JP2008187669A - Image processing device, and image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing device and image processing program that compresses a two-tone image at high speed and high compression rate. <P>SOLUTION: By means of the image processing device, the image processing is carried out simply and speedily since a number of expansion times 1388 to indicate coincidence with the line data prior to one line is stored if it is decided that a comparison line is coincided with the processing line rotating data according to the compression processing (S6). Further, the data size of the number of expansion times 1388 is small and thus, a high compression rate is obtained since the number of expansion times 1388 corresponds to the line number of the processing line rotating data that is judged to be in accordance with the comparison line. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image processing program, and more particularly to an image processing apparatus and an image processing program capable of compressing data of a two-tone image at a high speed and with a high compression rate.

  As an image compression method, a compression method using a run-length code using a continuous number of the same color is known. In this compression method, when a plurality of pixels of the same color are continuous, the data is compressed by replacing the continuous color value with a value of “color value × number of times”. Therefore, more effective compression is possible as the number of consecutive identical colors increases.

On the other hand, in order to simulate the gradation of a multi-gradation image, a gradation conversion process by a dither method may be performed. In this case, since the image data after gradation conversion has a reduced number of consecutive identical colors, the compression efficiency is low in the run-length encoding. In view of this, a method has been proposed in which a bit string is rearranged according to a dither pattern prior to run-length encoding to increase the same number of continuous colors and increase the compression rate (see, for example, Patent Document 1).
JP 2002-335404 A

  However, in the technique described in Patent Document 1, it is necessary to perform rearrangement of bit strings in a plurality of patterns, and also to compare the rearrangement results to select the rearrangement having the highest compression rate, which is complicated. However, there is a problem that processing takes time.

  Accordingly, an object of the present invention is to provide an image processing apparatus capable of compressing a two-tone image at a high speed and a high compression rate.

  To achieve this object, the image processing apparatus according to claim 1 is a gradation that converts a gradation value of each pixel constituting a multi-gradation image into a gradation value of two gradations using a dither matrix. Conversion means, and compression means for compressing image data composed of a plurality of rows of line data composed of pixel gradation values converted by the gradation conversion means. And comparing means for comparing the row data of each row of the image data with the row data of the previous row of each row, and the comparing means stores the row data of the previous row of the row to be compared as comparison target data. Comparison target data storage means, and rotation data in which each gradation value constituting the row data of the row to be compared is rotated by a predetermined number of pixels in a predetermined direction parallel to the row direction. Rotate data creation And the compression means, when it is determined that the comparison target data and the rotate data match as a result of the comparison by the comparison means, information indicating that the data matches the previous row data, It is characterized in that it is provided with a previous line coincidence data storage means for memorizing as the previous line coincidence data.

  The image processing apparatus according to claim 2 is the image processing apparatus according to claim 1, wherein the compression unit determines that the comparison target data and the rotation data do not match as a result of the comparison by the comparison unit. In this case, it is characterized by comprising compressed data storage means for compressing the row data used when creating the rotation data by a predetermined algorithm and storing it as compressed data for one row.

  The image processing apparatus according to claim 3 is the image processing apparatus according to claim 1 or 2, wherein the one-line previous coincidence data storage unit is configured to compare the comparison target data, the rotation data, and the rotation data as a result of comparison by the comparison unit. Between the comparison data by the comparison means and the value corresponding to the number of rows of the rotation data determined to match the rotation data before the comparison means It is memorized as data.

  5. The image processing apparatus according to claim 4, wherein the gradation converting unit converts a gradation value using a dither matrix that forms a line pattern. It is a thing to do.

  The image processing device according to claim 5 is the image processing device according to any one of claims 1 to 4, wherein the rotation direction information and the rotation amount information corresponding to the dither matrix used by the gradation conversion unit are acquired. Rotation condition acquisition means for performing comparison, and the comparison rotation data creation means based on the rotation amount information in a direction based on the rotation direction information, each of the gradation values constituting the row data of the row to be compared. Rotation data rotated by the number of pixels is created, and the compression means includes rotation condition storage means for storing rotation direction information and rotation amount information acquired by the rotation condition acquisition means, To do.

  The image processing apparatus according to claim 6 is the image processing apparatus according to any one of claims 1 to 4, wherein the comparison rotation data creation unit includes a gradation value that forms row data of a row to be compared. Rotation data is created by rotating each pixel one by one.

  The image processing program according to claim 7 is image data obtained by converting a gradation value of each pixel constituting a multi-gradation image into a gradation value of two gradations using a dither matrix. A program for causing an image processing apparatus to execute a compression step of compressing image data composed of a plurality of rows of row data composed of pixel gradation values for one row, wherein each row of the image data A comparison step of comparing the row data of the previous row with the row data of the previous row of each row, wherein the comparison step stores the row data of the previous row of the row to be compared as comparison target data. And a rotation data for comparison in which each of the gradation values constituting the row data of the row to be compared is rotated by a predetermined number of pixels in a predetermined direction parallel to the row direction. And a compressing step indicating that the comparison target data matches the previous row data when it is determined that the comparison target data and the rotate data match. It is characterized by comprising a preceding line matching data storing step for storing information as preceding line matching data.

  The image processing program according to claim 8 is the image processing program according to claim 7, wherein, as a result of comparison in the comparison step, the comparison step data is determined not to match the rotation target data. In this case, it is characterized in that a compressed data storing step for compressing the row data used when creating the rotated data by a predetermined algorithm and storing it as compressed data for one row is provided.

  The image processing program according to claim 9 is the image processing program according to claim 7 or 8, wherein the one-line previous coincidence data storage step includes the comparison target data, the rotation data, and the result of comparison in the comparison step. Before the line is determined to be inconsistent, a value corresponding to the number of lines of the rotation data determined to match between the comparison target data and the rotation data as a result of the comparison in the comparison step, It is memorized as data.

  An image processing program according to a tenth aspect is the image processing program according to any one of the seventh to ninth aspects, wherein a gradation value of each pixel constituting the multi-tone image is converted into a two-tone using a dither matrix. A gradation conversion step for converting to a gradation value is executed by the image processing apparatus, and the gradation conversion step is for converting a gradation value by using a dither matrix for forming a line pattern. It is characterized by being.

  An image processing program according to claim 11, further comprising a rotation condition acquisition step of acquiring rotation direction information and rotation amount information corresponding to the dither matrix in the image processing program according to any one of claims 7 to 10, The comparison rotation data creation step is a rotation data obtained by rotating each gradation value constituting the row data of the row to be compared in the direction based on the rotation direction information by the number of pixels based on the rotation amount information. The compression step includes a rotation condition storage step for storing the rotation direction information and rotation amount information acquired by the rotation condition acquisition step.

  An image processing program according to a twelfth aspect is the image processing program according to any one of the seventh to tenth aspects, wherein the comparison rotation data creation step includes a gradation value constituting the row data of the row to be compared. Rotation data is created by rotating each pixel one by one.

  According to the image processing apparatus of the first aspect, the comparison unit compares the row data of each row of the image data with the row data of the previous row of each row. Here, the comparison target data storage unit stores the row data immediately before the row to be compared as comparison target data, and the comparison rotation data creation unit sets the row data of the row to be compared. Rotation data is created in which each value is rotated by a predetermined number of pixels in a predetermined direction parallel to the row direction. Then, as a result of the comparison by the comparison means, if it is determined that the comparison target data and the rotation data match, information indicating that it matches the previous row data is stored as the previous row matching data. Is simple, can be processed at high speed, and can compress data at a high compression rate.

  According to the image processing device of claim 2, in addition to the effect produced by the image processing device of claim 1, when it is determined that the comparison target data and the rotation data do not match as a result of comparison by the comparison unit, Since the row data used when creating the rotation data is compressed by a predetermined algorithm and stored as one row of compressed data, the data can be compressed at a high compression rate.

  According to the image processing apparatus of the third aspect, in addition to the effect produced by the image processing apparatus of the first or second aspect, as a result of comparison by the comparison means, it is determined that the comparison target data and the rotation data do not match. In the meantime, as a result of the comparison by the comparison means, the value corresponding to the number of rows of the rotation data determined to match the comparison target data and the rotation data is stored as the previous row matching data. It is simple and has the effect of being able to process at high speed. Further, even when there are a lot of rotation data determined to match the comparison target data and the rotation data, a value corresponding to the number of rows is stored, so that compression can be performed at a high compression rate. There is an effect.

  According to the image processing device of claim 4, in addition to the effect produced by the image processing device according to any one of claims 1 to 3, the gradation conversion means uses a dither matrix that forms a line pattern, Since the gradation value is converted, there is a high possibility that it is determined that the comparison target data and the rotation data match, and there is an effect that a high compression rate can be obtained.

  Here, the line pattern is a pattern that looks like parallel lines that are regularly arranged in a dense manner, and the gradation is expressed in a pseudo manner by changing the thickness of the parallel lines according to the pixel density. It is a pattern that can be done. Looking at an enlarged line of an image formed with such a line pattern, the line is composed of regularly arranged pixels to which color material is not fixed and pixels to which color material is fixed. Has been. When a plurality of lines constituting an area showing a certain gradation are enlarged, the arrangement of the color material fixing areas in each line corresponds to the arrangement of the color material fixing areas in the previous line. Therefore, when the gradation conversion means converts the gradation value using a dither matrix that forms a line pattern, there is a possibility that it is determined that the gradation conversion data of the previous line and the rotation data match. High compression efficiency can be obtained.

  According to the image processing apparatus of the fifth aspect, in addition to the effect produced by the image processing apparatus according to any one of the first to fourth aspects, the rotation condition acquisition unit can cope with the dither matrix used by the gradation conversion unit. Rotation direction information and rotation amount information are acquired, and each of the gradation values constituting the row data of the row to be compared is rotated in the direction based on the rotation direction information by the number of pixels based on the rotation amount information. Since the rotation data is created, there is a high possibility that the comparison target data and the rotation data are determined to match, and there is an effect that a high compression ratio can be obtained.

  According to the image processing device of the sixth aspect, in addition to the effect produced by the image processing device according to any one of the first to fourth aspects, the row data for the row on which the comparison processing is performed is configured by the comparison rotate data creating means. Rotation data in which each gradation value to be rotated is rotated by one pixel is created. Therefore, when the dither matrix used by the gradation converting unit forms a pattern shifted by one pixel every time one line is shifted, it is highly likely that the comparison target data and the rotated data match. There is an effect that a high compression ratio can be obtained.

  According to the image processing program of the seventh aspect, in the comparison step, the line data of each line of the image data is compared with the line data before one line of each line. Here, the comparison target data storage step stores the previous row data as the comparison target data as the comparison target data, and the comparison rotation data creation step generates the row data of the comparison target row. Rotation data is created in which each value is rotated by a predetermined number of pixels in a predetermined direction parallel to the row direction. Then, as a result of the comparison in the comparison step, when it is determined that the comparison target data and the rotation data match, information indicating that the comparison is the previous row data is stored as the previous row matching data. Is simple, can be processed at high speed, and can compress data at a high compression rate.

  According to the image processing program of claim 8, in addition to the effect produced by the image processing program of claim 7, as a result of comparison by the comparison step, when it is determined that the comparison target data and the rotate data do not match, Since the row data used when creating the rotation data is compressed by a predetermined algorithm and stored as one row of compressed data, the data can be compressed at a high compression rate.

  According to the image processing program of the ninth aspect, in addition to the effect produced by the image processing program according to the seventh or eighth aspect, as a result of comparison in the comparison step, it is determined that the comparison target data and the rotation data do not match. In the meantime, as a result of the comparison in the comparison step, a value corresponding to the number of rows of the rotation data determined to match the comparison target data and the rotation data is stored as the previous row matching data. It is simple and has the effect of being able to process at high speed. Further, even when there are a lot of rotation data determined to match the comparison target data and the rotation data, a value corresponding to the number of rows is stored, so that compression can be performed at a high compression rate. There is an effect.

  According to the image processing program of claim 10, in addition to the effect produced by the image processing program according to any one of claims 7 to 9, the gradation conversion step uses a dither matrix that forms a line pattern, Since the gradation value is converted, there is a high possibility that it is determined that the comparison target data and the rotation data match, and there is an effect that a high compression rate can be obtained.

  According to the image processing program of claim 11, in addition to the effect produced by the image processing program according to any one of claims 7 to 10, the rotation condition information and the rotation amount information corresponding to the dither matrix are obtained by the rotation condition acquisition step. Rotation data is generated in which each of the gradation values constituting the row data of the row to be compared is rotated in the direction based on the rotation direction information by the number of pixels based on the rotation amount information. There is a high possibility that it is determined that the comparison target data and the rotate data match, and there is an effect that a high compression ratio can be obtained.

  According to the image processing program of the twelfth aspect, in addition to the effect produced by the image processing program according to any one of the seventh to tenth aspects, the row data of the row to be subjected to the comparison processing is configured by the comparison rotation data creation step. Rotation data in which each gradation value to be rotated is rotated by one pixel is created. Therefore, when the dither matrix forms a pattern shifted by one pixel every time it is shifted, there is a high possibility that the comparison target data and the rotated data are judged to match, and a high compression ratio can be obtained. There is.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing the overall configuration of a printing system including a personal computer 10 (hereinafter referred to as a PC 10) that functions as an image processing apparatus according to the present invention. A printing system as shown in FIG. 1 includes a PC 10 and a printer 50 connected to the PC 10.

  The PC 10 generates data for printing on the recording paper in the printer 50 based on the image data input to the PC 10 by image data transmission processing (see FIG. 6), which will be described later, compresses the data, and transmits the data to the printer 50. Device.

  As shown in FIG. 1, the PC 10 includes a CPU 11, a ROM 12, a RAM 13, and an HDD 14, which are connected to each other via a bus line 200. The bus line 200 is also connected to the input / output port 19. An interface 18 (I / F 18) for connecting to the input device 15, the display device 16, and the printer 50 is connected to the input / output port 19.

  The CPU 11 is a central processing process that comprehensively controls the PC 10, and executes various programs such as a program that executes the processes shown in the flowcharts of FIGS. The ROM 12 is a non-rewritable memory that stores various control programs executed by the CPU 11 and data necessary for executing the control programs by the CPU 11.

  The RAM 13 is a memory for temporarily storing data and programs necessary for various processes executed by the CPU 11. The RAM 13 includes an input data storage area 131, a color conversion data storage area 132, a binarized data storage area 133, a processing line storage area 134, a processing line rotate data storage area 135, and a comparison line storage area 136. A compressed data storage area 137 for one line, a decompression number counter 138, and a compressed data storage area 139 are provided.

  In the input data storage area 131, a print instruction is issued for an image (an example of a multi-tone image described in claims) created by an application such as general document data creation software, spreadsheet software, or graphic design software. In this case, it is a memory into which data of the image to be printed is input. Data stored in the input data storage area 131 (hereinafter referred to as input data) is bitmap format data, and the gradation value of each pixel is R (red), G (green), B ( For each color of blue, for example, the data is expressed in 256 gradations from 0 to 255. The input data stored in the input data storage area 131 is converted into color conversion data by color conversion processing described later.

  The color conversion data storage area 132 is an area in which color conversion data obtained by color conversion processing is stored. In this color conversion data, the gradation value of each pixel is expressed in 256 gradations from 0 to 255 for each color of C (cyan), M (magenta), Y (yellow), and K (black), for example. It is data. Data stored in the color conversion data storage area 132 is converted into binarized data by binarization processing.

  The binarized data storage area 133 is an area for storing binarized data obtained by binarization processing. This binarized data is binary data in which the gradation value of each pixel is set to, for example, “1” or “0”.

  With reference to FIG. 2A, data stored in each of the input data storage area 131, the color conversion data storage area 132, and the binarized data 133 will be further described. FIG. 2A is a diagram schematically showing input data, color conversion data, and binarized data. In order to facilitate understanding, only 8 pixels of each data are illustrated here.

  As shown in FIG. 2A, the input data is composed of respective gradation values of R, G, and B which are color systems for expressing colors on the PC 10. Here, description will be made assuming that the eight pixels are red (red) pixels and the gradation value of each pixel is (R, G, B) = (255, 0, 0). Then, the R, G, B gradation values are converted into C, M, Y, K gradation values, which are the color systems for forming an image by the printer 50, by the color conversion process (S2) shown in FIG. The color conversion data is obtained by converting to.

  As shown in FIG. 2A, the color conversion data is composed of C, M, Y, and K gradation values. Here, the gradation value of each pixel is (C, M, Y, K) = (0, 220, 133, 0) by color conversion. That is, the combination of the magenta tone 220 and the yellow tone 133 represents the red color of the original image.

  As described above, the input data and the color conversion data are data in which the gradation value of each color is expressed by 256 gradations from 0 to 255. In the printer 50, is the color material fixed for each pixel? The image is expressed by either fixing the coloring material or not fixing the coloring material. Therefore, as shown in FIG. 2, the 256-gradation color conversion data is separated into C, M, Y, and K colors by the binarization process (S4) shown in FIG. Are converted into binarized data of four colors in which “1” or “0” is set.

  Here, a description will be given assuming that a process using a dither matrix is performed as the binarization process. The dither matrix is, for example, data in which a threshold value for converting the gradation value of each pixel into “1” or “0” is set in each 40 × 40 matrix. This dither matrix is superimposed on the color conversion data, and the threshold value of each matrix is compared with the gradation value of each corresponding pixel to determine “1” or “0”. In this way, by comparing the value of each pixel of the color conversion data with the threshold value of the dither matrix, the processing contrast color “1” or “0” is set based on a certain rule according to the gradation of the original pixel. "Appears, and the halftone can be expressed in a pseudo manner by the appearance frequency of" 1 ". As will be described later, since different types of dither matrices are applied to each color, as shown in FIG. 2A, the pattern formed by the pixels set to “1” is different for each color. Is different.

  FIG. 2B is a diagram schematically showing the magenta binarization data obtained by the binarization process using the dither matrix. Each horizontal column in FIG. 2B represents one row. Construct a minute pixel. In FIG. 2B, a pixel having a gradation value “1” is colored, and a pixel having a gradation value “0” is not colored. Hereinafter, a pixel having a gradation value of “1” is referred to as a dot-on pixel, and a pixel having a gradation value of “0” is referred to as a dot-off pixel.

  As shown in FIG. 2B, when the gradation value of each pixel is binarized using a dither matrix, dot-on pixels appear based on a certain rule. Will be formed. FIG. 2B illustrates a pattern in which seven dot-on pixels are consecutive in one row and then three dot-off pixels are consecutive. In this way, 70% of gradations can be expressed as a whole by turning on 7 out of 10 pixels.

  Here, in the pattern shown in FIG. 2B, the pattern formed by the dot-on pixels in one row is a pattern obtained by moving the pattern in the previous row by three pixels. Therefore, a pattern formed by combining a plurality of rows of such patterns looks like parallel lines that are densely arranged as a whole, and is called a line pattern.

  Here, an area where dots on in one line are continuous is referred to as a color material fixing area. As shown in FIG. 2B, the angle formed by the line in which the centroids P of the color material fixing regions are arranged and the row direction is hereinafter referred to as a dither pattern angle θ. The dither pattern angle θ varies depending on the type of dither matrix used in the binarization process. When the dither pattern angle θ is 0 °, the parallel line pattern forms a parallel line pattern parallel to the row direction. When the dither pattern angle is 90 °, the parallel line pattern forms a pattern of parallel lines perpendicular to the row direction. On the other hand, a line pattern whose dither pattern angle θ is other than 0 °, 90 °, and 180 °, that is, a line pattern that obliquely intersects the row direction is referred to as an oblique line pattern.

  In this embodiment, the C, M, Y, and K gradation values are binarized using different dither matrices. Therefore, each color of C, M, Y, and K forms a different pattern.

  Returning to FIG. The processing line storage area 134 is an area in which row data (hereinafter referred to as a processing line) for one row to be processed read from the binarized data is stored. The processing line rotation data 135 is processing line rotation data created by rotating each gradation value constituting a processing line by a predetermined number of pixels in a predetermined direction parallel to the row direction (described in claims). This is an area in which one example of rotation data is stored. The comparison line storage area 136 is an area in which row data one row before the processing line (hereinafter referred to as a comparison line) is stored. The one-line compressed data storage area 137 is an area for storing one-line compressed data obtained by performing run-length compression on the processing line. The expansion number counter 138 is a counter that stores the number of expansions described later. The compressed data storage area 139 is an area in which compressed data created by compressing binarized data in a compression process described later is stored. The compressed data stored in the compressed data storage area 139 is output to the printer 50 via the interface 18.

  With reference to FIG. 3, each of the processing line, rotate data, comparison line, compressed data for one line, number of expansions, and compressed data will be described. FIG. 3 is a diagram schematically showing a flow until compressed data is created from binarized data. FIG. 3A is a diagram schematically showing binarized data of magenta. First, from the binarized data (an example of the image data described in the claims) composed of a plurality of row data composed of the gradation values of pixels for one row, the first row data Is read out and stored in the comparison line storage area 136 as a comparison line (an example of comparison target data described in the claims). Next, the row data of the next row of the comparison line is read and stored in the processing line storage area 134 as a processing line.

  FIG. 3B is a diagram schematically showing processing line rotation data created by rotating a processing line. “Rotate” here refers to moving each gradation value of a processing line composed of gradation values of pixels for one row as a gradation value of pixels shifted by a predetermined number of pixels in a predetermined direction parallel to the row direction. In addition, the gradation value overflowing at one end in the predetermined direction is added as the gradation value of the pixel at the other end. Here, among the pixels in each row, the leftmost pixel in FIG. 3 is referred to as the first pixel, and the opposite pixel is referred to as the last pixel.

  FIG. 3B illustrates an example in which rotation is performed by three pixels from the end toward the top (leftward as viewed in FIG. 3). As described above, if the gradation value of each pixel is moved as the gradation value of the pixel on the leading side for three pixels, the gradation value for three pixels overflows on the leading side of one row. The gradation values for the three pixels are added to the end of one line. In this way, processing line rotation data is created.

  FIG. 3C is a diagram showing the comparison line and the processing line rotation data side by side, and illustrates the case where the comparison line and the processing line rotation data are in a matching relationship. That is, when the gradation value of each pixel constituting the comparison line and the gradation value of each pixel constituting the processing line rotation data are compared between pixels having the same position in the row direction, the gradation of all the pixels The values match.

  As described above, the line pattern formed by the magenta binarized data has one line of the color material fixing area in the end direction of three pixels (toward FIG. 3) than the color material fixing area of the previous line. The pattern is formed by moving to the right). Therefore, if the gradation value of the processing line and the gradation value of the comparison line are directly compared for each pixel, it is unlikely that they are determined to match.

  On the other hand, in this embodiment, processing line rotation data is generated by rotating the processing line by three pixels to the head side, and the gradation value of the processing line rotation data is compared with the gradation value of the comparison line. Therefore, as shown in FIG. 3C, there is a high possibility that both are determined to match. If it is determined that the two match, 1 is added to the value of the expansion counter 138 (see FIG. 1).

  In this way, the row data of each row of the binarized data is compared with the row data (comparison line) one row before each row over all rows. The row data here is data composed of the gradation values of the pixels for one row, and the data for one row read from the binarized data and the data for the one row are based on the data. This means that the processing line rotation data created in the above is included. In FIG. 3, a case will be described in which it is determined that all the processing line rotation data in the second and subsequent rows match the comparison line.

  FIG. 3D schematically shows an example in which a plurality of lines of binarized data are compressed into one line of compressed data and the number of expansions of the one line of compressed data. That is, the number of lines (in this case, 10) of the processing line rotation data determined to match the comparison line after the line that is the source of the compressed data for one line is stored as compressed data in association with the compressed data for one line. Will be. In this way, the processing is simple, the processing can be performed at high speed, and the binary data of a plurality of rows can be compressed at a high compression rate.

  FIG. 4A is a diagram schematically showing compressed data stored in the compressed data storage area 139. As shown in FIG. 4A, the compressed data includes a rotation direction 1381, a rotation amount 1382, and a compressed data main body 1383. The rotation direction 1381 is information indicating the direction in which the gradation values of the processing line are rotated when the processing line rotation data is created from the processing line. The rotation amount is information indicating how many pixels the gradation value of the processing line is rotated when the processing line rotation data is created from the processing line. The rotation direction 1381 and the rotation amount 1382 are referred to in the apparatus that has received the compressed data, and are used in a decompression process (see FIG. 9) for decompressing the compressed data.

  FIG. 4B is a diagram schematically showing the compressed data main body 1383. As shown in FIG. 4B, the compressed data body 1383 is data including a previous line reference flag 1385, a data size 1386, one line of compressed data 1387, and the number of expansions 1388.

  The previous line reference flag 1385 stores a value of “on” or “off”. When the previous line reference flag 1385 is off, the data size 1386 and the compressed data 1387 for one line are continuously stored in the previous line reference flag 1385. The data size 1386 is information indicating the data size of the compressed data 1387 for one line that immediately follows. The one-line compressed data 1387 is data created by run-length compressing one line of line data.

  On the other hand, when the previous line reference flag 1385 is on, the next data is the number of expansions 1388. The number of expansions 1388 is information indicating the number of lines that can be expanded based on the compressed data 1387 for one line immediately before the previous line reference flag 1385.

  Returning to FIG. The hard disk drive 14 (hereinafter referred to as the HDD 14) is a rewritable storage device, and a printer driver 141 that causes the PC 10 to execute the processes shown in the flowcharts of FIGS. 7 and 8 and binarization processing of cyan gradation values. C dither data 142 including a dither matrix, M dither data 143 including a dither matrix for binarizing magenta tone values, and binarizing yellow tone values Y dither data 144 including the dither matrix and K dither data 145 including the dither matrix for binarizing the black gradation values are provided.

  Each of the dither data 142, 143, 144, and 145 is a dither matrix that forms a line pattern, but the patterns formed by the C, M, Y, and K colors interfere with each other to generate interference fringes. In order to prevent this, the dither matrix of each color is set so that the dither pattern angle θ formed by each dither matrix is different from each other with a predetermined angle.

  The configuration of dither data will be described with reference to FIG. FIG. 5 is a diagram schematically showing the configuration of the M dither data 143. As shown in FIG. 5, the M dither data 143 includes a dither ID 1431, a rotation direction 1432, a rotation amount 1433, and a dither matrix 1434 used for binarizing magenta gradation values among color conversion data. It is configured to include. The dither ID 1431 is a code assigned to identify each dither data 142, 143, 144, 145.

  The rotation direction 1432 and the rotation amount 1433 are data referred to when the binary data is compressed. As described with reference to FIG. 3, in the line pattern formed by the dither matrix 1434, the pattern of each row is, for example, a pattern shifted by 3 pixels from the top to the end with respect to the pattern of the row on the first row. In some cases, in order to match the pattern of each row with the pattern of the row above one row, the gradation value of one row may be moved by 3 pixels from the end to the head side. In this case, the rotation direction 1432 stores the direction from the end to the head, and the rotation amount 1433 stores 3 pixels. In this case, the processing line rotation data created according to the rotation direction 1432 and the rotation amount 1433 is highly likely to match the comparison line. The rotation direction 1432 and the rotation amount 1433 have specific values for each dither data in accordance with the dither pattern angle θ.

  The dither matrix 1434 is data in which, for example, a threshold value for converting the gradation value of each pixel into either “dot on” or “dot off” is set in each 40 × 40 matrix. 7 is data used in the binarization process (S4) shown in FIG.

  Returning to FIG. The input device 15 is used to input data or commands to the PC 10 and includes a keyboard and a mouse. The display device 16 displays characters, images, and the like in order to visually confirm the processing contents executed by the PC 10, input data, and the like, and is configured by, for example, a CRT display or a liquid crystal display. Yes. The I / F 18 connects the PC 10 and the printer 50, and the PC 10 transmits the compressed data compressed by the compression process (see FIG. 8) described later to the printer 50 via the I / F 18. The printer 50 can execute printing.

  Although FIG. 1 illustrates a state where one PC 10 and the printer 50 are directly connected, a configuration in which a plurality of PCs 10 share one printer 50 via a network may be used. .

  As shown in FIG. 1, the printer 50 includes a CPU 51, a ROM 52, and a RAM 53, which are connected to each other via a bus line 201. The bus line 201 is also connected to the input / output port 59. An I / F 57 for connecting to the PC 10 and an image forming unit 56 are connected to the input / output port 59.

  In the configuration as described above in the printer 50, the CPU 51 controls the operation of the printer 50, and executes various programs such as a program for executing the processing shown in the flowchart of FIG. The ROM 52 is a memory in which a program for controlling the operation of the printer 50 is stored. Here, a program for executing the processing shown in the flowchart of FIG. 9 is stored in the ROM 52.

  The RAM 53 is a readable / writable memory for temporarily storing data necessary for the processing of the CPU 51. The RAM 53 includes a compressed data storage area 531, a decompressed data storage area 532, and a reference line rotate data storage area 533. It has been. The compressed data storage area 531 is an area in which compressed data (see FIG. 4A) input from the PC 10 is stored. The decompressed data storage area 532 is an area in which decompressed data created by decompressing the compressed data stored in the compressed data storage area 531 is stored. The reference line rotate data storage area 533 is an area in which reference line rotate data created by rotating reference lines among the expanded data stored in the expanded data storage area 532 is stored.

  With reference to FIG. 6, the reference line and the reference line rotation data will be described. FIG. 6 is a diagram schematically illustrating a flow from the development of a plurality of rows of data from one row of reference lines. FIG. 6A is a diagram schematically showing one line of data stored in the expanded data storage area 532. First, this one line of data is used as a reference line.

  FIG. 6B is a diagram schematically showing the reference line and the reference line rotation data created by rotating the reference line. FIG. 6B illustrates an example in which the gradation value of each pixel on the reference line is rotated by three pixels from the beginning to the end (rightward in FIG. 6). If the gradation value of each pixel is moved as the gradation value of the pixel on the end side by three pixels, the gradation value for three pixels overflows at the end of one line. The key value is added to the head of one line. Note that the rotation direction in this rotation is opposite to the rotation direction 1381 included in the compressed data. Further, the rotation amount in this rotation is equal to the rotation amount 1382 included in the compressed data (see FIG. 4A).

  The reference line rotate data created in this way is stored in the expanded data storage area 532 as expanded data for one line. Next, as shown in FIG. 6C, among the expanded data stored in the expanded data storage area 532, the latest expanded data for one line is used as a reference line. Then, based on the reference line, reference line rotation data is created by the same processing, and the reference line rotation data is stored in the expanded data storage area 532. In this way, the process is repeated as shown in FIGS. 6 (d) and 6 (e). The number of repetitions is determined based on the number of expansions 1388 (see FIG. 4B) included in the compressed data.

  FIG. 6F is a diagram schematically showing the developed data obtained as a result of repeating the process with the number of repetitions determined based on the number of developments 1388. Here, among the decompressed data, the first line is data obtained by decompressing one line of compressed data 1387 (see FIG. 4B) included in the compressed data. When “10” is stored as the number of expansions 1388 following the one-line compressed data 1387, the process of creating reference line rotation data and storing it in the expansion data storage area 532 (see FIG. 1) is repeated ten times. In this way, decompressed data from the first line to the eleventh line is created based on the compressed data 1387 for one line and the number of expansions 1388. When the expansion for 1388 times is completed, the next line of compressed data 1387 (see FIG. 4B) is acquired from the compressed data, and the process of expanding the line of compressed data 1387 is repeated.

  Returning to FIG. The printer 50 is a so-called laser printer, and the image forming unit 56 includes a photosensitive drum, a charger, an exposure unit, and a development unit. The surface of the photosensitive drum is uniformly charged by a charger, and light is irradiated from the exposure unit according to data to form an electrostatic latent image on the surface of the photosensitive drum. Next, a developer (coloring material) is attached to the surface of the photosensitive drum, and the electrostatic latent image on the surface of the photosensitive drum is visualized. Then, the visualized developer image is moved to the transfer position as the photosensitive drum rotates. When the recording paper is supplied to the transfer position by a paper feed roller and a transport roller (not shown), a bias is applied between the transfer roller and the photosensitive drum, and the developer image is transferred to the recording paper. An image is formed on the recording paper by fixing the developer image on the recording paper by heating and pressing. In the present embodiment, the printer 50 is described as a laser printer. However, the printer 50 may be configured by other types of printers such as a sublimation printer and an inkjet printer.

  Next, the image data transmission process executed in the PC 10 configured as described above will be described with reference to the flowcharts of FIGS. 7 and 8.

  FIG. 7 is a flowchart showing image data transmission processing executed in the PC 10. This image data transmission process is a process that is started when data of a print target image is input to the input data storage area 131 (see FIG. 1) in response to a print instruction from the user in the PC 10. First, color conversion processing is performed on the input data input to the input data storage area 131 (S2). Then, the color conversion data obtained by the color conversion process is binarized using a dither matrix (S4). As described above, dither data 142, 143, 144, and 145 for each color is stored in advance for each color of C, M, Y, and K. In this binarization processing, the dither data of the corresponding color is stored. 142, 143, 144, 145 are read out.

  Next, a compression process for compressing the binarized data obtained by the binarization process (S4) is executed (S6). This compression processing will be described later with reference to FIG. Then, the compressed data obtained by the compression process is transmitted to the printer 50 (S8). Since the data is compressed at a high compression rate by the compression process (S8), data transmission to the printer 50 can be performed in a short time.

  The compression process will be described with reference to FIG. FIG. 8 is a flowchart showing compression processing executed in the PC 10, and is processing for compressing the binary data stored in the binary data storage area 133. As described above, the binarized data is created for each color of C, M, Y, and K, but the flowchart shown in FIG. 8 shows a process of compressing the binarized data of one color. That is, by executing this compression process for each of the four color binarized data, the binarized data for all four colors is compressed. Here, a case of compressing magenta binarized data will be described, but the same processing is performed for other colors.

  First, the rotation direction and rotation amount corresponding to the dither matrix used in the binarization process (S6) are acquired and stored in the compressed data storage area 139 (S860).

  Here, since the case of compressing the magenta binarized data is described, the rotation direction 1432 and the rotation amount 1433 (see FIG. 5) are acquired from the M dither data 143. The acquired rotation direction 1432 and rotation amount 1433 are stored in the compressed data storage area 139 as a rotation direction 1381 and a rotation amount 1382 (see FIG. 4A) constituting the compressed data.

  Next, the number of processing lines is set to “1” (S862). Then, the row data of the row designated by the number of processing lines is acquired from the binarized data storage area 133 and stored in the processing line storage area 134 (S864). Next, it is determined whether or not the processing line is the first line (S866). Initially, the processing line is determined to be the first line (S866: Yes), and the process proceeds to S874.

  Then, the value of the expansion number counter 138 is set to “0” (S874), and the processing line is written as a comparison line in the comparison line storage area 136 (see FIG. 1) (S876). Next, the processing line is run-length compressed to generate one-line compressed data 1387 (see FIG. 4B), the previous line reference flag 1385 is turned off, and the data size 1386 indicating the data size of the one-line compressed data 1387 is displayed. At the same time, it is stored in the compressed data storage area 139 (S878). As a result, the data in the first row of the binarized data is compressed.

  Next, “1” is added to the number of processing lines (S880), and it is determined whether or not the processing of all rows has been completed (S882). If all the lines have not been processed (S882: No), the process returns to S864, and the line data of the next line is acquired as a process line (S864). Since this line is not the first line (S886: No), next, process line rotate data is created from the process line and stored in the process line rotate data storage area 135 (S868). Here, the processing line is rotated according to the rotation direction and the rotation amount acquired in the processing of S860.

  Next, the processing line rotation data stored in the processing line rotation data storage area 135 is compared with the comparison line stored in the comparison line storage area 136 to determine whether or not they match (S870). That is, as described with reference to FIG. 3, it is determined whether or not the processing line rotation data created by rotating the processing line matches the comparison line that is the previous row data of the processing line. To do.

  When the processing line rotation data matches the comparison line (S870: Yes), “1” is added to the value of the development counter 138 (S884). Next, the processing line stored in the processing line storage area 134 is written in the comparison line storage area 136 as the next comparison line (S886). Then, “1” is added to the number of processing lines (S880), and the processing returns to S864 and is repeated while the processing of all the rows is not completed (S882). In this way, while it is determined that the processing line rotation data matches the comparison line (S870: Yes), “1” is added to the value of the development number counter 138 (S884). That is, the number of times that it is continuously determined that the processing line rotate data matches the comparison line is counted.

  While the process is repeated in this manner, if it is determined that the comparison line and the process line rotate data do not match as a result of the comparison in S870 (S870: No), the previous line reference flag 1385 (FIG. 4B) )) Is turned on. Then, the value of the expansion number counter 138 is stored in the compressed data storage area 139 as compressed data together with the previous line reference flag 1385 as the number of expansions 1388 (see FIG. 4B) (S872). In this way, the number of expansions 1388 is continuously determined when the comparison line and the processing line rotation data match before it is determined that the comparison line and the processing line rotation data do not match. The value indicates the number of lines of the processed line rotation data.

  Next, the value of the expansion counter 138 is set to “0” (S874), the processing line is written as a comparison line in the comparison line storage area 136 (S876), the processing line is run-length compressed, and one line of compressed data is stored. create. Then, the previous line reference flag 1385 (see FIG. 4B) is turned off, and one line of compressed data is stored in the compressed data storage area 139 together with the data size 1386 (S878). That is, if it is determined that the comparison line and the processing line rotation data do not match (S870: No), the processing line used to create the processing line rotation data is run-length compressed (in the claims) And is stored in the compressed data storage area 139 as one line of compressed data 1387.

  When the processing for all the lines is completed while repeating the processing in this way (S882: Yes), it is next determined whether or not the value of the expansion counter 138 is “0” (S888), and the expansion counter If the value of 138 is “0” (S888: Yes), the process is terminated as it is. On the other hand, when the value of the expansion number counter 138 is not “0” (S888: No), the previous line reference flag 1385 is turned on, the value of the expansion number counter 138 is set as the expansion number 1388, and the compressed data together with the previous line reference flag 1385. The data is stored in the storage area 139 (S890), and the process ends.

  As described above, according to the compression process (S6), when it is determined that the comparison line and the process line rotate data match, the number of expansions 1388 indicating that the line data matches the previous line data (see FIG. 4). Is stored, the processing is simple and can be performed at high speed. Further, since the number of expansions 1388 is the number of processed line rotation data determined to match the comparison line, the expansion is performed even if the number of processed line rotation data determined to match the comparison data is large. The data size of the number of times 1388 is small, and a high compression rate is obtained.

  If it is determined that the comparison line and the processing line rotation data do not match, the row data used to create the processing line rotation data is compressed by a predetermined algorithm and stored as compressed data for one line. Therefore, data can be compressed at a high compression rate.

  In addition, since the dither matrix used for binarizing magenta described in the above embodiment forms a diagonal line pattern, the comparison line matches the processing line rotation data. The possibility of being judged is high, and a high compression rate is obtained.

  Further, the rotation direction 1432 and the rotation amount 1433 corresponding to the dither matrix used in the binarization processing (S4) are acquired, and each of the gradation values constituting the row data of the row on which the comparison processing is performed is the rotation direction. Rotation data that is rotated by the number of pixels based on the rotation amount 1433 is generated in the direction based on 1432, so that there is a high possibility that the comparison line and the processing line rotation data match, and a high compression ratio is obtained. It is done. In addition, since the rotation direction and the rotation amount corresponding to the dither pattern angle θ are determined for each dither data for each color, a high compression rate can be obtained for any type of line pattern. .

  Next, the expansion process will be described with reference to the flowchart of FIG. FIG. 9 is a flowchart showing a developing process executed in the printer 50. This decompression process is a process executed by the printer 50 when the compressed data compressed in the above-described compression process (S6) in the PC 10 is transmitted from the PC 10 to the printer 50. In the PC 50, the received compressed data is stored in the compressed data storage area 531. Further, as described above, the compressed data is created for each color of C, M, Y, and K, but the flowchart shown in FIG. 9 shows a process of expanding the compressed data of one color. That is, by executing this decompression process for each of the four color compressed data, the compressed data for all four colors is decompressed. Here, a case where the magenta compressed data is expanded will be described, but the same processing is performed for other colors.

  First, the rotation direction 1381 and the rotation amount 1382 (see FIG. 4A) are acquired from the compressed data (S902). Then, the compressed data main body 1383 (see FIG. 4B) included in the compressed data is checked from the head, and it is determined whether or not the head previous line reference flag 1385 is on (S904). Since it is currently the first loop, the leading previous line reference flag 1385 is off (S904: No), and next one line of compressed data 1387 is expanded (S906). The expanded data is stored in the expanded data storage area 532 (S908).

  Next, it is determined whether or not all the compressed data has been processed (S910). If not all have been processed (S910: No), the process returns to S904, and the next previous line reference flag included in the compressed data main body 1383 is determined. It is determined whether 1385 is ON. Here, a case where the previous line reference flag 1385 is on will be described. If the previous line reference flag 1385 is on (S904: Yes), the number of expansions 1388 (see FIG. 4B) is stored behind the previous line reference flag 1385. Is acquired (S912). Here, as described in the above compression processing, the number of expansions 1388 is a value indicating the number of lines that can be expanded based on the compressed data 1387 for one line immediately before.

  Next, the number of expansions is set to “1” (S914). Then, the development data for one line most recently written in the development data storage area 532 is acquired as a reference line (S916). That is, the expanded data for one line expanded based on the compressed data 1387 for the immediately preceding line is used as a reference line.

  Next, the reference line is rotated based on the rotation direction 1381 and the rotation amount 1382 acquired from the compressed data, and the reference line rotation data is created (S918). Here, for example, when the rotation direction 1381 indicates the head direction from the end, it means that when generating the processing line rotation data in the compression process, the gradation value of the pixel for one line is changed from the end to the head direction. It is shown that the predetermined pixels are moved to each other. Therefore, here, when rotating the reference line, the reference line is rotated in the direction opposite to the direction indicated by the rotate direction 1381 to create the reference line rotate data (see FIG. 6B). The created reference line rotate data is stored in the reference line rotate data storage area (S920).

  Next, “1” is added to the number of expansions (S922), and it is determined whether or not the number of expansions is greater than the number of expansions 1388 (S924).

  When the number of expansions is equal to or less than the number of expansions 1388 (S924: No), the process returns to S916 and repeats the process. That is, the development data for one line most recently written in the development data storage area 532 (reference line rotation data created most recently) is acquired as a reference line (S916), and the reference line rotation is performed based on the reference line. Data is created (S 920), and the reference line rotate data is stored in the expanded data storage area 532. By repeating such processing as many times as the number of expansions 1388, expanded data having the same number of rows as the number of expansions 1388 is obtained.

  If the number of expansions 1388 becomes larger than the number of expansions while repeating the processing in this way (S924: Yes), it is then determined whether all the compressed data has been processed (S910), and all the compressed data is processed. When it has not finished (S910: No), it returns to S904.

  When all the compressed data has been processed while the processing is repeated in this way (S910: Yes), the decompression processing ends.

  According to the expansion process, the data compressed in the compression process (S6) described with reference to FIG. 8 can be expanded with a simple process. Therefore, the developing process can be executed even if the processing capacity of the CPU 51 of the printer 50 is not so high, and the inexpensive printer 50 can be used.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications and changes can be easily made without departing from the spirit of the present invention. Can be inferred.

  For example, in the above-described embodiment, it has been described that the compression process (S6) is performed when data is transmitted from the PC 10 to the printer 50. However, when the data is transmitted to a device other than the printer 50, the compression process (S6) is performed. ) May be executed.

  In the above-described embodiment, when the processing line rotation data is created and when the reference line rotation data is created, the rotation amount is set to 3 pixels, and the gradation values for 3 pixels are moved. This rotation amount is an amount corresponding to the angle θ of the dither pattern. For example, in a line pattern in which the dither pattern angle θ is 45 °, a pattern shifted by one pixel is formed every time one line is shifted. Therefore, in the compression process (S6), each gradation value constituting the processing line is rotated pixel by pixel to create processing line rotation data, thereby creating a line pattern having a dither pattern angle θ of 45 °. Even when a dither matrix in which is formed is used, a high compression ratio can be obtained.

1 is a block diagram illustrating an overall configuration of a printing system including a personal computer that functions as an image processing apparatus according to the present invention. (A) is a diagram schematically showing input data, color conversion data, and binarized data, and (b) is a magenta binarization obtained by binarization processing using a dither matrix. It is a figure which shows data typically. (A) is a figure which shows typically the binarization data of magenta, (b) is a figure which shows the process line rotation data produced by rotating a process line typically, (c ) Is a diagram showing the comparison line and the processing line rotation data side by side, and (d) shows the binarized data for a plurality of lines, the compressed data for one line, and the number of expansions of the compressed data for that line. A compressed example is schematically shown. (A) is a figure which shows typically the compression data memorize | stored in a compression data storage area, (b) is a figure which shows a compression data main body typically. It is a figure which shows typically the structure of the dither data for M. It is a figure which shows typically the flow until several lines of data are expand | deployed from the reference line of 1 line. It is a flowchart which shows the image data transmission process performed in PC. It is a flowchart which shows the compression process performed in PC. 6 is a flowchart illustrating an expansion process executed in the printer.

Explanation of symbols

10 PC (an example of an image processing apparatus)
136 Comparison line storage area (an example of comparison target data storage means)
1381 Rotate direction (an example of rotate direction information)
1382 Rotate amount (an example of rotate amount information)
141 Printer driver (an example of an image processing program)
1434 Example of Dither Matrix S4 Binarization (Example of Tone Conversion Means, Tone Conversion Step)
S6 Compression processing (example of compression means and compression step)
S860 Example of rotation condition acquisition means and rotation condition acquisition step S860 Example of rotation condition storage means and rotation condition storage step S868 Example of comparison rotation data creation means and comparison rotation data creation step S862 to S882 Example of comparison means and comparison step S872 One-line-preceding coincidence data storage means, example of one-line-preceding coincidence data storage step S876, S886 Comparison target data storage step S878 Example of compressed data storage means, compressed data storage step

Claims (12)

A gradation conversion unit that converts the gradation value of each pixel constituting the multi-gradation image into a gradation value of two gradations using a dither matrix, and a pixel of one row converted by the gradation conversion unit In an image processing apparatus comprising compression means for compressing image data composed of a plurality of lines of line data composed of gradation values,
Comparing means for comparing the row data of each row of the image data with the row data of the previous row of each row,
The comparison means includes
Comparison target data storage means for storing the row data of the row before the row to be compared as comparison target data;
A rotation data creation unit for comparison that creates rotation data in which each of the gradation values constituting the row data of the row to be compared is rotated by a predetermined number of pixels in a predetermined direction parallel to the row direction;
The compression means includes
As a result of the comparison by the comparison means, when it is determined that the comparison target data and the rotate data match, information indicating that the data matches with the previous row data is stored as the previous row match data. An image processing apparatus comprising data storage means. The compression means includes
As a result of comparison by the comparison means, if it is determined that the comparison target data and the rotation data do not match, the row data used when creating the rotation data is compressed by a predetermined algorithm and compressed by one row 2. The image processing apparatus according to claim 1, further comprising compressed data storage means for storing data.   The one-line-preceding coincidence data storage means is the result of the comparison by the comparison means until the comparison object data is determined not to match the rotation data as a result of the comparison by the comparison means. 3. The image processing apparatus according to claim 1, wherein a value corresponding to the number of rows of the rotation data determined to match the data and the rotation data is stored as the previous row matching data.   The image processing apparatus according to claim 1, wherein the gradation converting unit converts a gradation value using a dither matrix that forms a line pattern. Rotation condition acquisition means for acquiring rotation direction information and rotation amount information corresponding to the dither matrix used by the gradation conversion means,
The comparison rotation data creating means rotates each of the gradation values constituting the row data of the row to be compared in the direction based on the rotation direction information by the number of pixels based on the rotation amount information. Is to create
5. The image processing apparatus according to claim 1, wherein the compression unit includes a rotation condition storage unit that stores rotation direction information and rotation amount information acquired by the rotation condition acquisition unit. .   2. The comparison rotation data creation means creates rotation data in which each gradation value constituting the row data of the row to be compared is rotated by one pixel. 5. The image processing device according to any one of 4. This is image data obtained by converting the gradation value of each pixel constituting a multi-gradation image into a gradation value of two gradations using a dither matrix. An image processing program for causing an image processing apparatus to execute a compression step for compressing image data composed of a plurality of lines of configured line data,
A comparison step of comparing the row data of each row of the image data with the row data of the previous row of each row;
The comparison step includes
A comparison target data storage step for storing, as comparison target data, the row data preceding the row to be compared;
A rotation data creation step for comparison, which creates rotation data in which each gradation value constituting the row data of the row to be compared is rotated by a predetermined number of pixels in a predetermined direction parallel to the row direction.
The compression step includes
As a result of the comparison in the comparison step, when it is determined that the comparison target data and the rotate data match, information indicating that the data matches with the previous row data is stored as the previous row match data. An image processing program comprising a data storage step. The compression step includes
As a result of the comparison in the comparison step, when it is determined that the comparison target data and the rotation data do not match, the row data used for creating the rotation data is compressed by a predetermined algorithm and compressed by one row 8. The image processing program according to claim 7, further comprising a compressed data storing step for storing as data.   In the previous line coincidence data storing step, as a result of the comparison in the comparison step, the comparison target data and the rotation data are determined to be inconsistent with each other as a result of the comparison in the comparison step. 9. The image processing program according to claim 7, wherein a value corresponding to the number of rows of the rotation data determined to match the data and the rotation data is stored as previous row matching data. Causing the image processing apparatus to execute a gradation conversion step of converting a gradation value of each pixel constituting a multi-gradation image into a gradation value of two gradations using a dither matrix;
10. The image processing program according to claim 7, wherein the gradation conversion step converts the gradation value using a dither matrix that forms a line pattern. A rotation condition acquisition step of acquiring rotation direction information and rotation amount information corresponding to the dither matrix;
The comparison rotation data creation step is a rotation data obtained by rotating each gradation value constituting the row data of the row to be compared in the direction based on the rotation direction information by the number of pixels based on the rotation amount information. Is to create
The image processing program according to any one of claims 7 to 10, wherein the compression step includes a rotation condition storage step for storing the rotation direction information and the rotation amount information acquired by the rotation condition acquisition step. .   8. The comparison rotation data creation step creates rotation data by rotating each gradation value constituting the row data of the row to be compared one pixel at a time. The image processing program according to claim 10.

Images