JP2017196765A - Image processing system and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to easily add a pixel for suppressing ink discharge failure to an image.SOLUTION: A raster generation part 104 generates a raster image for every plural color plates, and displays tag data which represents a colorless for a colorless pixel. An image quality adjustment part 105 corrects a gradation of a color pixel, in which tag data, which represents a colorless, is not generated, by a lookup table, and corrects a graduation of a pixel, in which tag data, which represents a colorless, is generated, into a predetermined color graduation. A screen processing part 106 performs screen processing of a raster image after a graduation is corrected by the image quality adjustment part 105, and thereby forming an image of a dot.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image processing apparatus and an image forming apparatus.

  An apparatus for forming an image by ejecting ink has a function of preventing defective ejection of ink. As an invention relating to this function, for example, there is an invention disclosed in Patent Documents 1-3. The apparatus disclosed in Patent Literature 1 adds dots according to a predetermined pattern to an image to be formed, and prints the dots of the pattern dispersed in different passes. In the invention disclosed in Patent Document 2, dots are added to pixels that do not have ink color data for which preliminary ejection is performed, and preliminary ejection is performed using the added dots. In the invention disclosed in Patent Document 3, a non-periodic screen mask in which pixels for performing preliminary ejection are embedded, and a non-periodic screen mask adjacent to the non-periodic screen mask and performing a preliminary ejection. A screen mask having different pixel positions is generated, and the received image is processed by the generated screen mask.

JP 2004-25627 A JP 2007-83576 A JP 2014-37071 A

  An object of the present invention is to easily add pixels for suppressing ejection failure of ink to an image.

  An image processing apparatus according to claim 1 of the present invention includes a correction unit that acquires a raster image for each of a plurality of color plates and corrects colorless pixels in the raster image to colored pixels having a predetermined gradation. A screen processing unit that performs screen processing on the raster image whose gradation has been corrected by the correction unit, and an output unit that outputs the raster image after the screen processing is performed by the screen processing unit.

  An image processing apparatus according to claim 2 of the present invention includes a generation unit that generates tag data representing colorlessness for colorless pixels of the raster image in the image processing apparatus according to claim 1, The correction unit specifies colorless pixels of the raster image based on the tag data, and corrects the specified pixels to colored pixels having a predetermined gradation.

  An image processing apparatus according to a third aspect of the present invention is the image processing apparatus according to the second aspect, wherein the screen processing unit performs a first screen process on pixels for which the tag data has not been generated. A second screen process in which halftone dots are reduced as compared with the first screen process is performed on the pixels for which the tag data is generated.

  An image processing apparatus according to a fourth aspect of the present invention is the image processing apparatus according to the second aspect, wherein in the raster image of a plurality of color plates, the correction unit is configured such that each of the pixels having the same coordinates is colorless. The gradation of the pixel is corrected to a colored pixel having a predetermined gradation.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to fourth aspects, and a raster image output from the output unit on a recording medium by ejecting ink. An image forming unit to be formed.

According to the image processing apparatus of the first aspect, pixels for suppressing ink ejection defects can be easily added to an image.
According to the image processing device of the second aspect, it is possible to quickly perform the process of correcting the colorless pixel to the colored pixel as compared with the configuration in which the tag data is not generated.
According to the image processing apparatus of the third aspect, the number of pixels for suppressing ejection defects can be reduced as compared with a case where the same screen processing is performed on all the pixels.
According to the image processing apparatus of the fourth aspect, pixels that are colorless before gradation correction can be used as pixels for suppressing ejection defects.
According to the image forming apparatus of the fifth aspect, it is possible to easily add pixels for suppressing ink ejection defects to an image and form an image with the pixels added on a sheet.

2 is a block diagram showing a hardware configuration of the image processing apparatus 10. FIG. 5 is a flowchart showing a flow of processing performed by a raster generation unit 104. The figure for demonstrating the operation example of embodiment. 6 is a flowchart showing a flow of processing performed by the image quality adjustment unit 105. The block diagram which showed the hardware constitutions of 10 A of image processing apparatuses. The flowchart which showed the flow of the process which 106A of screen processing parts perform.

[First Embodiment]
[Configuration of First Embodiment]
FIG. 1 is a block diagram showing a hardware configuration of an image processing apparatus 10 according to the first embodiment of the present invention. The image processing apparatus 10 is an apparatus that supplies data representing an image to be formed on a sheet to an image forming apparatus that forms an image on a sheet by ejecting ink. Each unit of the image processing apparatus 10 is connected to the bus 100 and exchanges data with other blocks via the bus 100.

The interface unit 103 has a communication interface function, and acquires image data supplied from an external device via a communication line. The interface unit 103 outputs data representing an image to the image forming apparatus. The interface unit 103 is an example of an output unit according to the present invention.

In the present embodiment, the image data is described in PDL (Page Description Language). The control unit 101 includes a central processing unit (CPU), a random access memory (RAM), and a read only memory (ROM). When the CPU of the control unit 101 executes a program stored in the ROM, the control unit 101 controls each unit in accordance with the executed program. The storage unit 102 has a nonvolatile memory that permanently stores data, and stores the image data acquired by the interface unit 103.

  The raster generation unit 104 generates a raster image (bitmap image) from the image data stored in the storage unit 102. In this embodiment, since the image forming apparatus forms an image with four colors of ink of cyan, magenta, yellow, and black, the raster generation unit 104 generates a raster image for each of four plates of cyan, magenta, yellow, and black. Is generated. In the present embodiment, the gradation of the pixels of the raster image is represented by a pixel value that ranges from 0 to 255. When the color is colorless, the pixel value is 0, and the pixel value increases as the gradation becomes darker. Has increased.

  Further, the raster generation unit 104 refers to the pixel value of the generated raster image and generates tag data. The raster generation unit 104 is an example of a generation unit according to the present invention. Specifically, the raster generation unit 104 adds pixels of pixels having the same coordinates when a raster image of a cyan plate, a raster image of a magenta plate, a raster image of a yellow plate, and a raster image of a black plate are superimposed. When all the values are 0 (that is, colorless), tag data with a value of 1 is generated and associated with the pixel group of the corresponding coordinate, and the pixel value of any version of the pixel is 1 or more Then, tag data with a value of 0 is generated and associated with the pixel group of the coordinate.

  The image quality adjustment unit 105 has a function of performing image processing on cyan, magenta, yellow, and black raster images, and performs gradation correction image processing on the raster images. The image quality adjustment unit 105 is an example of a correction unit according to the present invention. The image quality adjustment unit 105 determines the coordinates of a pixel of interest in each of the cyan, magenta, yellow, and black raster images when performing gradation correction. The image quality adjustment unit 105 corrects the pixel value with reference to a predetermined lookup table when the value of the tag data associated with the pixel of the determined coordinate is 0. The image quality adjustment unit 105 corrects the pixel value to 1 when the value of the tag data associated with the pixel having the determined coordinate is 1.

  For example, for the pixel at the determined coordinate, the image quality adjustment unit 105 has a pixel value of 0 in the cyan plate, 20 in the magenta plate, 115 in the yellow plate, and 115 in the black plate. When the pixel value is 0, in the magenta and yellow plates, the pixel value is other than 0 and the value of the associated tag data is 0. The pixel value is corrected with reference to the up table. Further, the image quality adjustment unit 105 determines that each pixel value of the determined coordinate is 0 in the cyan, magenta, yellow, and black versions, and the associated tag data value is 1. For the pixel of the plate, the pixel value which is 0 is corrected to 1.

  The screen processing unit 106 acquires a raster image of each plate after the pixel value is corrected by the image quality adjustment unit 105. The screen processing unit 106 performs screen processing on the raster image, and is an example of the screen processing unit according to the present invention. The screen processing unit 106 has a dither matrix predetermined for each of the cyan, magenta, yellow, and black plates, and applies a dither matrix corresponding to the plate to the acquired raster image to apply a network using a dither method. Generate a point image. In this embodiment, a value selected from the range of 1 to 255 is stored in the dither matrix as a threshold value.

[Operation Example of First Embodiment]
Next, an operation example of the first embodiment will be described. When the user causes the image forming apparatus connected to the image processing apparatus 10 to form an image, the user operates the computer apparatus and supplies the image data described in PDL to the image processing apparatus 10. The interface unit 103 acquires image data supplied from the computer device. Image data acquired by the interface unit 103 is stored in the storage unit 102.

  The control unit 101 supplies the image data stored in the storage unit 102 to the raster generation unit 104. When the image data is supplied, the raster generation unit 104 executes the process shown in FIG. First, the raster generation unit 104 generates a cyan plate raster image, a magenta plate raster image, a yellow plate raster image, and a black plate raster image from the supplied image data (step S1). Next, the raster generation unit 104 refers to the pixel value of each version of the raster image and generates tag data (step S2).

  Assume that a cyan plate raster image, a magenta plate raster image, a yellow plate raster image, and a black plate raster image are generated as shown in the left column of FIG. In this case, in the cyan, magenta, and yellow raster images, the pixel values of all the pixels are 0, and there are no pixels that have a pixel value of 1 or more. Further, in the black raster image, the pixel values of the pixels other than the triangular region and the rectangular region are zero. That is, the pixel value of the pixel in the region indicated by the left-down hatching in the center column in FIG. The raster generation unit 104 pays attention to the pixels having the same coordinates in the four raster images, generates tag data having a value of 1 for the pixels having a pixel value of 0 in all the four plates, and associates them. . Further, regarding the triangular area and the rectangular area shown in white in the center column of FIG. 3, when focusing on the same coordinates in the raster image of the four plates, the pixel value does not become 0 in the black plate. Tag data having a value of 0 is generated and associated with each pixel in the region.

  When the raster generation unit 104 finishes the process of FIG. 2, the control unit 101 supplies the raster image associated with the tag data to the image quality adjustment unit 105. When the raster image with the tag data generated is supplied, the image quality adjustment unit 105 executes the processing shown in FIG.

  Specifically, the image quality adjustment unit 105 determines the coordinates of a pixel of interest as a pixel for which gradation correction is performed (step S11). Next, the image quality adjustment unit 105 corrects the pixel value of the pixel at the determined coordinate (step S12). Here, the image quality adjustment unit 105 refers to the tag data associated with the determined coordinate pixel in each of the cyan, magenta, yellow, and black raster images. When the value of the tag data associated with the determined coordinate pixel is 1, the image quality adjustment unit 105 converts the pixel value of the coordinate pixel determined in step S11 to 1. In addition, when the value of the tag data associated with the pixel of the coordinate determined in step S11 is 0, the image quality adjustment unit 105 refers to the lookup table for the pixel value of the pixel of the coordinate determined in step S11. To correct.

  For example, the image quality adjustment unit 105 sets the upper left of the raster image as the origin, the right direction as the positive direction of the X axis, and the lower direction as the positive direction of the Y axis. When the image quality adjustment unit 105 determines the coordinate of the pixel of interest as the origin (0, 0), in the example of the raster images of cyan, magenta, yellow, and black shown in FIG. 3, the origin (0, 0) Since the value of the tag data associated with this pixel is 1, the pixel value of the pixel at the coordinates (0, 0) is corrected to 1 in each of the cyan, magenta, yellow, and black raster images.

  When the image quality adjustment unit 105 determines the coordinate of the pixel of interest to be (x1, y1) in the triangular area of the raster image shown in FIG. 3, the value of the tag data associated with the pixel of this coordinate Since 0 is 0, the pixel value of the pixel at the coordinates (x1, y1) in each raster image is corrected with reference to the lookup table. In each of the cyan, magenta, and yellow raster images, the pixel value of the pixel at the coordinates (x1, y1) remains 0 after correction.

  When the process of step S12 is completed, the image quality adjustment unit 105 determines whether gradation correction processing has been performed for all pixels of the raster image (step S13). If the gradation correction processing has not been completed for all pixels (NO in step S13), the image quality adjustment unit 105 returns the processing flow to step S11 and changes the coordinates of the pixel of interest. In addition, when the gradation correction processing has been completed for all the pixels (YES in step S13), the image quality adjustment unit 105 ends the gradation correction processing.

  For example, as shown in the center column of FIG. 3, when tag data having a value of 1 is added to the hatched area with the lower left corner, the processing shown in FIG. The pixel value in the hatching portion that falls to the right is 1.

  When the tone correction processing is completed in the image quality adjustment unit 105, the control unit 101 supplies the raster image after the tone correction to the screen processing unit 106. The screen processing unit 106 binarizes the supplied cyan, magenta, yellow, and black raster images by performing screen processing. When the image quality adjustment unit 105 performs screen processing on the raster image, in the cyan, magenta, yellow, and black raster images, the pixel values of the pixels in the lower right hatched portion shown on the right side of FIG. Pixels having a pixel value equal to or greater than the dither matrix threshold value have a pixel value of 1, and pixels having a pixel value less than the dither matrix threshold value have a pixel value of 0. Since the dither matrix has a threshold value of 1, in the raster image of cyan, magenta, yellow, and black after screen processing, the portion where the pixel value becomes 1 or more after the gradation correction (before gradation correction) In the portion shown in FIG. 3 as hatched, halftone dots are formed according to the dither matrix.

  When the screen processing is completed, the control unit 101 supplies data representing the raster image after the screen processing is performed from the interface unit 103 to the partial image forming apparatus. The image forming apparatus acquires data supplied from the image processing apparatus 10. The image forming apparatus ejects ink onto a sheet based on the supplied data to form a halftone dot image on the sheet.

  When the configuration of the present embodiment is not provided, for a pixel whose pixel value is 0 in each of the cyan, magenta, yellow, and black plates when the raster image is generated, that is, a colorless pixel, Since tone correction processing is not performed, the pixel value remains 0 in each raster image when performing screen processing. In the cyan, magenta, and yellow raster images, the pixel values of all the pixels remain 0 even when screen processing is performed. Therefore, ink is not ejected during image formation, and the nozzle that ejects ink is clogged. May occur.

  On the other hand, in the present embodiment, when the raster image is generated by the raster generation unit 104, the pixel values of the pixels having the same coordinates are all 0, that is, pixels that are colorless are subjected to gradation correction processing, and the pixel value is 1 is a colored pixel. Among the pixels that have changed from colorless to colored, there are pixels that become halftone dots by screen processing. For this reason, during image formation, halftone dots are formed in portions that were colorless before gradation correction, ink is ejected during image formation, and clogging is less likely to occur in nozzles that eject ink.

  In the above-described embodiment, the image quality adjustment unit 105 refers to the tag data, and in all the raster images of cyan, magenta, yellow, and black, the tag data associated with the pixel of the coordinate of interest. When the value is 1, the pixel value of the pixel of the coordinate of interest is corrected from 0 to 1 with four versions, but the configuration for correcting the pixel value is not limited to the configuration of the embodiment. Absent. For example, when the tag data is generated, if the pixel value of the pixel of interest is 0 in any of the four plates, tag data having a value of 1 is generated for the pixel at the coordinate. Then, in the gradation correction process, when 1 tag data is added to the pixel of the coordinate of interest, the pixel value of the pixel of the coordinate of interest may be corrected from 0 to 1. . In this configuration, the raster images of the cyan, magenta, and yellow plates have pixel values in the non-hatched areas (in the white triangle area and white square area) shown in the right column of FIG. Are converted from 0 to 1, and halftone dots are also formed in regions where the halftone dots are not formed in the above-described embodiment in the raster images of cyan, magenta, and yellow.

  In the above-described embodiment, tone correction is performed with reference to tag data. However, the configuration for performing tone correction is not limited to the configuration of the embodiment. For example, in the raster generation unit 104, It is good also as a structure which does not add tag data. In the case of this configuration, the image quality adjustment unit 105 refers to the pixel value of the pixel of the coordinate of interest, and when the pixel value is 0 in all the raster images of the plate, The pixel value of each plate may be corrected to 1. Also, the image quality adjustment unit 105 has a pixel value of 0 for any version of the pixel of interest, and a pixel value of 0 for a pixel having a pixel value of 1 or more in the other version. In the plate, the pixel value may be corrected to 1, and in the plate having a pixel value of 1 or more, the pixel value may be corrected by referring to a predetermined lookup table.

  In the above-described embodiment, the pixel value is corrected to 1 when correcting the gradation of the pixel whose pixel value is 0. However, the corrected pixel value is not limited to 1, and 2 You may correct | amend to the above value.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing a hardware configuration of an image processing apparatus 10A according to the second embodiment of the present invention. The image processing apparatus 10 </ b> A includes the same control unit 101, storage unit 102, interface unit 103, and raster generation unit 104 as the image processing apparatus 10. The image processing apparatus 10 </ b> A replaces the image quality adjustment unit 105 and screen processing unit 106 of the first embodiment. 105A and screen processing unit 106A. The description of the control unit 101, the storage unit 102, the interface unit 103, and the raster generation unit 104 having the same configuration as that of the first embodiment will be omitted, and the image quality adjustment unit 105A and the screen processing unit 106A that are different from those of the first embodiment will be described below. Will be described.

  The image quality adjustment unit 105A performs tone correction image processing on cyan, magenta, yellow, and black raster images. The image quality adjustment unit 105A is an example of a correction unit according to the present invention. The image quality adjustment unit 105A determines the coordinates of the pixel of interest in each raster image of cyan, magenta, yellow, and black when performing gradation correction. The image quality adjustment unit 105A determines a predetermined look-up table when tag data having a value of 0 is associated with a pixel at a determined coordinate in a raster image of cyan, magenta, yellow, or black. The pixel value is corrected with reference to FIG. Also, the image quality adjustment unit 105 corrects the pixel value to 2 when tag data having a value of 1 is associated with the pixel of the determined coordinate in all the cyan, magenta, yellow, and black raster images. To do.

  For example, for the pixel at the determined coordinate, the image quality adjustment unit 105A has a pixel value of 0 for the cyan plate, 20 for the magenta plate, 115 for the yellow plate, and 115 for the black plate. When the pixel value is 0, tag data having a value of 0 is associated, and therefore the pixel value of the pixel having this coordinate is corrected with reference to a predetermined lookup table. Further, when the pixel value of the determined coordinate pixel is 0 in the cyan, magenta, yellow, and black versions, the image quality adjustment unit 105A has tag data having a value of 1 in the pixel of the coordinate of interest. Since it is associated, the pixel value which is 0 for this pixel is corrected to 2. The corrected pixel value is not limited to 2, and may be 3 or more.

  The screen processing unit 106A acquires a raster image of each plate after the pixel value is corrected by the image quality adjustment unit 105A. The screen processing unit 106A performs screen processing on the raster image, has a predetermined dither matrix, and generates a halftone image by the dither method by applying the dither matrix to the acquired raster image. To do. The screen processing unit 106A is an example of a screen processing unit according to the present invention.

  When performing the screen processing, the screen processing unit 106A determines the coordinates of the pixel of interest in each of the cyan, magenta, yellow, and black raster images. When the tag data having a value of 0 is associated with the pixel of the determined coordinate, the screen processing unit 106A performs a first screen process for generating a halftone dot by applying a predetermined first dither matrix. Do.

  Further, when the tag data having a value of 1 is associated with the pixel of the determined coordinate, the screen processing unit 106A applies a predetermined second dither matrix to generate a halftone dot. Process. In the present embodiment, the second dither matrix is a dither matrix obtained by adding 1 to each threshold value of the first dither matrix. For example, the threshold value is 2 for a portion where 1 is stored in the first dither matrix. Yes. The second dither matrix is not limited to the above, but may be another dither matrix. For example, when the pixel value of a colorless pixel is corrected to 3 or more, the dither matrix including the corrected value may be used as the second dither matrix.

[Operation Example of Second Embodiment]
Next, an operation example of the second embodiment will be described. The operation from the time when the image processing apparatus 10A acquires image data to the time when the raster data is added to the raster image by the raster generation unit 104 is the same as that in the first embodiment, and a description thereof will be omitted.

  When the raster generation unit 104 finishes the process of FIG. 2, the control unit 101 supplies the raster image associated with the tag data to the image quality adjustment unit 105A. When the raster image associated with the tag data is supplied, the image quality adjustment unit 105A executes the process shown in FIG.

  The image quality adjustment unit 105A determines the coordinates of a pixel of interest as a pixel to be subjected to gradation correction (step S11). Next, the image quality adjustment unit 105A corrects the pixel value of the pixel at the determined coordinate (step S12). Here, the image quality adjustment unit 105A refers to the tag data associated with the pixel of the determined coordinate in each of the cyan, magenta, yellow, and black raster images. When the value of the tag data associated with the determined coordinate pixel is 1, the image quality adjustment unit 105A converts the pixel value of the coordinate pixel determined in step S11 to 2. Further, when the value of the tag data associated with the pixel having the coordinates determined in step S11 is 0, the image quality adjustment unit 105A refers to the lookup table for the pixel value of the pixel having the coordinates determined in step S11. To correct.

  For example, when the image quality adjustment unit 105A determines the coordinate of the pixel of interest as the origin (0, 0), in the example of the raster images of cyan, magenta, yellow, and black shown in FIG. , 0), the tag data value associated with the pixel is 1, so that the pixel value of the pixel at the coordinates (0, 0) is corrected to 2 in each of the cyan, magenta, yellow, and black raster images.

  Further, when the image quality adjustment unit 105A sets the coordinate of the pixel of interest as (x1, y1) in the triangular area of the raster image shown in FIG. 3, the value of the tag data associated with the pixel of this coordinate is Therefore, the pixel value of the pixel at the coordinates (x1, y1) in each raster image is corrected with reference to the lookup table. In each of the cyan, magenta, and yellow raster images, the pixel value of the pixel at the coordinates (x1, y1) remains 0 after correction.

  When the process of step S12 is completed, the image quality adjustment unit 105A determines whether the gradation correction process has been performed for all the pixels of the raster image (step S13). If the gradation correction processing has not been completed for all pixels (NO in step S13), the image quality adjustment unit 105A returns the processing flow to step S11 and changes the coordinates of the pixel of interest. Further, the image quality adjustment unit 105A ends the gradation correction process when the gradation correction process has been completed for all the pixels (YES in step S13).

  When the tone correction processing is completed in the image quality adjustment unit 105A, the control unit 101 supplies the raster image after the tone correction to the screen processing unit 106A. The screen processing unit 106A performs binarization by performing screen processing on the supplied raster image of cyan, magenta, yellow, and black.

  FIG. 6 is a flowchart showing the flow of screen processing performed by the screen processing unit 106A. First, the screen processing unit 106A determines the coordinates of a pixel of interest as a pixel to be screened (step S21). Next, the screen processing unit 106A determines whether the value of the tag data associated with the determined coordinate pixel is 1 (step S22). Specifically, the screen processing unit 106A refers to the tag data associated with the determined coordinate pixel. When the value of the referenced tag data is 1 (YES in step S22), the screen processing unit 106A performs screen processing on the pixel at the coordinate determined in step S21 using the second dither matrix (step S23). . On the other hand, when the value of the tag data associated with the determined coordinate pixel is 0 (NO in step S22), the screen processing unit 106A applies the first dither matrix to the coordinate pixel determined in step S21. And screen processing is performed (step S24).

  When the processing of step S23 or step S24 is completed, the screen processing unit 106A determines whether screen processing has been performed for all pixels of the raster image (step S25). When the screen processing has not been completed for all the pixels (NO in step S25), the screen processing unit 106A returns the processing flow to step S21 and changes the coordinates of the pixel of interest. Further, when the screen processing unit 106A completes the screen processing for all the pixels (YES in step S25), the screen processing unit 106A ends the screen processing.

  When the screen processing unit 106A performs screen processing on the raster image, in the raster images of cyan, magenta, yellow, and black, the pixels in the lower right hatched portion shown in the right column of FIG. Screen processing is performed by the second dither matrix on the pixels of the colorless portion before the tone correction. Further, the pixels in the triangular area and the rectangular area, that is, the pixels in the colored portion before the gradation correction are subjected to screen processing by the first dither matrix.

  When the screen processing unit 106A finishes the screen processing, the control unit 101 supplies the raster image after the screen processing is performed from the interface unit 103 to the partial image forming apparatus. The image forming apparatus acquires a raster image supplied from the image processing apparatus 10A. The image forming apparatus ejects ink onto a sheet based on the supplied raster image to form an image on the sheet.

  According to the second embodiment, screen processing is performed with a dither matrix having a high threshold value for a portion that has been colorless before tone correction, so the amount of ink ejected to the portion that has been colorless is the first. Less than the embodiment.

  In the above description, the pixel value is corrected to 2 when correcting the gradation of the pixel having a pixel value of 0. However, the corrected pixel value is not limited to 2, but 3 or more. You may correct | amend to the value of.

[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It can implement with another various form. For example, the present invention may be implemented by modifying the above-described embodiment as follows. In addition, you may combine each of embodiment mentioned above and the following modifications.

  In the above-described embodiment, the image processing apparatuses 10 and 10A are separated from the image forming apparatus. However, the image forming apparatus includes the image processing apparatuses 10 and 10A, and the image processing apparatuses 10 and 10A and the image forming apparatus are formed. The structure which is integral with the apparatus may be sufficient.

  The processing performed by the raster generation unit 104, the image quality adjustment units 105 and 105A, and the screen processing units 106 and 106A described above is not performed by hardware, but may be performed by the control unit 101 according to a program stored in the ROM. Good.

  In the above-described embodiment, the pixel value is set to 1 when the pixel value is greater than or equal to the dither matrix threshold value in the screen processing, and the pixel value is set to 0 when the pixel value is less than the threshold value. When the range is 0 to 254, the pixel value may be set to 1 when the pixel value is larger than the threshold value of the dither matrix, and the pixel value may be set to 0 when the pixel value is less than or equal to the threshold value.

  DESCRIPTION OF SYMBOLS 10, 10A ... Image processing apparatus, 100 ... Bus, 101 ... Control part, 102 ... Memory | storage part, 103 ... Interface part, 104 ... Raster production | generation part, 105, 105A ... Image quality adjustment part, 106, 106A ... Screen processing part.

Claims (5)

A correction unit that acquires a raster image for each of a plurality of color plates and corrects colorless pixels in the raster image to colored pixels of a predetermined gradation;
A screen processing unit that performs screen processing on the raster image after the gradation is corrected by the correction unit;
An image processing apparatus comprising: an output unit that outputs a raster image after the screen processing is performed by the screen processing unit. For a colorless pixel of the raster image, a generation unit that generates tag data representing colorlessness,
The image processing apparatus according to claim 1, wherein the correction unit specifies colorless pixels of the raster image by the tag data, and corrects the specified pixels to colored pixels having a predetermined gradation. The screen processing unit performs a first screen process on the pixels for which the tag data has not been generated, and has fewer halftone dots than the first screen process for the pixels for which the tag data has been generated. The image processing apparatus according to claim 2, wherein a second screen process is performed. The correction unit corrects the gradation of the pixel to a colored pixel having a predetermined gradation when each of the pixels having the same coordinates is colorless in a plurality of color raster images. Image processing apparatus. An image processing apparatus according to any one of claims 1 to 4,
An image forming apparatus comprising: an image forming unit configured to form a raster image output from the output unit on a recording medium by ejecting ink.

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