JP2012129685A - Image processing device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing device and a program capable of suppressing deterioration of a color boundary part when converting binary image information converted from multivalued image information, to new multivalued image information.SOLUTION: An image processing device 1 is provided with: a flag holding part 47 which holds positional information expressing the position of the pixel column adjacent to the boundary between the area of a first color and the area of a second color in the multivalued image information and holds reference information which expresses the positions of pixels where colors to be used for composition are referred to, in boundary color overprint processing which sets the color of the pixel column adjacent to the boundary to be a color obtained by composing the first color and the second color; and a second converter 49 which converts the binary image information converted from the multivalued image information to new multivalued image information, the second converter 49 determining the color of the pixel column identified with the positional information on the basis of the colors of the pixels identified with the reference information.

Description

  The present invention relates to an image processing apparatus and a program.

  Patent Document 1 discloses an image processing apparatus that includes a buffer memory for binary image information and a writing unit that draws multi-value image information, and converts the binary image information into multi-value image information as necessary. Has been.

JP 05-061971 A

  The present invention provides an image processing apparatus and a program capable of suppressing deterioration of a color boundary portion when binary image information converted from multi-value image information is converted into new multi-value image information. The main purpose.

  In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that each pixel includes two or more colors, and the first color region of the multi-value image information in which each color is represented by three or more gradations. A holding unit that holds position information indicating a position of a pixel column adjacent to the boundary between the first color region and the second color region; and direction information indicating a direction in which the boundary is adjacent to the pixel column; A conversion unit that converts binary image information converted from value image information, each pixel including two or more colors, and each color represented by two gradations into new multi-value image information, the position An image processing apparatus comprising: a conversion unit that determines a color of each pixel included in a pixel row specified by information based on a color of a pixel in a direction specified by the direction information.

  In the invention according to claim 2, the holding unit further holds color information indicating a color of a pixel column adjacent to the opposite side of the boundary from the pixel column adjacent to the boundary. When the pixel column specified by the position information of the binary image information includes a pixel of the color of the pixel column adjacent to the opposite side, the color of the pixel is used for multi-leveling of the binary image information. The image processing apparatus according to claim 1, which is not used.

  According to a third aspect of the present invention, the first color region and the second color are included in the multi-value image information in which each pixel includes two or more colors and each color is represented by three or more gradations. And a generation unit that generates position information indicating a position of a pixel column adjacent to the boundary with the region and direction information indicating a direction in which the boundary is adjacent to the pixel column. It is a processing device.

  According to a fourth aspect of the present invention, the first color region and the second color are included in the multivalued image information in which each pixel includes two or more colors and each color is represented by three or more gradations. A multi-value image information, a processing unit that executes a boundary color weighting process for changing the color of a pixel column adjacent to the boundary with the region to a color obtained by combining the first color and the second color, A first conversion unit that converts each pixel to binary image information in which each pixel includes two or more colors and each color is expressed in two gradations; position information that indicates a position of a pixel column adjacent to the boundary; and the pixel Direction information indicating a direction in which the boundary is adjacent to a column; a generation unit that generates a direction; a holding unit that holds the position information and the direction information; and the binary image information as new multi-value image information. A second conversion unit for converting the color of each pixel included in the pixel row specified by the position information according to the direction information; An image processing apparatus characterized by comprising, a second conversion unit for determining on the basis of the color of the direction of the pixel specified.

  According to a fifth aspect of the present invention, the first color region and the second color are included in the multivalued image information in which each pixel includes two or more colors and each color is represented by three or more gradations. A holding unit that holds position information indicating the position of the pixel column adjacent to the boundary with the region and direction information indicating the direction in which the boundary is adjacent to the pixel column, and conversion from the multi-value image information A conversion unit that converts binary image information in which each pixel includes two or more colors and each color is expressed by two gradations into new multi-value image information, and is specified by the position information A program that causes a computer to function as a conversion unit that determines the color of each pixel included in a pixel column based on the color of a pixel in a direction specified by the direction information.

  According to a sixth aspect of the present invention, the first color region and the second color are included in the multi-value image information in which each pixel includes two or more colors and each color is represented by three or more gradations. Is a program that causes a computer to function as a generation unit that generates position information indicating the position of a pixel column adjacent to the boundary with the region and direction information indicating the direction in which the boundary is adjacent to the pixel column. .

  According to the first, fourth, and fifth aspects of the invention, the first color and the second color of the pixel row adjacent to the boundary between the first color region and the second color region are synthesized. It is possible to suppress color deterioration.

  According to the second aspect of the present invention, it is possible to prevent the other color from being mixed in the first color region and the second color region.

  According to the third and sixth aspects of the present invention, the first color and the second color of the pixel row adjacent to the boundary between the first color region and the second color region are combined. Information for suppressing deterioration can be provided.

It is a figure showing the example of a structure of the image processing apparatus which concerns on one Embodiment of this invention. It is a figure showing the example of a function of the image processing apparatus concerning the embodiment. It is a figure showing the example of original multi-value image information. It is a figure showing the example of the multi-value image information after a trapping process. It is a figure showing the example of flag information. It is a figure showing the example of flag information. It is a figure showing the example of the binary image information after multi-value-binary conversion. It is a figure showing the example of the multi-value image information after binary-multi-value conversion. It is a figure showing the example of the multi-value image information after correction | amendment.

  Embodiments of an image processing apparatus and a program according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration example of an image processing apparatus 1 according to an embodiment of the present invention. The image processing apparatus 1 includes a control unit 21, an image processing unit 22, an operation unit 23, a storage unit 24, a communication unit 25, a display unit 26, an image forming unit 27, and an image reading unit 28.

  The control unit 21 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). When the CPU executes a program stored in the ROM or the storage unit 24, image processing is performed. Each part of the apparatus 1 is controlled. The image processing unit 22 includes an ASIC (Application Specific Integrated Circuit) that executes specific image processing.

  The operation unit 23 includes a plurality of keys, receives a user operation, and outputs a signal corresponding to the operation to the control unit 21. The storage unit 24 is a nonvolatile auxiliary storage device such as an HDD (Hard Disk Drive), and stores various programs and data. The communication unit 25 includes a communication interface and communicates with other devices via a communication path such as a LAN (Local Area Network). The display unit 26 includes a liquid crystal display screen and a liquid crystal drive circuit, and displays the progress of processing, information for guiding operations to the user, and the like based on information supplied from the control unit 21.

  The image forming unit 27 is a photosensitive drum that holds an image, an exposure unit that forms an electrostatic latent image on the photosensitive drum by performing exposure based on image information, and develops the electrostatic latent image to form a toner image. A developing unit to be formed, a transfer unit for transferring the toner image to the recording paper, and a fixing unit for fixing the toner image transferred to the recording paper to the recording paper are provided. The image reading unit 28 includes an image sensor such as a CCD (Charge Coupled Device), reads an image formed on a recording sheet by the image sensor, and generates image information representing the read image.

  FIG. 2 is a diagram illustrating an example of functions of the image processing apparatus 1. The image processing apparatus 1 includes a trapping processing unit 41, a flag generation unit 43, a first conversion unit 45, a flag holding unit 47, and a second conversion unit 49. The second conversion unit 49 includes a multilevel conversion unit 49a and a correction unit 49b.

  Each of the above units is realized by the CPU included in the control unit 21 executing a program stored in the ROM or the storage unit 24. The program may be provided from a computer-readable information recording medium such as a CD-ROM, or may be provided via a communication line such as the Internet.

  In addition, each of the above units may be configured as a circuit included in the image processing unit 22. For example, in one desirable aspect, the control unit 21 implements a trapping processing unit 41, a flag generation unit 43, and a first conversion unit 45, and the image processing unit 22 includes a flag holding unit 47 and a second conversion unit 49. .

  The trapping processing unit 41 performs trapping processing on the input multivalued image information, and outputs the multivalued image information subjected to the trapping processing to the first conversion unit 45. Further, the trapping processing unit 41 outputs processing information related to the trapping process to the flag generation unit 43.

  As shown in the example of FIG. 3, the multi-value image information input to the trapping processing unit 41 has a plurality of pixels arranged two-dimensionally, and each pixel includes two or more types of colors. Yes. In this example, each pixel includes four types of colors, C (cyan), M (magenta), Y (yellow), and K (black). Each color of each pixel is represented by three or more gradations (for example, eight gradations).

  Further, as shown in the example of FIG. 3, the multi-value image information input to the trapping processing unit 41 has a plurality of regions having different colors, and the trapping process is performed at a boundary portion between the plurality of regions. To be applied.

  The trapping process is a boundary color weighting process in which the color of the pixel column adjacent to the boundary between the first color area and the second color area is changed to a color obtained by combining the first color and the second color. It is. For example, as shown in the example of FIG. 3, in the multi-value image information, the first color region that does not include the second color, and the second color region that includes the first color. If an area that does not include is adjacent, there is a risk that plate misregistration will occur during image formation, resulting in a blank between the two areas. Therefore, in order to suppress misregistration, as shown in the example of FIG. 4, the color of the pixel column adjacent to the boundary between the two regions is a combination of the colors of the two regions. Note that the present invention is not limited to this, and the first color and the second color may be a color in which a plurality of types of colors are mixed. For each type of color, if there is a difference in gradation between two areas that is greater than or equal to a predetermined value, the boundary between these areas may be the target of the trapping process.

  That is, in the trapping process, the color of the region adjacent to the other is combined with the pixel column adjacent to one side in the boundary width direction, and the color of the region adjacent to one side is combined with the pixel column adjacent to the other in the boundary width direction. Is synthesized. The width direction of the boundary is a direction orthogonal to the extending direction of the boundary. In other words, in the trapping process, each of the two adjacent regions is enlarged in the width direction of the boundary, and the colors are superimposed. In addition, the pixel row | line | column with which a color is synthesize | combined may be one or both of the two pixel row | line | columns adjacent to the both sides of a boundary. In addition, the pixel row in which the colors are combined may be a pixel row having a width of two pixels or more adjacent to the boundary.

  In the example of FIGS. 3 and 4, an area where the gradation of K color is 50% (hereinafter referred to as “K color 50%”) and an gradation of M color is 50% (hereinafter referred to as “M color 50%”). The color types and gradations of the pixel columns adjacent to both sides of the boundary with the area (2) are K color 50% and M color 50%. The color combination is not limited to this mode. Each region is not limited to a single color of CMYK, and may be a mixed color of these.

  Specifically, the trapping processing unit 41 performs the trapping process as follows. In the first step, the boundary of each color is detected in the multi-value image information. The boundary mentioned here is a boundary between a region including the target color and a region not including the color. For example, a window including a pixel of interest and surrounding pixels surrounding it, such as 3 × 3 pixels, is scanned for multi-value image information, and the gradation of the pixel of interest is compared with the gradation of each surrounding pixel. When the difference is greater than or equal to the threshold value, the corresponding pixel is determined as a boundary. Thereby, the position of the pixel adjacent to the boundary and the direction in which the boundary is adjacent to the pixel are obtained. In the second step, it is determined whether different color regions are adjacent to each other, that is, whether different color boundaries coincide with each other. As a result, the boundary between the first color area having a predetermined gradation or more and the second color area having a predetermined gradation or more is set as a processing target. In the third step, as described above, it is assumed that the colors of the pixel columns adjacent to the boundary between the different color areas are combined with the colors of the two areas. For example, when changing the color of each pixel included in the pixel column, the color type and gradation of the pixel adjacent on the opposite side across the boundary are referred to. However, the present invention is not limited to this, and the color type and gradation of two or more adjacent pixels across the boundary may be referred to.

  The flag generation unit 43 receives processing information related to the trapping process from the trapping processing unit 41, and generates flag information based on the processing information. For example, the processing information includes boundary information determined in the first and second steps. Specifically, the processing information includes information on the position of the pixel adjacent to the boundary, information on the direction in which the boundary is adjacent to the pixel, information on the color of the pixel adjacent to the boundary, and the like.

  As shown in the example of FIG. 5A, the flag information has the same pixel arrangement as that of the multi-value image information, and the position of each pixel corresponds to each pixel of the multi-value image information. In the flag information, boundary information is represented by the value of each pixel. As shown in the example of FIG. 5B, the value of each pixel is described by a value of several bits, for example. For the sake of explanation, the meaning of each value is described at the right end of the table in FIG. 5B. In the table of FIG. 5B, combinations of K color and other colors are described, but the combination of colors is not limited to these.

  The flag information includes position information indicating the position of each pixel belonging to the pixel column adjacent to the boundary. Specifically, the value of each pixel can be roughly divided into a value indicating a pixel adjacent to the boundary (in the example of FIG. 5A, a hatched pixel) and another pixel (in the example of FIG. 5A, And a value representing a blank pixel). For this reason, such a value specifies the position of each pixel adjacent to the boundary. In the example of FIG. 5B, when at least one bit is 1, a pixel adjacent to the boundary is represented, and when all bits are 0, other pixels are represented. Here, the position specified by the position information corresponds to the position of the pixel adjacent to the boundary where color synthesis is performed in the trapping process.

  Further, the flag information includes direction information indicating the direction in which the boundary is adjacent to each pixel belonging to the pixel column adjacent to the boundary. In the example of FIG. 5A, of the two pixel columns arranged on the left and right with the boundary between them, the left pixel column has a boundary adjacent in the right direction, and the right pixel column has a boundary adjacent in the left direction. . As shown in the example of FIG. 5B, the value of each pixel includes a bit indicating a direction such as up, down, left, and right. If the pixel is not adjacent to the boundary, all the bits indicating the direction are set to 0. Here, the direction specified by the direction information corresponds to the direction of the pixel that refers to the color used for the synthesis based on the target pixel in the trapping process.

  Further, the flag information includes color information indicating the type of color of the pixel adjacent to the opposite side of the boundary with respect to each pixel belonging to the pixel column adjacent to the boundary. That is, in the example of FIG. 5A, of the two pixel columns arranged on the left and right with the boundary between them, the left pixel column has color information indicating the color type of the right pixel column, and the right pixel column is the left pixel column. It has color information indicating the color type of the pixel column. As shown in the example of FIG. 5B, each pixel value includes a bit representing a color such as YMC. If the pixel is not adjacent to the boundary, all the bits indicating the color type are set to 0. Here, the color specified by the color information corresponds to the color used for composition, which is referred to from the pixel adjacent to the target pixel and the boundary in the trapping process.

  The first conversion unit 45 receives the multi-valued image information subjected to the trapping process from the trapping processing unit 41, and converts the multi-valued image information into binary image information (so-called binarization). The binarization method is not particularly limited.

  As shown in the example of FIG. 6, the binary image information converted by the first conversion unit 45 has the same pixel arrangement as the multi-value image information, and each pixel has two or more kinds of colors. Contains. In this example, each pixel includes four types of colors, C (cyan), M (magenta), Y (yellow), and K (black). Each color of each pixel is represented by two gradations.

  Further, as illustrated in the example of FIG. 6, the binary image information converted by the first conversion unit 45 is a plurality of different colors corresponding to a plurality of regions included in the multi-value image information. It has the area of. In each region, the color density of the region is represented by the ratio of the colored pixels in the region, that is, the density of the colored pixels.

  Here, in the multi-value image information subjected to the trapping process, the colors of the pixel columns adjacent to the boundary between the first color area and the second color area are the first color and the second color. In the binary image information converted from the multi-value image information, a part of the pixels included in the pixel column adjacent to the boundary is the color of the region on the opposite side across the boundary. It has become.

  Specifically, the first conversion unit 45 converts the multi-value image information into binary image information as follows. The density of the colored pixels in each area of the binary image information is determined according to the color gradation of each area of the multi-value image information. Thereby, binary image information as shown in the example of FIG. 6 is obtained.

  In this embodiment, the multi-value image information that has been subjected to the trapping process is input to the first conversion unit 45. However, the present invention is not limited to this, and the multi-value image information that has not been subjected to the trapping process is the first. The conversion unit 45 may be input.

  The flag information generated by the flag generation unit 43 and the binary image information generated by the first conversion unit 45 may be directly output to the flag holding unit 47 and the second conversion unit 49, respectively. Alternatively, it may be stored once in the storage unit 24 and read out to each of the flag holding unit 47 and the second conversion unit 49 in response to an input from the operation unit 23 or the like. When stored in the storage unit 24, the binary image information and the flag information are associated with each other.

  The flag holding unit 47 holds the flag information generated by the flag generating unit 43, and outputs the flag information to the multi-value quantization unit 49a and the correction unit 49b included in the second conversion unit 49. As described above, the flag information includes position information, direction information, and color information.

  The multi-value conversion unit 49a included in the second conversion unit 49 converts the binary image information generated by the first conversion unit 45 into multi-value image information (so-called multi-value conversion), and this multi-value image information. Is output to the correction unit 49b. Note that the multi-value method is not particularly limited.

  As shown in the example of FIG. 6, the multi-value quantization unit 49 a is a pixel adjacent to the boundary of one of the first color area and the second color area included in the binary image information. When a column includes a pixel of the color of the other region, the color of the pixel is not used for multilevel conversion. Here, the position of the pixel row adjacent to the boundary is specified by the position information included in the flag information, and whether or not the pixel is a color pixel in the other region is determined by the color information included in the flag information. That is, when the pixel column specified by the position information includes a pixel of the color type specified by the color information, the multi-value conversion unit 49a does not use the color of the pixel for multi-value conversion.

  The fact that the color of the pixel is not used at the time of multi-leveling means that the existence of the color of the pixel is not considered when performing calculation for multi-leveling. For example, when obtaining the density of colored pixels in each area of the binary image information, the pixels are not counted as colored pixels but counted as colorless pixels. Based on the density of the colored pixels in each area of the binary image information thus determined, the color gradation of each area of the multivalued image information is determined. Thereby, it is suppressed that the color of an adjacent area | region is mixed with each whole area | region of multi-value image information.

  In the example of FIG. 6, the M pixel is included in the pixel column adjacent to the boundary with the M color region in the K color region, and the density of the colored pixels in the K color region is obtained. The M color pixel is counted as a colorless pixel. On the other hand, a pixel row adjacent to the boundary with the K color region in the M color region includes K color pixels, and this K color is obtained when obtaining the density of the colored pixels in the M color region. The pixels are counted as colorless pixels.

  The color information is not limited to the color specified by the color information in the pixel column specified by the position information so that the color information represents the color type of each pixel belonging to the pixel column adjacent to the boundary. If a pixel of the color is included, the color of the pixel may not be used for multi-value conversion.

  The multi-value image information converted by the multi-value conversion unit 49a has the same pixel configuration as the multi-value image information input to the trapping processing unit 41, as shown in the example of FIG. The multi-value image information has a plurality of regions having different colors corresponding to the plurality of regions included in the binary image information.

  In this multi-value image information, the first color region and the second color region are adjacent to each other, as in the multi-value image information input to the trapping processing unit 41. As described above, when the trapped multivalued image information is converted into binary image information, and the binary image information is converted into multivalued image information, the obtained multilevel image information is subjected to the trapping process. It becomes the same as the multi-value image information that is not. That is, in the obtained multi-value image information, the color of the pixel column adjacent to the boundary is not a color obtained by combining the first color and the second color.

  As shown in the example of FIG. 7, the correction unit 49b included in the second conversion unit 49 includes each pixel belonging to the pixel column adjacent to the boundary in the multi-value image information input from the multi-value conversion unit 49a. Is corrected based on the color of the pixel adjacent to each pixel across the boundary. Here, the position of the pixel row adjacent to the boundary is specified by position information included in the flag information, and the direction of the pixel adjacent to each pixel across the boundary is specified by the direction information included in the flag information. That is, the correction unit 49b corrects the color of each pixel belonging to the pixel column specified by the position information based on the color of the pixel in the direction specified by the direction information.

  Specifically, the correction of the pixel color includes the color type and gradation value of each pixel belonging to the pixel column specified by the position information, and the color type and gradation of the pixel in the direction specified by the direction information. This is done by combining the values. Note that the pixel in the direction specified by the direction information is not limited to the pixel adjacent to the target pixel, and may be two or more adjacent pixels.

  For example, as shown in the example of FIG. 7, 50% of the M color of the pixel in the right direction specified by the direction information is combined with each pixel belonging to the pixel column adjacent to the left side of the boundary, and on the right side of the boundary. For each pixel belonging to the adjacent pixel column, 50% of the K color of the pixel in the left direction specified by the direction information is synthesized. As a result, as shown in the example of FIG. 8, the pixel columns adjacent to both sides of the boundary are set to 50% K color and 50% M color.

  The corrected multi-valued image information obtained as described above includes the pixel row adjacent to the boundary between the first color region and the second color region as the first color and the second color. The color is a composite of In other words, the corrected multi-value image information is the same as the multi-value image information subjected to the trapping process as shown in the example of FIG.

  As described above, when the flag information generated by the flag generation unit 43 and the binary image information generated by the first conversion unit 45 are temporarily stored in the storage unit 24, the multi-value image information is stored in the storage unit 24. The capacity required for storage can be reduced as compared with the case where data is temporarily stored in the storage unit 24.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made by those skilled in the art.

  DESCRIPTION OF SYMBOLS 1 Image processing apparatus, 21 Control part, 22 Image processing part, 23 Operation part, 24 Storage part, 25 Communication part, 26 Display part, 27 Image formation part, 28 Image reading part, 41 Trapping process part, 43 Flag generation part, 45 1st conversion part, 47 Flag holding part, 49 2nd conversion part, 49a Multi-value quantization part, 49b Correction part.

Claims (6)

Of the multi-value image information in which each pixel includes two or more colors and each color is represented by three or more gradations, the pixel column adjacent to the boundary between the first color region and the second color region A holding unit that holds position information representing a position, and direction information representing a direction in which the boundary is adjacent to the pixel row;
A conversion unit for converting binary image information converted from the multi-value image information, each pixel including two or more colors and each color represented by two gradations into new multi-value image information, A conversion unit that determines the color of each pixel included in the pixel column specified by the position information based on the color of the pixel in the direction specified by the direction information;
An image processing apparatus comprising: The holding unit further holds color information representing the color of a pixel column adjacent to the pixel column adjacent to the boundary on the opposite side of the boundary;
When the pixel column specified by the position information of the binary image information includes a pixel of a color of the pixel column adjacent to the opposite side, the conversion unit performs multi-leveling of the binary image information. Do not use pixel color,
The image processing apparatus according to claim 1. Of the multi-value image information in which each pixel includes two or more colors and each color is represented by three or more gradations, the pixel column adjacent to the boundary between the first color region and the second color region A generating unit that generates position information representing a position and direction information representing a direction in which the boundary is adjacent to the pixel column;
An image processing apparatus comprising: Of the multi-value image information in which each pixel includes two or more colors and each color is represented by three or more gradations, the pixel column adjacent to the boundary between the first color region and the second color region A processing unit that executes a boundary color weighting process for making a color a color obtained by combining the first color and the second color;
A first conversion unit that converts the multi-value image information into binary image information in which each pixel includes two or more colors and each color is represented by two gradations;
A generating unit that generates position information indicating a position of a pixel column adjacent to the boundary and direction information indicating a direction in which the boundary is adjacent to the pixel column;
A holding unit for holding the position information and the direction information;
A second conversion unit that converts the binary image information into new multi-value image information, wherein the color of each pixel included in the pixel column specified by the position information is specified by the direction information. A second conversion unit that is determined based on the color of the pixel of
An image processing apparatus comprising: Of the multi-value image information in which each pixel includes two or more colors and each color is represented by three or more gradations, the pixel column adjacent to the boundary between the first color region and the second color region A holding unit that holds position information representing a position, and direction information representing a direction in which the boundary is adjacent to the pixel row;
A conversion unit for converting binary image information converted from the multi-value image information, each pixel including two or more colors and each color represented by two gradations into new multi-value image information, A conversion unit that determines the color of each pixel included in the pixel column specified by the position information based on the color of the pixel in the direction specified by the direction information;
As a program that allows the computer to function. Of the multi-value image information in which each pixel includes two or more colors and each color is represented by three or more gradations, the pixel column adjacent to the boundary between the first color region and the second color region A generating unit that generates position information representing a position and direction information representing a direction in which the boundary is adjacent to the pixel column;
As a program that allows the computer to function.

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