raster j lag behind the pixels of raster i by 2 pixels. In this way, when a plurality of rasters are processed in parallel, the positional relationship of each pixel included in each raster can be determined according to the range of diffuse tone error. While maintaining such a positional relationship, whether or not dots are formed in the pixels of these rasters is judged in parallel.

FIG. 10( b ) is an explanatory diagram showing a state in which the presence or absence of dot formation is continuously determined for the pixel Pi2 of the raster i and the pixel Pj0 of the raster j. The numbers marked with the circles in the figure indicate which pixel is judged whether to form dots or not among the pixels of raster i and raster j. In addition, the thick arrow pointing from the pixel Pi2 to the surrounding pixels conceptually shows that the hue error generated in the pixel Pi2 is diffused to the surrounding pixels according to the error diffusion matrix. If the color tone error of the pixel Pi2 is diffused to the surrounding pixels, it is judged whether or not the pixel Pj0 has dot formation. Among the hue errors occurring in the pixel Pj0 , the diffusion error assigned to the pixel of raster j is stored in the register of CPU 102 , and the diffusion error assigned to the pixel of raster k is stored in RAM 106 . The hollow arrows pointing from pixel Pj0 to the pixels of raster k indicate that the diffusion errors assigned to these pixels are stored in RAM 106 . As indicated by the sequence in the circle, the presence or absence of dot formation is determined alternately for the pixel of raster i and the pixel of raster j in the order of pixel Pj01, pixel Pi3, and pixel Pj1. The diffusion error assigned to the pixel of raster i or raster j is stored in the register of CPU 102 , and the diffusion error assigned to raster k is stored in RAM 106 . Repeat the above processing, if the judgment of whether there is dot formation is carried out for all the pixels of grating i and grating j, the position of the processed grating is moved down by 2 lines, and the same process is repeated for grating k and the grating below it. The process of using the error diffusion matrix shown in Figure 10 (a) can be used in parallel to determine whether there are dots in the two gratings.

In this way, when grating i and grating j are judged whether or not dots are formed in parallel, it is also judged whether or not dots are formed in pixels of raster j immediately after or soon after the pixels of raster i. Therefore, the presence or absence of dot formation in the pixel of raster j can be directly judged without temporarily storing the diffusion error diffused from the pixel of raster i to the surrounding pixels in the error buffer, thereby reducing the number of reads to the error buffer. Write frequency. As a result, by reducing the frequency of reading and writing to the error buffer, it is possible to shorten the time required for judging whether or not dots are formed.

(3) Modification 3

In the above various embodiments, the case where the hue error generated in the target pixel is diffused to the pixels of the raster of the target pixel and the pixels of one raster below the raster has been described, but the case is not limited to such a case. For example, if the error diffusion matrix shown in FIG. 6(d) is used, the color tone error occurring in the target pixel is diffused from the pixels of the next two rasters below the target pixel. FIG. 11 is an explanatory diagram conceptually showing, as an example, the process of judging whether or not dots are formed on three rasters in parallel when the error diffusion matrix shown in FIG. 6( d ) is used.

For ease of understanding, the error diffusion matrix used is shown in FIG. 11( a ). This matrix is the same matrix as that of Fig. 6(d). It is assumed that the presence or absence of dot formation is judged in parallel for three gratings of grating i, grating j, and grating k. The hue error occurring in the pixel of grating k is diffused according to the pixel diffusion of the three gratings from grating k to grating m under the error diffusion matrix in Fig. 11(a). After the processing of the three rasters of raster i to raster k is completed, it is judged whether or not dots are formed. Therefore, the errors diffused to the grating L and the grating m are stored in the RAM 106 . In FIG. 11( b ), the pixels where the diffused errors are stored in the RAM 106 are indicated by oblique lines. Thus, when the error diffusion matrix shown in FIG. 11( a ) is used, the rasters where the diffused errors are stored in the register of CPU 102 and the two rasters that are stored in RAM 106 appear alternately.

(4) Modification 4

When spreading the tone error over a wide range, it can be spread to the error buffer when spreading from the target pixel to a distance beyond a specified distance. For example, an error diffusion matrix shown in FIG. 12( a ) can be used assuming that an error diffused from a target pixel to a distance of 3 pixels or more is diffused to a pixel existing in an error buffer. In FIG. 12( a ), two rasters are straddled from the target pixel to the distance, and the pixels are displayed as a whole by dotted lines, indicating that errors in these areas diffuse to the rasters where error buffers exist in the two rasters. Next, it demonstrates concretely with reference to FIG.12 (b), (c). Consider the case where the pixel of interest lies on a raster where an error buffer exists. At this time, the error buffer is located on the raster of the target pixel and the two rasters below it, so the result is the same as the case where errors are diffused according to the matrix shown in FIG. 12(b). Next, consider the situation where the target pixel is located on a raster that does not have an error buffer. At this time, the error buffer is located on two rasters sandwiching the target pixel's raster from top to bottom. Therefore, the result is the same as that shown in FIG. 12( The same is true for the matrix diffusion error shown in c).

Comparing the error diffusion matrix in Fig. 12(a) with the corresponding error diffusion matrix in Fig. 6(c), we can see that the error diffused to the pixel K03 and pixel K13 in Fig. 6(c) is in Fig. 12(a) Then gather together and spread to the area 3 pixels away from the target pixel (indicated as K3 in the figure). Similarly, the errors diffused to pixel K04 and pixel K14 in FIG. 6( c ) are concentrated and diffused to the area 4 pixels away from the target pixel (indicated as K4 in the figure) in FIG. 12( a ).

When an error occurring in a target pixel is diffused to a distant place, it is known empirically that even if the position of the pixel where the error is diffused is shifted to some extent, there will be no significant deterioration in image quality. Therefore, when color tone errors are diffused over a wide range, image quality does not deteriorate even if distant pixels are diffused to pixels with error buffers. In the various embodiments described above, when the error is not diffused to the error buffer, it is stored in the register of the CPU 102 . Therefore, by storing distant pixels in the error buffer, it is possible to save registers used for judging whether or not dots are formed. If the number of registers storing errors is reduced, the processing can be simplified, and if the saved registers are used for other purposes, the presence or absence of dot formation can be quickly judged.

In the above description, it is assumed that the error is diffused to pixels spanning two rasters. However, if the error diffusion matrix shown in FIG. 12(d) is used, the error may be diffused across three rasters. In this way, when spreading to more rasters, the error that spreads far can be easily and quickly processed without degrading the image quality if it is spread to the error buffer.

C. Example 2

In the various embodiments described above as the tone number conversion processing of the first embodiment, the tone error generated in the target pixel by judging the presence or absence of dot formation is transferred to the surrounding pixels according to the error diffusion coefficient set in the error diffusion matrix. diffusion. In this sense, the method of Embodiment 1 can be considered to be based on a method called a so-called error diffusion method. It is also possible to judge whether or not dots are formed in a plurality of gratings in parallel by a method called the so-called average error minimum method, not based on such a method. Next, the tone number conversion processing of the second embodiment will be described.

C-1. Hue Number Conversion Processing of Embodiment 2

FIG. 13 is an explanatory diagram conceptually showing the principle of quickly performing the determination of the presence or absence of dot formation by performing the processing of a plurality of rasters eccentrically in the tone number conversion processing of the second embodiment. Before proceeding to the detailed description of the tone number conversion process in the second embodiment, a method called the method of minimizing the average error will be briefly described using FIG. 13 as a preparation.

In the average error minimum method, when judging the presence or absence of dots in the target pixel, the color tone error occurring in each pixel is read from the surrounding pixels for which the presence or absence of dots has been judged. formed judgments. Next, these processes will be described with reference to FIG. 13( a ). FIG. 13( a ) is an explanatory diagram showing a state of judging the presence or absence of dot formation in the pixel Pi0. To determine whether or not dots are formed in pixel Pi0, the specified weight coefficient is multiplied by the color tone error occurring in the pixel Ph0 and the pixel Ph1 around the pixel Pi0, and the value obtained by adding them is calculated. In FIG. 13( a ), the symbols respectively indicated as Eh0 and Eh1 in the pixel Ph0 and the pixel Ph1 indicate hue errors Eh0 and Eh1 that occur in the respective pixels. Next, the image data of the pixel Pi0 is corrected with the calculated value, and the presence or absence of dot formation is judged based on the magnitude relationship between the obtained correction value and the specified threshold value. The weight coefficient to be multiplied by the hue error is set in advance for each pixel based on the relative positional relationship between each pixel and the target pixel. FIG. 13( b ) is an explanatory diagram showing a case where a weight coefficient is set for each surrounding pixel centering on the target pixel. The obliquely drawn pixels in the figure are the target pixels. For example, for the pixel adjacent to the left of the target pixel, set its weight coefficient to "K0-1". The matrix for setting weight coefficients for each pixel around the target pixel is not limited to the matrix shown in FIG. 13(b), and various matrices shown in FIG. 14 can be used.

In this way, when the determination of the presence or absence of dot formation is performed on the pixel Pi0, the determination of the presence or absence of dot formation on the pixel Pi1 adjacent to the right begins. When judging the presence or absence of dot formation in pixel Pi1, the presence or absence of dot formation is performed in consideration of color tone errors occurring in pixel Ph0, pixel Ph1, pixel Ph2, and pixel Pi0 according to the matrix set in FIG. 13(b). judge. If the determination of the pixel Pi1 ends, the determination of the adjacent pixel Pi2 on the right starts. In this way, whether or not dots are formed is judged pixel by pixel along the raster. The color tone error generated as a result of the judgment of dot formation is stored in the error buffer provided in the RAM, and after the dot formation judgment is completed for all the pixels on the raster currently being processed, the In the processing of the next raster, it is read from the error buffer of RAM again and used.

As mentioned above, in order to judge the presence or absence of dot formation using the method of minimizing the average error, every time the judgment of the presence or absence of dot formation is performed on the target pixel, it is necessary to read the color tone of the surrounding pixels from the error buffer provided in RAM. In addition, in order to use the color tone error generated in the target pixel by the judgment to judge the presence or absence of dot formation in other pixels, it must be stored in the error buffer in advance. In this way, since color tone errors are frequently read and written to the error buffer, it takes a certain amount of time to determine whether or not dots are formed.

On the other hand, in the tone number conversion process of the second embodiment described below, by performing the processing of a plurality of rasters in parallel, it is possible to quickly determine the presence or absence of dot formation. Next, the principle of quickly performing the determination of the presence or absence of dot formation by performing the processing of a plurality of rasters in parallel will be described with reference to FIG. 13 .

FIG. 13 is an explanatory diagram showing, as the simplest example, the principle of judging the presence or absence of dot formation with respect to two gratings in parallel. Here, it is assumed that the presence or absence of dot formation is determined in parallel for two gratings of grating i and grating j immediately below it.

First, whether or not dots are formed is determined for the leftmost pixel Pi0 of the raster i. FIG. 13( a ) conceptually shows the state of judging the presence or absence of dot formation in the pixel Pi0. In order to judge the target pixel Pi0, the hue error Eh0 of the pixel Ph0 and the hue error Eh1 of the pixel Ph1 are used in the same manner as the average error diffusion method described above. These color tone errors are stored in the RAM 106 of the computer 100 . The image data of the target pixel Pi0 is corrected by multiplying the respective color tone errors read from the RAM 106 by the weight coefficients set in the matrix of FIG. 13( b ). Whether or not dots are formed in the pixel Pi0 is judged based on the correction value thus obtained. In FIG. 13( a ), the thick arrow pointing from the pixel Ph0 or Ph1 to the target pixel Pi0 conceptually indicates that the color tone error of the pixel Ph0 or Ph1 is taken into consideration in order to determine whether the target pixel Pi0 has dot formation.

After the pixel Pi0 has been judged to have dot formation, the color tone error that has occurred is temporarily stored in the register of the CPU 102 , and then the pixel Pi1 adjacent to the right side of the pixel Pi0 is judged to have dot formation or not. As set in FIG. 13( b ), in determining the presence or absence of dot formation in the pixel Pi1 , the hue error occurring in each pixel of the pixel Ph0 , the pixel Ph1 , the pixel Ph2 , and the pixel Pi0 is taken into consideration. In FIG. 13( a ), the thin line arrows pointing from each pixel to the pixel Pi1 conceptually indicate that in order to determine whether the target pixel Pi1 has dot formation or not, the hue error of these pixels is taken into consideration. Among the four color tone errors, the color tone error Eh0 of the pixel Ph0 and the color tone error Eh1 of the pixel Ph1 store the values used in the determination of the presence or absence of dots in the pixel Ph0 just now, so these values can be used. In addition, the value obtained just now can be used for the hue error of the pixel Pi0. Therefore, only the hue error Eh2 of the pixel Ph2 is read from the RAM 106 to determine whether or not dots are formed on the pixel Pi1. The hue error generated in the pixel Pi1 as a result of the determination is stored in a register of the CPU 102 in advance.

In the tone number conversion process of the second embodiment, if the presence or absence of dot formation is determined for pixels Pi0 and Pi1 located on raster i, then the presence or absence of dot formation is determined for pixel Pj0 located on raster j. FIG. 13( c ) is an explanatory diagram conceptually showing a state of judging the presence or absence of dot formation in the pixel Pj0 . From the matrix in FIG. 13( b ), it can be seen that the presence or absence of dot formation in the pixel Pj0 can be determined by only considering the hue error between the pixel Pi0 and the pixel Pi1. As described above, these hue errors Ei0 and Ei1 are calculated before the pixel Pj0 and stored in the register of the CPU 102 . Therefore, the presence or absence of dot formation can be determined for the pixel Pj0 without reading the color tone error from the RAM 106 . In this way, if the pixel Pj0 is judged as to whether or not dots are formed, the color tone error generated in the pixel Pj0 is stored in the register of the CPU 102 and the error buffer of the RAM 106, and then the pixel of the raster i and the pixel of the raster j are stored. The pixels are alternately judged whether or not dots are formed.

The reason why the hue error of pixel Pj0 is stored in the error buffer of RAM 106 is that, after the processing of raster i and raster j is completed, the hue error Ej0 is used when judging the presence or absence of dot formation on the pixel located on raster k. . In addition, storing not only in the error buffer but also in the register of the CPU 102 is used for judging whether the adjacent pixel Pj1 has a dot or not. The hue error stored in the RAM 106 is read out and used when determining whether or not dots are formed in the pixel Pi0 or the pixel Pi1 described above. In FIG. 13, oblique lines are drawn in the pixels of raster h and raster j to indicate that the hue errors of these pixels are stored in the error buffer.

In FIG. 13( d ), the sequence in the circled symbols in the pixels indicates the order in which the presence or absence of dot formation is performed for each pixel. As shown in FIG. 13( d ), the pixel for determining presence or absence of dot formation subsequent to the pixel Pj0 is a pixel of the pixel Pi2 located on the raster i. The color tone errors considered in the determination of the presence or absence of dot formation of such pixels are the four color tone values of the pixel Ph1, the pixel Ph2, the pixel Ph3, and the pixel Pi1. The presence or absence of dot formation can be determined by reading out the color tone error occurring in the pixel Ph3. In addition, after the pixel Pi2, it is determined whether or not the pixel Pj1 of the raster j has dot formation. In judging the presence or absence of dots in the pixel Pj1, the color tone errors of the pixels Pi0, Pi1, Pi2, and Pj0 are used. Therefore, the presence or absence of dot formation can be determined for the pixel Pj1 without reading the color tone error from the RAM 106 . In this way, when the color tone error Ej1 of the pixel Pj1 is obtained, the color tone error Ej1 is stored in the register of the CPU 102 and the error buffer of the RAM 106 .

As described above, the determination of the presence or absence of dot formation is alternately performed on the pixel of the raster i and the pixel of the raster j located on the lower left of the pixel. In this way, as long as the processing of the raster j adjacent to the raster i can be performed in parallel, the presence or absence of dot formation can be determined for the pixel of the raster j without reading the hue error from the RAM 106 . That is, the frequency of reading and writing to the error buffer of RAM 106 can be reduced, and it is possible to quickly determine whether or not dots are formed.

As shown in FIG. 13, for the pixel Pi0 at the left end of the raster i, since there is no pixel of the raster j at the lower left of the pixel, the pixel Pi1 located on the same raster i is modified after the pixel Pi0. deal with. Assume an overhead pixel Pj-1 at the lower left of pixel Pi0, after the overhead pixel Pj-1 is processed immediately after pixel Pi0, such overhead pixel Pj-1 can be discarded without using the judgment result of dot formation . In this way, for the pixels at the left end, the usual processing can also be performed on the overhead pixels, so there is no need for flexible processing.

FIG. 15 is a flowchart showing the flow of processing for judging the presence or absence of dot formation for two rasters in parallel. This processing is performed by the computer 100 . Like the tone number conversion process of the first embodiment, the tone number conversion process of the second embodiment is performed for each color of the color printer, and the color of the ink dot is not specified in order to avoid complicating the description. In addition, when a so-called variable dot printer is used, the tone number conversion process of the second embodiment is performed for each band of dots, which is the same as the case of the first embodiment described above.

When the tone number conversion process of the second embodiment is started, first, image data of a pixel for which dot formation is to be determined is acquired from the first raster of rasters processed in parallel (step S300 ). Here, as in Embodiment 1, it is assumed that the pixel to be processed (target pixel) is each nth pixel Pin of the raster i. Image data Cdin is stored in RAM 106 .

Next, the hue error of the surrounding pixels of the target pixel Pin is read (step S302). Peripheral pixels are pixels within a specified area away from the target pixel for which color tone errors are taken into account when determining whether or not the target pixel is dot-formed. When judging whether or not a target pixel has dots, pixels in various ranges can be considered as peripheral pixels. However, in order to avoid complicating the description, the peripheral pixels shown in the matrix of FIG. 14( a ) are considered below. In step S302, when the color tone error of the surrounding pixels is read, as described with reference to FIG. In step S302, only the hue error not stored in the register can be read out from RAM106.

Correction data Cxin of the target pixel Pin is calculated based on the hue error of the peripheral pixels read in this way and the image data Cdin of the target pixel Pin (step S304). That is, a predetermined weight coefficient determined for each peripheral pixel is multiplied by the color tone error of the peripheral pixel, and the sum of these calculated values and the image data Cdin of the target pixel Pin is obtained as correction data Cxin. The weight coefficients of peripheral pixels are determined for each pixel by the matrix shown in FIG. 14( a ).

Comparing the correction data Cxin obtained in this way with the specified threshold th (step S306), if the correction data is large, it is judged that a dot is formed in the pixel Pin, and the value "1" indicating that a dot is formed is written into the variable representing the judgment result Cr (step S308). Otherwise, it is determined that no dot is formed in the pixel Pin, and a value "0" indicating that no dot is formed is written into the variable Cr (step S310).

When it is determined whether or not dots are formed on the pixel Pin of the raster i, the key error Ein accompanying the determination is calculated and stored in the register of the CPU 102 (step S312). As in the first embodiment, the hue error Ein can be obtained by subtracting the resultant value of the target pixel Pin from the correction data Cxin.

As mentioned above, if the pixel Pin on the raster i is judged to have dot formation or not and the hue error is stored in the register of the CPU 102, the pixel Pjn-1 of the raster j located at the lower left of the pixel Pin is started to be determined. Handling of judgments without point formation. First, the image data Cdin-1 of the pixel Pjn-1 is read from the RAM 106 (step S314), and the color tone error of each surrounding pixel is read from the register of the CPU 102 (step S316). When the pixel Pin is the pixel Pi0 located at the left end of the raster i, the same process is performed on the overhead pixel Pj-1.

Next, the reason why the hue error of the peripheral pixels can be read from the register but not from the error buffer of the RAM 106 in step S316 will be described. As mentioned above, the range shown in Fig. 14(a) is considered as the surrounding pixels, so the hue error of the pixels located on the same raster i is taken into consideration when judging whether a pixel on raster j has dot formation or not and the hue error of the pixels of raster j. Here, since the determination of the presence or absence of dot formation is performed on the pixels of raster i and the pixels of raster j in parallel, when the determination of the presence or absence of dot formation of pixels on raster j is performed, all the surrounding pixels are all performed just before. Pixels for judging whether or not dots are formed. Therefore, if the color tone error generated by judging the presence or absence of dot formation is temporarily stored in the register of CPU 102, the color tone error of all peripheral pixels can be read out from the register without reading from the error buffer of RAM 106.

In this way, if the color tone error of the surrounding pixels is read out for the pixel Pjn-1, as in the case of the pixel Pin, the presence or absence of dot formation can be judged, and the color tone error Ejn-1 generated due to this judgment can be calculated. That is, the correction data Cxin-1 is calculated according to the hue error of the surrounding pixels and the image data Cdin-1 of the target pixel Pjn-1 (step S318), and the obtained correction data Cxjn-1 is compared with the specified threshold th (step S320), if If the correction data is large, it is judged that a dot is formed in the pixel Pjn-1, and a value "1" indicating that a dot is formed is written into the variable Cr indicating the judgment result (step S322). Otherwise, it is determined that a dot is not formed in the pixel Pjn-1, and a value "0" indicating that a dot is not formed is written into the variable Cr (step S324). Then, the value obtained by subtracting the target pixel Pjn-1 from the correction data Cxjn-1 is calculated to calculate the hue error Ejn-1 generated in the target pixel Pjn-1.

When the color tone error Ejn-1 of pixel Pjn-1 on raster j is obtained through the above processing, the color tone error Ejn-1 is stored in the register of CPU 102 and the error buffer of RAM 106 (step S328). Here, the reason for storing the hue error in the register and the error buffer is as follows. That is, the color tone error Ejn-1 of the pixel Pjn-1 is used to determine the presence or absence of dots in the adjacent pixel Pjn and the presence or absence of dots in the pixel on the next raster k. Here, since the processing of grating i and grating j is performed in parallel, the judgment of whether the adjacent pixel Pjn has dot formation is carried out quickly, but the judgment of the pixel located on grating k needs to be performed between grating i and grating j. Tsai proceeds after the processing of j is completed. Therefore, the hue error Ejn-1 of the pixel Pjn-1 is stored in the register of the CPU 102 in order to use it in the determination of the pixel Pjn, and is also stored in the error buffer of the RAM 106 in order to be used in the determination of the pixel of the raster k. .

Through the above processing, if the determination of the presence or absence of dot formation for the pixels of raster i and the pixels of raster j is completed, it is judged whether the processing for all the pixels of raster i and raster j is completed (step S330). If there are unprocessed pixels, the position of the pixel is moved to the right by 1 pixel, that is, "n" is replaced with the value of "n+1", and the process returns to step S300 to continue a series of processing. If there are no unprocessed pixels, it is judged whether the processing of all rasters has ended (step S332), and if there are unprocessed rasters, the raster position is moved down by 2 rasters, i.e. use "i+2" Replace "i" with the value of , and then return to step S300 to continue a series of processing. If there is no more unprocessed raster, the tone number conversion process shown in FIG. 15 ends, and returns to the image data conversion process shown in FIG. 4 .

As described above, according to the tone number conversion process of the second embodiment, the determination of the presence or absence of dot formation is alternately performed on the pixels of the raster i and the pixels of the raster j in parallel. In this way, the pixel of raster j is judged immediately after the pixel of raster i or whether there is dot formation or not. Therefore, even if the color tone error that occurs at the pixel of raster i is not stored in the error buffer in advance, It is also possible to judge whether or not dots are formed on the pixels of the raster j. If the color tone error generated in the pixel of raster i can not be stored in the error buffer, the frequency of writing to the error buffer can be reduced, and the presence or absence of dot formation can be quickly judged. Of course, the number of gratings to be processed in parallel is not limited to two, and the presence or absence of dot formation may be determined in parallel for more gratings. As the number of rasters processed in parallel increases, the frequency of writing to the error buffer decreases, so that the presence or absence of dot formation can be quickly determined.

C-2. Variations

In the tone number conversion process of the second embodiment described above, the presence or absence of dot formation is determined by a method based on a so-called mean error least square method. That is, the color tone error that occurs in the target pixel is stored in the target pixel in advance, and the presence or absence of dot formation is determined in consideration of the color tone error stored in the surrounding pixels when a new pixel is judged whether to form a dot or not. . In addition, in the tone number conversion process of the first embodiment described above, the presence or absence of dot formation is determined using a method based on a so-called error diffusion method. That is, the color tone error that occurs in the target pixel is diffused to the surrounding pixels, and when the determination of whether a new pixel has dot formation is performed, the accumulated diffusion error diffused from the surrounding judged pixels is considered, and the presence or absence of dot formation is performed. judge. Contrary to them, it is also possible to use the least square of average error and the error diffusion method to judge whether there is a point formed or not. Hereinafter, such a modified example of the second embodiment will be briefly described.

16 is an explanatory diagram conceptually showing tone number conversion processing in a modified example of the second embodiment. To avoid complicating the description, it is assumed here that raster i and raster j are processed in parallel. In addition, when the color tone error is diffused to the surrounding pixels, it is diffused according to the simple error diffusion matrix shown in FIG. The simple matrix shown takes into account the hue error for each pixel.

FIG. 16( a ) is an explanatory diagram showing a state of judging the presence or absence of dot formation for the pixel Pi0 at the left end of the raster i. When judging whether or not dots are formed in pixels on raster h, color tone errors generated in each pixel are diffused to and stored in each pixel of raster i. For example, the diffusion error Edi0 diffused from the raster h is stored in the pixel Pi0, the diffusion error Edi1 diffused from the raster h is stored in the pixel Pi1, and the diffusion error Ei2 is stored in the pixel Pi2. For ease of understanding, the error diffusion matrix used is shown in FIG. 16(b). In addition, in FIG. 16( a ), the arrows pointing from the pixels of raster h to the pixels of raster i conceptually indicate that errors are diffused from each pixel.

If the pixel Pi0 is judged to have dots or not, the hue error Ei0 generated by the judgment is stored in the register of CPU 102, and then the pixel Pi1 adjacent to the right is judged to have dots or not. Whether or not dots are formed in the pixel Pi1 is determined in the same manner as the tone number conversion process of the first embodiment described with reference to FIG. 7 . That is, the diffusion error Edi1 previously diffused and stored in the pixel Pi1 is read out, and the presence or absence of dot formation is performed based on the image data in consideration of the diffusion error Edi1 and the error diffused from the pixel Pi0 for which the determination of the presence or absence of dot formation has been performed just now. judge. In this way, when the determination of the presence or absence of dot formation is performed on the pixel Pi1, the color tone error generated by the determination is stored in the register of the CPU 102 as in the case of the pixel Pi0.

Through the above-described processing, once the presence or absence of dot formation has been determined for the pixels Pi0 and Pi1 on the raster i, the determination is made for the pixel Pj0 located at the left end of the raster j. FIG. 16( c ) is an explanatory diagram showing a state of judging the presence or absence of dot formation with respect to the pixel Pj0 of the raster j. For judging the pixels of grating j, use the method based on the method of minimum average error to judge whether there are dots formed. That is, it is considered that the presence or absence of dot formation is determined based on the specified weight determined for each pixel by the matrix for the color tone error occurring in the peripheral pixels. For ease of understanding, the matrix used is shown in Fig. 16(d).

As shown in the matrix of FIG. 16( d ), the color tone error generated between the pixel Pi0 and the pixel Pi1 can be used to determine the presence or absence of dot formation in the pixel Pj0 . As described above, these color tone errors have been obtained and stored in the registers of the CPU 102, so that the presence or absence of dots can be quickly determined for the pixel Pj0. As a result of judging the pixel Pj0 in this way, a hue error occurs, so now, the diffusion error is distributed to the surrounding pixels on the raster k according to the error diffusion matrix. For distribution of diffusion errors, the error diffusion matrix shown in Fig. 16(b) is used. Here, since the pixels of raster i and raster j are processed in parallel, the determination of the presence or absence of dot formation in the pixels of raster k is after the processing of these rasters is completed. Therefore, the diffusion error diffused to each pixel of raster k is stored in the error buffer of RAM 106 in advance. In FIG. 16( c ), hollow arrows pointing from the pixel Pj0 to the pixels Pk0 and Pk1 on the raster k indicate storage in the error buffer of the RAM 106 .

As described above, for the pixels of raster i, whether or not dots are formed is determined by the error diffusion method, and for the pixels of raster j, whether or not dots are formed is determined by the method of minimizing the average error. The hue error generated in the pixel of raster j is diffused to surrounding pixels by the error diffusion method. By repeating such processing, the presence or absence of dot formation can be alternately determined for the pixels of raster i and raster j. FIG. 16( e ) is an explanatory diagram conceptually showing such processing. In FIG. 16(e), the diffusion error diffused from raster h has been stored in the pixels of raster i by slashing the pixels of raster i. Likewise, the diffusion error diffused from raster j has been stored in the pixel of raster k by slashing the pixel of raster k. In addition, the numerals shown together with the encircled symbols in each pixel in FIG. 16( e ) indicate the order of judging the presence or absence of dot formation in the pixel. As shown in the figure, the pixel of grating i and the pixel of grating j located at the lower left are regarded as a group, and the position of the processed group is moved to the right by 1 pixel to judge whether there is dot formation or not, so that parallel The processing of raster i and raster j is performed accordingly.

In this way, as long as the pixels of raster i and raster j are alternately judged whether or not dots are formed in parallel, the pixel of raster j can be judged whether or not there are dots formed by using the hue error that occurs in the pixels of raster i. , so that there is no need to store the hue error of the pixel of raster i into the error buffer. As a result, the frequency of reading and writing to the error buffer can be reduced, so that the presence or absence of dot formation can be judged quickly.

In the above description, the method based on the error diffusion method is applied to the judgment of the presence or absence of dot formation on the pixel of the grating i, and the method based on the minimum average error method is applied to the judgment of the pixel of the grating j. However, the The method based on the method of minimum average error is applied to the judgment of the pixel of the grating i, and the judgment of the pixel j can also obtain the same effect.

In addition, in the modified example of the second embodiment described above, the processing of two rasters of raster i and raster j is performed in parallel, but it is also possible to perform the determination of the presence or absence of dot formation on pixels of more rasters in parallel. .

Various embodiments have been described above, but the present invention is not limited to all the above-mentioned embodiments, and can be implemented in various forms within a range not departing from the gist. For example, a software program (application program) realizing the above functions may be supplied to the memory of the computer system or an external storage device through a communication line for execution. Of course, it can also be read into a software program stored in a CD-ROM or a floppy disk for execution.

In addition, in the various embodiments described above, the image data conversion processing including the tone number conversion processing is executed in the computer, but it is also possible to use a printer-side or dedicated image processing device to execute a part of the image data conversion processing or all.

In addition, the image display device is not limited to a printing device that forms ink dots on a printing medium to print an image, and may be, for example, a liquid crystal display device that expresses an image with continuously changing hues by dispersing bright spots with appropriate brightness on a liquid crystal display screen.

As described above, according to the image processing device, printing control device and image processing method of the present invention, image data can be quickly converted without deteriorating the image quality, so it is very suitable for use in image output devices. In particular, it is very suitable for a printing device that processes large-sized image data to print high-quality images or quickly prints images without degrading the image quality.

Claims (19)

1. the view data of a tone value that receives each pixel of expression and form and this view data is transformed to have or not the image-processing system of the form that a formation represents by judging along the grating of the row of this pixel in each pixel that constitutes this grating, to have or not, it is characterized in that

Have:

The grating all living creatures becomes the unit, and this grating all living creatures becomes the unit that mutual many adjacent described gratings are gathered generation grating group;

Raster transform unit, end, this raster transform unit, end are selected to be arranged in the end grating at the end of above-mentioned grating group and are formed and this end raster transform is had or not the point range of a formation for expression by each pixel that constitutes this end grating being judged have or not;

The 1st error diffusion unit, the 1st error diffusion unit calculate by judging each pixel that constitutes above-mentioned end grating and above-mentionedly have or not the hue error that forms and take place and it a plurality of pixel of not judging to the periphery that is positioned at this each pixel is spread in each pixel;

The first raster converter unit, this first raster converter unit is selected to be arranged in the first raster of the grating group beginning position adjacent with above-mentioned end grating and by having or not a formation for taking in and each pixel that constitutes this first raster judged to the above-mentioned hue error of each pixel diffusion of this first raster from this end grating, this first raster is transformed to the point range that expression has or not a formation;

The 2nd error diffusion unit, the above-mentioned hue error that the 2nd error diffusion unit will take place in each pixel that constitutes above-mentioned first raster is to the pixel of the not judging diffusion of the periphery that is positioned at this each pixel; And

All the other raster transform unit, these all the other raster transform unit, as for from above-mentioned grating group except all the other gratings of above-mentioned first raster, just by for being subordinated to the grating group identical and having judged the above-mentioned hue error of the pixel diffusion that has or not a formation and judged that each pixel of these all the other gratings has or not a formation with these all the other gratings, so as to the processing that this first raster is transformed to above-mentioned point range be point range side by side with these all the other raster transforms.

2. by the described image-processing system of claim 1, it is characterized in that:

Above-mentioned the 1st error diffusion unit and above-mentioned the 2nd error diffusion unit are that the error that will spread in not belonging to the pixel of judging the above-mentioned grating group that pixel comprised who has or not a formation stores the 1st error storage part into, and the error that will spread in belonging to the pixel of judging the grating group that pixel comprised who has or not this some formation stores the unit of the 2nd error storage part into

Above-mentioned the 2nd error storage part be than above-mentioned the 1st error storage part can promptly carry out the storage of data or read at least one side's storage part.

3. by the described image-processing system of claim 2, it is characterized in that:

Above-mentioned the 1st error storage part is can be with the error of the above-mentioned diffusion storage part to store simultaneously with the pixel count of the identical number of pixel that constitutes above-mentioned first raster at least, and above-mentioned the 2nd error storage part is the storage part that the error of above-mentioned diffusion is stored simultaneously with the pixel count that lacks than the pixel that constitutes above-mentioned first raster.

4. by the described image-processing system of claim 3, it is characterized in that:

Use a computer and carry out the conversion of above-mentioned view data, the arithmetic unit that above-mentioned the 1st error storage part is the aforementioned calculation machine writes or the memory element of sense data indirectly, and above-mentioned the 2nd error storage part is that arithmetic unit directly writes or the memory element of sense data.

5. by the described image-processing system of claim 2, it is characterized in that:

Above-mentioned the 1st error diffusion unit be as with the pixel of having judged the grating group that the above-mentioned pixel that has or not a formation is different, and only to the unit of the pixel diffusion of the above-mentioned first raster adjacent with above-mentioned end grating.

6. by the described image-processing system of claim 2, it is characterized in that:

It is that mutual 2 adjacent above-mentioned gratings are concentrated in together the unit that generates above-mentioned grating group that above-mentioned grating all living creatures becomes the unit, above-mentioned the 1st error diffusion unit is with the unit of above-mentioned hue error to the pixel diffusion of the pixel of above-mentioned end grating and the above-mentioned first raster adjacent with this end grating, above-mentioned the 2nd error diffusion unit is the above-mentioned hue error that will take place in the pixel of above-mentioned first raster to the unit of the pixel diffusion of the pixel of this first raster and follow-up above-mentioned end grating after this first raster, above-mentioned all the other raster transform unit be with the processing of the above-mentioned first raster of conversion be the unit of point range with above-mentioned end raster transform abreast.

7. by the described image-processing system of claim 2, it is characterized in that:

At least one side in above-mentioned the 1st error diffusion unit or above-mentioned the 2nd error diffusion unit be above-mentioned hue error during from the pixel diffusion of the distant place of pixel more than designated value that this hue error takes place only to the unit of the pixel diffusion of having judged the grating group that the above-mentioned pixel that has or not a formation is different.

8. the view data of a tone value that receives each pixel of expression and form and this view data is transformed to have or not the image-processing system of the form that a formation represents by judging along the grating of the row of this pixel in each pixel that constitutes this grating, to have or not, it is characterized in that

Have:

The grating all living creatures becomes the unit, and this grating all living creatures becomes the unit that mutual many adjacent gratings are gathered generation grating group;

Select the grating converter unit, this selection grating converter unit selects to comprise at least the grating of the end grating that is positioned at the end of this grating group from above-mentioned grating group, have or not a formation by each pixel of the grating that constitutes this selection is judged, the raster transform of this selection is had or not the point range of a formation for expression;

The 1st hue error memory cell, the 1st hue error memory cell is calculated by judge the above-mentioned hue error that forms and take place that has or not in each pixel each pixel of the grating that constitutes above-mentioned selection, make it corresponding, and store in the 1st storage part with each pixel of having carried out this judgement;

The first raster converter unit, this first raster converter unit selects to be arranged in the first raster of the grating group's adjacent with above-mentioned end grating beginning position, by judging that for being stored in the periphery that is arranged in each pixel that constitutes this first raster and the above-mentioned hue error that has or not a formation to carry out the neighboring pixel of judgement having been taken in this pixel has or not a formation, so as to this first raster is transformed to point range;

The 2nd hue error memory cell, the 2nd hue error memory cell make the above-mentioned hue error that takes place in each pixel that constitutes above-mentioned first raster corresponding with each pixel of having carried out above-mentioned judgement, and store in the 2nd storage part; And

All the other raster transform unit, these all the other raster transform unit as for from above-mentioned grating group except remaining grating of above-mentioned first raster,, be point range side by side just with these all the other raster transforms so as to the processing that above-mentioned first raster is transformed to above-mentioned point range by for belonging to the grating group identical and having judged that the above-mentioned hue error that takes place in the pixel that has or not a formation takes in each pixel of judging these all the other gratings and has or not a formation with these all the other gratings.

9. by the described image-processing system of claim 8, it is characterized in that:

Above-mentioned the 2nd storage part be can than above-mentioned the 1st storage part promptly carry out the storage of data or read at least one side's storage part.

10. by the described image-processing system of claim 8, it is characterized in that:

Above-mentioned the 1st storage part is the storage part that the hue error that takes place in each pixel that constitutes above-mentioned end grating can be stored simultaneously with the pixel count identical with the pixel count that constitutes this end grating, and above-mentioned the 2nd storage part is the hue error that will take place in each pixel that constitutes above-mentioned first raster with the storage part of the pixel count body storage of lacking than the pixel count that constitutes this first raster.

11., it is characterized in that by the described image-processing system of claim 8:

Use a computer and carry out the conversion of above-mentioned view data, the arithmetic unit that above-mentioned the 1st storage part is the aforementioned calculation machine writes or the memory element of sense data indirectly, and above-mentioned the 2nd storage part is that arithmetic unit directly writes or the memory element of sense data.

12., it is characterized in that by the described image-processing system of claim 8:

Above-mentioned the 1st hue error memory cell is the unit that the hue error that takes place in each pixel of above-mentioned end grating that only will be in constituting above-mentioned grating group stores above-mentioned the 1st storage part into.

13., it is characterized in that by the described image-processing system of claim 8:

It is that mutual 2 adjacent above-mentioned gratings are concentrated in together the unit that generates above-mentioned grating group that above-mentioned grating all living creatures becomes the unit, above-mentioned the 1st hue error memory cell is the unit that the hue error that only will take place in the grating of above-mentioned end stores above-mentioned the 1st storage part into, and above-mentioned all the other raster transform unit are that the processing with the above-mentioned first raster of conversion is the unit of point range with above-mentioned end raster transform abreast.

14., it is characterized in that by claim 1 or the described image-processing system of claim 8:

Thereby above-mentioned all the other raster transform unit are to judge by the above-mentioned hue error of considering to be subordinated to the grating group identical with these all the other gratings and carried out having or not the pixel diffusion of the judgement of a formation to have or not the unit that to form these all the other raster transforms be point range with above-mentioned all the other raster transform point ranges the time.

15., it is characterized in that by claim 1 or the described image-processing system of claim 8:

Thereby above-mentioned all the other raster transform unit are by considering to belong to the grating group identical with these all the other gratings and carried out having or not the above-mentioned hue error that takes place in the pixel of judgement of a formation to judge to have or not the unit that to form these all the other raster transforms be point range when above-mentioned all the other raster transforms are point range.

16. print control, receive the view data of the tone value of each pixel of expression, form and this view data is transformed to the printed data of representing with the form that has or not a formation by judging along the grating of the row of this pixel in each pixel that constitutes this grating, to have or not, and control this Printing Department by export this printed data to Printing Department, this Printing Department forms ink dot so as to the printing image on print media, this print control is characterised in that

Have:

The grating all living creatures becomes the unit, and this grating all living creatures becomes the unit that mutual many adjacent described gratings are gathered generation grating group;

Raster transform unit, end, this raster transform unit, end are selected to be arranged in the end grating at the end of above-mentioned grating group and are formed and this end raster transform is had or not the point range of a formation for expression by each pixel that constitutes this end grating being judged have or not;

The 1st error diffusion unit, the 1st error diffusion unit calculate by judging each pixel that constitutes above-mentioned end grating and above-mentionedly have or not the hue error that forms and take place and it a plurality of pixel of not judging to the periphery that is positioned at this each pixel is spread in each pixel;

The first raster converter unit, this first raster converter unit is selected to be arranged in the first raster of the grating group beginning position adjacent with above-mentioned end grating and by having or not a formation for taking in and each pixel that constitutes this first raster judged to the above-mentioned hue error of each pixel diffusion of this first raster from this end grating, this first raster is transformed to the point range that expression has or not a formation;

The 2nd error diffusion unit, the above-mentioned hue error that the 2nd error diffusion unit will take place in each pixel that constitutes above-mentioned first raster is to the pixel of the not judging diffusion of the periphery that is positioned at this each pixel;

All the other raster transform unit, these all the other raster transform unit, as for from above-mentioned grating group except all the other gratings of above-mentioned first raster, just have or not a formation by taking in each pixel of judging these all the other gratings for the above-mentioned hue error that is subordinated to the grating group identical and has judged the pixel diffusion that has or not a formation with these all the other gratings, so as to the processing that this first raster is transformed to above-mentioned point range be point range side by side with these all the other raster transforms; And

The printed data output unit, this printed data output unit is exported as above-mentioned printed data the point range of the first raster of above-mentioned conversion and the point range of above-mentioned all the other gratings to above-mentioned Printing Department,

Above-mentioned the 1st error diffusion unit and above-mentioned the 2nd error diffusion unit are that the error that will spread in not belonging to the pixel of judging the above-mentioned grating group that pixel comprised who has or not a formation stores the 1st error storage part into, and will judge that the error that spread in the pixel that has or not the grating group that pixel comprised that this point forms stores the unit of the 2nd error storage part into to belonging to.

17. print control, receive the view data of the tone value of each pixel of expression, form and this view data is transformed to the printed data of representing with the form that has or not a formation by judging along the grating of the row of this pixel in each pixel that constitutes this grating, to have or not, and control this Printing Department by export this printed data to Printing Department, this Printing Department forms ink dot so as to the printing image on print media, this print control is characterised in that

Have:

The grating all living creatures becomes the unit, and this grating all living creatures becomes the unit that mutual many adjacent gratings are gathered generation grating group;

Select the grating converter unit, this selection grating converter unit selects to comprise at least the grating of the end grating that is positioned at the end of this grating group from above-mentioned grating group, have or not a formation by each pixel of the grating that constitutes this selection is judged, the raster transform of this selection is had or not the point range of a formation for expression;

The 1st hue error memory cell, the 1st hue error memory cell is calculated by judge the above-mentioned hue error that forms and take place that has or not in each pixel each pixel of the grating that constitutes above-mentioned selection, make it corresponding, and store in the 1st storage part with each pixel of having carried out this judgement;

The first raster converter unit, this first raster converter unit selects to be arranged in the first raster of the grating group's adjacent with above-mentioned end grating beginning position, by judging that for being stored in the periphery that is arranged in each pixel that constitutes this first raster and the above-mentioned hue error that has or not a formation to carry out the neighboring pixel of judgement having been taken in this pixel has or not a formation, so as to this first raster is transformed to point range;

The 2nd hue error memory cell, the 2nd hue error memory cell make the above-mentioned hue error that takes place in each pixel that constitutes above-mentioned first raster corresponding with each pixel of having carried out above-mentioned judgement, and store in the 2nd storage part;

All the other raster transform unit, these all the other raster transform unit as for from above-mentioned grating group except remaining grating of above-mentioned first raster,, be point range side by side just with these all the other raster transforms so as to the processing that above-mentioned first raster is transformed to above-mentioned point range by for belonging to the grating group identical and having judged that the above-mentioned hue error that takes place in the pixel that has or not a formation takes in each pixel of judging these all the other gratings and has or not a formation with these all the other gratings; And

The printed data output unit, this printed data output unit is exported as above-mentioned printed data the point range of the first raster of above-mentioned conversion and the point range of above-mentioned all the other gratings to above-mentioned Printing Department.

18. the view data of a tone value that receives each pixel of expression also forms and this view data is transformed to have or not the image processing method of the form that a formation represents by judging along the grating of the row of this pixel to have or not in each pixel that constitutes this grating, it is characterized in that: may further comprise the steps, promptly

(A) many adjacent described gratings gather the step that generates the grating group mutually;

(B) select to be arranged in the end grating at the end of above-mentioned grating group and form and this end raster transform is had or not the step of the point range of a formation for expression by each pixel that constitutes this end grating being judged have or not;

(C) each pixel that constitutes above-mentioned end grating is calculated by judge the above-mentioned hue error that forms and take place and will it step that spreads to a plurality of pixels of not judging of the periphery that is positioned at this each pixel of having or not in each pixel;

(D) select to be arranged in the first raster of the grating group beginning position adjacent and, this first raster is transformed to the step that expression has or not the point range of a formation by having or not a formation for taking in and each pixel that constitutes this first raster judged to the above-mentioned hue error of each pixel diffusion of this first raster from this end grating with above-mentioned end grating;

(E) the above-mentioned hue error that will take place in each pixel that constitutes above-mentioned first raster is to the step of the pixel of the not judging diffusion of the periphery that is positioned at this each pixel;

(F) as for from above-mentioned grating group except all the other gratings of above-mentioned first raster, just have or not a formation by taking in each pixel of judging these all the other gratings for the above-mentioned hue error that is subordinated to the grating group identical and has judged the pixel diffusion that has or not a formation with these all the other gratings, so as to the processing that this first raster the is transformed to above-mentioned point range step that is point range side by side with these all the other raster transforms;

Above-mentioned steps (C) and above-mentioned steps (E) are just to be stored to the 1st error storage part and just to having or not error that the identical grating group's of the pixel of this point formation pixel spreads to be stored to the step of the 2nd error storage part with judgement to the error with the pixel diffusion of judging the grating group that the above-mentioned pixel that has or not a formation is different.

19. the view data of a tone value that receives each pixel of expression also forms and this view data is transformed to have or not the image processing method of the form that a formation represents by judging along the grating of the row of this pixel to have or not in each pixel that constitutes this grating, it is characterized in that: may further comprise the steps, promptly

(A) many adjacent described gratings gather the step that generates the grating group mutually;

(B) the end grating that comprises the end that is arranged in above-mentioned grating group is at least selected grating from this grating group, has or not a formation by each pixel of the grating that constitutes this selection is judged, the raster transform of this selection is had or not the step of the point range of a formation for expression;

(C) each pixel of the grating that constitutes above-mentioned selection is calculated by judge the above-mentioned hue error that forms and take place that has or not in each pixel, made it corresponding and step that store with each pixel of having carried out this judgement;

(D) select to be arranged in the first raster of the grating group's adjacent beginning position with above-mentioned end grating, by judging that for being stored in the periphery that is arranged in each pixel that constitutes this first raster and the above-mentioned hue error that has or not a formation to carry out the neighboring pixel of judgement having been taken in this pixel has or not a formation, so as to this first raster being transformed to the step of point range;

(E) make the above-mentioned hue error that in constituting each pixel of above-mentioned first raster, takes place and distinguish mutually, while and the step of storing corresponding with each pixel of having carried out above-mentioned judgement in the hue error of described step C storage;

(F) as for from above-mentioned grating group except remaining grating of above-mentioned first raster, just by for belonging to the grating group identical and judging that the above-mentioned hue error that takes place in the pixel that has or not a formation takes in each pixel of judging these all the other gratings and has or not a formation, so as to the processing that above-mentioned first raster the is transformed to above-mentioned point range step that is point range side by side with these all the other raster transforms with these all the other gratings.

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