JP4075241B2 - Printing apparatus, printing method, and recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for forming a multi-tone image by forming a plurality of types of ink dots.
[0002]
[Prior art]
A printing apparatus that forms dots on a print medium and prints a multi-tone image is widely used as an output medium of an image device such as a computer. Since these printing apparatuses express an image based on whether dots are formed or not, there are few gradation values that can be expressed per pixel. For this reason, when expressing an intermediate gradation, the intermediate gradation is expressed as a whole area by forming dots dispersed in a predetermined ratio in the area to be expressed. That is, when looking at each pixel in the region, a gradation error occurs because a gradation different from the gradation value to be expressed is expressed regardless of whether a dot is formed or not. By reducing the error of the entire region, the target intermediate gradation is expressed. For example, when a dot is formed in a certain pixel, the gradation value of that pixel becomes higher than the target intermediate gradation, so an error in excess of the gradation value occurs. On the other hand, when dots are not formed, the gradation value of the pixel is lower than the target intermediate gradation, so that an error due to insufficient gradation values occurs. Accordingly, if the dot formation ratio is appropriately adjusted according to the gradation value to be expressed, the error of the entire region can be sufficiently reduced.
[0003]
Various methods are known as methods for forming dots at an appropriate ratio according to the gradation value, and representative methods include a method called an error diffusion method and a method called a systematic dither method. . In the error diffusion method, an error generated by determining whether or not dots are formed is diffused to surrounding pixels, and when determining dot formation for the surrounding pixels, dot formation determination is performed so as to eliminate the diffused error as much as possible. . For this reason, since the error remaining in the entire area is reduced, a good print image quality can be obtained by using the error diffusion method. On the other hand, the systematic dither method does not diffuse the generated error and reflect it in the dot formation determination of other pixels, so that quick processing is possible, but the image quality is inferior to the error diffusion method. Tend.
[0004]
In order to further improve the image quality of the printed image by the error diffusion method, it is preferable to improve the dot dispersibility by diffusing the error to a wide range of surrounding pixels. In particular, when printing an image having a relatively low gradation value, it is necessary to form the dots sufficiently apart from each other. For this purpose, it is necessary to diffuse an error caused by the formation of dots over a wide range. Since it becomes difficult to form dots in the range where the error is diffused, if the error is diffused over a wide range, the dots can be formed sufficiently apart from each other. Also, when printing an image with a relatively high gradation value, errors caused by the absence of dots are set in a wide range so that some of the pixels where dots are not formed are not close to each other. It needs to be diffused.
[0005]
[Problems to be solved by the invention]
However, the error diffusion method has a problem that the more pixels that diffuse the generated error, the longer the time required for the image printing because the diffusion process takes time. However, if the error is not diffused to many pixels, the advantage of the error diffusion method that a good image quality can be obtained cannot be obtained sufficiently.
[0006]
The present invention has been made in order to solve the above-described problems in the prior art, and is a technique capable of quickly printing an image while maintaining the advantage of the error diffusion method that a good image quality can be obtained. The purpose is to provide.
[0007]
[Means for solving the problems and their functions and effects]
  In order to solve at least a part of the problems described above, the printing apparatus of the present invention employs the following configuration. That is,
  By applying predetermined image processing to multi-tone image data, the image data is converted into an expression format in which a plurality of types of dots having different densities per unit area are mixed, and the image is converted using the plurality of types of dots. A printing device for printing,
  Dot formation determination means for determining whether or not each of the plurality of types of dots is formed for each pixel based on the image data;
  An error diffusing unit that distributes the error generated by the determination of the presence / absence of the dot to a plurality of peripheral pixels by a predetermined method and reflects it in the determination of the presence / absence of the formation of the plurality of types of dots;
  Dot forming means for forming the dots on a print medium based on the determination result of whether or not the plurality of types of dots are formed;
  An error diffusion table storing a plurality of types of error diffusion tables storing a ratio of distributing an error generated by the determination of the presence or absence of dot formation to a plurality of peripheral pixels; and
  The error diffusion means is
The error for high density dots per unit area is a means of distributing to fewer pixels than the error for low density dots, and
A first error diffusion table is selected from the stored error diffusion tables, and the first error diffusion table is used to diffuse an error of dots having a high density per unit area using the first error diffusion table. Means,
A second error diffusion table wider than the first error diffusion table is selected from the stored error diffusion tables, and dots having a low density per unit area are selected using the second error diffusion table. Second error diffusion means for diffusing the error of
With
Each of the first and second error diffusion means selects a plurality of types of error diffusion tables, and diffuses the error to each while switching the selected error diffusion tables by a predetermined method. The error diffusion table having the widest diffusion range used by the error diffusion means is a table having a narrower error diffusion range than the error diffusion table having the widest diffusion range used by the second error diffusion means.
  This is the gist.
[0009]
  Such printing equipmentIn placeIn the case of determining the dot formation presence / absence of the undetermined pixel while distributing the error generated by the dot formation determination / determination to surrounding pixels, the error generated by the formation presence / absence determination is determined by a predetermined method. When distributing to a plurality of peripheral pixels, one error diffusion table is selected from the plurality of stored error diffusion tables by combining the type of ink used for dot formation and the gradation of the image data. Error is diffused. As one of them, the error of dots with high density per unit area (hereinafter referred to as dark dots) is distributed to pixels that are less than the error of dots with low density per unit area (hereinafter referred to as light dots). . When dark dots and light dots are used in combination, the image quality of dark dots is not impaired even if the dispersibility of the dots is somewhat poor for the following reasons. Therefore, if dark dot errors are distributed to pixels that have fewer light dot errors than the pixels that disperse light dot errors, the printing time will be shortened by the amount of time required for error dispersion processing, and image quality will be reduced. There is no.
[0010]
In the following, the reason why the image quality will not be impaired even if the dark dot and the light dot are used together even if the dispersibility of the dark dot is somewhat bad is explained. As a preparation for this, two types of dots with different densities are used in combination. The ratio of the dots formed when the image is printed will be described.
[0011]
FIG. 12 is an explanatory diagram conceptually showing the ratio of dots recorded to pixels (hereinafter referred to as dot recording rate) with respect to the gradation value of image data to be printed. FIG. 12A shows a case where only one type of dot is used, and FIG. 12B shows a case where a dark dot and a light dot are used in combination. First, FIG. 12A will be described. FIG. 12A assumes that one type of dot is used, and that a gradation value 255 is expressed in the pixel on which the dot is formed. If such dots are used, for example, if the image to be printed is a solid image with a gradation value of 255, dots may be formed on all pixels. That is, the dot recording rate may be 100%. In the case of an image having a gradation value of 128, dots may be formed in half of the pixels (dot recording rate 50%). In this way, a desired image can be printed by increasing / decreasing the dot recording rate in accordance with the increase / decrease of the gradation value of the image data to be printed. FIG. 12A shows such a relationship between the gradation value of the image data to be printed and the dot recording rate.
[0012]
FIG. 12B is an explanatory diagram conceptually showing the relationship between the image data and the dot recording rate when two types of dots, dark dots and light dots, are used in combination. The dot recording rate of dark dots is indicated by a solid line, and the dot recording rate of light dots is indicated by a broken line. In FIG. 12B, the gradation value 255 is expressed in the pixel in which the dark dot is formed, and the gradation value 64 is expressed in the pixel in which the light dot is formed.
[0013]
For example, when printing image data represented by the gradation value 32, the dot recording rate of light dots may be 50%, that is, it may be formed in half of the pixels. In the case of image data having a gradation value of 64, the dot recording rate of light dots may be 100%. Here, since the dot recording rate of 100% is a state in which dots are formed in all pixels, if the gradation value of the image data exceeds 64, it cannot be expressed by only light dots. Therefore, dark dots are gradually formed as the gradation value of the image data increases, and light dots are reduced as dark dots are formed. Thus, when the gradation value of the image data finally becomes 255, the dot recording rate of dark dots is set to 100%. In this way, a desired image can be printed while forming a mixture of dark dots and light dots. FIG. 12B conceptually shows such a relationship between the gradation value of the image data and the dot recording rate of the light and dark dots.
[0014]
As shown in FIG. 12B, the use of light and dark dots can greatly improve the image quality. In brief, when image data to be printed has a low gradation value, when only dark dots are used (in the case of FIG. 12A), it is necessary to form dots sparsely. Since a dark dot alone is easily noticeable, it becomes a rough image and tends to deteriorate image quality. On the other hand, a light dot is not conspicuous. Therefore, if light dots are used in a low gradation area, a rough image is not formed in the low gradation area. In the intermediate gradation area, it is necessary to start forming dark dots in addition to the light dots. However, in the intermediate gradation area, the dark dots are not so noticeable, so that a rough image is not formed. As a result, good image quality can be obtained in all gradation regions.
[0015]
Note that the dot recording rates of the dark dots and the light dots shown in FIG. 12B are merely examples, and for example, dark dots can be formed at an earlier stage than the gradation value 64, and the gradation value Light dots can be formed after 128. That is, FIG. 12B conceptually illustrates how the dot recording rate of light and dark dots increases or decreases depending on the gradation value of image data to be printed.
[0016]
Based on the above, when dark dots and light dots are used together, the reason why the image quality is not impaired even if the dispersibility of the dark dots is somewhat poor will be described below.
[0017]
FIG. 13 conceptually shows how light dots are sparsely formed when a low gradation image is printed. FIG. 12B corresponds to the case of printing image data having a gradation value A. FIG. 13A shows a state in which the dispersibility of the dots is good, that is, a state where the dots are uniformly formed in the entire region. As described above, since the light dots are inconspicuous dots, if the dots are uniformly formed as shown in FIG. 13A, a good image quality in which the dots are not conspicuous can be obtained.
[0018]
FIG. 13B shows a state in which the dot recording rate is the same as that in FIG. 13A, but the dot dispersibility is poor. Compared to FIG. 13A, the distance between the dots is not uniform, and as a result, the dots are formed closer to each other. Light dots are dots that are difficult to stand out by themselves, but when multiple dots are formed close to each other in this way, they appear as if large dots are formed, resulting in a deterioration in print image quality. Let Therefore, when printing an image having a low gradation value, the image quality deteriorates unless the dot dispersibility is kept good.
[0019]
On the other hand, FIG. 14A shows a case where an image having an intermediate gradation (corresponding to the gradation value B in FIG. 12B) is printed. At gradation value B, a small amount of dark dots are formed while light dots are formed on almost one surface. The dot recording rate of dark dots at gradation value B is substantially the same as the dot recording rate of light dots at gradation value A (see FIG. 12B). The dispersibility of the dark dots in FIG. 14 (a) is not so good. FIG. 14B shows a case where the gradation value A is expressed by only light dots as a reference. The distribution state of the light dots in FIG. 14B is exactly the same as the distribution state of the dark dots in FIG. 14A, and neither dispersibility is very good. Comparing the two figures reveals the following. First, as shown in FIG. 13B, when only a single dot is sparsely formed on a print medium, if the dispersibility of the dots is poor, even if the dots are light dots that do not stand out well, Conspicuously deteriorates image quality. On the other hand, as shown in FIG. 14A, in the case where a light dot is formed on one side and a dark dot is formed, the dark dot is a dot that is more noticeable than the light dot. Even if the dispersibility of the dark dots is somewhat poor, the dots do not stand out and the image quality is not deteriorated.
[0020]
In this way, when dark dots and light dots are used together, dark dots are formed while the light dots are formed on one side, so even if the dispersibility of the dark dots is somewhat poor, the image quality is not impaired. is there.
[0021]
In the printing apparatus and the printing method of the present invention, based on such knowledge, the number of pixels for distributing an error caused by the determination of dot formation is different between a high density dot and a low density dot per unit area. It is That is, the dark dot error has a smaller number of pixels in which the error is distributed than the light dot error. As a result, the time required for image processing can be shortened, and the image can be printed quickly. Since the dark dots are formed while a large number of light dots are formed, the image quality is not deteriorated even if the number of pixels for distributing the error of the dark dots is reduced in this way.
[0022]
In such a printing apparatus, the error generated by the dot formation determination is distributed to peripheral pixels centering on the pixel forming the dot, and the dark dot error is distributed to pixels in a narrower range than the light dot error. You may make it do.
[0023]
It is desirable from the viewpoint of image quality that the error caused by the dot formation judgment is distributed to the periphery of the pixel forming the dot, and if the error of the dark dot is distributed to pixels in a range narrower than the error of the light dot, the dark Dot errors are distributed to pixels that are less than light dot errors. Accordingly, it is preferable because rapid printing can be performed while improving the image quality.
[0024]
In such a printing apparatus, a plurality of types of error diffusion tables storing a ratio of distributing errors to a plurality of peripheral pixels are stored, and errors generated by the determination of formation of dark dots and light dots are stored in the error diffusion table. It may be distributed as follows. That is, using the error diffusion table selected from the plurality of error diffusion tables, distribute the dark dot error to the surrounding pixels, and for the light dot error, select a table wider than the dark dot error diffusion table, You may distribute to a surrounding pixel using this selected error diffusion table.
[0025]
In this way, the dark dot error is distributed to the pixels that are smaller than the light dot error, so that it is possible to avoid the deterioration of the image quality while printing the image quickly.
[0026]
Such a printing apparatus may be a printing apparatus that diffuses dark dot errors while switching a plurality of error diffusion tables by a predetermined method, and diffuses light dot errors while switching a plurality of error diffusion tables. In such a printing apparatus, the widest error diffusion table used for error diffusion of dark dots is made narrower than the widest error diffusion table used for error diffusion of light dots.
[0027]
When a wide error diffusion table is used, it takes a long time for error diffusion. Therefore, the size of the widest error diffusion table tends to strongly influence the length of time required for error diffusion. Therefore, if the widest error diffusion table used for error diffusion of dark dots is narrower than the widest error diffusion table used for error diffusion of light dots, the time required for error diffusion of dark dots can be shortened. This is preferable because the printing time of the image can be shortened accordingly.
[0028]
Further, the above-described printing apparatus does not use a wide error diffusion table used for light dot error diffusion in order to diffuse dark dot errors. Therefore, it is possible to perform error diffusion of dark dots using fewer types of error diffusion tables than the types of error diffusion tables used for light dot error diffusion.
[0029]
This is preferable because the storage capacity can be saved to the extent that the type of error diffusion table for dark dots can be made smaller than the type of error diffusion table for light dots.
[0030]
Such a printing apparatus is a printing apparatus that discharges high-density ink to form dots with high density per unit area, and discharges low-density ink to form dots with low density per unit area. You can also. In such a printing apparatus, an error caused by forming dots by discharging high-density ink is distributed to pixels that are smaller than an error caused by forming dots by discharging low-density ink.
[0031]
By doing so, the number of pixels for distributing the error of the dots of the high density ink can be reduced, so that the image can be printed quickly. Further, since the dots of high density ink are formed while many dots of low density ink are formed, the image quality is not deteriorated even if the dispersibility of the dots of high density ink is somewhat poor.
[0032]
Such a printing apparatus may be a printing apparatus that forms dots having different densities per unit area by forming dots having different sizes on a print medium. In such a printing apparatus, an error caused by forming a large dot is distributed to pixels smaller than an error caused by forming a small dot.
[0033]
In this way, the number of pixels that distribute the error of a large dot can be reduced, so that an image can be printed quickly. Also, since large dots are formed while a large number of small dots are formed, the image quality is not deteriorated even if the dispersibility of the large dots is somewhat poor.
[0034]
  The present invention can also be applied to a printing apparatus that prints a color image as follows. That is, a printing apparatus that prints such a color image is
  By performing predetermined image processing on the color image data, at leastOf cyan, magenta and yellowThree primary color dotsAnd light cyan and light magenta dots with higher brightness than cyan and magentaA printing apparatus that prints a color image by converting the image data into a mixed expression format and forming dots of each color,
  Dot formation determination means for determining the presence or absence of formation for each color dot for each pixel based on the image data;
  An error diffusing means for distributing the error generated by the determination of the presence or absence of the dot to a plurality of peripheral pixels by a predetermined method and reflecting it in the determination of the presence or absence of each color dot;
  Dot forming means for forming the dots of the respective colors on a print medium based on the determination result of the formation of the respective color dots;
  With
  The error diffusion means has the highest brightness among the three primary colors.YellowDotAnd the cyan and magenta dotsThe gist is that the error is distributed to the pixels that are smaller than the error for the dots of other colors.
[0035]
  Also, a printing method corresponding to the printing apparatus that prints the color image described above is
  By performing predetermined image processing on the color image data, at leastOf cyan, magenta and yellowThree primary color dotsAnd light cyan and light magenta dots with higher brightness than cyan and magentaIs a printing method for printing a color image by converting the image data into a mixed expression format and forming dots of each color,
  The presence or absence of formation for each color dot is determined for each pixel based on the image data,
  Highest brightness among the three primary colorsYellowDotAnd the cyan and magenta dotsThe error generated by the determination of the presence / absence of the formation of the color is distributed to a plurality of surrounding pixels by a predetermined method, and the error of the dots of other colors is distributed to the pixels larger than the error of the dot of the color having the highest brightness , Reflecting each distributed error in the determination of the presence or absence of each color dot,
  The gist is to form the dots of the respective colors on the print medium based on the determination result of the presence or absence of the formation of the respective color dots in which the error is reflected.
[0036]
  In such a printing apparatus and printing method, when determining whether dots of undecided pixels are formed while distributing errors generated by determining whether dots of each color are formed to surrounding pixels, the lightness is the highest among the three primary colors.YellowDotAnd the cyan and magenta dotsIs distributed to pixels that are smaller than the error of other color dots. Highest brightnessYellowBecause the dots of are less conspicuous than other colors, they have the highest brightnessYellowEven if the dot dispersibility is somewhat poor, the image quality is not deteriorated. Therefore, if the pixels that disperse the error of the color dot with the highest brightness are distributed to pixels that are smaller than the errors of the dots of the other colors, the printing time is shortened by the amount of time required for error dispersion processing. In addition, the image quality is not deteriorated.
[0038]
  Since yellow dots are less conspicuous than other color dots, the image quality is not deteriorated even if the dispersibility of the yellow dots is somewhat poor. Therefore, if the pixel that disperses the error of the yellow dot is dispersed to the pixels that are smaller than the error of the other color dot,, WrongThis is preferable because the printing time is shortened by the time required for the difference dispersion processing and the image quality is not deteriorated.
[0039]
  The present invention relating to the printing method described above can also be realized by combining a printing apparatus and a computer that controls the printing apparatus, and controlling the operation of the printing apparatus by the computer. Therefore, the present invention includes various aspects as a recording medium in which a program for performing such processing is recorded so as to be readable by a computer. That is, like thisStateBy performing predetermined image processing on color image data,Of cyan, magenta and yellowThree primary color dotsAnd light cyan and light magenta dots with higher brightness than cyan and magentaIs a recording medium recorded with a computer-readable program for realizing a method of printing a color image by converting the image data into a mixed expression format and forming dots of each color,
  A function of determining the presence or absence of formation for each color dot for each pixel based on the image data;
  Highest brightness among the three primary colorsYellowDotAnd the cyan and magenta dotsThe error generated by the determination of the presence / absence of the formation of the color is distributed to a plurality of surrounding pixels by a predetermined method, and the error of the dots of other colors is distributed to the pixels larger than the error of the dot of the color with the highest brightness. A function of reflecting the distributed error in the determination of whether or not each color dot is formed;
  A function for controlling the formation of dots of each color based on the determination result of the formation of the dots of each color that reflects the error;
  It is the aspect as a recording medium which recorded the program which implement | achieves.
[0041]
When the program stored in these recording media is read into a computer and the computer performs various processes, in the first aspect, the time for distributing errors of high-density dots is shortened, thereby This is preferable because printing can be performed quickly and deterioration of image quality can be avoided. Further, in the second aspect, the time for distributing the error of the dot having the highest brightness is shortened, so that the image can be printed quickly and the deterioration of the image quality can be avoided. This is preferable because it is possible.
[0042]
DETAILED DESCRIPTION OF THE INVENTION
In order to more clearly describe the operation and effect of the present invention, embodiments of the present invention will be described below in the following order.
A. Device configuration:
B. Overview of the printing process:
C. Contents of binarization processing:
(1) First embodiment:
(2) Second embodiment:
[0043]
A. Device configuration:
FIG. 1 is an explanatory diagram illustrating a configuration of a printing apparatus as an embodiment of the present invention. As shown in the figure, the color printer 20 is connected to a computer 80, and a predetermined program is loaded and executed on the computer 80 so that the printing apparatus functions as a printing apparatus as a whole. A color document to be printed is taken in using the color scanner 21 connected to the computer 80, or an image created by various application programs 91 on the computer 80 is used. The image data ORG is converted into image data that can be printed by the color printer 20 by the CPU 81 in the computer 80 and output to the color printer 20 as image data FNL. The color printer 20 forms ink dots of each color on the print medium according to the image data FNL, and as a result, a color image corresponding to the color original is printed on the print paper.
[0044]
The computer 80 includes a CPU 81 that executes various arithmetic processes, a RAM 83 that temporarily stores data, a ROM 82 that stores various programs, a hard disk 26, and the like. If the SIO 88 is connected to the public telephone line PNT via the modem 24, necessary data and programs can be downloaded from the server SV on the external network to the hard disk 26.
[0045]
The color printer 20 is a printer capable of printing a color image. In this embodiment, a total of six colors of cyan, light cyan (light cyan), magenta, light magenta (light magenta), yellow, and black are printed on the printing paper. An ink jet printer that prints a color image by ejecting ink is used. However, the present invention is not limited to a color printer that ejects ink to form dots, and may be a color printer that forms dots by, for example, a sublimation type or a fusion type thermal transfer method. In addition, the ink discharge method of the ink jet printer used in this example employs a method using a piezo element PE as will be described later. However, it is assumed that a printer having a head for discharging ink by another method is used. Also good. For example, the present invention may be applied to a printer of a system that energizes a heater disposed in an ink passage and ejects ink by bubbles generated in the ink passage.
[0046]
The color printer 20 of this embodiment is a variable dot printer, that is, a printer that can form three types of dots of different sizes, large, medium, and small for each color. If the size of the dots to be formed is changed using a variable dot printer, it is possible to express multi-level gradation for each dot, so that an image with rich gradation expression can be printed. The color printer 20 of the present embodiment forms dots of three sizes using a single ink discharge nozzle by devising an ink discharge method. Such an ink ejection method will be described later. Further, as is apparent from the description of the ink ejection method, the size of the dots is not limited to three types, and more types of dots may be formed as necessary.
[0047]
FIG. 2 is a block diagram conceptually showing the software configuration of the printing apparatus. In the computer 80, all application programs 91 operate under an operating system. A video driver 90 and a printer driver 92 are incorporated in the operating system, and image data output from each application program 91 is output to the color printer 20 via these drivers.
[0048]
When the application program 91 issues a print command, the printer driver 92 of the computer 80 receives image data from the application program 91, performs predetermined image processing, and converts the image data into printable image data. As conceptually shown in FIG. 2, the image processing performed by the printer driver 92 is mainly composed of four modules: a resolution conversion module 93, a color conversion module 94, a halftone module 95, and an interlace module 96. . The contents of image processing performed by each module will be described later, but the image data received by the printer driver 92 is converted by these modules and then output to the color printer 20 as final image data FNL. The color printer 20 of this embodiment only serves to form dots according to the image data FNL, and does not perform image processing. Of course, the color printer 20 performs part of image conversion. There may be.
[0049]
FIG. 3 shows a schematic configuration of the color printer 20 of the present embodiment. As shown in the figure, the color printer 20 includes a mechanism for driving a print head 41 mounted on a carriage 40 to eject ink and forming dots, and the carriage 40 is reciprocated in the axial direction of a platen 36 by a carriage motor 30. The moving mechanism, the mechanism for transporting the printing paper P by the paper feed motor 35, and the control circuit 60 are included.
[0050]
The mechanism for reciprocating the carriage 40 in the axial direction of the platen 36 is an endless drive between the carriage motor 30 and the slide shaft 33 slidably holding the carriage 40 laid in parallel to the axis of the platen 36. A pulley 32 that stretches the belt 31 and a position detection sensor 34 that detects the origin position of the carriage 40 are configured.
[0051]
The mechanism for transporting the printing paper P includes a platen 36, a paper feed motor 35 that rotates the platen 36, a paper feed auxiliary roller (not shown), and a gear train that transmits the rotation of the paper feed motor 35 to the platen 36 and the paper feed auxiliary roller. (Not shown). The printing paper P is set so as to be sandwiched between the platen 36 and the paper feed auxiliary roller, and is fed by a predetermined amount according to the rotation angle of the platen 36.
[0052]
Inside the control circuit 60 are a PC interface 64 for exchanging data with the computer 80, a peripheral device input / output unit (PIO) 65 for exchanging data with the paper feed motor 35, the carriage motor 30 and the like, and an ink ejection unit. A drive buffer 67 for supplying dot on / off signals to the heads 44 to 49, a CPU 61 for controlling these, a RAM 63 for temporarily storing data, and the like are provided. The control circuit 60 also includes an oscillator 70 that outputs a drive waveform and a distribution output device 69 that distributes the output of the oscillator 70 to the ink ejection heads 44 to 49 at a predetermined timing.
[0053]
The CPU 61 outputs a trigger signal to the oscillator 70 while outputting a drive signal to the carriage motor 30, and reads an on / off signal of dots stored in the RAM 63 while synchronizing with the trigger signal, thereby driving the drive buffer 67. Output to. In this way, ink droplets are ejected from each nozzle provided in the nozzle unit while performing main scanning of the carriage 40 under the control of the CPU 61. Further, the CPU 61 controls the movement of the paper feed motor 35 in synchronization with the movement of the carriage. Thus, ink dots are formed at appropriate positions on the printing paper.
[0054]
The carriage 40 stores ink cartridges 42 that store black (K) ink, and inks of a total of five colors: cyan (C), light cyan (LC), magenta (M), light magenta (LM), and yellow (Y). An ink cartridge 43 is mounted. Of course, K ink and LC ink / LM ink may be stored in the same ink cartridge, or K ink and Y ink may be stored in the same ink cartridge. If a plurality of inks can be stored in one cartridge, the ink cartridge can be configured compactly. Ink heads 44, 45, 46, 47, 48, and 49 are formed on the print head 41 below the carriage 40 for K, C, M, Y, LC, and LM inks, respectively. Yes. An introduction tube (not shown) is erected on the bottom of the carriage 40 for each ink. When an ink cartridge is attached to the carriage 40, each ink in the cartridge passes through the introduction tube to each of the ink ejection heads 44 to 49. Supplied. The ink supplied to each head is ejected from the print head 41 by the method described below to form dots on the printing paper.
[0055]
FIG. 4A is an explanatory diagram showing the internal structure of each color head. The ink discharge heads 44 to 49 for each color are provided with 48 nozzles Nz for each color, and each nozzle is provided with an ink passage 50 and a piezo element PE on the passage. As is well known, the piezo element PE is an element that transforms electro-mechanical energy at a very high speed because the crystal structure is distorted by application of a voltage. In this embodiment, by applying a voltage having a predetermined time width between the electrodes provided at both ends of the piezo element PE, as shown in FIG. 4B, the piezo element PE is extended by the voltage application time, One side wall of the ink passage 50 is deformed. As a result, the volume of the ink passage 50 expands and contracts according to the expansion of the piezo element PE, and the ink corresponding to the contraction is ejected from the nozzle Nz as particles Ip. The ink Ip soaks into the printing paper P mounted on the platen 36, thereby forming dots on the printing paper P. It is possible to control the size of the ejected ink droplet by controlling the voltage waveform applied to the piezo element PE. By controlling the size of the ejected ink droplets, the size of the ink dots formed on the printing paper can be controlled.
[0056]
FIG. 5 is an explanatory diagram showing the arrangement of the inkjet nozzles Nz in the ink ejection heads 44 to 49. As shown in the figure, six sets of nozzle arrays for discharging ink of each color are formed on the bottom surface of the ink discharge head, and 48 nozzles Nz per set of nozzle arrays have a constant nozzle pitch k. It is arranged in a staggered pattern. Note that the 48 nozzles Nz included in each nozzle array are not necessarily arranged in a staggered manner, and may be arranged in a straight line. However, when arranged in a staggered pattern, there is an advantage that the value of the nozzle pitch k can be reduced.
[0057]
As shown in FIG. 5, the positions of the ink discharge heads 44 to 49 for the respective colors are shifted in the transport direction of the carriage 40. Further, the nozzles for each color head are also arranged in a zigzag pattern, so the positions are shifted in the conveyance direction of the carriage 40. The control circuit 60 of the color printer 20 discharges ink droplets by driving each PE element at an appropriate timing in consideration of the difference in nozzle positions while conveying the carriage 40.
[0058]
The color printer 20 having the hardware configuration as described above drives the carriage motor 30 to move the ink ejection heads 44 to 47 of the respective colors in the main scanning direction with respect to the printing paper P, and the paper feed motor. By driving 35, the printing paper P is moved in the sub-scanning direction. Under the control of the control circuit 60, the color printer 20 prints a color image on the printing paper by driving the nozzles and ejecting ink droplets at appropriate timing while repeating the main scanning and the sub scanning of the carriage 40. ing.
[0059]
B. Overview of the printing process:
As described above, the color printer 20 has a function of printing a color image in response to the supply of the image data FNL. The image data FNL supplied to the color printer 20 is subjected to predetermined image processing by the computer 80 on the color image. Generate by. FIG. 6 is a flowchart showing an outline of a process in which the computer 80 outputs the image data FNL to the color printer 20 and prints an image. Such processing is realized by using each function of the CPU 81 in the printer driver 92 of the computer 80. The outline of the printing process will be described below with reference to FIG.
[0060]
As shown in FIG. 6, when the printing process is started, the CPU 81 first inputs image data (step S100). This image data is data supplied from the application program 91 as described with reference to FIG. 2, and 256 gradations having values of 0 to 255 are provided for each color of R, G, and B for each pixel constituting the image. Data. The resolution of the image data changes according to the resolution of the original image data ORG.
[0061]
When the input of the image data is completed, the CPU 81 converts the resolution of the image data to a resolution for printing by the color printer 20 (step S102). When the image data is lower than the printing resolution, resolution conversion is performed by generating new data between adjacent original image data by linear interpolation. Conversely, when the image data is higher than the print resolution, resolution conversion is performed by thinning out the data at a constant rate.
[0062]
Next, the CPU 81 performs color conversion processing (step S104). The color conversion process is a process for converting image data composed of R, G, and B gradation values into gradation value data for each color C, M, Y, K, LC, and LM used in the color printer 20. It is. This processing is performed using a color conversion table LUT (see FIG. 2). In the LUT, C, M, and Y for expressing the color composed of the combination of R, G, and B by the color printer 20 are used. A combination of K, LC, and LM is stored.
[0063]
When the color conversion process ends, a binarization process is performed (step S106). In this embodiment, the image data after color conversion is a 256-gradation image of 6 colors of C, M, Y, K, LC, and LM. On the other hand, the color printer 20 of the present embodiment can take only two states, ie, whether or not dots are formed. Therefore, it is necessary to convert an image having 256 gradations into an image expressed in 2 gradations that can be expressed by the color printer 20. Processing for performing such conversion is binarization processing.
[0064]
When completing the binarization process, the CPU 81 starts the interlace process (step S108). This process is a process of rearranging the image data converted into a format representing the presence or absence of dot formation by the binarization process in the order to be transferred to the color printer 20. That is, as described above, the color printer 20 drives the print head 41 while repeating the main scanning and sub-scanning of the carriage 40 to form a dot row (raster) on the printing paper P. As described with reference to FIG. 5, since the plurality of nozzles Nz are provided in the ink ejection heads 44 to 49 for each color, a plurality of rasters can be formed by one main scanning. However, the rasters are separated from each other by the nozzle pitch k. Therefore, it is necessary to perform control such that a plurality of rasters separated by the nozzle pitch k are formed in one main scan, and then the head position is slightly shifted to form a new raster between the rasters. . When such control is performed, the order in which the color printer 20 actually forms the dots is different from the order of the pixels on the image data. Therefore, the image data is rearranged in the interlace processing.
[0065]
When the interlace processing is completed, the CPU 81 outputs the image data to the color printer 20 as image data FNL that can be printed by the printer (step S110). In accordance with the image data FNL, the color printer 20 forms dots so that an image is printed on the printing paper.
[0066]
C. Contents of binarization processing:
The color printer 20 of the present embodiment can print high-quality images by using the same color inks having the same hue and different densities for the C ink and the M ink. Hereinafter, C ink and M ink are collectively referred to as dark ink, and LC ink and LM ink are collectively referred to as light ink. In order to obtain a high-quality image, the error diffusion method with excellent image quality is used for both dot formation judgments for dark and light inks, so that errors generated by the determination of dot formation can be diffused over a wide range. It is desirable. If the error diffusion range is narrowed in order to shorten the printing time, the image quality improvement effect by the error diffusion method may not be sufficiently obtained. The color printer 20 of the present embodiment performs the following binarization process in order to print an image quickly without degrading the print image quality.
[0067]
(1) First embodiment:
FIG. 7 shows a flowchart in which the color printer 20 of this embodiment performs binarization processing using the error diffusion method. In the color printer 20 of this embodiment, the RGB gradation data is converted into 256 gradation data for each color of C, M, Y, K, LC, and LM in the color conversion process (step S104 in FIG. 6). Binary processing is performed for each color on the converted image data. In order to avoid complication of the explanation, the following explanation will be made without specifying a color unless necessary. When the binarization process is started, the CPU 81 reads image data Cd (step S200). This image data Cd is image data for each color having 256 gradations after color conversion.
[0068]
The CPU 81 generates correction data Cdx from the read image data Cd (step S202). As described above, the error diffusion process distributes the error (binarization error) generated by determining the presence or absence of dot formation by distributing the unprocessed pixels around the pixel with a predetermined weight. Judgment of dot formation for unprocessed pixels is made in consideration of binarization errors. Therefore, in step S202, the correction data Cdx is calculated by adding the error (ER) distributed from the peripheral processed pixels to the pixel (target pixel) for which dot formation is to be determined.
[0069]
FIG. 8 is an explanatory diagram showing how much the binarization error generated in the pixel of interest PP is distributed to which pixels in the periphery with what weight. A binarization error is distributed with a predetermined weight to the pixel of interest PP with respect to several pixels in the scanning direction of the carriage 40 and several adjacent pixels on the rear side in the conveyance direction of the paper P. As shown in FIG. 8, a table representing a ratio of binarization error distribution to surrounding pixels is referred to as an error diffusion table. As shown in FIG. 8, the color printer 20 of this embodiment is provided with two error diffusion tables of different sizes, and when performing dot formation determination of dark ink or Y ink, FIG. When the dot formation determination of other ink (light ink or K ink) is performed using the small error diffusion table shown in FIG. 8, the large error diffusion table shown in FIG. 8B is used. The error diffusion process will be described later. In step S202, the error diffused from the peripheral pixels is read according to the error diffusion table, and correction data Cdx is obtained in addition to the image data Cd of the pixel of interest.
[0070]
The CPU 81 compares the obtained correction data Cdx with a predetermined threshold th (step S204). If the correction data Cdx is larger than the threshold th, a dot is formed on the value Cdr representing the binarization result. Is substituted with a value “1” (step S206). Conversely, if the data Cdx is smaller than the threshold th, a value “0” indicating that no dot is formed is substituted for the value Cdr representing the binarization result (step S208). The threshold th is a value serving as a reference for determining whether or not to form dots in this way.
[0071]
Next, the CPU 81 calculates a binarization error caused by determining whether or not dots are formed (step S210). The binarization error is a value obtained by subtracting the gradation value expressed by the presence or absence of dot formation from the gradation value of the image data Cd. For example, it is assumed that the gradation value 255 is expressed when a dot is formed, and the gradation value of the image data Cd is 64. If a dot is formed in the pixel, the gradation value 255 is expressed where the gradation value 64 should be expressed, and therefore an error of 64-255 = −191 is generated. . Conversely, if no dot is formed in the pixel, an error of 64-0 = 64 occurs.
[0072]
When the binarization error is thus obtained, the type of ink being processed is determined (step S212). As described above, in the binarization process of the first embodiment, the error diffusion table used for dark ink or Y ink dot formation determination and the error diffusion table used for light ink or K ink are different from each other. Since the table is used, the type of ink being processed is determined prior to the subsequent error diffusion process.
[0073]
If the ink being processed is dark ink or Y ink, the small table shown in FIG. 8A is selected, and the binarization error is distributed to surrounding pixels according to the selected table (step S214). For example, if a binarization error of gradation value 32 occurs in the target pixel PP, an error of gradation value 8 is distributed to the adjacent pixel P1, and an error of gradation value 4 is distributed to the adjacent pixel P2. Is distributed.
[0074]
If the ink being processed is light ink or K ink, the wide table shown in FIG. 8B is selected to diffuse the binarization error. For example, if an error of gradation value 32 occurs in the pixel of interest PP, the darkness of gradation value 5 is distributed to the adjacent pixel P1, and the error of gradation value 4 is distributed to the adjacent pixel. The
[0075]
As described above, in the error diffusion process, the binarization error generated by the dot formation determination at the target pixel is distributed to a plurality of peripheral pixels. If this is seen from the opposite side, an error diffused from a plurality of pixels that have already been determined to form dots is accumulated in the target pixel. The error (ER) added to the image data Cd in step S202 described above is an error that is diffused from the surrounding pixels and accumulated in the target pixel.
[0076]
When the error diffusion process ends, the CPU 81 determines whether or not the binarization process has been performed for all the pixels (step S218). If there are any unprocessed pixels remaining, the process returns to step S200 to perform a series of subsequent processes. If no unprocessed pixels remain, it is determined that the binarization process has been completed for all pixels, and the binarization process is exited and the process returns to the print processing routine shown in FIG. After returning to the print processing routine, interlace processing is performed, and image data FNL that can be printed by the printer is output to the color printer 20.
[0077]
As described above, in the binarization process in the first embodiment, a small error diffusion table is used for dark ink or Y ink, and a large error diffusion table is used for light ink or K ink. If the error diffusion table to be used is small, the error distribution range becomes small, so the dispersibility of the dots may deteriorate and the image quality may deteriorate, but dark ink formed while light ink is formed above a certain level Alternatively, the Y ink dots do not deteriorate the image quality even if the dispersibility is somewhat inferior to other inks. Therefore, as in the first embodiment, if the error diffusion table used for binarization processing of dark ink or Y ink is made smaller than the error diffusion table used for binarization processing of other inks, By using a small table, the binarization process is accelerated, so that it is possible to print quickly, while avoiding a decrease in print image quality.
[0078]
In the above description, it is assumed that a small error diffusion table is used for all of C ink, M ink, and Y ink. However, it goes without saying that a small error diffusion table may be used for only some of these inks.
[0079]
In the above description, the size of dots that can be formed is substantially constant. However, printers capable of forming dots of different sizes called so-called variable dot printers are also widely used. In such a variable dot printer, the above description can be similarly applied to the case where each dot is formed or not using the error diffusion method. That is, a larger error diffusion table may be used when determining whether or not small dots are formed, and a smaller error diffusion table may be used when determining whether or not large dots are formed. By doing so, the binarization process is speeded up, and thus it is possible to print quickly, while avoiding a decrease in print image quality.
[0080]
(2) Second embodiment:
In the binarization processing by the error diffusion method, a technique has been proposed in which a plurality of types of error diffusion tables are provided and the error diffusion table is selected and used according to the gradation value of the image data (for example, Japanese Patent Application Laid-Open No. Hei 7). -226411 etc.). By using such a technique, it is possible to improve the printing speed and the image quality by properly using an appropriate error diffusion table according to the dot formation state. For example, when the dot recording rate is low, the average distance between the dots becomes large, so the dots must be formed as far as possible, so a wide error diffusion table is used. When the dot recording rate is high, the average distance between the dots is small, so that a small error diffusion table can be used. Therefore, in such a case, by switching to a small error diffusion table, it is possible to shorten the image processing time and print the image quickly. In addition, when the dots are formed with a high density, if the error is distributed over a wide range, the image quality may deteriorate due to the accumulation of errors. Even in such a case, deterioration of image quality can be avoided by switching to a small error diffusion table.
[0081]
In this way, the present invention can be extended and applied to a technique for switching and using a plurality of error diffusion tables. The second embodiment described below is an aspect applied when a plurality of error diffusion tables are switched and used.
[0082]
FIG. 9 shows a flowchart in which the color printer 20 of this embodiment performs binarization processing while switching between a plurality of error diffusion tables. The binarization process shown in FIG. 9 is also performed for each color in the same way as the binarization process of the first embodiment described above. However, in order to avoid complication of explanation, in the following, colors other than those necessary are used. It explains without specifying.
[0083]
In the binarization process of the second embodiment, as in the first binarization process, the CPU 81 first reads the image data Cd when the process is started (step S300), and the error diffused from the surrounding pixels is detected. In addition, correction data Cdx is generated (step S302).
[0084]
Next, the CPU 81 compares the correction data Cdx with a predetermined threshold th to determine whether or not dots are formed (step S304). If the correction data Cdx is larger than the threshold th, it is determined that a dot is to be formed (step S306). If the correction data Cdx is smaller than the threshold th, it is determined that no dot is to be formed (step S308). Thereafter, a binarization error due to the determination of dot formation is calculated (step S310).
[0085]
In the error diffusion method, the error thus obtained is diffused to surrounding pixels, and an error diffusion table to be used is selected before that. In this embodiment, error diffusion tables of three sizes of large, medium and small are prepared. Similarly to the first embodiment, the error diffusion table used is slightly different between the dark ink or Y ink dots and the light ink or K ink dots. Therefore, first, the size of the error diffusion table is selected (step S312). As described above, when the dot recording rate is small, the dots need to be formed apart from each other, so a large error diffusion table is selected. Conversely, when the dot recording rate is a large value, a small size error diffusion table is selected. In step S312, the size of the error diffusion table to be used is selected from three sizes, large, medium and small, according to the dot recording rate.
[0086]
If the size of the error diffusion table is selected, the type of ink is then determined (step S314). That is, the dark ink or Y ink dots do not deteriorate the image quality even if the dot dispersibility is somewhat worse than the light ink or K ink dots. It is used properly.
[0087]
FIG. 10 illustrates an error diffusion table used in the binarization process of the second embodiment. FIG. 10A shows an error diffusion table of size “small”, FIG. 10B shows an error diffusion table of size “medium”, and FIG. 10C shows an error diffusion table of size “large”. Yes.
[0088]
FIG. 11 shows a state where these error diffusion tables are selectively used depending on the type of ink. For the light ink and the K ink, the table shown in FIG. 10A is used when the size “small” is selected in the process of step S312. Similarly, when the size “medium” or the size “large” is selected in the processing of step S312, the table shown in FIG. 10B or FIG. 10C is used, respectively.
[0089]
For the dark ink and Y ink, when the size “small” is selected in the process of step S312, the error diffusion table of FIG. 10A is used, and either the size “medium” or “large” is used. Is selected, the error diffusion table of FIG. 10B is used. That is, for the dark ink or Y ink dots formed while the light ink is formed above a certain level, the image quality does not deteriorate even if the dispersibility of the dots is somewhat deteriorated, so the size “large” is selected. In this case, the smaller table in FIG. 10B is used instead of the error diffusion table in FIG.
[0090]
In the error diffusion process of step S316 or step S318 of FIG. 9, the binarization error is distributed to the peripheral pixels according to the error diffusion table selected as described above. Thereafter, the CPU 81 determines whether or not the binarization processing has been performed for all the pixels (step S320). If there are any unprocessed pixels, the CPU 81 returns to step S300 to perform a series of subsequent processing. If no unprocessed pixels remain, it is determined that the binarization process has been completed for all pixels, and the binarization process is exited and the process returns to the print processing routine shown in FIG.
[0091]
As described above, in the binarization processing of the second embodiment, since the widest error diffusion table is not used for dark ink or Y ink dots, the time required for image processing is shortened, and the image is printed quickly. It becomes possible to do. On the other hand, the print image quality of these dots does not deteriorate even if the dot dispersibility is somewhat deteriorated.
[0092]
In the above description, as shown in FIG. 11, the error diffusion table for the dot size “small” of the dark ink (and Y ink) is shared with the table for the size “small” of the light ink. The table for the ink size “medium” and the size “large” is shared with the table for the light ink size “medium”. Thus, if the error diffusion table is shared, the memory capacity for storing the error diffusion table can be saved.
[0093]
However, the type of error diffusion table for dark ink does not need to be smaller than the type of table for light ink. For example, a dedicated table smaller than the error diffusion table for the light ink size “large” may be used as the error diffusion table for the dark ink size “large”. In this way, if the dedicated table is used, the degree of freedom of setting is improved, so that the room for improving the image quality is expanded accordingly.
[0094]
Of course, the error diffusion table for the size “small” and the size “medium” of the dark ink may be a dedicated table. Furthermore, the types of error diffusion tables for dark ink may be increased from those for light ink. Even in this case, if the error diffusion table having the largest size for dark ink is made smaller than the widest error diffusion table for light ink, the entire binarization process can be performed while avoiding deterioration in image quality. It is possible to shorten the processing time and print the image quickly.
[0095]
Although various embodiments have been described above, the present invention is not limited to all the embodiments described above, and can be implemented in various modes without departing from the scope of the invention.
[0096]
For example, in the above description, when the binarization error is diffused, the error diffusion table is used and diffused to the peripheral pixels. However, the error diffusion table is not necessarily used. That is, for example, a function that stores in advance a function that determines an error distribution ratio according to the distance between a pixel in which a binarization error has occurred and a peripheral pixel, and diffuses the error according to this function may be used. good.
[0097]
A software program (application program) that realizes the above-described functions may be supplied to a main memory or an external storage device of a computer system via a communication line and executed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a printing apparatus according to an embodiment.
FIG. 2 is an explanatory diagram showing a configuration of software.
FIG. 3 is a schematic configuration diagram of a printer according to the present exemplary embodiment.
FIG. 4 is an explanatory diagram illustrating the principle of dot formation in the printer of this embodiment.
FIG. 5 is an explanatory diagram illustrating a state in which nozzles are arranged in the ink ejection head of the printer according to the present exemplary embodiment.
FIG. 6 is a flowchart illustrating a flow of a print processing routine in the present embodiment.
FIG. 7 is a flowchart showing a flow of binarization processing according to the first embodiment.
FIG. 8 is an explanatory diagram illustrating an error diffusion table used in the first embodiment.
FIG. 9 is a flowchart illustrating a flow of binarization processing according to the second embodiment.
FIG. 10 is an explanatory diagram illustrating an error diffusion table used in the second embodiment.
FIG. 11 is an explanatory diagram illustrating a state in which an error diffusion table is switched and used for each ink type in the second embodiment.
FIG. 12 is an explanatory diagram conceptually showing a relationship between image data and a dot recording rate.
FIG. 13 is an explanatory diagram showing a state in which image quality deteriorates when dot dispersibility deteriorates when the dot recording rate of light ink is low.
FIG. 14 is an explanatory diagram for explaining the reason why the image quality is unlikely to deteriorate even when the dot dispersibility deteriorates when the dot recording rate of dark ink is low.
[Explanation of symbols]
20 Color printer
21 ... Color scanner
24 ... modem
26: Hard disk
30 ... Carriage motor
31 ... Driving belt
32 ... Pulley
33 ... Sliding shaft
34. Position detection sensor
35 ... Paper feed motor
36 ... Platen
40 ... carriage
41 ... Print head
42. Ink cartridge
43. Ink cartridge
44-49 ... Ink ejection head
50 ... Ink passage
60 ... Control circuit
61 ... CPU
63 ... RAM
64 ... PC interface
67 ... Drive buffer
69 ... Distribution output device
70: Oscillator
80 ... Computer
81 ... CPU
82 ... ROM
83 ... RAM
88 ... SIO
90 ... Video driver
91 ... Application program
92 ... Printer driver
93 ... Resolution conversion module
94 ... Color conversion module
95 ... Halftone module
96 ... Interlace module

Claims (7)

By applying predetermined image processing to multi-tone image data, the image data is converted into an expression format in which a plurality of types of dots having different densities per unit area are mixed, and the image is converted using the plurality of types of dots. A printing device for printing,
Dot formation determination means for determining whether or not each of the plurality of types of dots is formed for each pixel based on the image data;
An error diffusing unit that distributes the error generated by the determination of the presence / absence of the dot to a plurality of peripheral pixels by a predetermined method and reflects it in the determination of the presence / absence of the formation of the plurality of types of dots;
Dot forming means for forming the dots on a print medium based on the determination result of whether or not the plurality of types of dots are formed;
An error diffusion table storing a plurality of types of error diffusion tables storing a ratio of distributing an error generated by the determination of the presence or absence of dot formation to a plurality of peripheral pixels; and
The error diffusion means is
The error for high density dots per unit area is a means for distributing to fewer pixels than the error for low density dots, and the first error diffusion table is selected from the stored error diffusion tables. A first error diffusion unit that selects and diffuses the error of the high density dots per unit area using the first error diffusion table;
A second error diffusion table wider than the first error diffusion table is selected from the stored error diffusion tables, and dots having a low density per unit area are selected using the second error diffusion table. A second error diffusion means for diffusing the error of
Each of the first and second error diffusion means selects a plurality of types of error diffusion tables, and diffuses the error to each while switching the selected error diffusion tables by a predetermined method. The error diffusion table having the widest diffusion range used by the error diffusion means is a table having a narrower error diffusion range than the error diffusion table having the widest diffusion range used by the second error diffusion means. The printing apparatus according to claim 1 ,
The printing apparatus, wherein the first error diffusion means uses a smaller number of types of the error diffusion table than the second error diffusion means. The printing apparatus according to claim 1,
The dot forming means is a printing apparatus that forms dots having different densities per unit area by discharging ink having different densities onto a print medium. The printing apparatus according to claim 1,
The dot forming means is a printing apparatus that forms dots having different densities per unit area by forming dots having different sizes on a print medium. By performing predetermined image processing on the color image data, the image is displayed in an expression format in which dots of at least three primary colors of cyan, magenta, and yellow and light cyan and light magenta that are lighter than cyan and magenta are mixed. A printing apparatus for printing a color image by converting data and forming dots of each color,
Dot formation determination means for determining the presence or absence of formation for each color dot for each pixel based on the image data;
An error diffusing unit that distributes the error generated by the determination of the presence or absence of the dot to a plurality of peripheral pixels by a predetermined method and reflects it in the determination of the presence or absence of the formation of each color dot;
A dot forming means for forming the dots of the respective colors on a print medium based on the determination result of the formation of the respective color dots,
The error diffusing unit is a unit that distributes an error for the yellow dot having the highest lightness among the three primary colors and the pixels for cyan and magenta to pixels having fewer errors than those for the other color dots. By performing predetermined image processing on the color image data, the image is displayed in an expression format in which dots of at least three primary colors of cyan, magenta, and yellow and light cyan and light magenta that are lighter than cyan and magenta are mixed. A printing method for printing a color image by converting data and forming dots of each color,
The presence or absence of formation for each color dot is determined for each pixel based on the image data,
The error generated by determining whether or not the yellow dot having the highest lightness among the three primary colors and the cyan and magenta dots are formed is distributed to a plurality of peripheral pixels by a predetermined method. Distributing the pixels to more pixels than the highest color dot error, and reflecting each distributed error in the determination of the presence or absence of each color dot,
A printing method for forming dots of each color on a print medium based on a determination result of whether or not each color dot is reflected, which reflects the error. By performing predetermined image processing on the color image data, the image is displayed in an expression format in which dots of at least three primary colors of cyan, magenta, and yellow and light cyan and light magenta that are lighter than cyan and magenta are mixed. A recording medium on which a program for realizing a method of printing a color image by converting data and forming dots of each color is recorded in a computer-readable manner,
A function of determining the presence or absence of formation for each color dot for each pixel based on the image data;
The error generated by determining whether or not the yellow dot having the highest brightness in the three primary colors and the cyan and magenta dots are formed is distributed to a plurality of peripheral pixels by a predetermined method. A function of distributing to the pixels more than the error of the color dot with the highest brightness and reflecting the distributed error in the determination of the presence or absence of the color dots;
A recording medium on which a program that realizes a function of controlling the formation of dots of each color based on the determination result of the formation of the dots of each color that reflects the error is recorded.

Images