JPH1086503A - Color image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image processor for ink jet recording using a black ink quickly permeating a paper and color inks slowing permeating a paper in which blotting is prevented in units of pixel. SOLUTION: Among pixels (K) to be printed in black, those containing a pixel (Y) to be printed in yellow within four pixels are recognized as belonging to the pixel group in an edge region 4 and replaced by color printing at first period. pixel group continuous thereto is recognized as belonging to the pixel group in an adjacent edge region 3 and replaced by color printing at second period. The ration of the pixel (CM) to be color printed with a mixed color of cyan and magenta is decreased as the distance between a pixel (y) to be printed in yellow and the region of pixel group to which a pixel belong increases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for a color printer using a black ink which penetrates slowly into paper and a color ink which penetrates quickly into paper, and more particularly to a good image having little bleeding between colors on plain paper. The present invention relates to an image processing apparatus capable of obtaining the following.

[0002]

2. Description of the Related Art A color ink jet recording apparatus for recording an image by ejecting a liquid ink droplet from a nozzle is a recording apparatus having a simple structure and low printing sound, and is a technique suitable for a small printer. However, since water-based ink is used, plain paper such as copy paper or report paper, which is not provided with an ink absorbing layer, has a drawback of causing color mixture bleeding at the boundary between colors. For this reason, by adding a surfactant or the like to the ink to increase the permeability to the paper, it is possible to suppress bleeding due to color mixing of the ink at the boundary between colors.

[0003] However, there is a problem that the density of the printed portion is reduced by increasing the permeability to paper, and the edges of lines and characters are not sharp. This is because the permeability of the ink to the paper increases and is absorbed quickly,
This is because the amount of the coloring agent remaining on the surface of the paper decreases, and the ink easily spreads along the fibers of the paper. For this reason, in particular, only black ink, which needs to reproduce lines and characters sharply and at high density, does not increase the permeability to paper, and color inks that also need to reproduce secondary colors A method of preventing color mixing and bleeding of ink has been attempted, assuming that only ink has improved permeability to paper. However, if you do this,
After all, it is not possible to prevent color mixture bleeding in the adjacent portion between the black print portion and the color print portion.

In order to solve this problem, a color ink jet recording apparatus using a black ink which penetrates slowly into paper and a color ink which penetrates paper rapidly has a selecting means for selecting a color document, and a color document print mode. Is selected, a portion to be printed with black ink droplets is replaced with a printing of a mixture of cyan, magenta, and yellow ink droplets at a predetermined ratio, and a color image processing device that prevents bleeding, or A color image processing apparatus has been devised in which black is added to this, and printing is performed by mixing ink drops of black, cyan, magenta, and yellow to prevent bleeding.

However, in these devices, once the color document print mode is selected, the black print portion is
In all areas, printing with a mixture of color inks or printing with a mixture of color and black is replaced at a predetermined rate. There is a problem of getting fat.

In order to reduce this problem, for example, as described in JP-A-6-136310 with reference to FIGS. 7 and 8, it is determined whether a black print portion is adjacent to a color print portion. There is an apparatus that analyzes the above by some means and performs the above-described bleeding prevention processing only on the black print portion adjacent to the color print portion. In this case, the image quality of the black printed portion not adjacent to the color printed portion can be improved, but the black printed portion adjacent to the color printed portion still has a problem.

Japanese Patent Application Laid-Open Nos. Hei 5-276373 and Hei 6-113155 disclose a method of detecting an adjacent state such as a distance between a black print portion and a color print portion and performing bleeding prevention processing in response thereto. Although known in the gazette and the like, the method of the bleeding prevention processing is different.

In addition, for example, as described with reference to FIGS. 12 to 17 in JP-A-6-206370, a color image / pixel adjacent to a black image to be focused on is detected by some means. Sometimes, a device is known that replaces a black image within a distance of 2 × 2 pixels vertically and horizontally around a color pixel with an extended pixel. Expansion pixels are 4
Of the dots, three dots are replaced by a mixture of color ink droplets (a mixture of cyan, magenta, and yellow and a mixture of yellow and cyan). In this case, the above-described problem is reduced in the black print portion as compared with the case where only black ink droplets are used.

Further, if a similar idea is used without introducing the concept of the extended pixel, only the region having the color pixel within a predetermined vertical and horizontal pixel distance centering on the black pixel can be obtained.
An apparatus that performs printing by replacing a part of a portion to be printed with black ink droplets with a mixture of color ink droplets or a mixture of black ink droplets and black ink droplets is considered. Also in this case, the above-described problem is reduced in the black print portion compared to the case where only black ink droplets are used.

However, in any case, there is a problem that a portion having a low density is generated between the black print region to which the above-described conversion processing is applied and the black print region to which the above conversion process is not applied, and the image looks like a pseudo contour. The cause will be described with reference to FIG.

FIG. 25 shows a case where a color image processing apparatus for preventing bleeding by replacing a part of black pixels in an edge area with a mixture of color inks is used. It is explanatory drawing of an image. The case where the color is yellow is exemplified. FIG.
FIG. 25A is an explanatory diagram illustrating print color information of a pixel near a boundary, and FIG. 25B is a cross-sectional view of paper illustrating the degree of ink penetration into plain paper. In the figure, 1 is plain paper, 2
Is the part printed with color ink with high permeability to paper,
4 is an edge region, 151 is a portion printed with black ink having low permeability to paper, and 152 is a portion from which the ink has flowed out.

In the edge region 4 adjacent to the portion 151 printed with black ink having low permeability to paper and the portion 2 printed with color ink having high permeability to paper, printing should be originally performed in black. A part of the pixel (K) is replaced with a pixel (CM) that is printed with a color ink of cyan and magenta, and a pixel (K) that is printed with black ink and a pixel that is printed with a mixed color of cyan and magenta ink. (CM) and 1
Printing is performed by combining them alternately in a checkered pattern at a ratio of one to one. Therefore, the ink penetrates the plain paper 1 relatively quickly,
It does not seep into the yellow part.

On the other hand, the portion printed with black ink and excluding the edge region 4 is the portion 151 printed with black ink having low permeability to paper, so that the print density is high. However, since the ink easily penetrates into the edge region 4, a phenomenon occurs in which the ink flows toward the edge region 4 at a portion in contact with the edge region 4. Therefore, the portion 152 where the ink has flowed out
The image density of the image is reduced, and the image looks like a pseudo contour.

As described above with reference to FIG. 18 of Japanese Patent Application Laid-Open No. 6-206370, when an extended pixel is used, the black ink in the extended pixel becomes farther away from the color ink pixel. It is known to increase the proportion. However, when performing replacement in units of 2 × 2 extended pixels on two dimensions, pixels to be printed in black to be subjected to bleeding processing often cannot be divided into regular 2 × 2 extended pixels.

For example, when the area of the pixel to be printed in black is smaller than the extended pixel, such as when the pixel (K) to be printed in black to be blurred is a single pixel, it is treated as one extended pixel. The bleeding process results in a reduction in black resolution. Further, even if the width of the region to be blurred is determined to be two extended pixels (for four pixels) from the boundary between the pixels to be printed in color, the pixels to be printed in color (C, M, Y) The boundary with the pixel (K) to be printed in black is 1
Since the bleeding process is performed on a pixel-by-pixel basis, performing the bleeding process on an extended pixel basis not only lowers the resolution of black, but also changes the width of the bleeding process. As described above, in the above-described conventional example, there is a problem that the resolution of black is lowered and the blurring process is varied.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in consideration of the above circumstances, and has been developed for color image processing for ink jet recording using black ink which has low penetration into paper and color ink which has high penetration into paper. It is an object of the present invention to provide a color image processing apparatus capable of preventing bleeding on a pixel-by-pixel basis.

[0017]

According to the first aspect of the present invention, there is provided a color image processing apparatus for ink jet recording using a black ink having a low penetration into paper and a color ink having a fast penetration into paper. A pixel to be printed is input, and an area dividing unit that divides the pixel to be printed in black into a plurality of pixel groups based on a distance to a pixel to be printed in color, and prints in the color among the plurality of pixel groups. A predetermined conversion rule is applied to pixels belonging to at least two pixel groups, which are a pixel group in a region where the distance to the pixel is the shortest and a pixel group in a region where the distance to the pixel to be printed in the color next to the region is the shortest. Pixel conversion means for replacing the print information based on the above, the conversion rule is to replace the print color information from black to color with a predetermined periodicity for the pixels to be printed in black Ri, for each of the pixel groups a pixel conversion is performed, and is characterized in that the ratio of pixels to replace the more distant the distance to the pixel to be printed by the color is determined so as to become smaller.

According to a second aspect of the present invention, in the color image processing apparatus according to the first aspect, the area dividing means includes at least one pixel at a predetermined relative distance from the pixel to be printed in black. The image processing apparatus further includes means for determining whether or not there is a pixel to be printed in the color in a set of reference pixels.

According to a third aspect of the present invention, in the color image processing apparatus according to the second aspect, the set of reference pixels is at least one of pixels within a predetermined relative distance from the pixels to be printed in black. It does not include one.

According to a fourth aspect of the present invention, in the color image processing apparatus according to any one of the first to third aspects, the conversion rule is that the print information is changed from black to a single color or a color obtained by mixing two colors. It is characterized by being a replacement.

According to a fifth aspect of the present invention, in the color image processing apparatus according to any one of the first to fourth aspects, the conversion rule is determined based on an absolute position of a pixel to be printed in black. It is characterized by having been done.

According to a sixth aspect of the present invention, in the color image processing apparatus, a reference pixel including at least one pixel that is printed in black and that is at a predetermined relative distance from the pixel printed in black. A pixel having a pixel to be printed in color in a set is defined as a pixel to be processed, and a pixel to be processed is added directly to the pixel to be processed or via a pixel to be printed in black and an adjacent pixel is added to the pixel to be processed. Having means,
The pixel to be printed in black, which has been determined as the pixel to be processed by the pixel to be processed extraction means, is selected from the group consisting of:
And outputting to the color image processing apparatus described in the item.

[0023]

FIG. 1 is an explanatory diagram of an image near a boundary between a black ink printing portion and a color ink printing portion when a first embodiment of a color image processing apparatus according to the present invention is used. . The case where the color ink is yellow is exemplified. FIG. 1A is an explanatory diagram showing print color information of a pixel near a boundary, and FIG. 2B is a cross-sectional view of paper showing the degree of ink penetration into plain paper. In the figure, the same parts as those in FIG. 3 is an adjacent edge area.

This embodiment, as exemplified in FIG. 1A, is a color image processing apparatus for ink-jet recording using black ink which has low penetration into paper and color ink which has high penetration into paper. Then, among the pixels (K) to be printed in black, those having pixels (Y) to be printed in yellow within four pixels are defined as pixels belonging to the pixel group of the edge region 4 adjacent to the pixels to be printed in color. Recognize and replace with color printing with a predetermined first periodicity, and recognize the pixel group connected to this pixel group as a pixel belonging to the pixel group of the adjacent edge area 3, and this pixel group is determined in advance. The second periodicity is replaced with color printing.

In the edge area 4, similarly to the edge area in FIG. 25, using the first pixel conversion rule, a pixel (K) to be printed in black is placed every other pixel in the horizontal and vertical directions and cyan and Pixels (CM) to be printed in a mixed color of magenta ink are used. In contrast,
Pixels (K) to be printed in black in the adjacent edge area 3
Using the second pixel conversion rule, for a pixel at a position where one column intersects two in the horizontal and vertical directions,
Pixels (CM) to be printed in a color based on a mixture of cyan and magenta inks are used.

The ratio between the pixel (K) printed in black and the pixel (CM) printed in a mixed color of cyan and magenta inks is 1: 1 in the edge area 4, In the adjacent edge region 3, the ratio is 3: 1. Therefore, the ratio of the pixels (CM) to be printed in the color by the mixed color of the cyan and magenta inks is lower for the pixels belonging to the pixel group in the region where the distance from the pixel (Y) to be printed in yellow is larger.

As shown in FIG. 1B, according to this embodiment, the edge region 4 is adjacent to the color ink portion 2 having high permeability to the plain paper 1 and the color contrast is high. large. Therefore, even if the black ink flows into the color portion even a little, the image quality is greatly deteriorated. For this reason, a relatively large percentage of pixels (K) to be printed with black ink, which slowly penetrates the paper, are replaced with pixels (CM) to be printed with color ink, which penetrates the plain paper 1 quickly.

On the other hand, in the adjacent edge area 3, comparison is made between replacement of pixels (K) printed with black ink, which penetrates slowly into paper, with pixels (CM) printed with color ink, which penetrates paper quickly. It may be performed at a very low rate. Therefore, a small amount of the color ink, which permeates the paper in a small amount, is printed in a mixed color also in the adjacent edge area 3, so that the permeability to the plain paper 1 is improved, and the flow to the edge area 4 is reduced. As a result, the problem that the image density of the portion where the ink has flowed out decreases and the image looks like a pseudo contour is suppressed. As a result, it is possible to minimize a decrease in density and a change in tint in a black print portion.

Returning again to FIG. 1A, the edge region 4
An outline of rules for recognition and replacement of the adjacent edge region 3 will be described. For each pixel (K) to be printed in black, the range between the pixel (K) to be printed in black and the pixel (Y) to be printed in yellow is determined, and the replacement process is also printed in black. This process is performed for each pixel (K). Therefore, since the bleeding prevention processing is performed on a pixel-by-pixel basis, the resolution of black is not reduced and the width of the bleeding processing is not changed unlike the related art having the above-described extended pixels.

The rule of replacement is to determine whether or not the pixel (K) to be printed in black, which is the object of the conversion process, should be replaced according to the relative distance from the pixel (Y) to be printed in yellow. it can. However, when the boundary with the pixel to be printed in color is close and exists in two or more directions, the evaluation of the relative distance becomes complicated. Therefore, conversion processing is performed using the first and second pixel conversion rules based on the absolute position of the pixel to be converted. That is,
In accordance with the coordinate position in the entire image, it is determined whether replacement is to be performed or pixels to be printed in black remain.

When the first and second pixel conversion rules based on the absolute position of a pixel are used, uniform pixel conversion according to the position of the pixel on the image is performed. Is suitable for an image in which is expressed in color. Therefore, a print mode for a document having such a color figure may be provided, and the image processing apparatus of the present invention may be operated in this mode.

For pixels to be printed with color ink by replacing pixels (K) to be printed in black, color inks of cyan, magenta, and yellow are used, or a mixture of two ink droplets is used. . Note that a mixture of three color ink droplets may be used as in the related art having the above-described extended pixels. However, although the quality of black is slightly reduced as compared with the case of mixing three colors, the total amount of ink droplets is reduced to 1/3 or 2/3. Problems such as generation of wrinkles are reduced.

FIG. 2 is a schematic configuration diagram for realizing the color image processing apparatus of the present invention. In addition, the positioning in the entire image processing apparatus is also shown. FIG. 3 is an explanatory diagram showing a pixel serving as a unit for storing print color information of a binarized image. 2 and 3 are also used for description in a second embodiment described later. In FIG. 2, 11 is a color correction unit, 12 is a binarization unit, 13 is a blur prevention processing unit, 1
4 is a pixel to be processed extraction unit, 15 is an area division unit, 16 is a conversion processing unit, 17 is a recording data storage unit, 18 is a recording control unit,
Reference numeral 19 denotes an inkjet head driving unit, and reference numeral 20 denotes an inkjet head.

The input image is input to a color correction unit 11, where the image is subjected to processes such as gamma correction, color conversion from RGB data to CMYK data, color adjustment by a user, and the like, and is output to a binarization unit 12. The color conversion process from RGB data to CMYK data may be a process of performing color conversion from RGB data to CMY data and then performing black (K) data generation, removal of under color (UCR, under color removal), and the like. Alternatively, color conversion from RGB data directly to CMYK data may be performed using a look-up table and an interpolation circuit.

As shown in FIG. 3, the image data that has been binarized by the binarization section 12 is an image composed of NI pixels in the horizontal direction and NJ pixels in the vertical direction. for _ij, cyan, magenta, yellow, oN for the black, OFF information _{K ij, C ij, M ij} , contains Y _ij. For each pixel, ON may be expressed as 1 and OFF may be expressed as 0 for each color, or ON or OFF for 8 or 16 pixels arranged horizontally for each color.
In some cases, information is represented in correspondence with each bit of a binary number.

The binary images of the four colors cyan, magenta, yellow, and black that have been binarized in this way are input to the bleeding prevention processing unit 13 and converted into images in which bleeding is prevented. In the bleed prevention processing unit 13, the binary image is input to the pixel-to-be-processed extraction unit 14, and is within a predetermined distance from a pixel that needs to be subjected to the bleed prevention processing, that is, a pixel printed in color. Pixels (K) to be printed in black are extracted.

In the first embodiment, a pixel to be printed in black is used as a pixel of interest, and a reference pixel within a predetermined relative distance includes pixels (C, M, Y) to be printed in color. Pixels that need to be processed and pixels that need to be subjected to bleed processing are added to the pixels that need to be processed by adding pixels adjacent to the pixels that need to be processed directly or via a pixel (K) that is printed in black. Extract.

As for the pixels to be processed, the pixels (C, M,
Based on the distance to Y), the edge region 4 shown in FIG.
And a pixel group of the adjacent edge region 3. In this way, recognition is performed for each pixel to determine what kind of blur prevention processing is to be performed on the pixel.

The conversion processing section 16 performs a conversion process on the pixels belonging to the divided pixel group based on a predetermined conversion rule determined for each pixel group. This conversion rule replaces the pixels printed in black with printing color information with a predetermined periodicity in color, and for each pixel group subjected to pixel conversion, the pixels that are replaced as the distance to the pixel printed in color increases. Is set to be small.

The recording data storage unit 17 performs the bleeding prevention processing 1
3 is stored. The recording control unit 18 reads image data from the recording data storage unit 17 and controls the inkjet head driving unit 19 and the like. The ink-jet head drive unit 19 follows the image data read from the print data storage unit 17,
A drive signal is sent to the inkjet head 20. The inkjet head 20 ejects ink of each color corresponding to the dots driven by the inkjet head drive unit 19, and actually performs recording on the recording medium.

The functions of the above-described units may be realized by hardware such as a digital circuit.
It may be realized by software using U. You may use both together as needed. In the bleeding prevention processing 13, image processing other than bleeding prevention may be performed simultaneously. Further, the pixel-to-be-processed extraction unit 14 may be configured to process all the pixels (K) to be printed in black as in a second embodiment described later.

In the description with reference to FIGS. 1 to 3, the first
The outline of the embodiment has been described. Hereinafter, the bleeding prevention processing will be described in more detail with reference to the flowcharts shown in FIGS.

FIGS. 4 to 6 are first to third flow charts for explaining a process for converting a binary image into an image on which bleeding has been prevented in the first embodiment of the present invention. . The flowchart illustrated in FIG. 4 corresponds to the initialization processing in the processing-required pixel extraction unit 14 illustrated in FIG. A bleed prevention code B _{ij is used} to determine whether to perform bleed prevention processing.
To secure and initialize a memory area for storing for each pixel.

In S31, j = 0 indicates the 0th vertical direction. In S32, i = 0 indicates the 0th horizontal direction.
j for the pixel indicated by j.
Set j to 0. In S34, the value of i is advanced by 1, and in S35, if the value of i is less than the number of pixels NI in the horizontal direction shown in FIG.
Is greater than or equal to NI, the process proceeds to S36. S36
In, the value of j is advanced by 1, and in S37,
If the value of j is less than the number of pixels NJ in the vertical direction shown in FIG. 3, the process returns to S32. If the value of j is equal to or more than NJ, the process of this flow ends and the process of FIG. Proceed. Through the above processing steps, the bleeding prevention code _Bij is set to 0 for all the pixels shown in FIG.

FIG. 5 is a block diagram showing the processing required pixel extracting unit 1 shown in FIG.
In accordance with the function No. 4, a process for finding a pixel to be subjected to the bleeding prevention process is performed. This process is repeated twice or more for one page image. This repetition continues until it is no longer possible to find another pixel to be subjected to the bleeding prevention processing. The processing flag F in S41 is a flag for determining whether or not to continue the repetition.

In step S41, the processing flag F is set to "O" when the search for pixels to be subjected to the bleeding prevention processing is started for one page.
ff. In S42, j = 0 is designated for the 0th vertical direction, and in S43, i = 0 is designated for the 0th horizontal direction to initialize the position of the pixel of interest. In S44, for the pixel of _interest P _ij ,
Bleeding prevention code B _ij is 0, and, K _ij in P _ij
Is On and C _ij , M _ij , and Y _ij are Off, S
If the bleed prevention code B _ij is not 0, or if K _{ij in} P _ij is Off or any of C _ij , M _ij , Y _ij is On, S46 is skipped and the process proceeds to S47. Advance.

As a result, for a pixel (K) to be printed in black and for which the bleeding prevention code B _{ij is} still 0,
In S45 and S46 to be described later, a process of finding a new pixel to be subjected to the bleeding prevention process is performed.

In S45, any of C, M, and Y of reference pixels in a first surrounding pixel search window described later is On or a bleed prevention code B of a reference pixel in a second surrounding pixel search window described later. Is 1
The process proceeds to S46. All of the reference pixels in the first surrounding pixel search window are off, and the bleeding prevention code B of the reference pixel in the second surrounding pixel search window
Is 0, S46 is skipped and the process proceeds to S47.

FIG. 7 is an explanatory diagram of a surrounding pixel search window for finding a pixel to be subjected to bleeding prevention processing.
FIG. 7A is an explanatory diagram of a first surrounding pixel search window, and FIG. 7B is an explanatory diagram of a second surrounding pixel search window. In the figure,
81 is a first surrounding pixel search window, 82 is a target pixel, 83 is a reference pixel, and 84 is a second surrounding pixel search window.

The first surrounding pixel search window 81 has a pixel of interest 82 at the center. As an example, a surrounding pixel located at a distance of two pixels in the horizontal and vertical directions from the pixel of interest 82 is set as a reference pixel 83. , To search whether or not any of C, M, and Y of the reference pixel 83 is On. Therefore, the first surrounding pixel search window determines the distance from the pixel (C, M, Y) to be printed in color to the pixel (K) to be printed in black, and determines the pixel (C, M, Y) to be printed in color. ) To recognize the boundary.

If the bleeding process is performed only when the area of the pixel (K) to be printed in black and the area of the pixel (C, M, Y) to be printed in color are directly adjacent to each other, The above-mentioned distance may be set to 1. However, when the accuracy of the position where the ink droplet lands on the paper is not high, the pixel (K) to be printed in black is adjacent to the pixel (C, M, Y) to be printed in color across a colorless narrow region. If you have
Color ink droplets and black ink droplets may intermingle with each other to cause bleeding. Therefore, in order to perform the bleeding processing even in such a case, the distance is set to 2 or more in accordance with the positional accuracy of the ink droplets of the ink jet recording apparatus.

The second surrounding pixel search window 84 has a pixel of interest 82 at the center. For example, a pixel directly adjacent to the pixel of interest 82 in four horizontal and vertical directions is used as a reference pixel 83. This is for searching whether or not the bleeding prevention code B of the pixel 83 is 1. Accordingly, 1 is added to the bleeding prevention code B, and the pixel (K) to be printed in black adjacent to the pixel subjected to the bleeding processing is also subjected to the bleeding processing.

Returning to the flowchart shown in FIG. 5, the description will be continued. In S45, if any of C, M, and Y is On for the reference pixel in the first surrounding pixel search window 81, or the reference pixel in the second surrounding pixel search window 84 is blurred. When the prevention code B is 1, this pixel of interest 82 is recognized as a pixel to be subjected to a new bleeding prevention process. In S46, Bij is set to 1 and the processing flag F is turned on. The process proceeds to S47. Processing flag F
Indicates that at least one new pixel to be subjected to the bleeding prevention processing has been found in this one-page processing.

In S47, the value of i is advanced by one,
In S48, when the value of i is less than NI, S
44, and if the value of i is equal to or greater than NI, S
The process proceeds to 49. In S49, the value of j is incremented by 1. In S50, the process returns to S43 when the value of j is less than NJ, and proceeds to S51 when the value of j is equal to or more than NJ. In S51, when the processing flag F is On, the process returns to S42,
When the processing flag F is Off, the processing of this flow is terminated and the flow proceeds to the flow shown in FIG. As a result, even if the processing for one page is completed, no new pixel to be subjected to the bleeding prevention processing is found, that is, the processing flag F is set to O.
Until the FF remains, the processing of S41 to S51 is repeated.

By the above-described repetitive processing, of the pixels (K) to be printed in black, the pixels that need to be recognized as pixels to be subjected to the bleeding prevention processing are processed directly or via other pixels (K) to be printed in black. Neighboring pixels are additionally recognized as pixels that need to be subjected to the bleeding prevention processing, and as a result, bleeding occurs for pixels that are printed in black and that are connected within a predetermined distance to pixels (C, M, and Y) that are printed in color. Preventive processing will be performed. That is, pixels (C, M,
Pixel (K) to be printed in black within a predetermined distance from Y)
, The pixel (K) printed in black, that is, the pixel (K) printed in black directly or through another pixel (K) printed in black, has the bleeding prevention code B Becomes 1, but the bleeding prevention code remains 0 in the area of the pixel (K) printed in black, which is isolated by a predetermined distance in the white background.

The flowchart shown in FIG. 6 corresponds to the functions of the area dividing section 15 and the conversion processing section 16 shown in FIG. In S61, the value of j is set to 0,
At 62, the value of i is set to 0, the position of the pixel of interest is initialized, and thereafter, the processing is performed for all the pixels. First, in S63, when the value of B _ij of the pixel of _interest is 1, the process proceeds to S64 to start the blur prevention process, and when it is 0, the process proceeds to S65.

In S64, if any one of C, M, and Y of the reference pixel in the third surrounding pixel search window described later is On, it is determined that the pixel is the edge area 4 shown in FIG. Advance, C, M, Y are all O
If ff, the process proceeds to S67 assuming that it is the adjacent edge region 3 shown in FIG.

FIG. 8 shows a third example for searching for an edge area.
It is an explanatory view of a surrounding pixel search window. In the figure, FIG.
The same reference numerals are given to the same parts as those described above, and the description is omitted. 9
Reference numeral 1 denotes a third surrounding pixel search window. The third surrounding pixel search window 91 has a pixel of interest 82 at the center, and as an example, four pixels in the horizontal and vertical directions from the pixel of interest 82.
A surrounding pixel located at a distance of the pixel is set as a reference pixel 83, and is used to search whether any of C, M, and Y of the reference pixel 83 is On.

The third surrounding pixel search window 91 determines the distance from the pixel (K) to be printed in black to the pixel (C, M, Y) to be printed in color and recognizes a pixel to be an edge area. It is for. This distance is determined by the degree of bleeding of the ink into the plain paper. In this example, the distance is set to 4 pixels and the distance is set to 2 pixels in the first surrounding pixel search window 81 shown in FIG. Is also long.

In S65, K _{ij of the} pixel of _interest P _ij ,
With the On and Off states of C _ij , M _ij and Y _ij kept as they are, the process proceeds to S68 without replacing the four colors of the target pixel with ON and OFF.

In S66, K _ij , C _ij , M _ij , and P _ij of the pixel of _{interest divided} into the edge region 4 shown in FIG.
Regarding the On and Off states of Y _ij , a first pixel conversion rule (M1K _ij , M1C _ij , M1M _ij , M1Y _ij ) described later.
, K _ij , C _ij , M _ij of the target pixel P _ij , and On and Of of Y _ij
The f state is replaced, and the process proceeds to S68.

In S67, the second pixel conversion rules (M2K _ij , M2C _ij , M2M) are applied to the pixels (K) to be printed in black which are divided into the adjacent edge areas 3 shown in FIG.
_ij , M2Y _ij ), K _ij , C _ij , M _ij , Y of the pixel of interest P _ij
The On and Off states of _ij are replaced, and the process proceeds to S68.

FIG. 9 is an explanatory diagram showing the first and second pixel conversion rules. FIG. 9A is an explanatory diagram of the first pixel conversion rule applied to the edge area. (B) is an explanatory diagram of a second pixel conversion rule applied to an adjacent edge area. Since each pixel is determined based on the absolute coordinates (i, j) of the image and has periodicity, only 8 × 8 pixels near the origin (0, 0) are illustrated.

The first pixel conversion rule shown in FIG.
This is a conversion rule applied to a region closest to the color image among black image regions adjacent to the color image. Regarding the value of i representing the position of the pixel in the horizontal direction and the value of j representing the position of the pixel in the vertical direction, if the value of i is even and the value of j is odd, or if the value of i is odd, If the value of j is an even number, the print color information of the pixel (K) that is originally printed in black is replaced with a color (CM) of a mixed color of cyan and magenta inks, and the remaining pixels are not replaced. That is.

The second pixel conversion rule shown in FIG.
When the value of i is an even number and the value of j is an odd number, the printing color information of the pixel (K) that is originally printed in black is replaced with the color (CM) by mixing the cyan and magenta inks. The remaining pixels are not replaced.

FIGS. 10 and 11 are explanatory diagrams showing the ON and OFF states of each color when the first pixel conversion rule shown in FIG. 9A is used for actual processing.
(A) is a black matrix M1K _ij, FIG. 10 (B) Cyan matrix M1C _ij, FIG 11 (A) is magenta matrix M1M _ij, FIG 11 (B) is a schematic diagram of a matrix M1y _ij yellow is there.

Similarly, FIGS. 12 and 13 are explanatory diagrams showing the ON and OFF states of each color when the second pixel conversion rule shown in FIG. 9B is used for actual processing. FIG. 12A shows a black matrix M2K _ij ,
13B is an explanatory diagram illustrating a cyan matrix M2C _ij , FIG. 13A is a diagram illustrating a magenta matrix M2M _ij , and FIG. 13B is a diagram illustrating a yellow matrix M2Y _ij .

Returning to FIG. 6, the processing flow will be described.
In S68, the value of i is incremented by 1. In S69, if the value of i is less than NI, the process proceeds to S63. If the value of i is equal to or more than NI, the process proceeds to S70. In S70, the value of j is advanced by one. In S71, if the value of j is less than NJ, the process proceeds to S62. If the value of j is equal to or more than NJ, the blur prevention process ends.

Regarding the bleeding prevention processing described above, the sizes and shapes of the first to third surrounding pixel search windows 81, 84, 91, the first pixel conversion rule, and the second pixel conversion rule are as follows.
It is not limited to the specific example described above. For example, the size of the surrounding pixel search window can be changed. Good image quality differs depending on the properties of ink and paper, the amount of ink drops, the printing speed, the image resolution, and the like. Next, an example in which the first pixel conversion rule and the second pixel conversion rule are changed will be described.

FIG. 14 is an explanatory diagram showing another example of the first and second conversion rules different from the first and second conversion rules shown in FIG. 9, and FIG. FIG. 14B is an explanatory diagram of the second conversion rule. This conversion rule is different from the conversion rules shown in FIGS. 9A and 9B in that the print information of the pixel (K) to be printed in black is converted into a color (CM) of two colors of cyan and magenta. ) Instead of a single color (C,
M). As monochromatic color inks, cyan and magenta are evenly arranged.

In the first conversion rule shown in FIG. 14A, M, C, C, and M are repeated every +1 in the horizontal direction, and + 3, + 1,
+3, −3, +3, +1, +3, −3,... Are repeated in a horizontal direction with periodicity. When viewed in the vertical direction, C, M, M, and C are repeated every +1 and +3, +1, +3,
-3, +3, +1, -3,... Are repeatedly shifted in the vertical direction. The ratio of C to M is 1: 1.

In the second conversion rule shown in FIG. 14B, C, M, M, and C are repeated every +1 in the horizontal direction, and +4 in the horizontal direction each time the value is lowered by +2 in the vertical direction. It is repeated and shifted. When viewed in the vertical direction, C, M, C, and M are repeated every +1, and each time the pixel moves rightward by +2 in the horizontal direction, the period is shifted in the vertical direction by -2, 0, +2, 0,. Repeatedly. The ratio of C to M is 1: 1.

Instead of executing the processing of the flowcharts shown in FIGS. 4 and 5, it may be simply determined whether or not the target pixel is a pixel (K) to be printed in black. Even in this case, FIG. 8 in step S64 shown in FIG.
In the search using the third surrounding pixel search window 91 shown in (1), the area of the pixel to be subjected to the bleeding prevention processing can be recognized. However, when the processing of the flowcharts shown in FIGS. 4 and 5 is executed, the target pixel is subjected to the bleeding prevention processing in accordance with the properties of ink and paper, the drop amount of ink droplets, the printing speed, the image resolution, and the like. And the criteria for
There is a degree of freedom in that a reference for recognizing the inside of the edge region can be set individually. That is, the distance from the target pixel, which is a pixel (K) to be printed in black, to the pixel (C, M, Y) to be printed in color can be individually set.

FIG. 15 shows an example of specific processing when the above-described color image processing apparatus of the first embodiment is used.
18 will be described with reference to FIG. As the first and second pixel conversion rules, those shown in FIG. 9 are used.

FIG. 15 is a specific example of image data that has been binarized by the binarization unit shown in FIG. The color image processing apparatus according to the first embodiment is applied to this image data. In this example, the horizontal, an image consisting of 20 pixels in the vertical direction, in the drawing, for each pixel P _ij, black, cyan, magenta, ON for yellow, OFF information K
_ij , C _ij , M _ij , Y _{ij instead} of K, C, M, Y
Represents pixels to be printed with a single ink of black, cyan, magenta, and yellow. A region surrounded by a thick solid line is a region of a pixel (K) to be printed in black.

FIG. 16 is an explanatory diagram of the setting state of the bleeding prevention code for the image data shown in FIG. FIG.
Is the processing output of the processing-necessary pixel extracting unit 14 shown in FIG. At the same time, it is the state of the processing result of the flowchart shown in FIG. This is a state in which _Bij is set using the first and second surrounding pixel search windows 81 and 84 shown in FIG.
In the figure, 0,1 indicates that the bleeding prevention code Bij is 0,1. In this specific example, as shown in FIG. 15, all the pixels (K) to be printed in black are connected to the pixels (Y) to be printed in yellow, so as shown in FIG. The bleeding prevention codes of all the pixels (K) to be printed in black are set to 1.

FIG. 17 is an explanatory diagram showing an edge area and an adjacent edge area. 3 is a processing output of the area dividing unit 15 shown in FIG. At the same time, it also represents the result of performing the processing in steps S63 and S64 shown in FIG.
Using the third surrounding pixel search window 91 shown in FIG. 8 for the pixel group in which the bleeding prevention code B _ij shown in FIG. 16 is 1, the pixel group shown in FIG. The region 4 is a region where one pixel group is the adjacent edge region 3 shown in FIG.
Is recognized. The edge area has a width of exactly four pixels from the boundary between the pixel (Y) printed in yellow and the pixel (K) printed in black.

FIG. 18 is an explanatory diagram of the image data after the bleeding prevention processing is performed by applying the first and second pixel conversion rules to the edge area and the adjacent edge area. It is an output of the conversion processing unit 16 shown in FIG. At the same time, the state represents the processing result of the steps S65, S66, and S67 shown in FIG. For the pixel group shown in FIG. 17, O is calculated using the first pixel conversion rule shown in FIGS.
N and OFF are changed, and ON and OFF are performed for one pixel group shown in FIG. 17 using the second pixel conversion rule shown in FIGS. As a result, an image on which bleeding prevention processing has been performed is generated.

At the pixels to which the first pixel conversion rule is applied, the speed of penetration of the ink into the paper is increased, and the bleeding to the adjacent color image is eliminated. Further, even in the pixel to which the second pixel conversion rule is applied, the speed of penetration of the ink into the paper is slightly increased, and the flow of the ink to the adjacent pixel to which the first pixel conversion rule is applied is reduced. Further, since the second pixel conversion rule is applied to most of the adjacent edge regions as compared with the first pixel conversion rule being applied to a narrow range adjacent to the color image, the black image of the black image adjacent to the color is Compared with the case where all are replaced by the first pixel conversion rule, the ratio of the color ink to be printed in the black image can be reduced, the image density is increased, and the color shift is reduced.

Next, the second embodiment of the color image processing apparatus of the present invention will be described.
An embodiment will be described. In the schematic configuration diagram of the functional blocks shown in FIG. 2, the required pixel extraction unit 14 of the bleeding prevention processing unit 13 simply simplifies the processing for pixels (K) to be printed in black.

The area dividing section 15 determines whether or not there is a pixel (C, M, Y) to be printed in color within a first predetermined distance with the processing target as a pixel of interest. If it is determined that there is a pixel to be printed in color within a predetermined distance, it is recognized as a pixel group in the edge area, and the pixels (C, M, Y) to be printed in color within a first predetermined distance. ) Is not available,
It is determined whether there is a pixel (C, M, Y) to be printed in color within a second predetermined distance larger than the first predetermined distance, and printing is performed in color within a second predetermined distance from the pixel of interest. When it is determined that there is a pixel, the pixel is recognized as a pixel group of the adjacent edge area 3. That is, the adjacent edge area is an area where there is no pixel to be printed in color within the first predetermined distance among the black pixels, but a color image exists within the second predetermined distance.

The conversion processing section 16 replaces the print color information with color according to a first pixel conversion rule having a predetermined periodicity for pixels in the edge area, and converts pixels in the adjacent edge area in advance. The print color information is replaced with a color according to a second pixel conversion rule having a predetermined periodicity. For pixels that were not recognized in either the edge area or the adjacent edge area, the pixels to be printed in black (K)
Does not perform conversion processing.

FIG. 19 is a flow chart for explaining a second embodiment of the color image processing apparatus according to the present invention. S103 corresponds to the processing of the processing-necessary pixel extraction unit 14 shown in FIG.
S106 to S108 correspond to the conversion processing unit 16
And the processing is performed for all the pixels.

In S101, j = 0 indicates the 0th vertical direction of the binary image. In S102, i = 0 indicates the 0th horizontal direction of the binary image.
3, the pixel of _interest P _ij designated by i and j
Is checked, and if only _Kij is On, the process proceeds to S104. If _Kij is Off or any of _Cij , _Mij , and _Yij is On, the process is skipped to S106.

In S104, C, M, Y On, Of of pixels in a first surrounding pixel search window, which will be described later,
f, and if any of them are On, the process proceeds to S107. If all of C, M, and Y of the pixels in the first surrounding pixel search window are Off, S105 is performed.
Processing proceeds to In S105, the On, Off of C, M, and Y of the pixels in the second surrounding pixel search window are checked. If any of them is On, the process proceeds to S108, and the process proceeds to S108. Pixel C,
If both M and Y are Off, the process proceeds to S106.

FIG. 20 is an explanatory diagram of a surrounding pixel search window. FIG. 20A is a diagram of a first surrounding pixel searching window 121, and FIG. 20B is a diagram of a second surrounding pixel searching window 122. is there. The first and second surrounding pixel search windows 121 and 122 have the same window size as the first surrounding pixel search window 81 shown in FIG. 7 and the third surrounding pixel search window 91 shown in FIG. However, the processing result is different as described later.

In S106, K _ij , C _ij , M _ij ,
The process proceeds to S109 while keeping the On and Off states of Y _ij as they are. In S107, the first conversion rule shown in FIG. _{9 (A) (M1K ij,} M1C ij, M1M ij, M1
Y _ij ), actually, the On, Off of the C, M, K, and Y data is changed using those shown in FIGS. 10 and 11. In S108, the second conversion rules (M2K _ij , M2C _ij , M2M _ij , M2Y _ij ) shown in FIG.
Practically, C and C shown in FIGS.
On, Off of M, K, Y data is changed.

In S109, the value of i is incremented by 1. In S110, if the value of i is less than NI, the process returns to S103. If the value of i is equal to or more than NI, the process proceeds to S111. In S111,
The value of j is advanced by one, and in S112, the value of j is N
If it is less than J, the process returns to S102, and if the value of j is more than NJ, the bleeding prevention process ends.

With the above-described processing, the pixels (C, M, Y) to be printed in color are printed in black within the distance of two pixels based on the first surrounding pixel search window 121 shown in FIG. The pixel (K) is recognized as an edge area in step S104, and the print color information is replaced using the first pixel conversion rule in step S107. Based on the second surrounding pixel search window 122 shown in FIG. 20B, pixels (C, M, and Y) to be printed in color within a distance of 4 pixels, except for the edge area, are printed in black ( K) is recognized as an adjacent edge area in step S105, and is replaced using the second pixel conversion rule in step S108.

Further, based on the second surrounding pixel search window 122 shown in FIG. 20 (B), there are no pixels (C, M, Y) to be printed in color within a distance of 4 pixels. Regarding K), step S105, S10
No replacement process is performed in step 6. Therefore, an area of a pixel (K) to be printed in black isolated on a white background having no pixels (C, M, Y) to be printed in color over a distance of 4 pixels, and another pixel (K) to be printed in black )
Pixels to be printed in color even when connected to (C, M, Y)
The replacement process is not performed on the pixel (K) to be printed in black, which exceeds the distance of 4 pixels from.

FIG. 2 shows an actual example of specific processing when the above-described color image processing apparatus of the second embodiment is used.
1, will be described with reference to FIG.

FIG. 21 is an explanatory diagram showing an edge area and an adjacent edge area. It is a processing output of the area dividing unit 15 shown in FIG. 2 for the image data shown in FIG. At the same time, it also represents the result of performing the processing in steps S103, S104, and S105 shown in FIG.

The On, Off of C, M, and Y of the pixels in the first surrounding pixel search window 121 shown in FIG. 20 are checked, and a pixel which becomes On is regarded as a pixel of the edge area by 1 as one of On. Then, the On, Off of C, M, and Y of the pixels in the second surrounding pixel search window 122 are checked, and a pixel having any of On is indicated as 2 as a pixel in the adjacent edge area. The edge area is composed of pixels (Y) printed in yellow and pixels (K) printed in black.
The adjacent edge area has a width of exactly 4 pixels from the boundary between the pixel (Y) to be printed in yellow and the pixel (K) to be printed in black. It has a width of exactly two pixels from the boundary with the edge region.

FIG. 22 is an explanatory diagram of the image data after the bleeding prevention processing is performed by applying the first and second pixel conversion rules to the edge area and the adjacent edge area. It is an output of the conversion processing unit 16 shown in FIG. At the same time, it also represents the processing results of the steps S106, S107, and S108 shown in FIG. For the one pixel group shown in FIG. 21, ON and OFF are changed using the first pixel conversion rule shown in FIGS. 10 and 11, and for the two pixel groups shown in FIG. ON / OFF is changed using the second pixel conversion rule. As a result, an image on which bleeding prevention processing has been performed is generated.

By this processing, in the pixel to which the first pixel conversion rule is applied, the speed of penetration of the ink into the paper is increased, and the bleeding to the adjacent color image is eliminated. Further, even at the pixel to which the second pixel conversion rule is applied, the penetration speed of the ink into the paper is slightly increased, and the flow of the ink to the adjacent pixel to which the first pixel conversion rule is applied stops. Further, compared to the case where the pixels in the edge area and the adjacent edge area to which the first and second pixel conversion rules are applied are applied to a narrow area adjacent to the color image, most of the pixels (K ), The proportion of the color ink to be printed in the black image can be further reduced, the density of the image is increased, and the color shift is reduced.

In the above description, in the area dividing section 15 shown in FIG. 2, the pixel (K) to be printed in black is replaced with the edge area having the shortest distance to the pixel to be printed in color, and the distance is next to the edge area. The pixel group is divided into three groups, ie, an adjacent edge area and a long distance area, and the first and second pixel groups are divided into the edge area and the adjacent edge area.
A conversion process for replacing the print color information with the color using the pixel conversion rule described above.

However, by providing three or more types of a plurality of surrounding pixel search windows at different distance ranges from the target pixel, the pixels (K) to be printed in black are divided into four or more pixel groups. Different pixel conversion rules may be used according to each pixel group. At this time, the pixel conversion rule is set so that the ratio of the pixels for which the print color information is replaced with the color gradually decreases as the pixel group moves away from the pixels (C, M, Y) to be printed in color. At this time, the area farthest from the color image may be replaced, but the replacement may not be performed at all as shown in FIG.

That is, a plurality of pixel regions at one or more different distances from the target pixel are defined, and a pixel conversion rule of a certain periodicity is made to correspond to a pixel group in each region. Pixel to be printed in black (K)
Is determined as a target pixel, and if it is determined that there is a pixel (C, M, Y) to be printed in color in a pixel group within a predetermined first relative position range, Pixels are replaced with color printing according to a first pixel conversion rule having a predetermined periodicity, and similarly, color printing is performed in a pixel group within a range of a second and subsequent nth relative positions. When it is determined that there is a pixel to be printed, the process of replacing the print color information with the color of the pixel of interest according to the n-th pixel conversion rule having a predetermined periodicity is repeated.

In the above-described second embodiment, the size and shape of the surrounding pixel search window are not limited to those shown in FIG. The pixel conversion rules are not limited to those shown in FIGS. 9 to 13, but may be those shown in FIG. Good image quality depends on the properties of ink and paper, the amount of ink drops, the printing speed, the image resolution, and the like.

Further, in the schematic block diagram of the functional blocks shown in FIG. 2, the bleeding is prevented by the same method as in the first embodiment without simplification of the required pixel extraction unit 14 of the bleeding prevention processing unit 13. Pixels to be processed may be extracted, and the other pixels (K) to be printed in black may not be converted. It should be noted that the pixel-to-be-processed extraction unit 14 described in the first embodiment can be used in a conventional image processing apparatus that does not provide an adjacent edge region and replaces the print color information of the pixels in the edge region. It has the same effect of increasing the degree.

In the above description, the surrounding pixel search window is within a predetermined distance from the pixel of interest except for the second surrounding pixel search window 82 shown in FIG. 7B of the first embodiment. Is a set of all the pixels in. However, not all pixels need to be used as reference pixels.

FIG. 23 shows a first example of the surrounding pixel search window.
It is explanatory drawing of the modification of. For example, in the second embodiment, the second surrounding pixel search window 122 shown in FIG. 20 is used in S105 after the first surrounding pixel search window 121 is used in S104 of the flowchart shown in FIG. Things. Therefore, instead of using the surrounding pixel search window 122, a surrounding pixel search window 131 that does not use a pixel located at a distance of two pixels from the target pixel as a reference pixel can be used.
The same result as that of No. 22 can be obtained, and the processing speed of surrounding pixel search can be improved.

FIG. 24 shows a second example of the surrounding pixel search window.
It is explanatory drawing of the modification of. FIG. 24A shows a surrounding pixel search window 141 in which the distance from the target pixel is two pixels, and FIG.
FIG. 4B is an explanatory diagram of a surrounding pixel search window 142 whose distance from the target pixel is 4 pixels. The surrounding pixel search window 141 illustrated in FIG. 24A is a surrounding pixel search window that has a total of eight reference pixels 83 in the horizontal, vertical, and oblique directions that are two pixels away from the target pixel 82 printed in black. is there. The surrounding pixel search window 142 shown in FIG. 24B includes a set of a total of eight reference pixels including reference pixels 83 having a distance of 4 pixels in the horizontal, vertical, and oblique directions from the target pixel 82 printed in black. It is a surrounding pixel search window having. In any case, the remaining pixels in the search window are not used as reference pixels 83 to be searched.

The surrounding pixel search window 141 has the same window size as that of the first embodiment shown in FIG.
The first peripheral pixel search window 81 shown in FIG. 20A and the first peripheral pixel search window 121 shown in FIG. 20A in the second embodiment can be used. The surrounding pixel search window 142 is the third surrounding pixel search window 91 shown in FIG. 8 of the first embodiment, and the second surrounding pixel search window 142 shown in FIG. 20B of the second embodiment. It can be used instead of the surrounding pixel search window 122. It is inevitable that a certain degree of error will occur in recognizing whether there is a pixel (C, M, Y) to be printed in color within a predetermined range from a pixel (K) to be printed in black. Can be reduced, so that the processing speed of surrounding pixel search can be improved.

In the above description, one reference pixel 83 is set in each of the eight directions in the window. However, the number of reference pixels 83 may be smaller than eight. Pixels that are located or pixels whose distance is smaller than the window size may be added. Any pixel that does not include at least one of the pixels within a predetermined relative distance from the target pixel may be used. Note that the maximum value of the distance from the target pixel 82 to each reference pixel 83 is the window size of the surrounding pixel search window.

Therefore, when using at least one of the surrounding pixel search windows 141 and 142 described above, the surrounding pixel detection window is defined as a set of one or more reference pixels within a predetermined relative position from the pixel of interest. Then, by using one surrounding pixel detection window or a plurality of windows having different window sizes, it is determined whether there is a pixel to be printed in color in a set of reference pixels, and a pixel group of a plurality of regions is determined. The print information of the pixel (K) to be printed in black is replaced with color according to a certain periodicity replacement rule for each pixel group.

[0107]

As is clear from the above description, according to the first aspect of the present invention, a pixel to be printed in black is input,
Area dividing means for dividing the pixels printed in black into a plurality of pixel groups based on the distance to the pixels printed in color,
Of the plurality of pixel groups, a pixel group in a region where the distance to a pixel to be printed in color is the closest and a pixel group in a region in which the distance to a pixel to be printed in color is the next to this region,
Pixel conversion means for replacing print information for pixels belonging to at least two pixel groups based on a predetermined conversion rule, wherein the conversion rule is a method for printing color information with a predetermined periodicity for pixels to be printed in black. Is changed from black to color, and for each pixel group to be subjected to pixel conversion, the ratio of pixels to be replaced becomes smaller as the distance to the pixel to be printed in color becomes longer.

Therefore, bleeding can be prevented on a pixel-by-pixel basis, regardless of the size of the area of the pixel printed in black or the position of the boundary between the pixel printed in color and the pixel printed in black. There is an effect that the resolution does not decrease and the bleeding process does not vary. As a result, it is possible to obtain monochrome printing with high density and sharp edges even on plain paper, and color printing without bleeding in the boundary region between the black printing portion and the color printing portion.

According to the second aspect of the present invention, the area dividing means includes a set of reference pixels including at least one pixel located at a predetermined relative distance from a pixel to be printed in black, in which a pixel to be printed in color is included. Since there is a means for determining whether or not there is, there is an effect that a pixel to be printed in black can be easily divided into a plurality of pixel groups based on a distance to a pixel to be printed in color.

According to the third aspect of the present invention, since the set of reference pixels does not include at least one of the pixels within a predetermined relative distance from the pixel to be printed in black, the surrounding pixel search is performed. There is an effect that the processing speed can be improved.

According to the fourth aspect of the present invention, since the conversion rule replaces the print information from black to a single color or a mixed color of two colors, the conversion rule is smaller than the case of mixing three ink droplets. In addition, since the total amount of ink droplets is reduced, there is an effect that problems such as thickening of pixels, falling out of the back of the paper, and occurrence of wrinkles of the paper are reduced.

According to the fifth aspect of the present invention, since the conversion rule is determined based on the absolute position of the pixel to be printed in black, there is an effect that the conversion process is facilitated.

According to the sixth aspect of the present invention, a pixel to be printed in black and a reference pixel including at least one pixel at a predetermined relative distance from the pixel to be printed in black are included in a set of color pixels. A pixel having a pixel to be processed is designated as a pixel to be processed, and a pixel to be processed is added directly to the pixel to be processed or via a pixel to be printed in black to a pixel to be processed. A pixel to be printed in black, which is determined as a pixel to be processed by the processing pixel extracting means, is output to the color image processing apparatus according to claim 1. Based on the drop amount of ink droplet, printing speed, image resolution, etc., the standard to set the pixels to be printed in black as the target of bleeding prevention and the standard to divide into multiple pixel groups are set individually. If you have the freedom you can There is a cormorant effect.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an image near a boundary between a black ink print portion and a color ink print portion when the first embodiment of the color image processing apparatus of the present invention is used.

FIG. 2 is a schematic configuration diagram for realizing a color image processing device of the present invention.

FIG. 3 is an explanatory diagram illustrating a pixel serving as a unit for storing color information of a binarized image.

FIG. 4 is a first flowchart for explaining a process of converting a binary image into an image on which bleeding has been prevented in the first embodiment of the present invention.

FIG. 5 is a second flowchart illustrating a process of converting a binary image into an image on which bleeding has been prevented in the first embodiment of the present invention.

FIG. 6 is a third flowchart illustrating a process of converting a binary image into an image on which bleeding has been prevented in the first embodiment of the present invention.

7A and 7B are explanatory diagrams of a surrounding pixel search window. FIG. 7A is a first surrounding pixel search window, and FIG.
FIG. 9 is an explanatory diagram of a second surrounding pixel search window.

FIG. 8 is an explanatory diagram of a third surrounding pixel search window for searching for an edge area.

FIG. 9 is an explanatory diagram showing a first pixel conversion rule and a second pixel conversion rule. FIG. 9A is an explanatory diagram of a first pixel conversion rule applied to an edge area. (B) is an explanatory diagram of a second pixel conversion rule applied to an adjacent edge area.

10A and 10B are explanatory diagrams showing ON and OFF states for each color when the first pixel conversion rule shown in FIG. 9A is used for actual processing. FIG. 10A is a black matrix. M1K _ij , FIG. 10 (B) is a cyan matrix M1C
_ij and FIG. 11A is an explanatory diagram showing a magenta matrix M1M _ij .

FIG. 11 is an explanatory diagram showing ON / OFF states for each color when the first pixel conversion rule shown in FIG. 9A is used for actual processing; FIG. 11A shows a magenta matrix; M1M _ij , and FIG. 11B is an explanatory diagram showing a yellow matrix M1Y _ij .

12 is an explanatory diagram showing ON / OFF states for each color when the second pixel conversion rule shown in FIG. 9B is used for actual processing. FIG. 12A is a black matrix. M2K _ij , and FIG. 12B shows a cyan matrix M2C.
FIG. 9 is an explanatory diagram showing _ij .

13 is an explanatory diagram showing ON / OFF states for each color when the second pixel conversion rule shown in FIG. 9B is used for actual processing; FIG. 13A is a matrix of magenta M2M _ij , and FIG. 13B is an explanatory diagram showing a yellow matrix M2Y _ij .

FIG. 14 is an explanatory diagram showing an example of other first and second conversion rules different from the first and second conversion rules shown in FIG. 9; FIG. 14A shows the first conversion rule; FIG. 14B is an explanatory diagram of the second conversion rule.

FIG. 15 is a specific example of image data that has been binarized by the binarization unit shown in FIG. 2;

16 is an explanatory diagram of a setting state of a bleeding prevention code for the image data shown in FIG. 15;

FIG. 17 is an explanatory diagram illustrating an edge region and an adjacent edge region.

FIG. 18 is an explanatory diagram of image data after performing bleeding prevention processing by applying first and second pixel conversion rules to an edge region and an adjacent edge region.

FIG. 19 is a flowchart illustrating a color image processing apparatus according to a second embodiment of the present invention.

FIG. 20 is an explanatory diagram of a surrounding pixel search window for finding a pixel to be subjected to bleeding prevention processing, and FIG.
Is the first surrounding pixel search window, and FIG.
It is an explanatory view of a surrounding pixel search window.

FIG. 21 is an explanatory diagram illustrating an edge region and an adjacent edge region.

FIG. 22 is an explanatory diagram of image data after performing bleeding prevention processing by applying first and second pixel conversion rules to an edge region and an adjacent edge region.

FIG. 23 is an explanatory diagram of a first modification of the surrounding pixel search window.

FIG. 24 is an explanatory diagram of a second modification of the surrounding pixel search window.

FIG. 25 is an explanation of an image near a boundary between a black ink printing portion and a color ink printing portion when a color image processing apparatus that prevents bleeding by replacing a part of black pixels in an edge region with a mixture of color inks is used. FIG.

[Explanation of symbols]

1 ... plain paper, 2 ... part printed with color ink having high permeability to paper, 3 ... adjacent edge area, 4 ... edge area,
151: a portion printed with black ink having low permeability to paper; 152: a portion from which the ink has flowed out; 13: a bleeding prevention processing unit; 14: a pixel extraction unit to be processed;
16: conversion processing unit, 81: first surrounding pixel search window, 82: target pixel, 83: reference pixel, 84: second surrounding pixel search window, 91: third surrounding pixel search window, 121: first Surrounding pixel search window, 12
2. Second surrounding pixel search window, 131, 141,
142: Surrounding pixel search window.

Claims (6)

[Claims] In a color image processing apparatus for ink-jet recording using a black ink which penetrates slowly into paper and a color ink which penetrates quickly into paper, a pixel to be printed in black is inputted, and a pixel to be printed in black is inputted. Area dividing means for dividing into a plurality of pixel groups based on a distance to a pixel to be printed in color; and a pixel group and a region in a region of the plurality of pixel groups in which a distance to a pixel to be printed in color is the shortest. Next, the pixel group of the area where the distance to the pixel to be printed in the color is short, for pixels belonging to at least two pixel groups, pixel conversion means for replacing the print information based on a predetermined conversion rule, The conversion rule is to replace the print color information from black to color with a predetermined periodicity for the pixels to be printed in black. A color image processing apparatus characterized in that the ratio of pixels to be replaced is reduced as the distance to the pixels to be printed by the color is increased. 2. The image processing apparatus according to claim 1, wherein the area dividing unit determines whether there is a pixel to be printed in the color in a set of reference pixels including at least one pixel at a predetermined relative distance from the pixel to be printed in black. 2. The color image processing apparatus according to claim 1, further comprising: 3. The color image according to claim 2, wherein the set of reference pixels does not include at least one of the pixels within a predetermined relative distance from the pixel to be printed in black. Processing equipment. 4. The color image processing apparatus according to claim 1, wherein the conversion rule replaces print information from black to a single color or a mixture of two colors. 5. The color image processing apparatus according to claim 1, wherein the conversion rule is determined based on an absolute position of a pixel to be printed in black. . 6. At least one pixel to be printed in black and having a predetermined relative distance from the pixel to be printed in black.
A pixel that needs to be printed in color in the set of reference pixels that includes the pixel to be processed is defined as a pixel to be processed, and a pixel adjacent to the pixel to be processed directly or through the pixel that is printed in black is added to the pixel to be processed. 6. The color image processing apparatus according to claim 1, further comprising: a pixel to be processed which is to be printed in black and which has been determined to be the pixel to be processed by the pixel to be processed extraction. A color image processing device for outputting.