JP2017038279A - Image processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus which can determine the coincidence between a print image in the past and an image on a record paper, while reducing the amount of data to be stored for comparison.SOLUTION: The image processing apparatus includes: a determination data generation unit 31 which performs first processing on a part of a first image type (text) in print data to be transmitted to a print head 16, to generate first determination data, and performs second processing on a part of a second image type (graphic), to generate second determination data; a holding unit 32 that receives third determination data generated by performing the first processing on a part of the first image type in second print data, and fourth determination data generated by performing the second processing on a part of the second image type in the second print data; and a coincidence determination unit 33 which determines coincidence between an image printed based on first print data and an image printed based on the second print data, on the basis of the results of a comparison between the first and third determination data and a comparison between the second and fourth determination data.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image processing apparatus that determines the coincidence between past printing and an image printed on a recording sheet.

  In a printing shop, a reprint request for the same printed material as a printed material (original) delivered in the past may be received from a customer at a later date. In this case, printing is performed with the same settings as in past printing, but it is difficult to confirm that the output printed matter is completely the same as the original. If the original is provided as a sample by the customer, it is possible to determine the coincidence with the printed matter by comparing with the original, but the original is often not provided from the customer.

  Therefore, it is desirable to store all printed matter at a printing shop, but a vast storage space is required to store the actual product. Although a method of checking the identity by storing output data at the time of printing can be considered, even if a general compression process is performed, the amount of data becomes enormous and a storage device such as an HDD is also required.

  Japanese Patent Application Laid-Open Publication No. 2004-228561 discloses a technique for determining an image abnormality by comparing hash values of print data. The hash value is used for detection of data falsification and the like and confirmation of identity, and data consistency can be confirmed with a small amount of data.

JP 2014-037068 A

  In order to evaluate the coincidence of images actually printed on recording paper using the print data, it is desirable to confirm the coincidence of the print data as close to the print head as possible.

  However, the reproducibility (developability) of the image on the recording paper changes according to the printing environment and process conditions. Processing such as correction is generally performed. For this reason, even if the images on the recording paper are the same, the print data sent to the print head is not necessarily the same, and based on the match / mismatch of the print data, It cannot be determined whether or not they match. For example, even if a hash value of print data sent to the print head is obtained and it is simply determined whether or not the value matches that in the past printing, it is not possible to confirm the coincidence of images on the recording paper.

  The present invention is intended to solve the above-described problem, and can perform image processing capable of determining the coincidence between an image at the time of past printing and an image on a recording sheet while suppressing the amount of data to be stored for comparison. The object is to provide a device.

  The gist of the present invention for achieving the object lies in the inventions of the following items.

[1] First determination data that is subjected to a first process on a portion of the first print data whose image type is the first type and has a correlation that is unique or more than a certain value in the portion and that has a reduced amount of data. Generate and apply a second process different from the first process to a part of the first print data whose image type is the second type to reduce the amount of data with a unique or a certain correlation in the part A determination data generation unit for generating the second determination data,
A portion of the second print data in which the image type is the first type and third determination data generated by performing the first process, and a portion of the second print data in which the image type is the second type An original data input unit to which the fourth determination data generated by performing the second process is input;
Based on the result of comparison between the first determination data and the third determination data and the comparison between the second determination data and the fourth determination data, on the recording paper printed based on the first print data A consistency determination unit that determines the consistency between the image and the image on the recording paper printed based on the second print data;
An image processing apparatus comprising:

  In the above invention, the first print data is subjected to different processing for the first type portion and the second type portion to generate determination data for each image type, and the second print data An image printed on the recording paper based on the first print data and an image printed on the recording paper based on the second print data by comparing the determination data generated from the data for each image type Is determined to match.

[2] The first type is text,
The first process is a process for generating a hash value for each density as determination data,
The second type is a graphic,
The second processing generates a histogram of density of each block in a screen processing unit, and derives connectivity information indicating connectivity between the block and surrounding blocks for each block in each adjacent direction. The image processing apparatus according to [1], which is a process of generating a hash value of each connectivity information as determination data.

  In the above invention, a hash value for each density is generated as determination data for the text portion. For the graphic part on which screen processing is performed, a density histogram of each block as a screen processing unit and a hash value of connectivity information for each adjacent direction are generated as determination data. The density histogram confirms the density of the image, and the connectivity information confirms the consistency of the spatial connection.

[3] The coincidence determination unit has the same hash value within a predetermined density difference in the comparison between the first determination data and the third determination data, and the second determination data and the fourth determination data In the comparison [2], it is determined that there is a match when the density histograms have a certain similarity or more and the hash values in the adjacent directions match in a predetermined number of adjacent directions. The image processing apparatus described.

  In the above-described invention, the printing apparatus performs density correction of print data according to temperature, humidity, and the like at the time of printing. Therefore, when determining image consistency, the difference in density within the density correction range is determined. Allow.

[4] Fifth determination data that performs third processing on tag information indicating the image type of each portion of the first print data to generate fifth determination data that is unique to the tag information and has a reduced data amount A generator,
The original data input unit further inputs sixth determination data generated by performing the third process on tag information indicating the image type of each part of the second print data,
Any one of [1] to [3], wherein the coincidence determination unit further adds a result of comparison between the fifth determination data and the sixth determination data to determine the coincidence. The image processing apparatus described in one.

  In the above invention, tag information indicating the image type of each unit is further used to determine the matching of images.

[5] The image processing device according to [4], wherein the third process is a process of generating a hash value of the tag information.

[6] The coincidence determination unit determines that there is no coincidence when the fifth determination data and the sixth determination data do not match. [4] or [5] Image processing device.

  In the above invention, since the tag information is not affected by the density correction, it is determined whether the determination data matches.

[7] The image according to any one of [1] to [6], wherein the first print data and the second print data are data sent to a print head of a printing apparatus. Processing equipment.

  In the above invention, the determination data is generated based on the data immediately before being sent to the print head, so that the consistency of the image actually printed on the recording paper can be confirmed more accurately.

[8] The printing apparatus is an electrophotographic system,
The image processing apparatus according to [7], wherein gradation correction is performed on print data to be sent to the print head according to an operating environment.

  According to the image processing apparatus of the present invention, it is possible to determine the coincidence between the past printing and the image on the recording paper while suppressing the amount of data to be stored for comparison.

1 is a diagram illustrating a schematic configuration of an image forming apparatus including an image processing apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a schematic configuration of an image processing apparatus according to an embodiment of the present invention. It is a figure which shows the conversion characteristic of output data. It is a figure which shows the printing data of the original image K color density 128. FIG. FIG. 6 is a diagram illustrating print data of a reprint image, K color, and density of 128. FIG. 6 is a diagram illustrating print data of a reprint image K color density 120. It is a figure which shows the density histogram of an original image. It is a figure which shows the density histogram of a reprint image. It is a figure which shows the density histogram of the reprint image which does not correspond with an original image. It is a figure which shows an example of an attention block and surrounding 8 blocks. It is a figure which shows an example of the information which shows the connectivity of an attention block and its surrounding blocks. It is a figure which shows the adjacent direction of the surrounding block with respect to an attention block. It is a figure which shows the example which produced the connection value by making each block of A to L into an attention block, respectively. It is a figure which shows the data which connected and consolidated the connection value of FIG. 13 according to the adjacent direction with respect to the block of interest. It is a flowchart which shows the process in which an image process part determines the coincidence of an image. It is a figure which shows an example of the data amount of original data and determination data.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic mechanical configuration of an image forming apparatus 5 according to an embodiment of the present invention. The image forming apparatus 5 forms an image based on print data input from the outside on the recording paper, and forms a copy image on the recording paper for outputting a document image optically read by the scanner unit 8 on the recording paper. It performs the printing function to output. Connected to the front stage of the image forming apparatus 5 is a paper feeding device 6 that can accommodate a large amount of recording paper and feeds the recording paper one by one to the image forming apparatus 5 during printing. A post-processing device that performs a function of performing processing such as folding, binding, and punching on the recording paper output from the image forming apparatus 5 and a function of accommodating a large amount of printed recording paper are provided at the subsequent stage of the image forming apparatus 5. 7 is connected.

  The image forming apparatus 5 forms a two-dimensional image in which pixels are arranged in a main scanning direction and a sub-scanning direction orthogonal to the main scanning direction. The conveyance direction of the recording paper is the sub-scanning direction. The image forming apparatus 5 includes an intermediate transfer belt 11 having a predetermined width that is looped endlessly, and yellow (Y), magenta (M), and magenta (M) that form a single color toner image on the intermediate transfer belt 11. Four image forming units 12Y, 12M, 12C, and 12K for each color of cyan (C) and black (K), and a fixing device 13 that fixes the toner image formed on the recording paper by pressurizing and heating the recording paper. I have. The color image forming units 12Y, 12M, 12C, and 12K are collectively referred to as an image forming unit 12.

  The image forming units 12Y, 12M, 12C, and 12K have the same structure although the colors of the toners used are different. The image forming units 12Y, 12M, 12C, and 12K have a cylindrical photosensitive drum 14 as an electrostatic latent image carrier on which an electrostatic latent image is formed, and a charging device, a developing device, A transfer device, a cleaning device, and the like are arranged and provided. A print head (laser unit) 16 including a laser diode (LD), which is a laser element, a polygon mirror, various lenses, a mirror, and the like is provided.

  In each of the image forming units 12Y, 12M, 12C, and 12K, the photosensitive drum 14 is driven by a driving unit (not shown) to rotate in a certain direction, and the charging device uniformly charges the photosensitive drum 14, and the print head 16 Scans the photosensitive drum 14 with a laser beam that is on / off controlled in accordance with print data of the corresponding color (scanning in the main scanning direction) to form an electrostatic latent image on the surface of the photosensitive drum 14.

  The developing device visualizes the electrostatic latent image on the photosensitive drum 14 with toner. The toner image formed on the surface of the photosensitive drum 14 is transferred to the intermediate transfer belt 11 at a location where it contacts the intermediate transfer belt 11. The cleaning device removes and collects toner remaining on the surface of the photosensitive drum 14 after the transfer by rubbing with a blade or the like.

  The intermediate transfer belt 11 is wound around a plurality of rollers and circulates in the direction of arrow A in the figure. In the process of turning, images (toner images) of each color in the order of Y, M, C, and K are superimposed on the intermediate transfer belt 11 by the image forming units 12Y, 12M, 12C, and 12K, and a full-color color image is synthesized. . This color image is transferred from the intermediate transfer belt 11 to the recording paper at the secondary transfer position D. Further, the toner remaining on the intermediate transfer belt 11 is removed by a cleaning device 17 provided downstream of the secondary transfer position D. The fixing device 13 is provided at a position downstream of the secondary transfer position D in the middle of the recording paper conveyance path 18.

  The conveyance path 18 functions to convey the recording paper fed from the paper feeding device 6, pass the secondary transfer position D and the fixing device 13, and discharge the recording paper to the post-processing device 7 at the subsequent stage. The conveyance path 18 includes a conveyance roller and a guide that form a conveyance path, and a motor that drives the conveyance roller.

  As an electrical control circuit, the image forming apparatus 5 has an overall control unit 21 that controls the operation of the entire apparatus, a process for rasterizing print data in PDL (Page Discription Language) format, and an inclination correction for an image to be imaged. And an image processing unit 22 as an image processing apparatus according to the present invention that performs processing such as micro scaling, screen processing, gradation correction, and processing for confirming the consistency between an image printed in the past and an image printed this time. ing. In addition, the thing related to past printing shall be the original.

  The overall control unit 21 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk device, a communication I / F (Interface), and the like. A program executed by the CPU is stored in the ROM or the hard disk device.

  In addition, the image forming apparatus 5 includes a scanner unit 8 that reads a document set on a document table by a user, an operation panel 9 that receives operations from the user and displays various screens.

  FIG. 2 shows a schematic configuration of the image processing unit 22. The image processing unit 22 includes a RIP processing unit 24, a determination data generation unit 31, a holding unit 32, a consistency determination unit 33, and the like.

  The overall control unit 21 of the image forming apparatus 5 receives print data described in a page description language (PDL) generated by a printer driver of the terminal device from an external terminal device connected via a network. . The RIP processing unit 24 of the image processing unit 22 translates and rasterizes the print data, and prints data in bitmap format for each color of C, M, Y, and K, and an image (object that includes the pixel for each pixel). The tag information indicating the type of) is output.

  The image processing unit 22 generates C, M, Y, and K color print data to be sent to the print head 16 by performing image processing according to the type (image type) of each object included in the print data in the PDL format. . For example, character data is replaced with specified font data and rasterized, and photo and graphic data are subjected to halftone processing (screen processing) with excellent gradation stability to generate image data to be output to the print head 16. To do.

  The determination data generation unit 31 takes in the print data (C, M, Y, K, and tag information) sent from the image processing unit 22 to the print head 16 and determines the consistency of the print image from the print data Generate data. The determination data is data in which the data amount is sufficiently reduced as compared with the print data sent to the print head 16. The determination data is, for example, a hash value or density histogram generated from the print data. Details will be described later. The determination data generated by the determination data generation unit 31 is output to the outside and stored by the administrator of the printing shop.

  The holding unit 32 (original data input unit) inputs and holds the determination data generated and output to the outside by the determination data generation unit 31 during past printing. The coincidence determination unit 33 compares the determination data generated by the determination data generation unit 31 with the original determination data held by the holding unit 32, and the determination data held in the holding unit 32 is generated. The consistency between the original image printed on the recording paper in the past printing and the image printed on the recording paper in the current printing is determined.

  Since an image forming apparatus such as the image forming apparatus 5 forms an image by an electrophotographic method, developability changes depending on temperature and humidity. Therefore, the printing environment (temperature and humidity), process conditions, or actually developed toner density Based on the value detected by the sensor, parameters are set in the RIP processing unit 24 to correct the density of the print data output from the image processing unit 22 to the print head 16.

  FIG. 3 exemplifies density correction characteristics of print data. Under certain environmental conditions, density correction (tone correction) is performed using the first characteristic 41, and under other environmental conditions, density correction is performed using the second characteristic 42. As described above, since the density correction characteristics and the like are switched depending on the printing environment, even if the print data in the PDL format is the same, if the environment changes, the image processing unit 22 sends the print data to the print head 16. Print data value changes. For this reason, a match / mismatch between the original determination data generated from the print data sent to the print head 16 at the time of past printing and the determination data generated from the print data sent to the print head 16 at the time of the current printing is simply determined. Even if the determination is made, it is not possible to confirm the consistency of the images printed on the recording paper.

  Therefore, it is possible to determine the coincidence between the image printed on the recording paper in the past printing and the image printed on the recording paper in the current printing based on the determination data generated from the print data sent to the print head 16. Therefore, the determination data generation process and the determination process based on the determination data are switched according to the image type. Here, different generation processing (determination data generation processing) / determination processing (images) for tag information indicating the image type of the print data, that is, the text portion, the graphic portion, and the image type of each portion of the print data The consistency of the print image is determined by applying the above-described matching process.

  Hereinafter, the determination of the consistency of print images will be described in more detail.

  In order to reduce the amount of data, a hash value generated by applying a hash function to print data is used as determination data. A hash function is generally used for detection of data alteration and confirmation of identity. There is no inverse function as a feature of the hash function, and a different hash value is generated when data change or order change occurs. That is, the generated hash value is a value that is unique or has a certain correlation or more with the data input to the hash function. In SHA-1, which is one of the frequently used hash functions, a fixed hash value of 160 bits is generated.

  Next, determination data generation processing / determination processing to be applied to tag information of print data, determination data generation processing / determination processing to be applied to a text portion of an image type, determination to be applied to a graphic portion of an image type Each of the data generation process / determination process will be described. Hereinafter, SHA-1 is used as a hash function.

<Processing applied to tag information>
Tag information does not change even when the printing environment such as temperature and humidity changes. Therefore, the hash value (original hash value) generated at the time of past printing is compared with the hash value generated at the time of the current printing, and the coincidence / mismatch is determined. Specifically, the determination data generation unit 31 inputs the tag information of each pixel from the beginning to the end of the page to be printed into the hash function and calculates a hash value (referred to as a tag hash value) as one of the determination data. To do. The coincidence determination unit 33 compares the tag hash value calculated by the determination data generation unit 31 with the original tag hash value held in the holding unit 32. If they are different, the submitted print data is It is determined that there is a mismatch or improper imposition or conversion in the print data creation process.

<Process applied to text part>
For the text portion, the density of the output data (print data output to the print head 16) may change due to the tone correction, so a hash value is calculated for each color and density. Specifically, the determination data generation unit 31 scans only the text portion in the page from the top to the end of the page and sequentially checks whether each pixel is a pixel having a specific density (for example, density 128). Intermediate data is generated as “1” if the density is specific, and “0” if it is not the specific density, and a hash value of the intermediate data (referred to as a density hash value) is generated as determination data.

  Here, since intermediate data is generated for each color and each gradation to generate a density hash value, for example, when there are C, M, Y, and K color components each having a density width of 256 gradations, C 256 density hash values are generated for the color, 256 density hash values for the M color, 256 density hash values for the Y color, and 256 density hash values for the K color. Each hash value is 160 bits.

  FIG. 4 shows an example of intermediate data generated for K color and density 128 of print data (original image) printed in the past. FIG. 5 shows an example of intermediate data generated for the K color and density 128 of the print data (reprinted image) at the time of printing this time. Since gradation correction is performed, the intermediate data of the original image and the intermediate data of the reprinted image may be different even at the same gradation.

  However, if the K color density 128 of the original image is converted to the K color density 120 by gradation correction during reprinting, the intermediate color generated for the K color and density 120 of the reprint image shown in FIG. The data is the same as the intermediate data generated for the K color and density 128 of the original image shown in FIG.

  Therefore, in the determination process for the text portion, the consistency determination unit 33 does not match the density hash value generated at the time of reprinting and the density hash value generated at the time of original printing with the same color and the same gradation. If the same color matches with different gradations within the gradation correction range, it is determined that the color components of the text portion have matching of images. If there is no matching density hash value within the range of gradation correction, it can be seen that there is a difference in the input data and a character processing (font selection).

<Process applied to graphic part>
There is a possibility that the density of the output data (print data output to the print head 16) of the graphic part (screen-processed part) also changes due to the gradation correction. Since the graphic process is subjected to screen processing, the density is expressed in units of a block composed of a plurality of pixels corresponding to the screen matrix. For example, gradation is expressed with 8 × 8 pixels as one block. For this reason, the graphic portion treats the block as if it were one pixel, and determines image consistency. In addition, since there is a possibility that a density different from 2 to 3 gradations may be converted to the same density by gradation correction, a hash value of intermediate data is created for each density as employed in the text portion, and gradation correction is performed. The method of comparing the original hash value within the range cannot evaluate the coincidence of images.

  Therefore, for the graphic portion, the image consistency is determined by evaluating the similarity of the density histogram for each color and the matching of the spatial connection of the images.

  The determination data generation unit 31 examines the density for each color from the top to the end of the page for the graphic part, and creates a density histogram as one of the determination data. FIG. 7 shows a density histogram for a specific color of print data (original image) when printed in the past. FIG. 8 shows a density histogram for a specific color of print data (reprinted image) at the time of printing this time. The coincidence determination unit 33 evaluates these similarities in the determination process.

  For example, the density histogram of the original image shown in FIG. 7 and the density histogram at the time of reprinting shown in FIG. 8 do not completely match, but the frequency of density 1 matches, and the density histograms 4-9 in the density histogram of the original image match. The situation of the frequency distribution and the situation of the frequency distribution of densities 3 to 8 in the density histogram at the time of reprinting are almost the same. Therefore, it is determined that these density histograms have a certain similarity or more.

  For example, if the density histogram at the time of reprinting is as shown in FIG. 9, it is evaluated that the similarity with the density histogram of the original image is below a certain level and low. Evaluation of histogram similarity may be performed by any method.

  Image consistency cannot be determined only by density histogram consistency. For example, it is assumed that the density histogram of an image in which a red object exists on the right side of the page matches the density histogram of an image in which the same red object exists on the left side of the page. Therefore, for the graphic part, the spatial connection method (connectivity) of images is further evaluated.

  In the evaluation of connectivity, the aforementioned block is used as a unit. As shown in FIG. 10, the determination data generation unit 31 checks the density difference between the central block of interest and the eight surrounding blocks. A block having a density difference equal to or greater than a threshold value (for example, 50 gradations in 256 gradations) has a connectivity value of “1”, and if the density difference is less than the threshold value, a connectivity value is generated with a connectivity value of “0”. FIG. 11 shows a concatenated value generated from the block of interest in FIG. In the case of FIG. 10, since the density of the block of interest is 100 and the density of surrounding blocks is 0, 0, 80, 0, 120, 80, 100, 80, each connected value is 0, 0, 1, 0, 1 , 1, 1, 1.

  As described above, in the case of the screen processing, there is a possibility that different densities of two to three gradations may be converted to the same density by gradation correction. For this reason, in the original image, there may occur a case where a surrounding block whose density difference is equal to or less than a threshold and has no connectivity with the block of interest changes to connectivity with the block of interest during reprinting, or vice versa. . Therefore, as shown in FIG. 12, the connectivity is evaluated for each adjacent direction with respect to the block of interest, and when it is evaluated that there is connectivity in a predetermined number of adjacent directions from the first adjacent direction to the eighth adjacent direction. , It is determined that the spatial connection of the images matches.

  Specifically, the determination data generation unit 31 sets each block as a target block from the beginning to the end of the page, and obtains a concatenated value of eight surrounding blocks for each target block. Then, data obtained by connecting the connected values in the first adjacent direction with respect to the block of interest is input to a hash function to generate a hash value in the first adjacent direction. In the same manner, the hash value in the second adjacent direction is generated by inputting, to the hash function, data obtained by connecting the connected values in the second adjacent direction with respect to the target block. Similarly, a hash value in the third adjacent direction to a hash value in the eighth adjacent direction is generated. Hash values in the first to eighth adjacent directions are generated as connectivity determination data. The hash value in each adjacent direction is set as a concatenated hash value.

  In the example of FIG. 13, an example is shown in which a concatenated value is created using each block from A to L as a target block. FIG. 14 shows data obtained by concatenating the concatenated values of FIG.

  The coincidence determination unit 33 includes the original connected hash value in the first to eighth adjacent directions held in the holding unit 32 and the first adjacent direction to eighth adjacent generated by the determination data generation unit 31 during reprinting. The connected hash values of the directions are compared for each adjacent direction, and if the connected hash values match in a predetermined number (for example, 6) or more of the adjacent directions, it is determined that the spatial connection methods of the images match. For example, even if the linked hash values in the two directions do not match, if the linked hash values match in the remaining six directions, it is determined that the spatial connection of the images matches.

  The coincidence determination unit 33 determines that there is no image coincidence when the image coincidence is denied by any of the determination based on the tag information, the determination on the text portion, and the determination on the graphic portion.

  FIG. 15 shows a flow of processing in which the image processing unit 22 determines image matching.

  In the holding unit 32, determination data generated at the time of past printing (determination data for determining the consistency of tag information, determination data for determining the consistency of text portions, and the consistency of graphic portions are determined. Is input and held (step S101).

  The determination data generation unit 31 generates determination data for determining the consistency of tag information for the determination target page from the input print data (step S102), and determines the consistency of the text portion. Generation of determination data (step S103) and generation of determination data for determining the consistency of the graphic portion (step S104) are performed.

  The consistency determination unit 33 determines the consistency between the determination data (tag hash value) for determining the consistency of the tag information held by the holding unit 32 and the tag information generated by the determination data generation unit 31. Are compared with the determination data (tag hash value) (step S105).

  If they do not match (step S106; No), it is determined that the images do not match, a determination result indicating the mismatch is output (step S112), and this process ends.

  If they match (step S106; Yes), the consistency of the text portion is determined (step S107). That is, the density hash value for each density held by the holding unit 32 and the density hash value for each density generated by the determination data generating unit 31 are compared altogether within a range where the density difference is tone correction. If there is no matching density hash value (step S108; No), it is determined that the images do not match, a determination result indicating the mismatch is output (step S112), and this process ends.

  If there is a density hash value that matches the density difference within the gradation correction range (step S108; Yes), the consistency of the graphic area is determined (step S109). That is, the similarity of the density histogram and the coincidence between the spatial connection of images are evaluated. If there is similarity above a certain level, that is, if there is a similarity above a certain level in the density histogram and there is spatial connectivity in the adjacent direction more than a predetermined number (concatenated hash values match) (step) (S110; Yes), it is determined that the images have a match, a determination result indicating a match is output (step S111), and the process ends.

  If the density histogram has no similarity above a certain level, or the density histogram has a similarity above a certain level, but there is no spatial connectivity in the adjoining direction more than a predetermined number (concatenated hash values do not match) (step) (S110; No), it is determined that the images do not match, a determination result indicating the mismatch is output (step S112), and the process ends.

  As described above, the tag information, the text type of the text part, and the graphic part of the print data are subjected to different processing to generate determination data according to the properties of the data, Since the determination data is compared by a suitable method, it is possible to determine the coincidence of images with sufficient accuracy while reducing the data amount of the determination data. Further, since the hash value is used as the determination data, it is possible to determine the coincidence of the data from which the hash value is generated with high accuracy with a small amount of data.

  Next, an example of the data amount of the determination data is shown.

  FIG. 16 shows an example of the data amounts of the original data and the determination data. As shown in FIG. 16, for the A3 size print data (1 Gbyte) with a resolution of 1200 dpi, the judgment data is 25236 bytes, and the image consistency is evaluated with data as small as 0.002% of the original data amount. can do. In addition, since the stored data is a hash value, density histogram, and connectivity information for which there is no inverse function, the original data cannot be restored from these data, and there is a problem even if judgment data leaks outside. No data and security is ensured.

  The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the scope of the present invention. Are also included in the present invention.

  The process for determining image matching is not limited to a method that is performed in real time simultaneously with printing. For example, all the print data directed from the RIP processing unit 24 to the print head 16 is stored in the memory, the data is read from the memory after the printing is finished, the determination data generating unit 31 generates the determination data, and the determination data is held. The coincidence determination unit 33 may compare the determination data held by the unit 32 to determine the image consistency.

  In particular, when the print data is held in the memory as described above and image consistency is determined after printing, the CPU performs the functions of the determination data generation unit 31, the holding unit 32, and the consistency determination unit 33 by software processing. It may be made like.

  The determination data is not limited to that exemplified in the embodiment. For example, instead of a hash value, compressed data by a compression method that can detect tampering may be used.

DESCRIPTION OF SYMBOLS 5 ... Image forming apparatus 6 ... Paper feeding apparatus 7 ... Post-processing apparatus 8 ... Scanner part 9 ... Operation panel 11 ... Intermediate transfer belt 12 ... Image forming unit 13 ... Fixing apparatus 14 ... Photoconductor drum 16 ... Print head 17 ... Cleaning apparatus DESCRIPTION OF SYMBOLS 18 ... Conveyance path 21 ... Overall control part 22 ... Image processing part 24 ... RIP processing part 31 ... Determination data generation part 32 ... Holding part 33 ... Consistency determination part 41 ... 1st characteristic 42 ... 2nd characteristic

Claims (8)

First processing is performed on a portion of the first print data whose image type is the first type, and first determination data that has a correlation that is unique or more than a certain value in the portion and that has a reduced data amount is generated. A second process different from the first process is applied to a portion of the first print data whose image type is the second type, and the portion has a correlation that is unique or more than a certain value and has a reduced data amount. 2 a determination data generation unit for generating determination data;
A portion of the second print data in which the image type is the first type and third determination data generated by performing the first process, and a portion of the second print data in which the image type is the second type An original data input unit to which the fourth determination data generated by performing the second process is input;
Based on the result of comparison between the first determination data and the third determination data and the comparison between the second determination data and the fourth determination data, on the recording paper printed based on the first print data A consistency determination unit that determines the consistency between the image and the image on the recording paper printed based on the second print data;
An image processing apparatus comprising: The first type is text,
The first process is a process for generating a hash value for each density as determination data,
The second type is a graphic,
The second processing generates a histogram of density of each block in a screen processing unit, and derives connectivity information indicating connectivity between the block and surrounding blocks for each block in each adjacent direction. The image processing apparatus according to claim 1, wherein the processing is a process of generating a hash value of each connectivity information as determination data. The coincidence determination unit has the same hash value within a predetermined density difference in the comparison between the first determination data and the third determination data, and in the comparison between the second determination data and the fourth determination data. 3. The image according to claim 2, wherein when there is similarity in a density histogram over a certain level and hash values for each adjacent direction match in a predetermined number or more adjacent directions, it is determined that there is a match. Processing equipment. A fifth determination data generation unit configured to perform a third process on tag information indicating an image type of each part of the first print data to generate fifth determination data that is unique to the tag information and has a reduced data amount; In addition,
The original data input unit further inputs sixth determination data generated by performing the third process on tag information indicating the image type of each part of the second print data,
4. The coincidence determination unit further adds a result of comparison between the fifth determination data and the sixth determination data to determine the coincidence. 4. The image processing apparatus described. The image processing apparatus according to claim 4, wherein the third process is a process of generating a hash value of the tag information. The image processing apparatus according to claim 4, wherein the coincidence determination unit determines that there is no coincidence when the fifth determination data and the sixth determination data do not match. The image processing apparatus according to claim 1, wherein the first print data and the second print data are data sent to a print head of a printing apparatus. The printing apparatus is an electrophotographic system,
The image processing apparatus according to claim 7, wherein gradation correction is performed on print data to be sent to the print head according to an operating environment.