JP2008143026A - Image processor, method for processing image, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To readily print adequate images irrespective of printing conditions. <P>SOLUTION: A color difference for each printing condition is corrected by using color difference absorption data and is converted to ink amount data by referencing a matching relationship. A difference between allowable amounts of ink due to a variation in printing conditions is absorbed according to allowable ink amount absorption data with respect to the acquired ink amount data, and then the final ink amount data are generated. Accordingly, a variation in coloring depending on the printing condition can be absorbed by the color difference absorption data and a difference between allowable ink amounts can be absorbed by the allowable ink amount absorption data, so that it is not necessary to selectively use a plurality of matching relationships depending on the printing condition, thereby readily printing an adequate image. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for converting color image data into ink amount data.

Due to advances in computer-related technology, it is now possible to easily handle images in the form of digital data. For example, photographing with a digital camera, creating color image data using an application program on a computer, and printing a color image by supplying these color image data to a printer Is also possible.

Here, the color image data expresses colors using light of R, G, and B corresponding to the three primary colors of light, but the printer uses C (cyan) and M (corresponding to the three primary colors of ink. Colors are expressed using inks of various colors obtained by adding K (black color) to three colors of magenta color and Y (yellow color). Since the color expression methods are different in this way, in order to print a color image, color image data (RGB image data) expressed by gradation values of RGB colors is expressed by gradation values of CMYK colors. It is necessary to convert it into converted image data (CMYK image data). Such conversion is usually called color conversion.

In general, since color conversion is conversion with extremely strong nonlinearity, it is difficult to analytically obtain a conversion formula. Therefore, RGB image data and corresponding CMYK image data are stored in advance as a color conversion table (LUT), and when RGB image data is received, the corresponding CMYK image is referred to by referring to the color conversion table. Searching for data is widely done.

Also, since the color development method of ink is slightly different depending on the type of print medium and the type of ink used at the time of printing, a color conversion table is prepared for each combination of the type of print medium and the type of ink. Furthermore, a technique for printing a more appropriate image using a color conversion table selected in consideration of not only the type of printing medium but also the printing environment has been proposed (Patent Document 1).

JP 2003-1876 A

However, if a color conversion table is prepared for each type of print medium and ink, and further for each combination of print medium and ink type, it is necessary to set various types of color conversion tables, which requires great effort. There was a problem that it was necessary.

The present invention has been made to solve the above-described problems in the prior art,
It is an object of the present invention to provide a technique that makes it possible to easily print an appropriate image even when the type of printing medium or ink is different.

In order to solve at least a part of the problems described above, the image processing apparatus of the present invention employs the following configuration. That is,
An image processing device that obtains color image data and performs predetermined image processing on the color image data to convert the color represented by the color image data into ink amount data for printing,
Correspondence relationship storage means for storing a correspondence relationship in which the color image data and the ink amount data are associated;
Color difference absorption data storage means for storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
An allowable ink amount difference absorbing means for storing allowable ink amount difference absorption data for absorbing a difference in ink amount allowed for each printing condition;
The color image data is corrected based on the color difference absorption data, and the corrected color image data is converted into provisional ink amount data with reference to the correspondence relationship, and then the ink amount The gist of the present invention is to include an ink amount data generating unit that corrects the data using the allowable ink amount difference absorption data to generate the final ink amount data.

The image processing method of the present invention corresponding to the above image processing apparatus is
An image processing method for obtaining color image data and performing predetermined image processing on the color image data to convert the color represented by the color image data into ink amount data for printing,
A first step of storing a correspondence relationship in which the color image data and the ink amount data are associated;
A second step of storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
A third step of storing permissible ink amount difference absorption data for absorbing permissible ink amount differences for each printing condition;
The color image data is corrected based on the color difference absorption data, and the corrected color image data is converted into provisional ink amount data with reference to the correspondence relationship, and then the ink amount And a fourth step of generating the final ink amount data by correcting the data using the allowable ink amount difference absorption data.

In the image processing apparatus and the image processing method according to the present invention, the color difference for each printing condition is corrected using the color difference absorption data, and then converted into ink amount data with reference to the correspondence. Then, the final ink amount data is generated by absorbing the difference in the allowable ink amount due to the difference in the printing conditions in accordance with the allowable ink amount difference absorption data with respect to the obtained ink amount data.

In this way, the color difference due to different printing conditions can be absorbed by the color difference absorption data, and therefore, even under different printing conditions, it can be converted into ink amount data using the same correspondence relationship. . Of course, if the printing conditions are different, the allowable ink amount is different. However, if the difference in the allowable ink amount is absorbed based on the allowable ink amount difference absorption data, it can be handled according to the printing condition from the viewpoint of the allowable ink amount. There is no need to use different relationships. After all, even if the printing conditions are different, it is only necessary to memorize the same correspondence, and it is not necessary to prepare a plurality of correspondences according to the printing conditions, so it is possible to easily print an appropriate image. Become.

In the image processing apparatus of the present invention described above, the following may be performed. First, an assumed printing condition, which is a printing condition assumed when performing image processing, is acquired. In addition, assuming a predetermined printing condition including at least the type of printing medium and the type of ink, correspondence that associates color image data with ink amount data for printing the color represented by the color image data Remember the relationship. In addition, in order to absorb the difference between the color when printing under the assumed printing condition and the color when printing under the printing condition (standard printing condition) assumed in the correspondence relationship, the correction content to be added to the color image data is represented. Data (color difference absorption data) is stored for each assumed printing condition. Furthermore, in order to absorb the difference between the allowable ink amount that can be used under the standard printing conditions and the allowable ink amount that can be used under the assumed printing conditions, data indicating the correction content to be added to the ink amount data (allowable) Ink amount difference absorption data) is stored for each assumed printing condition. When the color image data is received, the color image data is corrected based on the color difference absorption data corresponding to the assumed print condition, and the corrected color image data is provisionally converted with reference to the correspondence relationship. By converting the ink amount data into the ink amount data and correcting the obtained ink amount data based on the allowable ink amount difference absorption data corresponding to the assumed printing conditions, the ink amount data corresponding to the assumed printing conditions is generated. Also good.

The correspondence relationship between the color image data and the ink amount data is expressed by the color image data and the color image data in a state where a certain printing condition (for example, the type of printing medium or the type of ink) is specified. It is the table which matched the ink amount data which can obtain the same color as a color. Therefore, if the printing conditions (standard printing conditions) assumed when setting the correspondence are different from the printing conditions (assuming printing conditions) assumed for image processing,
The resulting color will be different. Therefore, data (color difference absorption data) for absorbing the color difference obtained between the standard printing condition and the assumed printing condition is stored for each assumed printing condition,
When the color image data is received, the influence due to the difference in printing conditions is absorbed based on the color difference absorption data, and then converted into ink amount data by referring to the correspondence relationship. In this way, it is possible to obtain ink amount data that can print an image with an appropriate color regardless of the difference in printing conditions. However, the amount of ink allowed when printing an image also differs depending on the printing conditions. Therefore, the obtained ink amount data is corrected by the allowable ink amount difference absorption data stored for each assumed printing condition. In this way, it is possible to absorb the difference in coloring due to different printing conditions and the difference in allowable ink amount, so the same correspondence can be used even under different printing conditions, and an appropriate image can be used. Can be printed easily.

In the image processing apparatus of the present invention, the allowable ink amount difference absorption data set based on the ink having the smallest allowable ink amount among a plurality of types of ink used for printing is stored. The ink amount data of the other ink may be corrected based on the same allowable ink amount difference absorption data.

When printing an image using a plurality of inks, if the method of correcting each ink amount data is different, the hue changes, so the allowable ink amount difference absorption data for the ink with the smallest allowable ink amount is used. Thus, it is preferable to correct each ink amount data because the color of the original image can be maintained.

In the image processing apparatus of the present invention, the following may be performed. First, a correspondence relationship in which color image data and ink amount data are associated is stored. In addition, color difference absorption data and allowable ink amount difference absorption data are stored for each printing condition. Then, based on the color difference absorption data, the correspondence relationship, and the allowable ink amount difference absorption data, a reflection correspondence relationship that reflects the printing condition is generated, and the generated reflection correspondence relationship is referred to. Thus, the ink amount data may be generated from the color image data.

A reflection correspondence that reflects the color difference absorption data and the allowable ink amount difference absorption data is generated, and when color image data is received, the reflection correspondence is referred to and converted into ink amount data. In other words, refer to the reflection correspondence without performing conversion to absorb the difference in color due to the difference in printing conditions or conversion to absorb the difference in allowable ink amount due to the difference in printing conditions. Thus, since it is possible to substantially execute these by a single conversion, the ink amount data can be quickly and appropriately converted.

In such image processing, image forming means for forming an image on a print medium based on the generated ink amount data may be provided.

In this way, the difference in the printing conditions can be absorbed by the color difference absorption data and the allowable ink amount difference absorption data, and the correspondence relationship only needs to be stored in the table corresponding to the standard printing conditions. Even under the conditions, an appropriate image can be printed.

Further, in the image processing apparatus and the image processing method of the present invention described above, if color image data is converted into ink amount data, color image data and ink amount data as described below are converted. It can also be grasped as a method of generating the associated correspondence. That is, the correspondence generation method of the present invention is
A method of generating a correspondence relationship in which color image data and ink amount data are associated with each other,
Storing a reference correspondence relationship in which the color image data and the ink amount data are associated;
A step (B) of storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
A step (C) of storing permissible ink amount difference absorption data for absorbing a difference in ink amount allowed for each printing condition for each printing condition;
After selecting one of the color image data and performing correction based on the color difference absorption data, the ink correspondence data is converted to ink amount data with reference to the reference correspondence relationship, and the obtained ink amount data is converted into the allowable ink. A step (D) of generating the correspondence relationship by correcting the ink amount data obtained based on the amount difference absorption data and storing the ink amount data finally obtained in association with the selected color image data. Is the gist.

Also in the correspondence generation method of the present invention, since the difference in printing conditions is corrected based on the color difference absorption data and the allowable ink amount difference absorption table with respect to the reference table stored in advance, the printing conditions It is possible to easily generate a corresponding relationship according to.

The present invention can also be realized by using a computer by causing a computer to read a program for realizing the above-described image processing method or correspondence generation method and executing a predetermined function. Accordingly, the present invention includes the following program or a mode as a recording medium on which the program is recorded. That is, the program of the present invention corresponding to the image processing method described above is
In order to realize a method of converting color ink data for printing by acquiring color image data and performing predetermined image processing on the color image data, using a computer. The program of
A first function for storing a correspondence relationship in which the color image data and the ink amount data are associated;
A second function for storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
A third function for storing permissible ink amount difference absorption data for absorbing permissible ink amount differences for each printing condition;
The color image data is corrected based on the color difference absorption data, and the corrected color image data is converted into provisional ink amount data with reference to the correspondence relationship, and then the ink amount The gist is to realize a fourth function for generating the final ink amount data by a computer by correcting the data using the allowable ink amount difference absorption data.

The recording medium of the present invention corresponding to the above program is
A program for converting color ink data for printing the color represented by the color image data by acquiring the color image data and performing predetermined image processing on the color image data is recorded in a computer-readable manner. A recording medium,
A first function for storing a correspondence relationship in which the color image data and the ink amount data are associated;
A second function for storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
A third function for storing permissible ink amount difference absorption data for absorbing permissible ink amount differences for each printing condition;
The color image data is corrected based on the color difference absorption data, and the corrected color image data is converted into provisional ink amount data with reference to the correspondence relationship, and then the ink amount The gist of the present invention is to record the fourth function for generating the final ink amount data by correcting the data using the allowable ink amount difference absorption data.

If these programs are read into a computer and the various functions described above are realized, it is possible to appropriately convert color image data into ink amount data without preparing a correspondence for each of various printing conditions. .

Furthermore, the program corresponding to the above-described correspondence generation method of the present invention is as follows:
A program for realizing, using a computer, a method for generating a correspondence relationship in which color image data and ink amount data are associated with each other.
A function (A) for storing a reference correspondence relationship in which the color image data and the ink amount data are associated;
A function (B) for storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
A function (C) for storing permissible ink amount difference absorption data for absorbing a difference in permissible ink amount for each printing condition for each printing condition;
After selecting one of the color image data and performing correction based on the color difference absorption data, the ink correspondence data is converted to ink amount data with reference to the reference correspondence relationship, and the obtained ink amount data is converted into the allowable ink. A function (D) for generating the correspondence relationship by storing the ink amount data finally corrected based on the amount difference absorption data in association with the selected color image data. The gist is to achieve this.

The recording medium of the present invention corresponding to the above program is
A program that generates a correspondence that associates color image data with ink amount data,
A recording medium recorded in a computer-readable manner,
A function (A) for storing a reference correspondence relationship in which the color image data and the ink amount data are associated;
A function (B) for storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
A function (C) for storing permissible ink amount difference absorption data for absorbing a difference in permissible ink amount for each printing condition for each printing condition;
After selecting one of the color image data and performing correction based on the color difference absorption data, the ink correspondence data is converted to ink amount data with reference to the reference correspondence relationship, and the obtained ink amount data is converted into the allowable ink. A function (D) for generating the correspondence relationship by storing the ink amount data finally corrected based on the amount difference absorption data in association with the selected color image data. The gist is that the program to be realized is recorded.

If these programs are read into a computer and the various functions described above are realized, it is possible to easily generate a correspondence relationship for each of various printing conditions.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Device configuration:
A-1. overall structure:
A-2. Internal configuration:
A-2-1. Internal configuration of the scanner unit:
A-2-2. Internal configuration of the printer unit:
B. Image processing overview:
C. Ink amount data generation processing:
D. Variation:

A. Summary of Examples:
A-1. overall structure :
FIG. 1 is a perspective view showing an external shape of a printing apparatus 10 in which the image processing apparatus of this embodiment is mounted. As illustrated, the printing apparatus 10 according to the present exemplary embodiment includes a scanner unit 100, a printer unit 200, an operation panel 300 for setting operations of the scanner unit 100 and the printer unit 200, and the like. The scanner unit 100 has a scanner function of reading a print image and generating color image data, and the printer unit 200 has a printer function of receiving color image data and printing an image on a print medium. . Further, if a color image read by the scanner unit 100 is output from the printer unit 200, a copy function can be realized. That is, the printing apparatus 10 according to the present embodiment is a so-called scanner / printer / copy combined apparatus that can independently realize a scanner function, a printer function, and a copy function (
Hereinafter, it is referred to as an SPC composite apparatus).

FIG. 2 shows a platen cover 1 provided on the upper part of the printing apparatus 10 for reading a print image.
It is explanatory drawing which shows a mode that 02 was opened. As shown in the drawing, when the document table cover 102 is opened upward, a transparent document table glass 104 is provided, and various mechanisms to be described later for realizing the scanner function are mounted therein. . When reading the print image, the platen cover 102 is opened and the print image is placed on the platen glass 104 as shown in FIG.
The button on the operation panel 300 is operated after the document table cover 102 is closed. This way
The print image can be immediately converted into color image data.

The scanner unit 100 is entirely housed in an integrated case, and the scanner unit 100 and the printer unit 200 are provided with a hinge mechanism 204 (FIG. 3) on the back side of the printing apparatus 10.
Reference). Therefore, by lifting the front side of the scanner unit 100, only the scanner unit 100 can be rotated at the hinge portion.

FIG. 3 is a perspective view illustrating a state in which the front side of the scanner unit 100 is lifted and rotated. As shown in the drawing, in the printing apparatus 10 of this embodiment, the upper surface of the printer unit 200 can be exposed by lifting the front side of the scanner unit 100. Inside the printer unit 200, various mechanisms to be described later for realizing the printer function, a control circuit 260 to be described later for controlling the operation of the entire printing apparatus 10 including the scanner unit 100, and the scanner unit 100 are further described. And a power supply circuit (not shown) for supplying power to the printer unit 200 and the like. Also, as shown in FIG. 3, an opening 202 is provided on the upper surface of the printer unit 200, which makes it easy to replace consumables such as ink cartridges, handle paper jams, and perform minor repairs. It is possible to do it.

A-2. Internal configuration:
FIG. 4 is an explanatory diagram conceptually showing the internal configuration of the printing apparatus 10 of this embodiment. As described above, the printing apparatus 10 includes the scanner unit 100 and the printer unit 200, and various configurations for realizing the scanner function are mounted in the scanner unit 100. Is equipped with various configurations for realizing the printer function. Hereinafter, the internal configuration of the scanner unit 100 will be described first, and then the internal configuration of the printer unit 200 will be described.

A-2-1. Internal configuration of the scanner unit:
The scanner unit 100 includes a transparent platen glass 104 for setting a print image, a platen cover 102 for holding the set print image, a reading carriage 110 for reading the set print image, and a reading carriage 110. The driving belt 120 is configured to move in the reading direction (main scanning direction), the driving motor 122 supplies power to the driving belt 120, the guide shaft 106 that guides the movement of the reading carriage 110, and the like. The operations of the drive motor 122 and the reading carriage 110 are controlled by a control circuit 260 described later.

When the drive motor 122 is rotated under the control of the control circuit 260, the movement is transmitted to the reading carriage 110 via the driving belt 120. As a result, the reading carriage 110 is
While being guided by the guide shaft 106, it moves in the reading direction (main scanning direction) according to the rotation angle of the drive motor 122. Further, the drive belt 120 is constantly adjusted to be in a moderately tensioned state by the idler pulley 124. Therefore, if the drive motor 122 is rotated in the reverse direction, the reading carriage 110 is moved in the reverse direction by a distance corresponding to the rotation angle. It is also possible to make it.

Inside the reading carriage 110 are a light source 112, a lens 114, a mirror 116, and a CC.
A D sensor 118 and the like are mounted. Light from the light source 112 is applied to the platen glass 104 and is reflected by a print image set on the platen glass 104. This reflected light is guided to the lens 114 by the mirror 116, collected by the lens 114, and detected by the CCD sensor 118. The CCD sensor 118 is configured by a linear sensor in which photodiodes that convert light intensity into an electrical signal are arranged in a row in a direction orthogonal to the moving direction (main scanning direction) of the reading carriage 110. Therefore, the print image can be converted into an electrical signal by irradiating the print image with the light from the light source 112 while moving the reading carriage 110 in the main scanning direction and detecting the reflected light intensity by the CCD 118.

The light source 112 is composed of light emitting diodes of three colors of RGB, and can sequentially irradiate light of R color, G color, and B color at a predetermined cycle. C
In the CD 118, the reflected light of R color, G color, and B color is sequentially detected. In general, the red portion of the image reflects R light, but hardly reflects G or B light.
The reflected color light represents the R component of the image. Similarly, the reflected light of G color is the G of the image.
The B color reflected light represents the B component of the image. Therefore, if the RGB three colors of light are applied to the print image while switching at a predetermined cycle, and the reflected light intensity is detected by the CCD 118 in synchronization with this, the R component, G component, and B component of the print image can be detected. It is possible to read a color image. Note that since the reading carriage 110 is moved even while the color of light emitted from the light source 112 is switched, the position of the image for detecting each component of RGB corresponds to the movement amount of the reading carriage 110 strictly. However, this deviation can be corrected by image processing after reading each component.

A-2-2. Internal configuration of the printer unit:
Next, the internal configuration of the printer unit 200 will be described. The printer unit 200 includes a control circuit 260 that controls the overall operation of the printing apparatus 10, a print carriage 240 that prints an image on a print medium, a mechanism that moves the print carriage 240 in the main scanning direction, and printing. A mechanism for feeding media is mounted.

The print carriage 240 includes an ink cartridge 242 that stores K ink, an ink cartridge 243 that stores various inks of C ink, M ink, and Y ink, a print head 241 provided on the bottom side, and the like. The print head 241 is provided with an ink discharge head for discharging ink droplets for each ink. When the ink cartridges 242 and 243 are mounted on the print carriage 240, each ink in the cartridge is supplied to the ink discharge heads 244 to 247 of each color through an introduction pipe (not shown). In the printer unit 200 shown in FIG. 4, the C ink, M ink, and Y ink have been described as being integrally stored in one ink cartridge 243, but these inks are formed separately. It can also be stored in a dedicated ink cartridge. In addition to these inks, low density C ink (LC ink), low density M ink (LM ink), low density K ink (LK ink), red ink (R ink), purple ink (
V ink), orange ink (O ink), and the like can be mounted.

The mechanism that moves the print carriage 240 in the main scanning direction includes a carriage belt 231 for driving the print carriage 240, a carriage motor 230 that supplies power to the carriage belt 231, and an appropriate tension is constantly applied to the carriage belt 231. Tension pulley 232 for holding the carriage, and carriage guide 233 for guiding the movement of the print carriage 240
And an origin position sensor 234 for detecting the origin position of the print carriage 240. When the carriage motor 230 is rotated under the control of the control circuit 260 described later,
The print carriage 240 can be moved in the main scanning direction by a distance corresponding to the rotation angle. Further, if the carriage motor 230 is rotated in the reverse direction, the print carriage 240 can be moved in the reverse direction.

The mechanism for feeding the print medium includes a platen 236 that supports the print medium from the back side, a paper feed motor 235 that feeds the paper by rotating the platen 236, and the like. If the paper feed motor 235 is rotated under the control of a control circuit 260 described later, the print medium can be fed in the sub-scanning direction by a distance corresponding to the rotation angle.

The control circuit 260 has a CPU, a ROM, a RAM, a D / A converter that converts digital data into an analog signal, and a peripheral device interface PIF for exchanging data with peripheral devices. It is composed of The control circuit 260 controls the overall operation of the printing apparatus 10 including the scanner unit 100, the printer unit 200, and the operation panel 300. The light source 112, the drive motor 122, and the CCD 1 mounted on the scanner unit 100 are controlled.
These operations are controlled while exchanging data with 18.

The control circuit 260 drives the carriage motor 230 and the paper feed motor 235 to perform main scanning and sub-scanning of the print carriage 240, and the ink ejection head 2 for each color.
Control is also performed to discharge ink droplets by supplying drive signals to 44 to 249. The drive signals supplied to the ink discharge heads 244 to 249 are generated by reading color image data from the computer 20 or the digital camera 30 and performing image processing to be described later. Of course, it is also possible to generate a drive signal by performing image processing on the color image data read by the scanner unit 100. In this way, under the control of the control circuit 260, the ink droplets are ejected from the ink ejection heads 244 to 247 to form the ink dots of the respective colors on the printing medium while the print carriage 240 is moved in the main scan and the sub scan. It is possible to print an image. Of course, instead of performing image processing in the control circuit 260, the image processed data is received from the computer 20,
It is also possible to drive the ink ejection heads 244 to 247 while performing main scanning and sub-scanning of the print carriage 240 according to this data.

The control circuit 260 is also connected to the operation panel 300 so as to exchange data. By operating various buttons provided on the operation panel 300, detailed operation modes of the scanner function and the printer function are set. It is possible to set. Further, it is possible to set a detailed operation mode from the computer 20 via the peripheral device interface PIF.

FIG. 5 is an explanatory diagram showing a state in which a plurality of nozzles Nz for ejecting ink droplets are formed in the ink ejection heads 244 to 247 for each color. As shown in the figure, six sets of nozzle rows for ejecting ink droplets of each color are formed on the bottom surface of the ink ejection head for each color, and 48 nozzles Nz are arranged in a nozzle pitch k in one set of nozzle rows. They are arranged in a zigzag pattern with an interval of. A drive signal is supplied from the control circuit 260 to each of the nozzles Nz, and each nozzle Nz discharges an ink droplet of each ink according to the drive signal.

Various methods can be applied to the method of ejecting ink droplets from the ink ejection head. That is, a method of ejecting ink using a piezo element, a method of ejecting ink droplets by generating bubbles in the ink passage with a heater arranged in the ink passage, and the like can be used. Also, instead of ejecting ink, use a method that uses ink transfer to form ink dots on printing paper using a phenomenon such as thermal transfer, or a method that uses static electricity to attach toner powder of each color onto the print medium. It is also possible to do.

C. Overview of image processing:
As described above, in order to print a desired image with the printer unit 200, it is necessary to perform appropriate image processing on the color image data to generate a drive signal for each nozzle, and to form dots based on the drive signal. is there. Hereinafter, an outline of such image processing will be described. In the printing apparatus 10 according to the present exemplary embodiment, image processing is performed in the control circuit 260 incorporated in the printer unit 200. Image processing is performed by the computer 20 provided outside, and the processed data is transmitted to the peripheral device interface. It is also possible to form dots by reading from the PIF.

FIG. 6 is a flowchart showing a flow of image processing for reading color image data and printing an image. Hereinafter, it demonstrates according to a flowchart. When image processing is started, the control circuit 260 first performs processing for acquiring image printing conditions (step S100). The printing conditions can be set in advance from a screen provided on the operation panel 300 of the printing apparatus 10.

FIG. 7 is an explanatory diagram showing a state in which image printing conditions are set for the printing apparatus 10. In the illustrated example, the type of printing paper on which an image is to be printed and the type of ink can be set as printing conditions. Of course, in addition to these, other printing conditions (for example,
It is also possible to set whether to give priority to image quality or priority to printing speed. FIG.
In the example shown in Fig. 1, when the downward arrow provided in the column for setting the print paper is selected, various print paper types are expanded in a selectable state, and the print paper type can be selected by selecting from these. It is possible to set. In the illustrated example, a state where “photo paper” is selected is shown.

In addition, the ink type is set to the type of ink mounted on the printer unit 200 of the printing apparatus 10. In the normal printing apparatus 10, the ink type is fixed, but when the ink type is configured to be replaceable, a radio button indicating the ink type can be selected on the screen, and the side where the ink is mounted The ink type can be selected. As for the ink type, an IC chip or the like may be incorporated in the ink cartridges 242 and 243, and the ink type may be automatically set by reading data stored in the IC chip or the like.

When the control circuit 260 incorporated in the printing apparatus 10 acquires the printing conditions set in this manner, the control circuit 260 reads the color image data of the image to be printed (step S).
102). Here, the color image data is represented by R, G, and B tone values.
GB image data.

Next, a process of converting the resolution of the read color image data into a resolution (printing resolution) for printing by the printer unit 200 is performed (step S104). When the resolution of the read color image data is lower than the printing resolution, the image is converted to a higher resolution by performing interpolation calculation between adjacent pixels and setting new image data. On the other hand, when the resolution of the read color image data is higher than the print resolution, the image data is converted to a lower resolution by thinning out the image data at a certain rate from between adjacent pixels. In the resolution conversion process,
A process of converting the resolution of the read color image data into the print resolution is performed by generating or thinning out the image data at an appropriate ratio with respect to the read color image data.

After converting the resolution of the color image data to the printing resolution in this way, the control circuit 260 starts the ink amount data generation process (step S106). What is ink amount data generation processing?
Converts color image data expressed by a combination of R, G, and B tone values into data (ink amount data) corresponding to the ink amounts of C, M, Y, and K inks mounted on the printer. It is processing to do. The conversion from color image data to ink amount data is a highly nonlinear conversion, and it is difficult to describe the conversion contents using mathematical formulas, so it is necessary to refer to a kind of numerical table called a color conversion table. It is normal that In the present specification, the color conversion table may be referred to as a “correspondence table”.

In addition, the correspondence table needs to be prepared for each printing condition (that is, for each type of printing paper, each type of ink, and each combination thereof). However, it is not easy to set the correspondence table (color conversion table), and a large amount of memory is used for storing the correspondence table. Therefore, in order to avoid such adverse effects, the printing apparatus 10 of the present embodiment.
Then, the ink amount data generation process is performed by a special method. This method will be described in detail later.

After the color image data is converted into ink amount data for each color of CMYK by the ink amount data generation processing, halftone processing is subsequently performed (step S108). Halftone processing is the following processing. The ink amount data for each color of CMYK obtained by the ink amount data generation process is data having 255 gradations (in the case of 1-byte data). On the other hand, since the printer unit 200 displays an image by forming dots, each pixel can only take a state of whether or not to form dots. Therefore, it is necessary to convert the ink amount data of each color of CMYK obtained by the ink amount data generation processing into data (dot data) indicating the presence or absence of dot formation for each pixel. Halftone processing is processing for converting ink amount data into dot data in this way.

As a method for performing the halftone process, various methods such as an error diffusion method and a dither method can be applied. The error diffusion method is to determine whether or not dots are formed for a certain pixel, so that the error in gradation expression that occurs in that pixel is diffused to the surrounding pixels and the error diffused from the surroundings is eliminated. This is a method of determining the presence or absence of dot formation for each pixel. Also, the dither method uses a threshold value and CM that are randomly set in the dither matrix.
Comparing the ink amount data of each color of YK for each pixel, it is determined that a dot is formed for a pixel having a larger ink amount data, and conversely, a dot is not formed for a pixel having a larger threshold value. This is a technique for obtaining dot data for each pixel.

FIG. 8 is an explanatory diagram illustrating an enlarged part of the dither matrix. In the illustrated matrix, threshold values that are uniformly selected from the range of gradation values 0 to 255 are randomly stored in a total of 4096 pixels, 64 pixels in the vertical and horizontal directions. Here, the gradation value of the threshold is 0 to
In this embodiment, the range of 255 is selected because the ink amount data of each color of CMYK obtained by the ink amount data generation processing is 1-byte data, and the gradation value is 0-2.
This corresponds to a value of 55. The size of the dither matrix is not limited to 64 pixels in the vertical and horizontal directions as illustrated in FIG. 8, and can be set to various sizes including those having different numbers of vertical and horizontal pixels. It is.

FIG. 9 is an explanatory diagram conceptually showing a state in which the presence / absence of dot formation is determined for each pixel with reference to the dither matrix. This determination is made for each color of CMYK, but in the following, in order to avoid complicated explanation, each color of the CMYK ink amount data is simply referred to as ink amount data without being distinguished.

When determining the presence or absence of dot formation, first, the gradation value of the ink amount data for the pixel of interest (the pixel of interest) to be judged is compared with the threshold value stored at the corresponding position in the dither matrix. To do. The thin broken arrow shown in the figure schematically represents that the ink amount data of the pixel of interest is compared with the threshold value stored at the corresponding position in the dither matrix. If the ink amount data of the pixel of interest is larger than the threshold value of the dither matrix, it is determined that a dot is formed for that pixel. vice versa,
When the threshold value of the dither matrix is larger, it is determined that no dot is formed for that pixel. In the example shown in FIG. 9, the ink amount data of the pixel at the upper left corner of the image is “97”.
And the threshold value stored at the position corresponding to this pixel on the dither matrix is “1”.
It is. Accordingly, for the pixel in the upper left corner, the ink amount data is larger than the threshold value of the dither matrix, and therefore it is determined that a dot is formed in this pixel. An arrow indicated by a solid line in FIG. 9 schematically shows a state in which it is determined that a dot is to be formed in this pixel and the determination result is written in the memory. On the other hand, for the pixel on the right side of this pixel, the ink amount data is “97”, and the threshold value of the dither matrix is “177”, and the threshold value is larger. . In this way, by comparing the ink amount data and the threshold value set in the dither matrix, it is possible to determine whether or not dots are formed for each pixel. In the halftone process (step S108 in FIG. 6), C
By applying the above-described dither method to the ink amount data of each color of MYK, processing for generating dot data by determining the presence or absence of dot formation for each pixel is performed.

When the ink amount data of each color of CMYK is converted into dot data as described above, interlace processing is started (step S110 in FIG. 6). The interlace process is a process in which the print head 241 rearranges the dot data in the order in which dots are formed and supplies them to the ink discharge heads 244 to 247 for each color. That is, as shown in FIG. 5, since the nozzles Nz provided in the ink discharge heads 244 to 247 are provided at intervals of the nozzle pitch k in the sub-scanning direction, the ink is moved while the print carriage 240 is main-scanned. When droplets are ejected, dots are formed at intervals of the nozzle pitch k in the sub-scanning direction. Therefore, in order to form dots in all the pixels, the relative position between the print carriage 240 and the print medium is moved in the sub-scanning direction, and new dots are formed in the pixels between the dots separated by the nozzle pitch k. Necessary. Thus, when an image is actually printed, dots are not formed in order from the pixel above the image. Furthermore, for pixels in the same row in the main scanning direction, instead of forming dots in a single main scan, the dots are divided into a plurality of main scans in response to image quality requirements. In this main scanning, dots are also widely formed on the pixels at the skipped positions.

Thus, when an image is actually printed, dots are not formed according to the order of pixel arrangement on the image. Therefore, before actually starting the dot formation, C, M,
The dot data obtained for each color of Y and K is rearranged in the order in which the ink ejection heads 244 to 247 form dots. Such a process is a process called interlace.

In the image processing shown in FIG. 6, when the interlace processing is completed, processing for actually forming dots on the print medium (dot formation processing) is started based on the data obtained by the interlace processing (step S112). That is, while the carriage motor 230 is driven to cause the print carriage 240 to perform main scanning, the rearranged dot data is supplied to the ink ejection heads 244 to 247. As described above, since the dot data is data indicating whether or not to form dots in each pixel, the ink ejection heads 244 to 2 are used.
If ink droplets are ejected according to dot data 47, ink dots can be appropriately formed in each pixel.

When one main scan is completed, the paper feed motor 235 is driven to feed the print medium in the sub-scanning direction, and then the carriage motor 230 is driven again to print the print carriage 2.
40. The ink discharge head 244 converts the dot data rearranged in the order of 40 to the main scanning.
To 247 to form dots. By repeating these operations,
On the print medium, dots of each color of C, M, Y, and K are formed with an appropriate distribution according to the gradation value of the image data, and a color image is obtained.

In the image processing described above, after color image data is converted into ink amount data, an image is printed by forming dots based on the obtained ink amount data. The color of the obtained image depends on the ratio of forming dots of C, M, Y, and K colors.
It depends on the ink amount data generated from the color image data. Therefore, in order to appropriately express the color represented by the color image data, it is necessary to generate appropriate ink amount data according to the printing conditions. Normally, this is realized by preparing a color conversion table (also referred to as a correspondence table in this specification) for each printing condition. However, a great deal of effort is required to prepare a correspondence table for each printing condition, and a large amount of memory is required to store the correspondence table for each printing condition. In view of these points, in this embodiment, color image data is converted into ink amount data by the following method.

C. Ink amount data generation processing:
FIG. 10 is a flowchart showing the flow of the ink amount data generation process performed during the image processing of this embodiment. As shown in the drawing, in the ink amount data generation process, first, a color difference absorption table corresponding to the printing conditions and the allowable ink amount difference absorption data are selected (step S200). Here, the printing conditions are the printing conditions acquired in step S100 of the image processing shown in FIG. The color difference absorption table is a table for absorbing a difference in color to be printed due to a difference in printing conditions. That is, even if an image is printed according to the same ink amount data, there are subtle differences in colors obtained depending on various printing conditions such as a combination of the type of printing paper and the type of ink. In other words, if the printing conditions are different, the ink amount data needs to be different in order to obtain the same color. Therefore, by applying appropriate correction according to the printing conditions to the color image data, the difference in color due to the printing conditions is absorbed. The allowable ink amount difference absorption table is a table for absorbing a difference in ink amount allowed for each printing condition. In other words, the allowable amount of ink that can be used per unit area varies depending on the printing conditions such as the type of printing paper or ink to be used. Ink amount difference absorption data) is stored for each printing condition. The allowable ink amount difference absorption table will be described later with reference to another drawing.

FIG. 11 is an explanatory diagram conceptually showing a state in which the color difference absorption table is stored in the control circuit 260 of the printing apparatus 10 of the present embodiment in accordance with the printing conditions. In the illustrated example, a color difference absorption table is stored for each combination of the type of printing paper and the type of ink. Each color difference absorption table is a one-dimensional conversion table in which an output value is associated with an input value for each RGB component of color image data. When the ink amount data generation process shown in FIG. 10 is started, a process of reading out the color difference absorption table corresponding to the printing conditions acquired in advance from the ROM of the control circuit 260 is performed.

Next, the RGB components of the color image data are corrected by referring to the read color difference absorption table (step S202). As shown in FIG. 11, in the color difference absorption table, output values corresponding to input values are associated with RGB components, so by referring to this table, RGB components of color image data can be easily obtained. Can be corrected.

Next, conversion to ink amount data is performed by referring to a standard color conversion table (that is, a correspondence table) based on the color image data in which the RGB components are corrected (step S204). Here, the standard color conversion table associates color image data with ink amount data that provides the color represented by the color image data under specific printing conditions defined as standard printing conditions. It is a table. Since what kind of color is obtained by the ink amount data depends on the printing conditions, standard printing conditions are determined in advance,
The correspondence between color image data and ink amount data obtained under the standard printing conditions is set as a correspondence table.

FIG. 12 is an explanatory diagram conceptually showing a standard color conversion table. As shown in the drawing, CMYK ink amount data corresponding to the RGB coordinate values of the grid points is set in the color conversion table for each grid point having RGB components. Step S204 shown in FIG.
The color image data is converted into ink amount data by referring to a standard color conversion table stored in the ROM of the control circuit 260.

Next, the ink amount data is corrected by referring to the allowable ink amount difference absorption table for the obtained ink amount data of each color of CMYK (step S206). This is the following process. First, if too much ink is ejected onto the printing paper, the image quality is greatly deteriorated due to the occurrence of ink bleeding or the swelling of the printing paper and the undulation of the surface. Therefore, the printing paper has a permissible ink amount (permissible ink amount) per unit area. The above-described color difference absorption table is a table for correcting that the color expressed by the difference in printing conditions is different. Therefore, the color difference due to the difference in printing conditions can be absorbed. The difference in the allowable ink amount due to the difference is not considered. Since the correspondence table referred to when converting the color image data into the ink amount data is a table corresponding to the standard printing condition, the obtained ink amount data is also an allowable value of the ink amount under the standard printing condition. (Acceptable ink amount). Therefore, a table for absorbing the difference in the allowable ink amount with respect to the standard printing conditions is obtained for each printing condition and stored in advance.

FIG. 13 is an explanatory diagram conceptually showing an allowable ink amount difference absorption table stored for each printing condition. In the example shown in FIG. 13, the allowable ink amount difference absorption table is stored for each type of printing paper. However, the allowable ink amount difference absorption table is set for each combination of printing paper type and ink type, and for each of various other printing conditions. An ink amount difference absorption table may be stored.

In the allowable ink amount difference absorption table, the ink amount data on the output side is associated with the ink amount data on the input side. For example, in the table for plain paper illustrated in FIG. 13, the ink amount data on the input side can take the gradation value 0 to the gradation value 255, whereas the value of the ink amount data on the output side is Clipping is performed with a gradation value of 255 × Kmin, and only a range from a gradation value of 0 to a gradation value of 255 × Kmin can be taken. In general, plain paper has a small allowable ink amount, and printing using ink in the same way as other printing papers may cause ink bleeding and paper swelling, which may greatly deteriorate image quality. If the value of the ink amount data is clipped in this way, an image can be printed without causing such a problem even when printing on plain paper. In step S206 in FIG. 10, with respect to the ink amount data of each color of CMYK obtained by referring to the color conversion table in FIG. 12, an ink amount is referred to by referring to an allowable ink amount difference absorption table as shown in FIG. Perform processing to correct the data.

The largest ink amount data among the CMYK ink amount data is clipped, but when other ink amount data is not necessarily clipped, the following may be performed. First, the rate of change of the ink amount due to being clipped is calculated. For example, when the original ink amount a is clipped to the ink amount b, the ink amount is b /
It is suppressed at the rate of a. Therefore, the ink amount of other inks may be suppressed at the same ratio (that is, b / a). In this way, even when ink to be clipped is generated, it is possible to avoid a significant change in the color to be reproduced due to a large change in the ratio with other inks. For this reason, it is possible to suppress deterioration in image quality due to clipping of the ink amount data.

Here, a setting method of the coefficient Kmin for clipping the ink amount in the allowable ink amount difference absorption table shown in FIG. 13 will be described. FIG. 14 is an explanatory diagram showing a method for setting the coefficient Kmin for clipping the ink amount. As described above, the printing apparatus 10 according to the present embodiment is equipped with inks of C, M, Y, and K colors.
The allowable ink amount of ink is DtyoC, the allowable ink amount for M ink is DtyoM, the allowable ink amount for Y ink is DtyoY, and the allowable ink amount for K ink is DtyoK. The allowable ink amount for each color ink can be determined in advance by an experimental method.

Next, with respect to printing conditions assumed for image processing (for example, plain paper), the allowable ink amount DtyC for C ink, the allowable ink amount DtyM for M ink, and the allowable ink amount Dty for Y ink
The allowable ink amount DtyK for Y and K inks is acquired. These values can also be obtained by an experimental method. Then, the ratio of the allowable ink amount under the assumed printing condition to the allowable ink amount under the standard printing condition is calculated for each color ink, and among them, the ink with the smallest ratio, in other words, the ink with the strictest allowable ink amount. Is selected as the coefficient Kmin for clipping the ink amount. If the ink amount of each color is clipped using the coefficient Kmin thus selected, the ink amount data can be suppressed to a value equal to or less than the allowable ink amount for any ink. In addition, since clipping is performed at the same ratio with respect to the ink amount data of each color, the ratio for each color is maintained, and as a result, the color of the print image does not change.

As described above, when the ink amount data of each color of CMYK is corrected according to the allowable ink amount difference absorption table corresponding to the assumed printing condition (step S206 in FIG. 10), FIG.
The ink amount data generation process of 0 is finished, and the process returns to the image process of FIG.

The allowable ink amount difference absorption table is not limited to that illustrated in FIG. 13, and various tables can be used. FIG. 15 is an explanatory diagram illustrating various modifications of the allowable ink amount difference absorption table. For example, in the allowable ink amount difference absorption table illustrated in FIG.
Rather than suddenly clipping when the ink amount data on the input side reaches the gradation value 255 × Kmin, the ink amount data on the output side is gradually suppressed before reaching the gradation value 255 × Kmin, When the gradation value of the ink amount data on the input side reaches 255, the gradation value of the ink amount data on the output side may reach 255 × Kmin. In the example shown in FIG. 15A, little by little from the time when the ink amount data on the input side reaches 80% of the upper limit value of the ink amount data on the output side (that is, the gradation value 255 × Kmin). The ink amount data on the output side is suppressed.

When the gradation value of the ink amount data on the output side is clipped when the ink amount data on the input side reaches the gradation value 255 × Kmin as in the allowable ink amount difference absorption table illustrated in FIG. In the above gradation range, the gradation change is crushed. In this respect, FIG.
As shown in a), when the gradation value of the ink amount data on the input side reaches the upper limit value 255, the output side ink amount data is suppressed little by little before reaching the upper limit value of the output side ink amount data. If the ink amount data of this is also just reached the upper limit value (255 × Kmin), it is possible to avoid the occurrence of a region where the change in gradation is crushed.

Alternatively, as shown in FIG. 15B, the output-side ink amount data may be suppressed so that the output-side ink amount data changes smoothly before reaching the upper limit value.
In this way, the gradation change is greatly crushed in the region close to the upper limit value (255 × Kmin) of the ink amount data on the output side, but in the region far from the upper limit value (region close to the intermediate gradation) The collapse of change can be reduced. Usually, the area close to the intermediate gradation has a larger influence on the image quality than the area close to the upper limit value of the ink amount data. Therefore, by reducing the collapse of gradation change in this area, good image quality can be maintained. This is preferable because it can be stored.

Even when these allowable ink amount difference absorption tables are used, as in the case where the ink amount data is clipped as shown in FIG. 13, when the ink amount data is suppressed for a certain ink, the suppressed ratio Thus, the ink amount data of other inks may be suppressed. In this way, even when an ink whose ink amount data is suppressed is generated, it is possible to avoid a large change in the usage ratio of each ink, and the color to be reproduced changes greatly. It becomes possible to avoid that.

Furthermore, when the allowable ink amount under the assumed printing conditions is larger than the allowable ink amount under the printing conditions (standard printing conditions) assumed when the color conversion table is set, FIG. An acceptable ink amount difference absorption table as shown in the figure may be used. Also in this case, the ink amounts of other inks may be changed at a rate at which the ink amount of a certain ink is changed. By doing so, the usage ratio of each ink can be kept substantially the same, so that it is possible to prevent the reproduced color from changing.

In the ink amount data generation process of this embodiment shown in FIG. 10, as described above,
After correcting for color differences due to differences in printing conditions, color image data is converted into ink amount data, and the resulting ink amount data absorbs differences in allowable ink amounts due to differences in printing conditions Thus, final ink amount data is generated. As described above, since the difference in the printing conditions is absorbed before and after the color image data is converted into the ink amount data with reference to the color conversion table (also referred to as a correspondence table in the present specification), each printing condition is There is no need to prepare a dedicated color conversion table. This point will be supplementarily described.

FIG. 16 is an explanatory diagram conceptually showing the reason why color image data can be converted into ink amount data corresponding to various printing conditions by referring to a standard color conversion table. First, a case where a color image is printed after converting color image data into ink amount data with reference to a standard color conversion table will be considered. FIG. 16A shows RGB image data as C
It shows a state in which an image is printed on printing paper in accordance with the obtained ink amount data after conversion into MYK ink amount data. The same CMYK ink amount data is always obtained for RGB image data, but the colorimetric values (for example, Lab values) of the expressed colors differ depending on the type of printing paper used, the type of ink, and the like. It will be a thing. FIG. 16A shows that the colorimetric value Lab is obtained under the printing conditions assumed as a standard, whereas the colorimetric value L′ a′b ′ is obtained under different printing conditions. . However, since the colorimetric value L'a'b 'is always obtained under this printing condition, in view of this, if different ink amount data can be obtained for this printing condition, the standard printing condition can be obtained. It is possible to obtain the same colorimetric value Lab.

Therefore, as shown in FIG. 16B, before referring to the standard color conversion table, the RGB image data is converted using the color difference absorption table, and the converted RGB image data is converted into the standard color conversion table. The ink amount data is converted with reference to the conversion table. Here, the color difference absorption table is set to a table that converts RGB image data in anticipation of a difference in colorimetric values due to a difference in printing conditions. The color difference absorption table can be obtained and set in advance for each printing condition. The ink amount data obtained by referring to the color conversion table from the RGB image data corrected by the color difference absorption table is no longer CMY as shown in FIG.
The ink amount data is different from the K ink amount data, but when printing under the assumed printing conditions (for example, printing paper type and ink type), the same as when printing under standard printing conditions A colorimetric value Lab can be obtained.

However, the ink amount data obtained in this way satisfies the allowable ink amount under the printing conditions assumed as a standard, but satisfies the allowable ink amount under the assumed printing conditions. Not necessarily. If the permissible ink amount exceeds the expected printing conditions, the expressed colorimetric value will be reproduced as the correct value, but ink bleeding or printing paper swelling will occur. Therefore, the image quality may be deteriorated. Therefore,
As shown in FIG. 16C, by correcting the ink amount data using the allowable ink amount difference absorption table, the allowable ink corresponding to the printing condition (the type of printing paper in the above-described embodiment). Absorb the difference in quantity.

If the printing conditions are different, even if an image is printed based on the same ink amount data, the colorimetric values of the obtained colors are different, and the allowable ink amount is also different. Thus, a dedicated color conversion table is prepared for each printing condition, and color image data is converted into ink amount data with reference to the color conversion table. However, differences in colorimetric values obtained due to differences in printing conditions are corrected in advance for RGB image data, and further differences in allowable ink amounts due to differences in printing conditions are corrected after conversion to ink amount data. By doing so, it becomes possible to always convert color image data into ink amount data using the same color conversion table regardless of printing conditions. Therefore, it is not necessary to generate a plurality of color conversion tables according to printing conditions, and an appropriate image can be easily output.

Of course, it is necessary to generate a color difference absorption table and an allowable ink amount difference absorption table for each printing condition. However, as shown in FIG. 11 or FIG.
It is much simpler than the color conversion table shown in FIG. 12, and does not require much labor for generation. Furthermore, since these color difference absorption tables and allowable ink amount difference absorption tables have a small amount of data, they should be stored in a much smaller memory amount than a color conversion table for each printing condition. Is possible. As a result, it is possible to avoid consuming the memory of the printing apparatus 10 by itself.

D. Modified example:
In the embodiment described above, during the ink amount data generation processing in the image processing, first, the color image data is converted using the color difference absorption table, and then the converted color image data is converted into the standard color conversion. It has been described that final ink amount data is obtained by converting into ink amount data using a table, and finally converting the obtained ink amount data using an allowable ink amount difference absorption table. This makes it possible to appropriately convert color image data into ink amount data without preparing a dedicated color conversion table for each printing condition.

However, if this idea is used in reverse, a color conversion table for each printing condition can be easily set. Hereinafter, such a color conversion table setting process will be described.

FIG. 17 is a flowchart illustrating a flow of color conversion table setting processing as a modification. As shown in the figure, in the color conversion table setting process, first, the printing conditions assumed when generating the color conversion table are acquired (step S300). Since the color conversion table associates color image data with ink amount data for printing the color represented by the color image data, printing conditions are assumed to generate the color conversion table. Must have been. Therefore, in the color conversion table setting process, first, an assumed printing condition is acquired.

Next, a color difference absorption table and an allowable ink amount difference absorption table stored corresponding to the assumed printing conditions are acquired (step S302). As described above with reference to FIGS. 11 and 13, the color difference absorption table and the allowable ink amount difference absorption table are stored in advance in association with the printing conditions.

After obtaining the color difference absorption table and the allowable ink amount difference absorption table corresponding to the printing conditions in this way, this time, among the plurality of grid points generated by subdividing the RGB color solid whose side length is 255 into a grid shape. Then, one target lattice point is selected (step S304). Then, the RGB coordinate values of the lattice points are corrected in accordance with the color difference absorption table acquired previously corresponding to the printing conditions (step S306). As described above with reference to FIG. 11, in the color difference absorption table, output values for input values are associated with RGB components.
By referring to such a table, the RGB coordinate values of the grid points can be easily corrected.

Next, by referring to the standard color conversion table, the corrected RGB coordinate values are converted into ink amount data (step S308), and the obtained ink amount data has been acquired in advance. Correction is performed according to the allowable ink amount difference absorption table (step S310).

The ink amount data finally obtained in this way is stored in the selected grid point (step S
312). Thereafter, it is determined whether or not the ink amount data is stored for all grid points provided by subdividing the RGB color solid (step S314), and it is determined that the processing for all grid points is not completed. If this is the case (step S314: no), the process returns to step S304 again, and after selecting a new grid point, the series of processes described above are performed, and the obtained ink amount data is converted to the selected grid point. Remember. In this way, when it is determined that the processing for all the lattice points has been completed (step S314: yes), the color conversion table setting processing shown in FIG. 17 is terminated.

In the color conversion table setting process described above, based on the color difference absorption table corresponding to the printing conditions, the allowable ink amount difference absorption table, and the standard color conversion table, the color conversion table corresponding to the printing conditions is immediately set. Can be generated. The color difference absorption table and the allowable ink amount difference absorption table need to be acquired for each printing condition. However, as described with reference to FIGS. 11 and 13, these tables are relatively simple tables. Can be easily obtained. As for the color conversion table, if one standard color conversion table is acquired, the color conversion table can be applied to any printing condition.
For this reason, it is possible to easily create a color conversion table corresponding to various printing conditions. Furthermore, the generated color conversion table may be deleted if it is no longer needed. That is,
If a standard color conversion table is stored, a color conversion table corresponding to the printing conditions may be generated as necessary, so that the memory amount can be saved also in this respect.

Although the printing apparatus of the present embodiment has been described above, the present invention is not limited to all the above-described embodiments, and can be implemented in various modes without departing from the scope of the present invention.

1 is a perspective view illustrating an external shape of a printing apparatus in which an image processing apparatus according to an embodiment is mounted. FIG. 4 is an explanatory diagram showing a state in which a document table cover provided on the upper part of the printing apparatus is opened to read a print image. It is the perspective view which showed a mode that the front side of the scanner part was lifted and rotated. It is explanatory drawing which showed notionally the internal structure of the printing apparatus of a present Example. It is explanatory drawing which showed a mode that the several nozzle Nz which discharges an ink drop to the ink discharge head of each color was formed. 6 is a flowchart illustrating a flow of image processing for reading color image data and printing an image. It is explanatory drawing which showed a mode that the printing condition of the image was set with respect to the printing apparatus. It is explanatory drawing which expanded and illustrated a part of dither matrix. It is explanatory drawing which showed notionally the mode that the presence or absence of dot formation was judged for every pixel, referring a dither matrix. 5 is a flowchart illustrating a flow of ink amount data generation processing performed during image processing according to the present exemplary embodiment. It is explanatory drawing which showed notionally the mode that the color difference absorption table was memorize | stored according to printing conditions in the control circuit of the printing apparatus of a present Example. It is explanatory drawing which showed the standard color conversion table notionally. It is explanatory drawing which showed notionally the permissible ink amount difference absorption table memorize | stored for every printing condition. It is explanatory drawing shown about the method to set the coefficient Kmin for clipping an ink amount. It is explanatory drawing which illustrated the various modifications of the allowable ink amount difference absorption table. FIG. 4 is an explanatory diagram conceptually showing the reason why color image data can be converted into ink amount data corresponding to various printing conditions by referring to a standard color conversion table. It is a flowchart which shows the flow of the color conversion table setting process as a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Printing apparatus, 12 ... Ink discharge head, 100 ... Scanner part,
200: Printer unit, 240: Print carriage, 241: Print head,
242 ... Ink cartridge, 243 ... Ink cartridge,
260 ... control circuit, 300 ... operation panel

Claims (8)

An image processing device that obtains color image data and performs predetermined image processing on the color image data to convert the color represented by the color image data into ink amount data for printing,
Correspondence relationship storage means for storing a correspondence relationship in which the color image data and the ink amount data are associated;
Color difference absorption data storage means for storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
An allowable ink amount difference absorbing means for storing allowable ink amount difference absorption data for absorbing a difference in ink amount allowed for each printing condition;
The color image data is corrected based on the color difference absorption data, and the corrected color image data is converted into provisional ink amount data with reference to the correspondence relationship, and then the ink amount An image processing apparatus comprising: an ink amount data generating unit that generates final ink amount data by correcting data using the allowable ink amount difference absorption data. The image processing apparatus according to claim 1,
An assumed printing condition acquisition means for acquiring an assumed printing condition that is a printing condition assumed when performing the image processing;
The correspondence storage means assumes color printing data and ink amount data for printing the color represented by the color image data, assuming predetermined printing conditions including at least the type of printing medium and the type of ink. Is a means for storing the correspondence relationship associated with
The color difference absorption data storage means absorbs the difference between the color when printed under the assumed printing condition and the color when printed under the standard printing condition as the printing condition assumed in the correspondence relationship. Means for storing the color difference absorption data, which is correction data to be added to image data, for each assumed printing condition;
The allowable ink amount difference absorption data storage means absorbs the difference between the allowable amount of ink that can be used under the standard printing conditions and the allowable value of ink amount that can be used under the assumed printing conditions.
A means for storing permissible ink amount difference absorption data as data representing correction contents to be added to the ink amount data for each assumed printing condition;
The ink amount data generation unit, upon receiving the color image data, corrects the color image data based on the color difference absorption data according to the assumed print conditions assumed,
The corrected color image data is converted into the provisional ink amount data with reference to the correspondence relationship, and the obtained ink amount data is converted into the allowable ink amount difference absorption data according to the assumed printing conditions. An image processing apparatus that is a unit that generates ink amount data corresponding to the assumed printing condition by performing correction based on the correction. The image processing apparatus according to claim 2,
The allowable ink amount difference absorption data storage means includes a plurality of types of ink used for printing.
An image processing apparatus as means for storing the allowable ink amount difference absorption data set based on the ink having the smallest ink amount allowable value. An image processing apparatus that generates ink amount data for printing a color represented by the color image data by acquiring color image data and performing predetermined image processing on the color image data,
Correspondence relationship storage means for storing a correspondence relationship in which the color image data and the ink amount data are associated;
Color difference absorption data storage means for storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
An allowable ink amount difference absorbing means for storing allowable ink amount difference absorption data for absorbing a difference in ink amount allowed for each printing condition;
A reflection correspondence generation unit that generates a reflection correspondence corresponding to a printing condition reflected based on the color difference absorption data, the correspondence, and the allowable ink amount difference absorption data;
An image processing apparatus comprising: an ink amount data generating unit configured to generate the ink amount data from the color image data by referring to the reflection correspondence generated by the reflection correspondence generating unit. The image processing apparatus according to claim 1, further comprising an image forming unit that forms an image on a print medium based on the ink amount data. An image processing method for obtaining color image data and performing predetermined image processing on the color image data to convert the color represented by the color image data into ink amount data for printing,
A first step of storing a correspondence relationship in which the color image data and the ink amount data are associated;
A second step of storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
A third step of storing permissible ink amount difference absorption data for absorbing permissible ink amount differences for each printing condition;
The color image data is corrected based on the color difference absorption data, and the corrected color image data is converted into provisional ink amount data with reference to the correspondence relationship, and then the ink amount And a fourth step of generating final ink amount data by correcting the data using the allowable ink amount difference absorption data. A method of generating a correspondence relationship in which color image data and ink amount data are associated with each other,
Storing a reference correspondence relationship in which the color image data and the ink amount data are associated;
A step (B) of storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
A step (C) of storing permissible ink amount difference absorption data for absorbing a difference in ink amount allowed for each printing condition for each printing condition;
After selecting one of the color image data and performing correction based on the color difference absorption data, the ink correspondence data is converted to ink amount data with reference to the reference correspondence relationship, and the obtained ink amount data is converted into the allowable ink. A step (D) for generating the correspondence relationship by correcting the ink amount data obtained based on the amount difference absorption data and storing the ink amount data finally obtained in association with the selected color image data. How to generate relationships. In order to realize a method of converting color ink data for printing by acquiring color image data and performing predetermined image processing on the color image data, using a computer. The program of
A first function for storing a correspondence relationship in which the color image data and the ink amount data are associated;
A second function for storing color difference absorption data for absorbing a color difference for each printing condition for each printing condition;
A third function for storing permissible ink amount difference absorption data for absorbing permissible ink amount differences for each printing condition;
The color image data is corrected based on the color difference absorption data, and the corrected color image data is converted into provisional ink amount data with reference to the correspondence relationship, and then the ink amount A program for realizing, by a computer, a fourth function for generating final ink amount data by correcting data using the allowable ink amount difference absorption data.

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