JP5838683B2 - Image processing apparatus, image processing method, and program - Google Patents

Description

  The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus that performs processing for reducing the amount of colorant used when forming a color image.

  In printers and copiers, a colorant usage reduction mode called an economy mode is often prepared. When this mode is designated, the amount of colorant used can be reduced as compared with the standard recording mode, and the recording running cost per sheet can be reduced.

  Various techniques for reducing the amount of colorant used for image formation are known. For example, there is a method (method 1) of multiplying input image data by a coefficient of 1 or less to reduce the density of the entire image. Since a large amount of colorant is required for high density expression, the amount of colorant used can be reduced by reducing the overall density. There is a method (Method 2) in which the amount of colorant used is reduced by performing masking processing on the image data after halftone processing and thinning out the image data at a constant rate. In a recording apparatus capable of forming multi-value dots, there is a method (method 3) in which the dot size to be recorded is reduced to reduce the amount of colorant used.

  However, any of the above methods 1, 2 and 3 has a problem that the image quality is considerably lowered as compared with a recorded image in the case where the amount of colorant used is not reduced. This is a problem that can be said to be a fate of the colorant usage reduction mode. However, in order to make this image quality deterioration inconspicuous at all, in recent years, the undercolor removal in the BG / UCR process has been actively carried out, and the color overlap portion has been removed. A method (method 4) is also known in which the color material usage is reduced by replacing the data with K (black) plate data as much as possible, and reducing the density of the color (CMY) plate data.

  In addition, a method (method 5) is also employed in which only the contour portion of the image is left and the colorant used inside the contour is reduced. In this method, the recorded image is naturally far from the original image data, but a great reduction in the colorant usage can be realized.

  There is also known a method (Method 6) for controlling the application of the above method for each image object (character, line drawing, graphics, photograph, etc.) and protecting an object for which image quality deterioration is not preferable.

  According to the method 4, it is possible to record the colorant usage reduction with higher image quality than the methods 1, 2, and 3. However, when aiming at a drastic reduction of the colorant usage, the deterioration of the image quality is ignored. It becomes a level that can not be. Specifically, the contrast, vividness, and gradation reproducibility of the image are reduced, and it becomes impossible to determine what is drawn. This tendency is prominent in photographic objects.

  In the method 5 as well, there is no problem in use for a character or graphic object whose shape itself becomes information by leaving the outline portion. However, for an image of a natural image such as a photograph, it is difficult to even guess the original image because of the exaggerated outline and loss of gradation.

  It is possible to take measures such as removing a photographic object or the like that is likely to cause a failure from the target for reducing the amount of colorant used, or reducing the amount of reduction in the amount of colorant used. However, the number of cases in which image data using a lot of photographs is output is increasing, and as a result, the effect of reducing the amount of colorant used is reduced.

  Further, in order to switch processing for each object, processing for separating the objects is required. When the image data can be output separately for each object as the OS function of the computer, it is sufficient to perform the processing individually. However, in the case of an incompatible OS or when processing an image captured from a scanner or the like Therefore, it is necessary to perform image area separation processing once to determine which object is one by one. Such processing is extremely computationally intensive, resulting in a decrease in throughput until output, and an increase in the cost of the image processing apparatus due to the installation of a high-performance processing circuit. In addition, there is always a possibility of erroneous conversion, and the image quality is not always as intended.

  In addition, as a method different from the above method, when data having a resolution of 1 / n of the output resolution is converted to the output resolution, ON dots (dots recorded using a colorant) are reduced to reduce the image information. A method of reducing the amount of colorant used while preventing disappearance is also known (see Patent Document 1).

  An object of the present invention is to provide a novel image processing apparatus and method capable of reducing the amount of colorant used for image recording while suppressing deterioration of image quality for color images.

In order to achieve the above object, an image processing apparatus according to the present invention is as described in claim 1.
First processing means for converting K (black) plane data to output resolution and converting other color plane data to a resolution of 1 / n of the output resolution (where n is an integer of 2 or more);
Second processing means for performing halftone processing on the K plane data and other color plane data converted by the first processing section;
as well as,
The ON dots of the other color plate data after the halftone processing by the second processing means are replaced with an n × n dot pattern including ON dots corresponding to the colorant usage reduction rate, and the other after the halftone processing. A third processing means for performing processing for replacing the OFF dots of the color plate data with an n × n dot pattern not including the ON dots;
In the third processing means, n × n dot patterns that are replaced with ON dots of other color plate data after the halftone process are made different between the plates, and other colors after the halftone process The plate data is changed for each dot position .

  The K plane data of the output resolution and other color plane data are obtained by the processing of the third processing means, but the dot pattern ON to be replaced with the ON dots of the K plane data or other color plane data prior to the processing is obtained. The amount of colorant used is reduced according to the number of dots. However, since the K plate data and other color plate data are stored in dot arrangement by halftone processing, gradation reproduction is good, and unpleasant moiré and texture like the method of simply thinning out are not present. Hard to occur. Furthermore, since the n × n dot pattern that is replaced with the ON dots of the K plate data and the other color plate data after the halftone process is made different between the plates, the overlap of ON dots of a plurality of plates is reduced, and the A decrease in saturation due to overlapping of ON dots is suppressed, and color development is improved. Further, since the dot pattern replaced with the ON dot is changed for each dot position of the K plane data and the other color plane data after the halftone process, the identification that causes a problem when the same dot pattern is used continuously. Problems such as the appearance of color lines and streaky omissions and the appearance of color misregistration are unlikely to occur. As described above, according to the present invention, it is possible to reduce the amount of colorant used for image recording while suppressing a decrease in image quality of a color image.

1 is a block diagram of an image processing apparatus according to an embodiment of the present invention. 3 is a flowchart for explaining Example 1; 6 is a flowchart for explaining a second embodiment; 10 is a flowchart for explaining a third embodiment; It is a figure which shows the example of a 2 * 2 dot pattern for reducing the coloring agent usage-amount to 1/2. FIG. 6 is a dot arrangement diagram for explaining an application example of the dot pattern of FIG. 5. It is a figure which shows the example of a 2 * 2 dot pattern for reducing the coloring agent usage-amount to 1/4. It is a schematic diagram for demonstrating the method of cutting out and using an nxn dot pattern from a large scatter dot pattern. It is a schematic diagram for demonstrating the principle of the resolution conversion in this invention, and the coloring agent usage-amount reduction. It is a figure which shows the error diffusion process result in an output resolution, and the error diffusion process result in a resolution lower than an output resolution. It is a figure which shows the error diffusion process result in an output resolution, and its thinning-out process result.

  FIG. 1 is a block diagram for explaining an embodiment of the present invention. In the image processing apparatus shown in FIG. 1, a color image is input as RGB data by the image data input unit 1, and an input color image is input by the image output unit 7 as K (black), C (cyan), M (magenta), and Y ( Yellow) is used for recording. As such an image output unit 7, for example, an electrophotographic or inkjet printer engine can be used. In the case of an electrophotographic printer engine, the colorant corresponds to toner. In the case of an ink jet printer engine, the colorant corresponds to ink.

  The image processing apparatus includes a color conversion processing unit 2 that converts RGB data of an input color image into KCMY color plate data recorded by the image output unit 7, and the CMYK color plate data of the image output unit 7. A γ correction processing unit 3 that performs γ correction processing according to γ characteristics, and a resolution scaling processing unit (A) 4 that converts the resolution of CMYK color plate data after the γ correction processing to a resolution lower than the output resolution by the image output unit 7. The halftone processing unit 5 for performing halftone processing (halftone processing) such as dither processing and error diffusion processing on the CMYK color plate data converted to the low resolution, and the resolution of the CMYK color plate data after the halftone processing A resolution scaling processing unit (B) 6 that converts the output resolution by the output unit 7 is provided, and the KCMY color plate data after the conversion is input to the image output unit 7.

  When the resolution of each color plate data converted by the resolution scaling processing unit (A) 4 is 1 / n of the output resolution, the resolution scaling processing unit (B) 6 outputs each color plate data after halftone processing. When converting to output resolution data, each dot of 1 / n resolution color plate data is replaced with an n × n dot pattern. In an n × n dot pattern that is replaced by OFF dots (dots not recorded) in 1 / n resolution color plate data, all dots are OFF dots. An n × n dot pattern replaced with ON dots (recorded dots) includes at least one ON dot, and the amount of colorant used can be reduced as the proportion of the ON dots is reduced. That is, the colorant usage reduction rate can be adjusted by the ratio of the ON dots of the n × n dot pattern that is replaced with the ON dots in the 1 / n resolution data.

  Some examples will be described in detail with a focus on the processing contents related to the reduction of the colorant usage amount.

  FIG. 2 shows a processing flow in the first embodiment.

  Image data (RGB data) is input by the image data input unit 1 (step 101). The RGB data is converted into CMYK color data by the color conversion processing unit 2 (step 102). This color conversion is performed by, for example, a known matrix calculation process for converting RGB data to CMY data and a known black generation / under color removal (BC / UCR) process. The CMYK color plane data generated in this way is subjected to γ correction processing by the γ correction processing unit 3 (step 103), and then the resolution scaling processing unit (A) 4 has a resolution of 1 / n of the output resolution. It is converted into data (step 104). However, n is an integer of 2 or more. The 1 / n resolution CMYK color plane data is subjected to halftone processing (dither processing, error diffusion processing) by the halftone processing unit 5 (step 105). In the resolution scaling processing unit (B) 6, the resolution is converted into the output resolution by replacing each dot of the CMYK color plate data after the halftone processing with an n × n dot pattern (steps 106K, 106C, 106M, 106Y). At this time, the nxn dot pattern to be replaced with the OFF dots is all OFF dots, but the nxn dot pattern to be replaced with the ON dots is different for each color material usage reduction rate and for each color plate. Those prepared in advance are used. The CMYK color plate data converted into the output resolution in this way and subjected to the colorant use amount reduction processing as necessary are input to the image output unit 7 to create each color plate and synthesize them. A color image is formed (step 107).

  Next, steps 106K to 106Y will be described in detail. Here, it is assumed that n = 2 for easy understanding.

  First, with respect to the basic advantages of the processing method for converting to output resolution and reducing the amount of colorant used by replacing ON dots of 1/2 resolution data with 2 × 2 dot patterns, FIG. 9, FIG. This will be described with reference to FIG.

  Reference is first made to FIG. In FIG. 9, (a) is color plate data (halftone processed) having a half resolution of the output resolution, and each dot is replaced with a 2 × 2 dot pattern (b) (c). Shown in (d). In the example of (b), all dots of the 2 × 2 dot pattern replaced with ON dots of 1/2 resolution data are ON dots, and the colorant usage amount in this case is set as a reference amount. In the example of (c), since half the dots of the 2 × 2 dot pattern replaced with the ON dots of the 1/2 resolution data are ON dots, the colorant usage amount is reduced to about half of the reference amount. In the example of (d), since only one dot of the 2 × 2 dot pattern that is replaced with the ON dot of the 1/2 resolution data is the ON dot, the colorant usage amount is reduced to about ¼ of the reference amount. . When only 3 dots in the 2 × 2 dot pattern are ON dots, the colorant usage is reduced to about 3/4 of the reference amount. More generally, the color plate data converted to 1 / n resolution of the output resolution is converted to output resolution after halftone processing, and each dot of 1 / n resolution data is converted into n × n at the time of this conversion. Replaced with dot pattern. Therefore, n is 3, 4, 5,. . . Since the number of dots in the replaced dot pattern increases, the reduction rate of the colorant usage can be adjusted more finely by increasing or decreasing the ratio of the ON dots.

  In the present invention, halftone processing is not performed on each color plate data in the state of output resolution, but halftone processing is performed in a state of being converted to a resolution lower than the output resolution. The effect of applying halftone processing at such a low resolution will be described with reference to FIG.

  In FIG. 10, the result of applying halftone processing (error diffusion processing) to a certain color plate data at the output resolution is schematically shown in (a), and halftone processing (error diffusion) at half the output resolution is shown. (B) schematically shows the result of the treatment. As can be seen in FIG. 10, when the resolution is halved, the dot diameter is approximately doubled, and conversely, the number of dots generated is approximately 1/4 (strictly speaking, it has dot gain and gradation characteristics). Depending on how you choose, the diameter and number will vary slightly). The difference in image quality between (a) and (b) appears in characteristics such as graininess and sharpness. However, even if the resolution is half as shown in (b), an appropriate halftone process corresponding to the resolution is performed. If performed, gradation is ensured, and unpleasant texture or the like does not occur.

  In the case of the present invention, for example, as described with reference to FIG. 9, the amount of colorant used is reduced when the data after half resolution processing of 1/2 resolution is converted to output resolution. Since the formed dot pattern is almost preserved, an unpleasant texture or the like does not occur, and gradation is ensured. In other words, in the data converted to the output resolution, although the dot lump changes in thickness / thickness according to the reduction rate of the colorant usage, the arrangement of the dot lump remains the ideal arrangement reproduced by halftone processing. Therefore, unpleasant moire and texture do not occur, and the number of dot clusters for each gradation does not change, so that a gradation difference is ensured.

  This is a significant advantage over the technique of reducing the amount of colorant used by performing dot thinning at a constant rate for each color plate data having an output resolution subjected to halftone processing. This will be described with reference to FIG. FIG. 11A schematically shows an image subjected to halftone processing at an output resolution of a certain color plate, and FIG. 11B shows an image obtained by thinning out the halftone image at a constant ratio. As can be seen from a comparison of (a) and (b), dots ideally arranged by halftone processing are locally lost by thinning processing, resulting in non-uniform dot distribution. Such uneven distribution of dots leads to unpleasant image quality degradation such as moire and texture.

  As described above, the n × n (here 2 × 2) dot pattern to be replaced with the ON dot of each 1 / n (here 1/2) resolution road plate data after the halftone process is What was prepared beforehand for every color plate use amount is used for every color-material usage-amount reduction rate.

  FIG. 5 shows an example of a 2 × 2 dot pattern applied to each color plate of KCMY. This example is used when the colorant usage is reduced to ½. FIG. 7 shows an example of a 2 × 2 dot pattern used when the colorant usage is reduced to ¼. 5 and 7, circles mean ON dots.

  5 and 7, four vertical dot patterns K are applied to the K plate, four dot patterns C are applied to the C plate, and four dot patterns M are applied to the M plate. The four dots pattern Y, which is a pattern to be applied, is a pattern applied to the Y plate.

  In steps 106K to 106Y in FIG. 2, the 2 × 2 dot pattern in FIG. 5 or FIG. 7 is the first stage, the second stage, the third stage, and the fourth stage again. Like things, they are used in order to rotate.

  An application example of the dot pattern of FIG. 5 is shown in FIG. FIG. 6A shows a dot arrangement of 1/2 resolution data, each circle is one dot, and a character in the dot represents a color plate name in which the dot is an ON dot. That is, in the example shown in (a), for the K, M, and Y plates, all dots are ON dots, and for the C plate, all dots are OFF dots. Assuming that each dot of the 1/2 resolution data is processed in raster order, the ON dot is changed to the first dot pattern, the second dot pattern, the third dot pattern, the fourth dot in FIG. Pattern, the first dot pattern. . . Replace with The dot arrangement of each color plane data returned to the output resolution by such dot pattern replacement is as shown in FIG. 6B. In (b), each circle is one dot, and the character in the dot represents a color plate name that is an ON dot.

  When only the dot pattern shown in the first row of FIG. 5 is used to replace the ON dots of the 1/2 resolution data shown in FIG. 6A, the result is as shown in FIG. 6C. Become. In (c), each circle is one dot, and the character in the dot is a color plate name that is an ON dot. In the example of (c), since the ON dots are continuous in the Y color plate, there arises a disadvantage that the Y line is conspicuous.

  Now, as can be understood by comparing the dot patterns K, C, M, and Y arranged in the same stage in FIG. 5 or FIG. 7, it is applied to each color plate so that ON dots do not overlap as much as possible between the KCMY color plates. The ON dot arrangement of the dot pattern is determined. Additive color mixing systems, such as TVs and color monitors, have the property of producing more vivid colors by overlapping colors. However, subtractive color mixing systems that print on recording paper cause color turbidity as the colors overlap. Becomes narrower. It is important to reduce the overlap of ON dots between color plates because the color gamut tends to narrow even when the amount of colorant used is reduced.

  Further, the dot patterns in the first to fourth stages in FIG. 5 are selected and applied in order so as to rotate. By doing so, each dot position of each color plate data of 1/2 resolution is applied. In addition, the ON dot position of the dot pattern can be varied. When the same dot pattern is continuously applied to each color plate, a certain color line or streak is noticeable or a certain color plate appears to be shifted as shown in the example of FIG. 6C. Such an inconvenience is more likely to occur in an image having a higher dot coverage. The occurrence of such inconvenience can be reduced by rotating the dot pattern.

  Note that the same effect can be obtained if the dot patterns as shown in FIG. 5 are not sequentially selected so as to be rotated but are selected and applied in random order. Thus, an aspect of selecting and applying in random order is also included in the present invention.

  Further, in steps 106K to 106Y, there is another method for obtaining a result similar to the method of selecting and using a predetermined dot pattern as shown in FIG. 5 or 7 in order so as to rotate or selecting in a random order. is there. For example, a distributed dot pattern 21 corresponding to the colorant usage reduction rate is prepared, which is larger than the n × n dot pattern schematically shown in FIG. The pattern 22 may be cut out, the cut-out position may be sequentially moved for each dot position of each KCMY color plate data after halftone processing, and the cut out n × n dot pattern may be replaced with ON dots in steps 106K to 106Y. The distributed dot pattern 21 is different for each color plate, or the common distributed dot pattern 21 is used for all color plates, but the cut-out position of the n × n dot pattern 22 is different between the color plates. If a pattern having characteristics called blue noise and green noise is used as the distributed dot pattern 21, the pattern generation rules are random and uniform, so that the inconvenience described with reference to FIG. 6C is effective. Can be avoided. The vertical and horizontal sizes of the distributed dot pattern 21 may be selected to be a multiple of the dot pattern size n. A mode in which an n × n dot pattern is cut out from a large-sized dispersed dot pattern corresponding to such a colorant usage reduction rate is also included in the present invention.

  In each of steps 106K to 106Y, an n × n dot pattern to be replaced may be obtained by calculation each time. As can be seen from FIG. 6B, even if an n × n dot pattern prepared in advance is rotated or randomly selected, a plurality of color dots are overlapped somewhere. In order to avoid this as much as possible, for example, an ON dot may be assigned to the farthest position based on the dot arrangement of the adjacent pixel position that has already been converted to the output resolution (upper conversion). Further, at this time, by calculating the position as far as possible from the color dots having low lightness, that is, sensuously close to black, it is possible to ensure the maximum color developability.

  In Steps 106K to 106Y, when an overlap between a black dot and a color dot occurs, a process for changing the color dot to an OFF dot or changing the black dot to an OFF dot may be performed. Such an embodiment is also included in the present invention.

  When overlapping of dots including black dots occurs, the color is black even if the color dots are somewhat overlapped. In this case, in order to reduce the amount of colorant used as much as possible, it is preferable not to record color dots at positions overlapping with black dots. In particular, in a recording apparatus that uses a liquid colorant, such as an ink jet recording apparatus, if color dots are overprinted more than necessary, problems such as bleeding and back-through tend to occur. Bleeding particularly causes the quality of characters and fine lines to be significantly degraded. Therefore, it is preferable to positively leave black dots for characters and fine lines. In order to enhance this effect, it is also possible to apply a sharpening process to the K plate in a process prior to the halftone process.

  On the other hand, black dots are very conspicuous, and also work to impair the vividness of the image (there is a possibility of exacerbating graininess and enhancing wrinkles and scratches on human skin). For bitmap images such as natural images and figures (painting) where gentle gradation is frequently used, it is preferable to leave color dots without recording black dots.

  In this way, since the preferred processing varies depending on the image type, in a system that can process input data for each image object (character / line drawing / painting / bitmap, etc.), whether overlapping black dots are left for each object. It is better to leave or switch color dots.

  FIG. 3 shows a processing flow in the second embodiment.

  Image data (RGB data) is input by the image data input unit 1 (step 201). The RGB data is converted into CMYK color data by the color conversion processing unit 2 (step 202). The CMYK color plate data is subjected to γ correction processing by the γ correction processing unit 3 (step 203). The subsequent processing flow is switched between the K plate and the color plate.

  First, the K plate data is converted into an output resolution by the resolution scaling processing unit (A) 4 (step 204), and halftone processing (dither processing, error diffusion processing, etc.) is performed on the K plate data of the converted output resolution. ) Is performed (step 205). The K plate data after the halftone process is output as it is by the image output unit 7 (step 209).

  On the other hand, the CMY color plane data is converted into data having a resolution of 1 / n of the output resolution by the resolution scaling unit (A) 4 (step 206). However, n is an integer of 2 or more. The 1 / n resolution CMY color plate data is subjected to halftone processing (dither processing, error diffusion processing) by the halftone processing unit 5 (step 207). In the resolution scaling processing unit (B) 6, the resolution is converted into the output resolution by replacing each dot of the CMY color data after halftone processing with an n × n dot pattern (steps 208C, 208M, 208Y). . At this time, the nxn dot pattern that is replaced with OFF dots is all OFF dots, but the nxn dot pattern that is replaced with ON dots includes ON dots, and the colorant is used depending on the ratio of the ON dots. The amount reduction rate is determined. As described in connection with the first embodiment, the n × n dot pattern applied in Steps 208C, 208M, and 208Y can be used by rotating a dot pattern prepared in advance or by selecting it randomly. Can be. Alternatively, an n × n dot pattern may be cut out from a distributed dot pattern such as a blue noise pattern or a green noise pattern. Further, an n × n dot pattern may be obtained by calculation. The CMY plane data of the output resolution that is the processing result of steps 208C, 208M, and 208Y is output by the image output unit 7 (step 209).

  In the present embodiment, a dot pattern having a higher resolution than the color plate can be formed on the K plate by performing halftone processing on the K plate at the output resolution. Most of the image objects recorded on the K plate, that is, the image objects recorded with the black colorant are characters and fine lines, and smoothness of edges is required as an important image quality characteristic of the characters and fine lines. Since the smoothness of the edge is almost determined by the height of the resolution, increasing the resolution of the K plate as in this embodiment is effective for expressing characters and fine lines more beautifully. In the present embodiment, the colorant usage is not reduced for the K plate.

  Also in this embodiment, when black dots and color dots are overlapped in steps 208C to 208Y, the color dots are changed to OFF dots, or the black dots are changed to OFF dots. Also good. Such an embodiment is also included in the present invention.

  FIG. 4 shows a processing flow in the third embodiment.

  Image data (RGB data) is input by the image data input unit 1 (step 301). The RGB data is converted into CMYK color plane data by the color conversion processing unit 2 (step 302). Each color plate data of CMYK is subjected to γ correction processing by the γ correction processing unit 3 (step 303). The subsequent processing flow is switched between the K plate and the color plate.

  First, the K plate data is converted to a resolution of 1 / m of the output resolution by the resolution scaling processing unit (A) 4 (step 304), and halftone processing (dithering) is performed on the K plate data of the output resolution after conversion. Processing, error diffusion processing, etc.) are performed (step 305). However, m is an integer greater than or equal to 2.

  On the other hand, the CMY color plane data is converted into data having a resolution of 1 / n of the output resolution by the resolution scaling processing unit (A) 4 (step 306). However, n is a multiple of 2 or more of m (for example, m = 2, n = 4). The 1 / n resolution CMY color data is subjected to halftone processing (dither processing, error diffusion processing) by the halftone processing unit 5 (step 307).

  The resolution scaling processing unit (B) 6 replaces each dot of the K plane data and the CMY color plane data after halftone processing with an m × n dot pattern and an n × n dot pattern, respectively, thereby changing the resolution to the output resolution. Conversion is performed (steps 308K to 308Y). At this time, the m × m dot pattern and the n × n dot pattern that are replaced with the OFF dot are all OFF dots, but the m × m dot pattern and the n × n dot pattern that are replaced with the ON dot are the ON dots. In addition, the color material usage reduction rate is determined by the ratio of the ON dots. The m × m dot pattern and the n × n dot pattern applied in Steps 308K to 308Y are selected in order so as to rotate a set of dot patterns prepared in advance as described in connection with the first embodiment. Can be used or selected at random. Alternatively, an m × m dot pattern and an n × n dot pattern may be cut out from a large dispersed dot pattern. In this case, the vertical and horizontal sizes of the dispersed dot pattern should be selected to be a common multiple of m and n. Further, an mxm dot pattern and an nxn dot pattern may be obtained by calculation.

  The CMY plane data of the output resolution that is the processing result of steps 308K, 308C, 308M, and 308Y is output by the image output unit 7 (step 309).

  In this embodiment, halftone processing is performed on the K plate at a higher resolution than the CMY plate (m <n), so that a higher resolution dot pattern can be formed on the K plate than on the CMY plate. This is effective for expressing characters and fine lines more beautifully as in the second embodiment. In this embodiment, the amount of colorant used can be reduced for the K plate.

  Also in this embodiment, when an overlap between a black dot and a color dot occurs in steps 308K to 308Y, the color dot is changed to an OFF dot, or the black dot is changed to an OFF dot. Also good. Such an embodiment is also included in the present invention.

  It should be noted that a program that causes a computer to function as each means from the image data input unit 1 to the resolution scaling processing unit (B) 6 shown in FIG. 1, or other than the image output steps 107, 209, and 309 shown in FIGS. A program that causes a computer to execute each of these steps is also included in the present invention. Such a program can be incorporated into a printer driver, or can be realized as plug-in software of an application or as a single application that mediates between the application and the printer driver.

  Storage media (CD-ROM, DVD-ROM, memory card, etc.) on which these applications or plug-in software are recorded are also included in the present invention.

DESCRIPTION OF SYMBOLS 1 Image data input part 2 Color conversion process part 3 γ correction process part 4 Resolution scaling process part (A)
5 Halftone processing unit 6 Resolution scaling processing unit 7 Image output unit

JP-A-9-277646

Claims (9)

First processing means for converting K (black) plane data to output resolution and converting other color plane data to a resolution of 1 / n of the output resolution (where n is an integer of 2 or more);
Second processing means for performing halftone processing on the K plane data and other color plane data converted by the first processing section;
as well as,
The ON dots of the other color plate data after the halftone processing by the second processing means are replaced with an n × n dot pattern including ON dots corresponding to the colorant usage reduction rate, and the other after the halftone processing. A third processing means for performing processing for replacing the OFF dots of the color plate data with an n × n dot pattern not including the ON dots;
In the third processing means, n × n dot patterns that are replaced with ON dots of other color plate data after the halftone process are made different between the plates, and other colors after the halftone process An image processing apparatus, wherein the image data is changed for each dot position of plate data. Convert K (black) plate data to 1 / m of output resolution (where m is an integer of 2 or more), and convert other color plate data to 1 / n of output resolution (where n is a multiple of m) First processing means for converting to a resolution of a multiple of
Second processing means for performing halftone processing on the K plane data and other color plane data converted by the first processing section;
as well as,
The M × m dot pattern and the n × n dot pattern including the ON dots corresponding to the colorant usage reduction rate are used for the ON dots of the K plate data and other color plate data after the halftone processing by the second processing means. And a third process for replacing the OFF dots of the K plate data and the other color plate data after the halftone process with m × m dot patterns and n × n dot patterns that do not include ON dots, respectively. Having means,
In the third processing unit, the K pattern data after the halftone process and the dot pattern to be replaced with the ON dots of other color plane data are made different between the plates, and the K plate after the halftone process An image processing apparatus, wherein the data is changed for each dot position of data and other color plate data. In the third processing means, for each dot position of the K plate data or the other color plate data after the halftone processing, a set of dot patterns from a plurality of sets of dot patterns prepared in advance in a predetermined or random order. 3. The image according to claim 1, wherein the selected dot pattern is used as a dot pattern that is replaced with an ON dot of the K plate data or other color plate data after the halftone processing. 4. Processing equipment. In the third processing means, a dot pattern to be replaced with the ON dots of the K plate data or other color plate data after the halftone processing is cut out from a distributed dot pattern having a larger size, and the cut out position is determined as the cut position. The image processing apparatus according to claim 1, wherein the image processing apparatus is moved for each dot position of the K plane data or the other color plane data after the halftone process. In the third processing means, the ON dot on either side of the K plate data and the other color plate data at the overlapping position of the K plate data and the other color plate data after the dot pattern replacement processing. The image processing apparatus according to claim 2 , wherein the value is changed to OFF dots. In the third processing means, at a point overlapping the ON dots of another color plane data processed replacement of K plane data and de Ttopatan after the halftone process, or a K plane data and other color plane data The image processing apparatus according to claim 1 , wherein an ON dot on the side of the image is changed to an OFF dot.   A first processing step of converting K (black) plane data into output resolution and converting other color plane data into a resolution of 1 / n of the output resolution (where n is an integer of 2 or more);
  A second processing step of performing halftone processing on the K plane data and other color plane data after conversion in the first processing step;
as well as,
  The ON dots of the other color plate data after the halftone process in the second processing step are replaced with an n × n dot pattern including ON dots corresponding to the colorant usage reduction rate, and the other after the halftone process. A third processing step of performing a process of replacing the OFF dots of the color plate data with an n × n dot pattern not including the ON dots,
  In the third processing step, n × n dot patterns that are replaced with ON dots of other color plate data after the halftone processing are made different between the plates, and other colors after the halftone processing An image processing method, wherein the image data is changed for each dot position of plate data.   Convert K (black) plate data to 1 / m of output resolution (where m is an integer of 2 or more), and convert other color plate data to 1 / n of output resolution (where n is a multiple of m) A first processing step for converting the resolution to a multiple of
  A second processing step of performing halftone processing on the K plane data and other color plane data after conversion in the first processing step;
as well as,
  The m × m dot pattern and the n × n dot pattern including the ON dots corresponding to the colorant usage reduction rate are used for the ON dots of the K plate data and the other color plate data after the halftone processing in the second processing step. And a third process for replacing the OFF dots of the K plate data and the other color plate data after the halftone process with m × m dot patterns and n × n dot patterns that do not include ON dots, respectively. Having a process,
  In the third processing step, the K pattern data after the halftone process and the K pattern data after the halftone process are made different from each other in the dot pattern to be replaced with the ON dots of the K color data and other color data. An image processing method, wherein the data and other color plate data are changed for each dot position. Program for causing a computer to function as each processing unit of the image processing apparatus according to any one of claims 1 to 6.