JP4629057B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus that converts the resolution of image data.

In an image forming apparatus such as a copying machine, a facsimile, a printer, and a complex machine of these, there is a case where it is desired to convert multi-value image data into higher-resolution binary image data. An image processing apparatus that performs such image processing Is used (for example, refer to Patent Document 1). In such an image processing apparatus, each pixel of the original image is made to correspond to a plurality of pixels in the image data with high resolution, and the number of print dots in the corresponding pixels is determined according to the density value of the pixels of the original image. The gradation of the original image is expressed by high-resolution binary image data.
JP 2002-185785 A

  By the way, in an image forming apparatus, particularly an image forming apparatus which forms an electrostatic latent image on a photosensitive drum, and develops and transfers the electrostatic latent image, the image forming apparatus forms discrete images on the photosensitive drum. It is known that the electrostatic latent image is more stable and the image quality is improved when the dots are concentrated to some extent than when the electrostatic latent image of dots is formed. Therefore, in an image processing apparatus that generates high-resolution image data from an original image, when generating high-resolution image data from the original image, the number of dots corresponding to the density value is not clustered and is agglomerated. It is conceivable that the image quality in the image forming apparatus can be easily improved by performing the dot positioning process to be arranged as described above.

  As a method for performing such dot positioning processing, for example, a combination of density values of the target pixel and surrounding pixels adjacent to the target pixel is stored in advance, and the dot arrangement is set for each pattern. By storing in association with each other, it is conceivable to generate high-resolution image data with a dot pattern corresponding to a combination of density values of each pixel by pattern matching when the resolution of the original image is increased. However, when the dot arrangement is determined by pattern matching in this way, the number of matching patterns and the number of corresponding dot patterns become enormous, and the memory capacity necessary to store these data increases. There was an inconvenience of doing. Further, when the dot arrangement determined in advance by pattern matching is used, there is a problem that the dot arrangement becomes regular and a pattern may appear in the image.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an image processing apparatus capable of performing dot positioning processing without performing pattern matching while increasing the resolution of image data. And

An image processing apparatus according to the present invention generates, from original image data in which the density of each pixel is represented by density values having a plurality of density gradations, high-resolution image data having a higher resolution than the original image data. In the processing device, the target pixel of the original image data is divided into a number of first pixels substantially equal to the number of density gradations in a grid pattern, and the density value of each first pixel is determined as the target pixel. Enlargement representing the target pixel by the plurality of first pixels by setting the density value obtained by interpolating between the density value of the pixel adjacent to the target pixel and the density value of the target pixel using linear interpolation A pixel-of-interest enlargement processing unit that generates pixel-of-interest data, and a density value of each first pixel in the enlarged pixel-of-interest data generated by the pixel-of-interest enlargement processing unit is ranked based on the magnitude relationship of each density value. 1 pixel ranking number A threshold data generation unit that generates density rank data as threshold data, and sets the density value of each first pixel of the enlarged pixel data to the value of each first pixel of the threshold data obtained by the threshold data generation unit. A binarized image generating unit that generates binarized data based on the binarized image data with higher resolution than the original image data.

  According to this configuration, the target pixel enlargement processing unit divides the target pixel of the original image data into a number of first pixels substantially equal to the number of density gradations of the original image data in a grid pattern. Further, the density value of each divided first pixel is set to a density value obtained by interpolating the difference in density value between the adjacent pixel adjacent to the target pixel and the target pixel in the original image data. Expanded pixel-of-interest data that represents a pixel by a plurality of first pixels is generated. Then, the threshold data generation unit ranks the density values of the first pixels in the enlarged pixel-of-interest data generated by the pixel-of-interest enlargement processing unit based on the magnitude relationship of the respective density values. Is generated as threshold value data. Then, since the density value of the first pixel increases as the density value of the adjacent pixel in the direction in which each first pixel is located when viewed from the center of the enlarged target pixel data, the value of each first pixel in the threshold data The density value of the adjacent pixel is reflected in. In addition, the binarized image generation unit binarizes the density value of each first pixel of the enlarged target pixel data based on the value of each first pixel of the threshold data obtained by the threshold data generation unit. It is generated as binary image data with higher resolution than the image data. Then, since the density value of the adjacent pixel is reflected in the value of each first pixel of the threshold data, the dot position is determined according to the density value of the adjacent pixel without performing pattern matching while increasing the resolution of the image data. Alignment processing can be performed.

  The density value indicates that the density increases as the value increases, and the threshold data generation unit ranks the density values of the first pixels in descending order, and sets the density ranking data. The binarized image generation unit includes a dot in which the density value is larger than the value of each first pixel in the threshold data, and the density value is greater than the value of each first pixel in the threshold data. It is preferable that the binarized image data is generated by setting the first pixel having a small dot size without dots.

  According to this configuration, since the density value indicates that the density increases as the value increases, the density of adjacent pixels in the direction in which each first pixel is located as viewed from the center of the enlarged pixel data of interest. As the density increases, the density value of the first pixel increases. As a result, the value of each first pixel in the threshold data increases as the density of the adjacent pixels increases. Then, the order number of each first pixel in the density order data, that is, the value of each first pixel in the threshold data becomes smaller as the density of the adjacent pixels is higher. Accordingly, if the first pixel having a density value larger than the value of each first pixel in the threshold data is set to have a dot and the first pixel having the density value smaller than the value of each first pixel in the threshold data is set to no dot, the density is set. Since the first pixel closer to the darker adjacent pixel is more likely to be set to have a dot, the dot positioning process is performed according to the density value of the adjacent pixel without performing pattern matching.

  Further, the enlarged pixel-of-interest data further includes a priority order storage unit that pre-stores priority order data in which the order in which dots should be preferentially set is set for each first pixel, and the threshold value data generation unit includes: When there are a plurality of first pixels having the same density value, it is preferable to rank the ranks between the first pixels having the same density value based on the priority data stored in the priority storage unit.

  According to this configuration, when there are a plurality of first pixels having the same density value, the priority data stored in the priority storage unit by the threshold data generation unit stores the rank between the first pixels having the same density value. Therefore, the order between the first pixels having the same density value can be set to the order in which the dots should be preferentially arranged.

  Further, the enlarged pixel-of-interest data further includes a priority order storage unit that pre-stores priority order data in which the order in which dots should be preferentially set is set for each first pixel, and the threshold value data generation unit includes: When the difference in density value between the pixels of the original image data is smaller than a preset density difference threshold, it is preferable to generate the priority order data stored in the priority order storage unit as the threshold data.

  According to this configuration, when the density value difference between the pixels of the original image data is smaller than a preset density difference threshold, the dots are preferentially arranged at positions where the dots should be arranged. As in the case where the dot positioning process is performed according to a slight density difference between them, the possibility of an inappropriate dot arrangement is reduced.

  Further, the enlarged pixel-of-interest data further includes a priority order storage unit that pre-stores priority order data in which the order in which dots should be preferentially set is set for each first pixel, and the threshold value data generation unit includes: When the difference in density value between the first pixels of the enlarged pixel-of-interest data generated by the pixel-of-interest enlargement processing unit is smaller than a preset density difference threshold, the priority order data stored in the priority order storage unit May be generated as the threshold data.

  According to this configuration, when the difference in density value between the first pixels of the pixel-of-interest data is smaller than a preset density difference threshold value, and accordingly, the difference in density value between the pixels of the original image data is small, Since dots are arranged at positions where dots should be arranged preferentially, there is a risk that dot arrangement will be invalid as in the case where dot positioning processing is performed according to a slight density difference between pixels. Reduced.

  Further, the priority data is set such that the order of the first pixels is set so that the order of the first pixel in the center in the enlarged pixel data is higher than the order of the first pixels in the peripheral part. When the total density value of each pixel in the original image data is larger than a preset overall density threshold value, the generation unit sets the first pixel order in the priority order data in the reverse order as the threshold value. It is preferable to generate as data.

  According to this configuration, the priority order data is such that the order of the first pixel in the central part in the enlarged noticed pixel data is higher than the order of the first pixel in the peripheral part, that is, the attention is given to the dot arrangement having a higher resolution. It is set so that it is easy to concentrate at the center of the pixel. When the total density value of each pixel in the original image data is larger than a preset overall density threshold, that is, when the density of the original image is overall high, the threshold data generation unit causes each of the first priority data to be A pixel in which the order of one pixel is reversed is generated as threshold data, so that the dot arrangement is easily concentrated on the periphery of the pixel of interest having a high resolution. As a result, the possibility that the dots are concentrated in the center of the pixel of interest whose resolution has been increased based on the priority order data despite the high density of the adjacent pixels, resulting in an inappropriate dot arrangement is reduced.

  In addition, a predetermined number of first pixels in the binarized image data generated by the binarized image generation unit are aggregated into a second pixel, and the value of the first pixel included in the second pixel is set. It is preferable that the image processing apparatus further includes a high-resolution image generation unit that generates image data obtained by setting the sum as the density value of the second pixel as the high-resolution image data.

  According to this configuration, since a predetermined number of first pixels in the binarized image data are assembled into the second pixel, a desired pixel consisting of the second pixel within a range not exceeding the resolution of the binarized image data. High resolution image data having resolution can be obtained. In addition, since the sum of the values of the first pixels included in the second pixel is set as the density value of the second pixel, the density value of the second pixel in the high resolution image data is calculated from the binarized image data. Easy to get.

  In the image processing apparatus having such a configuration, the target pixel of the original image data is divided into a number of first pixels substantially equal to the number of density gradations of the original image data in a grid pattern. Further, the density value of each divided first pixel is set to a density value obtained by interpolating the difference in density value between the adjacent pixel adjacent to the target pixel and the target pixel in the original image data. Expanded pixel-of-interest data that represents a pixel by a plurality of first pixels is generated. Then, density rank data indicating the rank number of each first pixel obtained by ranking the density values of the respective first pixels in the enlarged pixel data based on the magnitude relationship of the respective density values is generated as threshold data. Then, since the density value of the first pixel increases as the density value of the adjacent pixel in the direction in which each first pixel is located when viewed from the center of the enlarged target pixel data, the value of each first pixel in the threshold data The density value of the adjacent pixel is reflected in. In addition, data obtained by binarizing the density value of each first pixel of the enlarged target pixel data based on the value of each first pixel of the threshold data is generated as binary image data with higher resolution than the original image data. The Then, since the density value of the adjacent pixel is reflected in the value of each first pixel of the threshold data, the dot position is determined according to the density value of the adjacent pixel without performing pattern matching while increasing the resolution of the image data. Alignment processing can be performed.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of an image processing apparatus according to an embodiment of the present invention. The image processing apparatus 1 illustrated in FIG. 1 includes a target pixel enlargement processing unit 2, a threshold data generation unit 3, a binarized image generation unit 4, a high resolution image generation unit 5, and a priority order storage unit 6. It is prepared for.

  The image processing apparatus 1 may be configured by an integrated circuit such as an ASIC (Application Specific Integrated Circuit), for example, and an integrated circuit such as an ASIC and a nonvolatile memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory). May be combined. Alternatively, the image processing apparatus 1 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing and a non-volatile storage device such as a ROM (Read Only Memory) or a HDD (Hard Disk Drive) in which a predetermined control program is stored. And a RAM (Random Access Memory) that temporarily stores data and peripheral circuits thereof, and the like, and by executing a control program stored in the non-volatile storage device, a target pixel enlargement processing unit 2, the threshold data generation unit 3, the binarized image generation unit 4, and the high resolution image generation unit 5 may function.

  The target pixel enlargement processing unit 2 divides the target pixel P0 of the original image data G1 to be processed into a number of first pixels Q that are substantially equal to the number of density gradations of the original image data G1 in a grid pattern. By setting the density value of the first pixel Q to a density value obtained by interpolating the density value difference between the pixel adjacent to the target pixel P0 and the target pixel P0, the target pixel P0 is a plurality of first pixels. Expanded attention pixel data G3 represented by Q is generated.

  The priority order storage unit 6 is configured using a nonvolatile memory such as an EEPROM, for example, and in the enlarged pixel data G3, priority order data in which the order in which dots should be preferentially arranged is set for each first pixel Q. GY is stored in advance. In the priority order data GY, for example, the order of each first pixel Q is set so that the order of the first pixel Q at the center in the enlarged target pixel data G3 is higher than the order of the first pixel Q at the peripheral part. .

  The threshold data generation unit 3 ranks the density values of the first pixels Q in the enlarged pixel-of-interest data G3 generated by the pixel-of-interest enlargement processing unit 2 in descending order, and generates the density ranking data G4. This is generated as threshold data G5. In addition, when there are a plurality of first pixels Q having the same density value, the threshold data generating unit 3 stores the priority order between the first pixels Q having the same density value, which is stored in the priority level storage unit 6. The density ranking data G4 is generated by ranking based on the threshold value data G5.

  Then, when the difference in density value between the target pixel P0 and the pixel adjacent to the target pixel P0 in the original image data G1 is smaller than a preset density difference threshold value, the threshold data generation unit 3 Is generated as threshold data G5. Further, the threshold value data generation unit 3 determines that each of the priority data GY has a predetermined value when the sum of the density values of the target pixel P0 and the pixels adjacent to the target pixel P0 in the original image data G1 is larger than a preset overall density threshold value. The threshold data G5 is generated by rearranging the order of one pixel Q in the reverse order.

  The binarized image generation unit 4 sets the value of the first pixel Q having a density value larger than the value of each first pixel Q in the threshold data G5 to “1” and the density value from the value of each first pixel Q in the threshold data G5. The binarized image data G6 is generated by setting the value of the first pixel Q having a small value to “0”.

  The high resolution image generation unit 5 collects a predetermined number of first pixels Q in the binarized image data G6 generated by the binarized image generation unit 4 to form the second pixel R, and the second pixel Image data obtained by setting the total value of the first pixels Q included in R as the density value of the second pixel R is referred to as high-resolution image data G7.

  Next, an example of the operation of the image processing apparatus 1 configured as described above will be described. FIG. 2 is an explanatory diagram illustrating an example of original image data to be subjected to image processing by the image processing apparatus 1. The original image data G1 shown in FIG. 2 is, for example, image data of main scanning 600 dpi (dot per inch) and sub scanning 600 dpi, and the density of the target pixel P0 and eight pixels P1 to P8 adjacent to the periphery of the target pixel. Each value is shown. Each density value of the original image data G1 has, for example, 16 gradations of 0 to 15.

The target pixel enlargement processing unit 2 linearly interpolates between the density value of the target pixel P0 and the density values of the pixels P1 to P8 in the original image data G1 shown in FIG. 2 to thereby generate the target pixel P0 and the pixels P1 to P8. by generating a pixel fill between, for example, the main scanning direction four times, that generates an enlarged target pixel data G3 which enlarged four times in the sub-scanning direction.

  Thus, for example, when generating enlarged pixel data G3 enlarged by 4 times in the main scanning direction and 4 times in the sub-scanning direction, the original image data G1 shown in FIG. The image is enlarged by 8 times in the direction and 8 times in the sub-scanning direction, and the enlarged image data G2 shown in FIG. 3 is generated. In the enlarged image data G2 shown in FIG. 3, each pixel of the original image data G1 shown in FIG. In FIG. 3, each pixel of the enlarged image data G2 is indicated by XY coordinates in the X-axis direction (main scanning direction) and the Y-axis direction (sub-scanning direction). The XY coordinates are given in the range of −8 to +8 for the X coordinate and −8 to +8 for the Y coordinate, where the coordinate of the target pixel P0 arranged at the center of the enlarged image data G2 is (0, 0).

  In the enlarged image data G2, the region in which the pixel of interest P0 is enlarged 8 × 8 times is the center of the pixel at coordinates (−4, −4), the center of the pixel at coordinates (4, −4), and the coordinates ( This corresponds to a region (region surrounded by a broken line) surrounded by the center of the pixel of (4, 4) and the center of the pixel of coordinate (−4, 4). Similarly, the pixels P1 to P8 are enlarged by 8 × 8 times by the target pixel enlargement processing unit 2, so that the pixel P1 has coordinates (−8, −8), the pixel P2 has coordinates (0, −8), and the pixel P3 is coordinate (8, -8), pixel P4 is coordinate (-8,0), pixel P5 is coordinate (8,0), pixel P6 is coordinate (-8,8), pixel P7 is coordinate (0,8) ), The pixel P8 is arranged at the coordinates (8, 8).

  Further, the density of pixels arranged at the coordinates between the target pixel P0 and the pixels P1 to P8 by the target pixel enlargement processing unit 2 depends on the distance between the target pixel P0 and the pixels P1 to P8. By performing linear interpolation, the density value of each coordinate in the enlarged image data G2 is calculated.

In the enlarged image data G2 generated in this way, a portion surrounded by a thick line corresponds to the target pixel P0. Here, since each density value of the original image data G1 is expressed by 16 gradations, the attention pixel enlargement processing unit 2 determines the number of gradations of the density value from the area within the thick line frame corresponding to the attention pixel P0. The same 16 pixels (pixels indicated by hatching ) are acquired as the first pixels Q00 to Q03, Q10 to Q13, Q20 to Q23, and Q30 to Q33, and enlarged pixel data G3 shown in FIG. 4 is generated. Hereinafter, the first pixels Q00 to Q03, Q10 to Q13, Q20 to Q23, and Q30 to Q33 are collectively referred to as the first pixel Q.

  In this case, in the first pixel Q in the enlarged target pixel data G3 shown in FIG. 4, the target pixel P0 of the original image data G1 to be processed is equal to the number of density gradations of the original image data G1 in a grid pattern. The first pixel Q is divided into a plurality of first pixels Q, and the density value of each first pixel Q is obtained by interpolating the density value difference between the target pixel P0 and adjacent pixels P1 to P8 and the target pixel P0. It is said that.

  Each density value of the original image data G1 is not limited to 16 gradations. For example, if the density value is 256 gradations, the enlarged pixel data G3 may be formed in a 16 × 16 grid pattern.

  Next, the threshold value data generation unit 3 ranks the density values of the first pixels Q in the enlarged pixel-of-interest data G3 generated by the pixel-of-interest enlargement processing unit 2 in descending order of the values, as shown in FIG. Density ranking data G4 is generated. Then, the threshold data generation unit 3 generates threshold data G5 based on the priority order data GY and the density order data G4 stored in the priority order storage unit 6.

  Specifically, for example, as shown in FIG. 6, the priority order storage unit 6 is assigned a number from 0 to 15 corresponding to each first pixel Q, with “0” being the highest priority order. The priority order data GY configured as described above is stored. The priority order data GY is, for example, the order of the first pixels Q11, Q21, Q22, Q12 in the central portion in the enlarged pixel data G3 is the first pixels Q00, Q01, Q02, Q03, Q10, Q13, Q20, Q23 in the peripheral portion. , Q30, Q31, Q32, Q33, the order of each first pixel Q is set so as to be higher.

  Then, the threshold data generation unit 3 multiplies the rank number of each first pixel Q in the density rank data G4 by 16 which is the number of density gradations, and the multiplication result is multiplied by each first pixel Q in the priority rank data GY. Are added to generate the intermediate data G41 shown in FIG. Further, the threshold data generation unit 3 ranks the values of the first pixels Q in the intermediate data G41 in order from the smallest value, and generates threshold data G5 shown in FIG. The rank number of each first pixel Q in the threshold data G5 indicates that dots are preferentially arranged as the number is smaller. For example, in the threshold data G5 shown in FIG. 8, the dots gather in the upper right direction. This means that dot positioning processing is performed.

  Here, for example, when the density values of the first pixels Q are all different, as in the enlarged pixel-of-interest data G3 shown in FIG. 4, the density level is assigned to the rank number of each first pixel Q in the density rank data G4. After the key number 16 is multiplied, the number indicating the priority of each first pixel Q in the priority data GY is added, so the magnitude relationship between the values of each first pixel Q in the intermediate data G41 is Since the order of each first pixel Q in the density order data G4 is maintained, the threshold data G5 shown in FIG. 8 is the same as the order data G4 shown in FIG.

  On the other hand, for example, when the density values of the first pixels Q of the enlarged pixel data G3 are all equal, the rank numbers of the first pixels Q in the density rank data G4 are all “1” as shown in FIG. Become. Then, the threshold value data generating unit 3 multiplies the rank number of each first pixel Q in the density rank data G4 shown in FIG. 9 by 16 that is the number of density gradations, and the multiplication result is assigned to each priority rank data GY. As a result of adding the numbers indicating the priorities of the first pixels Q, intermediate data G41 shown in FIG. 10 is generated. Furthermore, when the threshold data generating unit 3 ranks the values of the first pixels Q in the intermediate data G41 shown in FIG. 10 in order from the smallest, the threshold data G5 shown in FIG. 11 is generated. Then, the threshold data G5 shown in FIG. 11 is given the rank number according to the priority of the priority data GY shown in FIG. 6 to each first pixel Q, and the dot position with the priority shown by the priority data GY. A misalignment process is performed.

  In addition, when there are a plurality of first pixels Q having the same density value, the threshold data generating unit 3 stores the priority order between the first pixels Q having the same density value by the priority order storage unit 6. For example, each first pixel Q of the enlarged pixel-of-interest data G3 shown in FIG. 4 is multiplied by 16 that is the number of density gradations, and then each first pixel Q in the priority data GY is ranked. The threshold data G5 may be generated by adding the numbers indicating the priorities of the numbers and ranking the addition results in descending order, or the threshold data G5 may be generated by other methods. May be. Thereby, when there are a plurality of first pixels Q having the same density value, ranking can be performed based on the priority order data GY.

  Further, the threshold data generation unit 3 determines a difference in density value between the pixels P1 to P8 in the original image data G1, for example, a difference between the maximum value and the minimum value of the density values of the pixels P1 to P8. When the difference threshold is smaller than “3”, for example, a fixed value obtained by adding “1” to the priority order data GY stored in the priority order storage unit 6 is generated as the threshold data G5. When the density difference between the pixels P1 to P8 is small, if the dot positioning process is performed based on such a small density difference, the arrangement of the dots may be inappropriate. Therefore, the threshold data generation unit 3 is based on the priority order data GY stored in the priority order storage unit 6 when the difference in density value between the pixels P1 to P8 is smaller than a preset density difference threshold. By generating the threshold value data G5, it is possible to reduce the possibility of improper dot positioning processing.

  The threshold data generation unit 3 generates threshold data G5 based on the priority order data GY when the difference in density value between the pixels P1 to P8 of the original image data G1 is smaller than a preset density difference threshold. The threshold value data G5 is generated based on the priority order data GY when the density value difference between the pixels P1 to P8 of the original image data G1 and the target pixel P0 is smaller than a preset density difference threshold. For example, when the density value difference between the first pixels Q of the enlarged target pixel data G3 is smaller than a preset density difference threshold value, threshold data G5 is generated based on the priority order data GY. You may do it.

  Further, the threshold data generation unit 3 determines a difference in density value between the pixels P1 to P8 in the original image data G1, for example, a difference between the maximum value and the minimum value of the density values of the pixels P1 to P8. When the difference threshold is smaller than “3”, for example, and the sum of the density values of the target pixel P0 and the pixels P1 to P8 in the original image data G1 is larger than a preset overall density threshold, for example “13”, that is, If the image is dark, the threshold data G5 is generated by rearranging the order of the first pixels Q in the priority order data GY in the reverse order.

  For example, as shown in FIG. 12, when the density values of the pixels P1 to P8 are all “0”, that is, white, the difference between the maximum value and the minimum value of the density values of the pixels P1 to P8 is from “3”. Since the threshold value data G5 is small, the value at the center is set small so that the dots gather at the center as shown in FIG. 11 based on the priority data GY. The binarized image data G6 of the target pixel P0 generated based on such threshold data G5 is image data in which dots are gathered at the center as shown in FIG. 12, and a reasonable result is obtained as a dot positioning process. It is done.

  On the other hand, as shown in FIG. 13, when the density values of the pixels P1 to P8 are all “15”, that is, black, the difference between the maximum value and the minimum value of the density values of the pixels P1 to P8 is from “3”. Since the threshold value data G5 is small, the value at the center is set small so that the dots gather at the center as shown in FIG. 13 based on the priority data GY. The binarized image data G6 of the target pixel P0 generated based on such threshold data G5 is image data in which dots are gathered at the center. Then, the dots are arranged so as to surround the outside of the target pixel P0, and the dots are arranged in the center of the target pixel P0 away from the surrounding dots, which is not appropriate as the dot positioning process.

  Therefore, the threshold data generation unit 3 has a density value difference between the pixels P1 to P8 in the original image data G1 smaller than a preset density difference threshold, for example, “3”, and the target pixel P0 in the original image data G1. And the sum of the density values of the pixels P1 to P8 is larger than a preset overall density threshold, for example, “13”, the threshold data is obtained by rearranging the order of the first pixels Q in the priority order data GY in the reverse order. G5 is generated. Then, as shown in FIG. 14, the binarized image data G6 of the target pixel P0 becomes image data in which dots are gathered outside, and the pixel of interest P0 is brought closer to the dots of the pixels P1 to P8 surrounding the target pixel P0. Since dots are arranged, a reasonable result can be obtained as the dot positioning process.

  Next, the threshold value data generation unit 3 arranges dots in the first pixel Q having a larger value of the pixel-of-interest pixel data G3 than, for example, the threshold value data G5 shown in FIG. 8 obtained as described above. The first pixel Q having a value of “1” indicating that the pixel-of-interest data G3 is smaller than the threshold data G5 is set to “0” indicating that no dot is arranged, and the binarized image data G6 illustrated in FIG. Generated.

  As described above, the target pixel enlargement processing unit 2, the threshold data generation unit 3, and the binarized image generation unit 4 can increase the resolution of the target pixel P0 from the original image data G1 shown in FIG. Since the binarized image data G6 shown in FIG. 15 is generated with the resolution of scanning 2400 dpi and sub-scanning 2400 dpi, the dot positioning process can be performed without performing pattern matching.

  Next, the binarized image data G6 shown in FIG. 15 is converted into high resolution image data G7 having a desired resolution by the high resolution image generation unit 5. For example, when image data having a resolution of 2400 dpi for main scanning and 2400 dpi for sub scanning is desired, the high-resolution image generation unit 5 uses the binarized image data G6 as it is as the high-resolution image data G7.

  Further, for example, when image data having a resolution of main scanning 1200 dpi and sub-scanning 1200 dpi is desired, the high resolution image generation unit 5 performs first pixel Q in the binarized image data G6 as shown in FIG. Are assembled into four second pixels R1, R2, R3, R4, and the total value of the first pixels Q included in each of the second pixels R1, R2, R3, R4 is the second pixels R1, R2. , R3 and R4 are set as respective density values. As a result, as shown in FIG. 17, high resolution image data G7 in which the pixel of interest P0 has a resolution of main scanning 1200 dpi and sub scanning 1200 dpi is obtained. In this case, the density values of the second pixels R1, R2, R3, and R4 are 5 gradations of 0 to 4.

  Further, for example, when image data having a resolution of 600 dpi in the main scanning and 1200 dpi in the sub-scanning is desired, the high resolution image generating unit 5 performs the first pixel Q in the binarized image data G6 as shown in FIG. Are assembled into eight second pixels R5 and R6, and the sum of the values of the first pixels Q included in the second pixels R5 and R6 is set as the density value of each of the second pixels R5 and R6. . Thereby, as shown in FIG. 19, high resolution image data G7 in which the pixel of interest P0 has a resolution of main scanning 600 dpi and sub scanning 1200 dpi is obtained. In this case, the density values of the second pixels R5 and R6 are 9 gradations from 0 to 8.

  As described above, the high resolution image generation unit 5 obtains the high resolution image data G7 having a desired resolution.

  As shown in FIG. 6, in the priority order data GY, the order of each first pixel Q is set so that the order of the first pixel Q in the central part is higher than the order of the first pixel Q in the peripheral part. For example, as shown in FIG. 20, the first pixels Q having higher ranks may be arranged so as not to be hardened, and other various priority order data GY can be used.

It is a block diagram which shows an example of a structure of the image processing apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the original image data used as the object of the image processing by the image processing apparatus shown in FIG. It is explanatory drawing which shows an example of enlarged image data. It is explanatory drawing which shows an example of expansion attention pixel data. It is explanatory drawing which shows an example of density | concentration order data. It is explanatory drawing which shows an example of priority order data. It is explanatory drawing which shows an example of intermediate data. It is explanatory drawing which shows an example of threshold value data. It is explanatory drawing which shows an example of order data. It is explanatory drawing which shows an example of intermediate data. It is explanatory drawing which shows an example of threshold value data. It is explanatory drawing which shows an example of a dot position alignment process. It is explanatory drawing which shows an example of a dot position alignment process. It is explanatory drawing which shows an example of a dot position alignment process. It is explanatory drawing which shows an example of binarized image data. It is explanatory drawing for demonstrating operation | movement of the high resolution image generation part shown in FIG. It is explanatory drawing which shows an example of high resolution image data. It is explanatory drawing for demonstrating operation | movement of the high resolution image generation part shown in FIG. It is explanatory drawing which shows an example of high resolution image data. It is explanatory drawing which shows an example of priority order data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image processing apparatus 2 Target pixel expansion process part 3 Threshold value data generation part 4 Binary image generation part 5 High resolution image generation part 6 Priority order memory | storage part G1 Original image data G2 Enlarged image data G3 Enlarged attention pixel data G4 Density order Data G41 Intermediate data G5 Threshold data G6 Binary image data G7 High resolution image data GY Priority data P0 Pixels of interest P1 to P8 Pixels Q, Q00 to Q03, Q10 to Q13, Q20 to Q23, Q30 to Q33 First pixel R, R1-R6 second pixel

Claims (7)

An image processing apparatus that generates high resolution image data having a higher resolution than the original image data from original image data in which the density of each pixel is represented by density values having a plurality of density gradations,
The target pixel of the original image data is divided into a number of first pixels that are substantially equal to the number of density gradations in a grid pattern, and the density value of each first pixel is determined as the density of a pixel adjacent to the target pixel . with density values obtained by interpolation using linear interpolation between the values and the density values of the pixel of interest, to generate an enlarged target pixel data representing the pixel of interest in the plurality of first pixel A target pixel enlargement processing unit;
Density rank data indicating the rank number of each first pixel obtained by ranking the density values of the first pixels in the enlarged pixel-of-interest data generated by the pixel-of-interest enlargement processing unit based on the magnitude relationship of the density values. A threshold data generation unit for generating data;
Data obtained by binarizing the density value of each first pixel of the enlarged pixel-of-interest data based on the value of each first pixel of the threshold data obtained by the threshold data generation unit has a higher resolution than the original image data An image processing apparatus comprising: a binarized image generation unit that generates the binarized image data. The concentration value indicates that the concentration increases as the value increases,
The threshold data generation unit ranks the density values of the first pixels in descending order to generate the density ranking data,
The binarized image generation unit has a dot in which the first pixel having the density value larger than the value of each first pixel in the threshold data, and the first density value is smaller than the value of each first pixel in the threshold data. The image processing apparatus according to claim 1, wherein the binarized image data is generated by setting pixels to have no dots. In the enlarged pixel-of-interest data, further comprising: a priority storage unit that stores in advance priority data in which the order in which dots should be preferentially arranged is set for each first pixel;
When there are a plurality of first pixels with the same density value, the threshold data generation unit ranks the ranks between the first pixels with the same density value based on the priority order data stored in the priority storage unit. The image processing apparatus according to claim 1, wherein the image processing apparatus is attached. In the enlarged pixel-of-interest data, further comprising: a priority storage unit that stores in advance priority data in which the order in which dots should be preferentially arranged is set for each first pixel;
The threshold data generation unit, when a difference in density value between each pixel of the original image data is smaller than a preset density difference threshold, the priority data stored in the priority storage unit is the threshold data The image processing device according to claim 1, wherein the image processing device is generated as: In the enlarged pixel-of-interest data, further comprising: a priority storage unit that stores in advance priority data in which the order in which dots should be preferentially arranged is set for each first pixel;
The threshold value data generation unit, when the difference in density value between the first pixels of the expanded pixel-of-interest data generated by the pixel-of-interest expansion processing unit is smaller than a preset density difference threshold, the priority storage unit 3. The image processing apparatus according to claim 1, wherein the priority order data stored in step 1 is generated as the threshold data. In the priority order data, the order of the first pixels is set so that the order of the first pixel in the central part in the enlarged pixel-of-interest data is higher than the order of the first pixels in the peripheral part.
The threshold data generation unit is configured such that when the total density value of each pixel in the original image data is larger than a preset overall density threshold, the order of each first pixel in the priority data is reversed. The image processing apparatus according to claim 4, wherein the threshold value data is generated. A predetermined number of first pixels in the binarized image data generated by the binarized image generation unit are aggregated into a second pixel, and the sum of the values of the first pixels included in the second pixel is calculated. The high-resolution image generation part which produces | generates the image data obtained by setting as a density value of the said 2nd pixel as said high-resolution image data is further provided. The image processing apparatus according to item 1.

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