JP5742198B2 - Image processing apparatus and program - Google Patents

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 capable of suppressing deterioration of a color or gradation (edge) boundary when converting binary image information converted from multi-value image information into new multi-value image information. The main purpose is to provide a device and a program.

In order to solve the above problem, the invention described in claim 1 is such that each pixel includes at least one color and each color is expressed by a predetermined value or more among multi-value image information represented by three or more gradations. A holding unit that holds position information indicating the position of the pixel row of the one color adjacent to the boundary between the two regions having the gradation difference, and each pixel converted from the multi-value image information has one or more A conversion unit that converts binary image information including colors and each color is expressed in two gradations into new multi-value image information, and performs conversion processing within a range of a pixel column specified by the position information. And a conversion unit that determines a gradation value of the one color, and the holding unit is a pixel group of the one color that does not belong to the pixel row of the one color adjacent to the boundary The position information indicating the position of the first color is further held, and the conversion unit converts the position information indicating the position of the pixel row of the one color Ri determines the range of the pixel columns specified, and the range of the pixel group identified by the position information indicating the position of the color pixel group of the 1, in the tone value of the first color individually, An image processing apparatus.

According to a second aspect of the present invention, in the conversion from the multi-value image information to the binary image information, the range of the pixel column specified by the position information indicating the position of the pixel column of the one color is the a range of the pixel group identified by the position information indicating the position of the first color pixel group, in the density of the color of the pixels of the individual 1 is determined, the image processing apparatus according to claim 1 It is.

According to a third aspect of the invention, each pixel includes at least one color, and among the multi-value image information in which each color is represented by three or more gradations, a gradation difference of a predetermined value or more is obtained. A processing unit that executes a boundary emphasis process for increasing a gradation value of a pixel row of one color adjacent to a boundary between two regions, and the multi-value image information, each pixel including one or more colors, A first conversion unit that converts the image data into binary image information expressed in two gradations, a generation unit that generates position information indicating the position of the pixel row of the one color adjacent to the boundary, and the position information And a second conversion unit that converts the binary image information into new multi-value image information by applying a conversion process within a range of pixel columns specified by the position information. , and a second conversion unit for determining a gradation value of the color of the 1, wherein the holding portion to adjacent the boundary Position information representing the position of the pixel group of the first color that does not belong to the pixel array of the one color is further held, and the second conversion unit is position information representing the position of the pixel array of the first color The gradation value of the one color is determined individually in the range of the pixel row specified by the above and in the range of the pixel group specified by the position information indicating the position of the pixel group of the one color. An image processing apparatus.

According to a fourth aspect of the present invention, each pixel includes at least one color, and among the multi-value image information in which each color is represented by three or more gradations, a gradation difference equal to or more than a predetermined value is obtained. A holding unit that holds position information indicating the position of the pixel row of the one color adjacent to the boundary between the two regions, and each pixel converted from the multivalued image information includes one or more colors, Is a conversion unit that converts binary image information expressed in two gradations into new multi-value image information, and applies a conversion process within a range of pixel columns specified by the position information, and A computer that functions as a conversion unit that determines a gradation value of one color, and the holding unit is a position of a pixel group of the one color that does not belong to the pixel column of the one color adjacent to the boundary The position information indicating the position of the pixel row of the one color is further stored. Determining a range of pixel columns specified, and the range of the pixel group identified by the position information indicating the position of the color pixel group of the 1, in the tone value of the first color individually by, It is a program.

According to the first, third, and fourth aspects of the present invention, it is possible to set individual gradation values at the boundary of color or gradation (edge) and the inside thereof.

According to the second aspect of the present invention, it is possible to set individual gradation values for the boundary of color or gradation (edge) and the inside thereof.

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 an edge enhancement 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 a screen pattern. It is a figure showing the example of a screen pattern. 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 binary image information after correction | amendment. It is a figure showing the example of the multi-value image information after binary-multi-value conversion. It is a figure showing the function example of the image processing apparatus which concerns on other embodiment of this invention. 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 is a CCD (Charge Coupled).
An image pickup device such as (Device) is provided, an image formed on a recording sheet is read by the image pickup device, and image information representing the read image is generated.

  FIG. 2 is a diagram illustrating an example of functions of the image processing apparatus 1. The image processing apparatus 1 includes an edge enhancement processing unit 31, a flag generation unit 33, a first conversion unit 35, a flag holding unit 37, and a second conversion unit 39.

  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 mode, the control unit 21 realizes the edge enhancement processing unit 31, the flag generation unit 33, and the first conversion unit 35, and the image processing unit 22 sets the flag holding unit 37 and the second conversion unit 39. Prepare.

  The edge enhancement processing unit 31 performs edge enhancement processing on the input multi-value image information, and outputs the multi-value image information subjected to the edge enhancement processing to the flag generation unit 33 and the first conversion unit 35.

  The multi-value image information input to the edge enhancement processing unit 31 has a plurality of pixels arranged two-dimensionally as shown in the example of FIG. 3, and each pixel includes one or more colors. It is out. In this example, each pixel includes four types of colors, C (cyan), M (magenta), Y (yellow), and K (black). Each pixel is represented by three or more gradations (for example, eight gradations).

  Further, in the multivalued image information input to the edge enhancement processing unit 31, as shown in the example of FIG. 3, a first area including a certain color and a second area not including the color are adjacent to each other. The edge enhancement process is applied to the boundary between these two areas. However, the present invention is not limited to this, and the edge enhancement processing may be performed on a boundary portion between two regions having a gradation difference equal to or greater than a predetermined value.

  The edge enhancement process is a boundary enhancement process for increasing the gradation value of a pixel row adjacent to the first area side of the boundary between the first area including a certain color and the second area not including the color. . For example, as shown in the example of FIG. 3, in a multi-valued image information, when a low gradation, band-like colored area including a certain color is adjacent to a colorless area not including the color, the colored area is visually recognized. May be inferior. Therefore, in order to improve the visibility, as shown in the example of FIG. 4, the gradation value of the color of the pixel row adjacent to the colored region side of the boundary between the colored region and the colorless region is increased. Note that the pixel column whose gradation value is increased may be a pixel column having a width of two pixels or more adjacent to the boundary.

  In the example of FIG. 3 and FIG. 4, on the colored region side of the boundary between the colored region where the gradation of K color is 25% and the colorless region not containing K color (that is, the region where the gradation of K color is 0). Adjacent pixel columns have a K color gradation increased to 50%. Note that the color of the colored region is not limited to the K color. A single color of CMYK may be used, or a mixed color of these may be used.

  Specifically, the edge enhancement processing unit 31 performs the edge enhancement processing as follows. In the first step, the boundary of each color is detected in the multi-value image information. 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. Is colorless and there is a gradation difference, the corresponding pixels are determined as a boundary. In the second step, as described above, the gradation value of the pixel column adjacent to the colored region side of the boundary between the colored region and the colorless region is increased. Note that when the gradation value of the pixel column is originally high, the gradation value does not need to be increased.

  The flag generation unit 33 receives the multivalued image information subjected to the edge enhancement processing from the edge enhancement processing unit 31, and generates flag information based on the multivalued image information. Specifically, each pixel of the multivalued image information that has been subjected to the edge enhancement processing is a pixel that belongs to a colored region and is included in a pixel column adjacent to the boundary (that is, a pixel having an increased gradation value). ) And a pixel belonging to a colored region and not included in a pixel group adjacent to the boundary, and a pixel belonging to a colorless region. The flag information includes such attribute information of each pixel.

  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, attribute information of each pixel 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.

  Depending on the value of each pixel, the flag information includes position information indicating the position of a pixel (hereinafter referred to as an “edge pixel”) included in a pixel column that belongs to the colored area and is adjacent to the boundary, and the colored area. Position information indicating the position of a pixel (hereinafter referred to as “inner pixel”) included in a pixel group that belongs to a pixel that is not adjacent to the boundary, and a pixel that belongs to a colorless area (hereinafter referred to as “other pixel”). And position information representing the position of. In the example of FIG. 5A, the edge pixels are cross-hatched, the inner pixels are hatched, and the other pixels are blank.

  The first conversion unit 35 receives the multivalued image information subjected to the edge enhancement processing from the edge enhancement processing unit 31 and converts the multivalued image information into binary image information (so-called binarization). The binarization method is not particularly limited.

  For binarization of multi-value image information, for example, a screen pattern as shown in the examples of FIGS. 6A and 6B is used. In the screen pattern, the colored pixels are periodically arranged, and the logical product of the colored pixels of the multi-valued image information and the colored pixels of the screen pattern becomes the colored pixels of the binary image information. FIG. 6A is an example of 50% K color, and pixels with cross-hatching represent colored pixels. FIG. 6B is an example of K color 25%, and hatched pixels represent colored pixels.

  By binarizing such multi-valued image information, binary image information as shown in the example of FIG. 7A is obtained. The binary image information has the same pixel arrangement as the multi-value image information, and each color of each pixel is represented by two gradations.

  The first conversion unit 35 receives flag information from the flag generation unit 33 and corrects binary image information based on the flag information. Specifically, the first conversion unit 35 individually adjusts the density of the colored pixels in the range of the edge pixel specified by the flag information, the range of the inner pixel, and the range of the other pixels. The density of the colored pixels in each range is determined according to the gradation value in each range in the multivalued image information that has been subjected to the edge enhancement processing. Thereby, the reproducibility of the original multi-value image information is improved by conversion from binary image information to multi-value image information, which will be described later.

  For example, as shown in the example of FIG. 7B, in the range of edge pixels, the gradation value is 50% K color in the multi-value image information, so that the density of colored pixels is also 50% within the range. Adjusted to In this example, since the density of the colored pixels was originally 50% in the range of the edge pixels, there is no change in the density of the colored pixels. Further, since the gradation value of the inner pixel range is 25% in the multi-value image information, the density of the colored pixels is adjusted to be 25% within the range. In this example, since the density of the colored pixels is originally 0% within the range of the inner pixels, the colored pixels are added to occupy 25% within the range. In the other pixel range, since the gradation value is 0% in the multi-value image information, the density of the colored pixels is adjusted to be 0% within the range. In this example, since the density of the colored pixels was originally 0% in the range of other pixels, there is no change in the density of the colored pixels.

  The flag information generated by the flag generation unit 33 and the binary image information generated by the first conversion unit 35 may be directly output to the flag holding unit 37 and the second conversion unit 39, respectively. Alternatively, it may be stored once in the storage unit 24 and read out to each of the flag holding unit 37 and the second conversion unit 39 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 37 holds the flag information generated by the flag generating unit 33, and outputs this flag information to the second conversion unit 39. As described above, the flag information includes pixel position information of each attribute.

  The second conversion unit 39 converts the binary image information generated by the first conversion unit 35 into multi-value image information (so-called multi-value conversion). At this time, the second conversion unit 39 individually applies the conversion process to the edge pixel range, the inner pixel range, and the other pixel range specified by the flag information, and individually converts the levels. Determine the key value. The gradation value of each range is determined according to the density of colored pixels in each range in the binary image information.

  For example, as shown in the example of FIG. 8, in the range of edge pixels, since the density of colored pixels is 50% of the range in the binary image information, the gradation value is set to 50%. In the range of the inner pixel, since the density of colored pixels is 25% of the range in the binary image information, the gradation value is set to 25%. For the other pixel range, since the density of the colored pixels is 0% in the range in the binary image information, the gradation value is set to 0%.

  In the multi-value image information obtained as described above, the gradation value of the color of the pixel row adjacent to the colored region side of the boundary between the colored region and the colorless region is increased. That is, the multi-value image information obtained here is the same as the multi-value image information subjected to the edge enhancement processing as shown in the example of FIG.

  As described above, when the flag information generated by the flag generation unit 33 and the binary image information generated by the first conversion unit 35 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.

  Hereinafter, other embodiments of the present invention will be described.

  FIG. 9 is a diagram illustrating a functional example of the image processing apparatus 1 according to another embodiment. 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. 10, 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. 10, the multi-value image information input to the trapping processing unit 41 has a plurality of regions having different colors from each other, and the trapping processing 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. 10, 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. 11, 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. 10 and 11, 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. 12A, 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. The value of each pixel is described by a value of several bits, for example, as shown in the example of FIG. 12B. For the sake of explanation, the meaning of each value is described at the right end of the table in FIG. 12B. In the table of FIG. 12B, 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 broadly divided into a value representing a pixel adjacent to the boundary (in the example of FIG. 12A, a hatched pixel) and another pixel (in the example of FIG. 12A, 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. 12B, 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. 12A, of the two pixel columns arranged on the left and right with the boundary interposed therebetween, the left pixel column has a right boundary adjacent thereto, and the right pixel column has a boundary adjacent leftward. . As shown in the example of FIG. 12B, the value of each pixel includes bits representing directions 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. 12A, 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 among the two pixel columns arranged on the left and right sides with the boundary. It has color information indicating the color type of the pixel column. As shown in the example of FIG. 12B, 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. 13, 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 shown in the example of FIG. 13, 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. 13 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. 13, 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. 13, an M color pixel is included in a 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. 14, 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. 14, 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. 15, 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 That is, 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, 31 Edge enhancement processing part, 33 Flag generation part 35 First conversion unit 37 Flag holding unit 39 Second conversion unit 41 Trapping processing unit 43 Flag generation unit 45 First conversion unit 47 Flag holding unit 49 Second conversion unit 49a Multi-value conversion unit, 49b correction unit.

Claims (4)

The multi-value image information in which each pixel includes at least one color and each color is expressed by three or more gradations is adjacent to the boundary between two regions having a gradation difference of a predetermined value or more. A holding unit for holding position information indicating the position of the pixel row of the color;
A conversion unit for converting binary image information converted from the multi-value image information, each pixel including one or more colors and each color represented by two gradations into new multi-value image information, A conversion unit that determines a gradation value of the one color by applying a conversion process within a range of a pixel column specified by the position information;
Equipped with a,
The holding unit further holds position information indicating a position of the pixel group of the one color that does not belong to the pixel row of the one color adjacent to the boundary;
The conversion unit includes a pixel group range specified by position information indicating the position of the one color pixel group and a pixel group range specified by position information indicating the position of the one color pixel group. The tone value of the one color is determined individually in and
Image processing device. In the conversion from the multi-value image information to the binary image information, the range of the pixel row specified by the position information indicating the position of the pixel row of the one color and the position of the pixel group of the one color are changed. The density of the pixels of the one color is determined individually within the range of the pixel group specified by the position information to be represented,
The image processing apparatus according to claim 1 . The multi-value image information in which each pixel includes at least one color and each color is expressed by three or more gradations is adjacent to the boundary between two regions having a gradation difference of a predetermined value or more. A processing unit that executes boundary enhancement processing for increasing the gradation value of the pixel row of the color;
A first conversion unit that converts the multi-value image information into binary image information in which each pixel includes one or more colors and each color is represented by two gradations;
A generating unit that generates position information indicating the position of the pixel row of the one color adjacent to the boundary;
A holding unit for holding the position information;
A second conversion unit configured to convert the binary image information into new multi-value image information, wherein a conversion process is applied to a range of a pixel column specified by the position information, and A second conversion unit for determining a key value;
Equipped with a,
The holding unit further holds position information indicating a position of the pixel group of the one color that does not belong to the pixel row of the one color adjacent to the boundary;
The second conversion unit includes a pixel specified by position information indicating the position of the pixel group within the range of the pixel column specified by the position information indicating the position of the pixel row of the first color and the position of the pixel group of the first color. In the range of the group, the gradation value of the one color is determined individually.
Image processing device. The multi-value image information in which each pixel includes at least one color and each color is expressed by three or more gradations is adjacent to the boundary between two regions having a gradation difference of a predetermined value or more. A holding unit for holding position information indicating the position of the pixel row of the color;
A conversion unit for converting binary image information converted from the multi-value image information, each pixel including one or more colors and each color represented by two gradations into new multi-value image information, A conversion unit that determines a gradation value of the one color by applying a conversion process within a range of a pixel column specified by the position information;
Cause the computer to function as,
The holding unit further holds position information indicating a position of the pixel group of the one color that does not belong to the pixel row of the one color adjacent to the boundary;
The conversion unit includes a pixel group range specified by position information indicating the position of the one color pixel group and a pixel group range specified by position information indicating the position of the one color pixel group. The tone value of the one color is determined individually in and
program.

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