JP2007124234A - Information processor and woven pattern printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discriminate between an original and its copy with features which are hardly reproduced in a copy image as to woven pattern printing. <P>SOLUTION: When printing a woven pattern image, a woven pattern image generation section 101 represents a latent image part with process black having an excellent gray balance which is hardly reproduced in a copy image, and represents a background part with black as one coloring material. Consequently, the gray balance of the latent image part is lost in the copy image while that can not be discriminated in the printed original image, and then the latent image part and background part has differences in color, so that the original document and its copy image can be discriminated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an information processing apparatus and a tint block printing method, and more particularly to printing a tint block image synthesized with a print image such as a document for the purpose of suppressing illegal forgery or information leakage by copying an important document or the like. Is.

  Some receipts, securities, certificates, etc. have a special pattern or the like printed on the background when certain characters or images appear when they are copied. This special pattern is generally called “counterfeit deterrence pattern”, and can be used to psychologically restrain the copying act or to suppress its use even if it is copied.

  This forgery-inhibited tint block is basically composed of two areas: an area where dots remain after copying and an area where dots disappear after copying. These two areas have almost the same density, and macroscopically, you cannot see that characters and images that appear after copying, such as “copy”, are hidden, but microscopically they have different dot characteristics. have. Hereinafter, these hidden characters and images are referred to as “latent images”. For example, an area where dots remain after copying (also referred to as a latent image portion) is composed of clustered dots in which each dot is concentrated, and each dot is dispersed in an area where dots disappear after copying (also referred to as a background or background portion). Consists of dots. As a result, two regions having substantially the same density on a macro scale and different dot characteristics on a micro scale can be formed.

  Concentrated dots and dispersed dots can be generated by halftone processing using halftone dots with different numbers of lines or dither processing using dither matrices with different features. In the case of halftone dot processing, a low dot number halftone dot is used to obtain a concentrated dot arrangement, and a high line number halftone dot is used to obtain a dispersed dot arrangement. In the case of dither processing using a dither matrix, a dot concentrated dither matrix is used to obtain a concentrated dot arrangement, and a dot dispersed dither matrix is used to obtain a dispersed dot arrangement. Thus, when a tint block image is generated using halftone processing, halftone processing with a low number of lines is suitable for the latent image portion, and halftone processing with a high number of lines is suitable for the background portion. When a copy-forgery-inhibited pattern image is generated using dither processing, dither processing using a dot concentration type dither matrix is suitable for the latent image portion, and dither processing using a dot dispersion type dither matrix is suitable for the background portion.

  On the other hand, a copying machine has a limit of image reproduction capability depending on an input resolution for reading minute dots of an original to be copied and an output resolution for reproducing minute dots. Therefore, if an isolated minute dot exceeding the limit of the image reproduction capability of the copying machine exists in the document, the minute dot cannot be completely reproduced, and the image due to the minute dot disappears in the copy or the density is low. It will be thin. In addition, the copying machine may be provided with a mode for executing a so-called “background removal” process in which the background of an original is removed when copying, thereby making it easier to read or read a copied image such as a copied character or image. Can be made easier. However, if this process is performed, minute dots are more difficult to reproduce.

  As described above, since the background portion of the forgery-inhibited tint block is created to exceed the limit of dots that can be reproduced by a copying machine, small dots (dispersed dots) in the forgery-inhibiting tint block cannot be reproduced, and large dots ( Only concentrated dots) can be reproduced. As a result, the background portion disappears and a hidden image (latent image) can emerge. Alternatively, even if dots dispersed by copying do not disappear completely, if the density of the background portion becomes light thereby, a density difference from the latent image is generated, and this can also cause the latent image to emerge.

  In copy-forgery-inhibited pattern printing, a technique called “camouflage” that makes it difficult to distinguish a latent image in a printed material is well known. In this camouflage, a pattern having a density different from that of the latent image portion and the background portion is arranged on the tint block image. Thereby, from a macro viewpoint, a camouflage pattern having a density different from that of the latent image portion and the background portion is conspicuous, and the latent image can be further inconspicuous.

  Further, a background pattern image provided with a camouflage pattern has an effect of giving a decorative impression to a printed matter as compared to a background pattern image without a camouflage pattern. In this camouflage pattern, it is desirable that the dots constituting the camouflage pattern disappear as much as possible so that the latent image can be easily distinguished when copied. For this purpose, the camouflage pattern is often composed of white that does not form dots from the beginning of the tint block image.

  Many of the anti-counterfeiting background patterns described above have been conventionally printed by a print paper manufacturer in advance on a dedicated paper that includes a background pattern including characters and images (latent images) such as “copy” and sells it as anti-copying paper. Is known as. Such copy-preventing paper is purchased by government agencies and companies, and a document whose originality is to be guaranteed is printed on the copy-preventing paper, thereby preventing copying of the printed matter.

  A technology that creates a tint block image in software and prints it together with an image such as a document (hereinafter referred to as an “on-demand tint block output method using a printer”). Is also known (for example, see Patent Document 1).

  This on-demand copy-forgery-inhibited pattern output method using a printer can print a copy-forgery-inhibited pattern image together with an image to be printed, such as a document, using plain paper, and therefore prints a document or the like in which a required number of copy-forgery-inhibited pattern images are arranged as necessary. be able to. Therefore, it is not necessary to prepare copy prevention sheets more than necessary as in the prior art. That is, the on-demand copy-forgery-inhibited pattern output method using a printer can greatly reduce the cost of paper compared to a conventional document copy suppression method using copy-preventing paper.

  In addition, users of conventional copy prevention paper can only use a latent image prepared in advance or a latent image ordered in a custom-made manner. On the other hand, the on-demand copy-forgery-inhibited pattern output method using a printer has an advantage that a latent image can be freely customized because a user can generate and print a copy-forgery-inhibited pattern image including a desired latent image by software processing every printing. Since this latent image can be selected on demand, various characters can be used as images and characters to be embedded as a latent image, in addition to conventionally used company logos and prohibited characters. For example, a serial number or IP address for identifying an output printer, a computer name or IP address for identifying a computer that has issued a print command, and a user name or login name for identifying a user who has issued a print command can be selected. Furthermore, it is possible to select various information such as a print job number, a printing date and time, a printing location, and a file name of an electronic document for identifying when and who the printing process was performed. As a result, the on-demand copy-forgery-inhibited pattern output method using a printer can realize a more advanced tracking function that could not be realized with conventional copy-prevention paper.

JP 2001-197297 A

  As described above, the copy-forgery-inhibited pattern image is configured so that the background portion disappears or the density difference from the background portion appears remarkably so that the latent image portion can be clearly recognized when copied. . However, when copied, the density difference does not appear remarkably including the case where the background portion does not disappear, and the latent image may not be clearly recognized. In such a case, it cannot be said that the function of the tint block image is exhibited.

  For example, when a document is copied in a mode in which the background removal process is not executed, the dots constituting the background portion are also easily reproduced, and the background is more difficult to disappear or thinner. In this case, the density of the latent image portion and the background portion of the copy image may be substantially equal.

  In some cases, the density difference between the latent image and the background portion is intentionally prevented from appearing in the copied image. That is, in recent years, scanners and printers, which are peripheral devices for personal computers (PCs), have been improved in performance and price, and these devices are generally spread. Under such circumstances, it is becoming impossible to combine these two devices to obtain a copy image close to the original document, that is, an image having no density difference between the latent image portion and the background portion. For example, an image with a copy-forgery-inhibited pattern image read by a scanner, processed on a PC to increase the density of the background portion, printed by a printer, and the density difference between the latent image portion and the background portion in the image. It is also possible to prevent this from occurring.

  As described above, when it is difficult to distinguish the difference between the original document and the copied image only by the difference between the density of the latent image portion after copying and the density of the background portion, it is possible to identify that the copied image is different from the original image. A mechanism is required.

  The present invention has been made to solve this problem, and an object of the present invention is to provide one of the latent image portion and the background portion of the copy-forgery-inhibited pattern image in the original image with features that are difficult to reproduce in the copied image. It is an object to provide an information processing apparatus and a tint block printing method.

  Therefore, according to the present invention, there is provided an information processing apparatus that generates print data of a tint block image including a latent image and a background, wherein either the latent image or the background is printed with only one color material, and the other is printed. Means for generating the print data so as to print using a plurality of color materials in a predetermined ratio is provided.

  A tint block printing method for printing a tint block image including a latent image and a background, wherein either the latent image or the background is printed with only one color material, and the other is printed at a predetermined ratio. It has the process of printing using a several coloring material, It is characterized by the above-mentioned.

  According to the above configuration, either the latent image or the background is printed using only one color material, and the other is printed using a plurality of color materials having a predetermined ratio. As a result, when the printed image is copied as an original, it is unlikely that the predetermined ratio is reproduced, and the colors of the plurality of coloring materials are different from the original.

  As a result, even when it is difficult to distinguish the difference between the original document and the copy document only by the difference between the density of the latent image portion after copying and the density of the background portion, the copy document can be identified.

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

  In the following embodiments, the image corresponding to the background portion is designed such that dots are discretely arranged using a dot dispersion type dither matrix, and the image corresponding to the latent image portion is a dot concentration type dither matrix. Design so that dots are concentrated and arranged. The dither matrix used for generating the background image is called a background dither matrix, and the dither matrix used for generating the latent image is called a latent image dither matrix. Then, a binary image is obtained by binarizing the pixel value of the input image signal with the threshold value (threshold pattern) of the corresponding dither matrix. Here, the obtained binary image has one bit (for example, 1) in the pixel value when the gradation of the input image signal is less than the threshold of the dither matrix, and the other bit (for example, 0) when the gradation is equal to or greater than the threshold. Is assigned. In this embodiment, the binary image constituting the background and the binary image constituting the latent image portion are respectively set so that the background portion and the latent image portion have substantially the same density when printed by a printer, as will be described later. It is assumed that an appropriate input image signal is input and generated in advance by a dither method.

  In the following description, a binary image forming the background portion is called a background threshold pattern, and a binary image forming the latent image portion is called a latent image threshold pattern. In the present embodiment, a combination of the background threshold pattern and the latent image threshold pattern is determined in advance so that the density of the background portion and the latent image portion becomes equal during printing. Then, a background pattern image is generated by executing a logical operation using a background threshold pattern, a latent image threshold pattern, and a latent image background area designating image which is a binary image designating each area of the latent image portion and the background portion. Further, when a camouflage image is given, a logical pattern is also used to generate a tint block image using a camouflage region designation image that is a binary image for designating a camouflage region. Here, the background threshold pattern and the latent image threshold pattern are parameters for determining the density at the time of printing the background portion and the latent image portion of the tint block image, and are specific components of the “background tint density parameter”.

  In addition, by executing a logical operation of dot on / off for the copy-forgery-inhibited pattern image for each pixel and generating the copy-forgery-inhibited pattern image, the amount of memory required for generating the copy-forgery-inhibited pattern image can be greatly reduced. .

  FIG. 1 is a block diagram showing internal processing of the tint block composition printing apparatus according to the first embodiment of the present invention. The tint block composition printing apparatus includes a tint block image generation unit 101, a composition unit 102, a print data processing unit 103, and a printing unit 104. Specifically, the tint block composition printing apparatus of the present embodiment can be a dedicated device that synthesizes a tint block image with an original image and performs printing. Alternatively, as will be described later, it may be constituted by a host computer and a printer. Furthermore, the following processing may be performed by a single printer.

  In FIG. 1, the copy-forgery-inhibited pattern image generation unit 101 includes an input background image 112, color information 111, processing area information 113, latent image threshold pattern 114, background threshold pattern 115, latent image background area designation image 116, camouflage area designation image 117. Enter each. Then, the tint block image generation unit 101 generates and outputs a tint block image 118 based on the above input. That is, the tint block image generation unit 101 performs image processing on the input background image 111 according to a predetermined rule, and generates a tint block image 118. The input background image 111 may be a multi-value image or a binary image. Further, the processing area information 113 is information indicating an area in the input image information where the background pattern embedding process is performed.

  The latent image background area designation image 115 is an image for designating a latent image portion and a background portion, and is composed of one pixel and one bit. One bit (for example, 1) of the latent image background area designation image 115 represents a latent image portion, and the other bit (for example, 0) represents a background portion. The camouflage area designating image 117 is an image for designating an area to be lightened or whitened in order to have a camouflage effect, and is composed of 1 bit per pixel as in the latent image background area designating image 115. The One bit (for example, 1) of the camouflage area designation image 117 indicates that it is not a camouflage area, and the other bit (for example, 0) indicates that it is a camouflage area whose density is lower than the surrounding area. FIG. 10A shows an example of the latent image background area designation image 115, and FIG. 10B shows an example of the camouflage area designation image 117.

  The background threshold pattern 116 and the latent image threshold pattern 114 perform threshold processing on appropriate image signals with the threshold values of the background dither matrix and the latent image dither matrix, respectively, so that they are output as equal densities when the copy-forgery-inhibited pattern image is printed. Is generated. 11A shows an example of the latent image threshold pattern 114, and FIG. 11B shows an example of the background threshold pattern 116.

  The tint block image 118 generated by the tint block image generation unit 101 is output to the synthesis unit 102. The combining unit 102 combines the input document image 119 and the generated tint block image 118 to generate a tint block composite output document image. Note that, when the copy-forgery-inhibited pattern image 118 is directly used as the copy-forgery-inhibited pattern output original image regardless of the contents of the input document image 119, the composition unit 102 does not need to refer to the input document image 119. At this time, the color matching process is executed for each object constituting the copy-forgery-inhibited pattern image 118 and the input document image 119, and then the object constituting the input document image 119 and the copy-forgery-inhibited pattern image 118 are combined to generate a copy-forgery-inhibited pattern output document image. May be. Alternatively, the color matching process may be executed on the copy-forgery-inhibited pattern synthesized output original image in the print data processing unit 103 at the subsequent stage.

  The print data processing unit 103 receives the copy-forgery-inhibited pattern synthesized output original image synthesized by the synthesizing unit 102 as drawing information via an OS (operating system) drawing interface. As the drawing interface, for example, Microsoft Graphic Device Interface (GDI), AppleComputer QuickDraw, or the like can be used. The received copy-forgery-inhibited pattern composite output document image is sequentially converted into a print command. At this time, image processing such as color matching processing, RGB-CMYK conversion, and halftone processing is executed as necessary. Then, the print data processing unit 103 uses a data format (for example, a data format described in a page description language or a data format developed in a print bitmap) that can be interpreted by the printing unit 104 as the copy-forgery-inhibited pattern output original image data. It is sent to the printing unit 104.

  The printing unit 104 prints and outputs a copy-forgery-inhibited pattern composite output document according to the information of the input copy-forgery-inhibited pattern output document image data. Here, the case of a laser beam printer will be described as an example. The printing unit 104 includes a printer controller and a printer engine (not shown). The printer controller includes a print information control unit, a page memory, an output control unit, and the like. The print information control unit analyzes the page description language (PDL) sent from the print data processing unit 103 and develops corresponding patterns for drawing and printing commands in the page memory.

  If necessary, image processing such as RGB-CMYK conversion and halftone processing is also executed. If it is determined that the print format is not the data format described in the page description language, the image data is expanded as it is in the page memory. The output control unit of the printing unit 104 converts the contents of the page memory into a video signal and outputs it to the printer engine. The printer engine includes, for example, a recording medium conveyance mechanism, a semiconductor laser unit, a photosensitive drum, a developing unit, a fixing unit, a drum cloning unit, a separation unit, and the like, and performs printing by a known electrophotographic process.

  As will be described later with reference to an embodiment of the present invention, in the tint block image generation unit 101, each pixel is intended to be printed out only with the primary colors of the printer (for example, cyan, yellow, magenta, black). A tint block image may be created. In that case, it is not desirable that these pixels be printed with a plurality of different color toners or inks. Therefore, in the print data processing unit 103 and the printing unit 104, each pixel value (cyan, magenta, yellow, black) corresponding to the copy-forgery-inhibited pattern image in the copy-forgery-inhibited pattern output original image is expressed by a plurality of toners of different colors at the time of printing. It is set so as not to be mixed colors.

  Specifically, color conversion processing such as color matching is not performed, and a setting for always printing each pixel with a single color ink or toner is introduced after the halftone processing is executed. However, this is not the case when one pixel of the copy-forgery-inhibited pattern image is expressed by dark, light ink or large and small ink dots of the same color by an inkjet printer. Further, as a variation in the color of the tint block image, for example, a tint block image that looks green at first glance can be generated by arranging cyan pixels and yellow pixels in a well-balanced manner. Also in this case, when one pixel of the tint block image is composed of the primary colors of the printer (cyan, yellow, magenta, black), the pixel is output only with the corresponding cyan or yellow toner. To do.

  Note that it is possible to generate an image that realizes the effect of the tint block even if one pixel of the tint block image is not printed out only with the primary color of the printer. Even if one pixel of a copy-forgery-inhibited pattern image is expressed by a plurality of different colors of ink or toner, it can be used as a forgery-proof copy-forgery-inhibited pattern if a latent image remains after copying.

  In the configuration described above in the present embodiment, the copy-forgery-inhibited pattern image, the input document image, the copy-forgery-inhibited pattern output document image, and the copy-forgery-inhibited pattern output document image data are all digital data, and the copy-forgery-inhibited pattern output document image represents an image printed on paper. And

  FIG. 2 is a flowchart showing a processing procedure of the copy-forgery-inhibited pattern image generation unit 101 shown in FIG.

  First, in step S201, the copy-forgery-inhibited pattern image generation process is started by an input through a user interface or the like. In step S202, the input background image 111, the background threshold pattern 116, the latent image threshold pattern 114, the latent image background area designation image 115, and the camouflage area designation image 117 are read. Next, in step S203, an initial pixel for generating a tint block image is determined. For example, when the entire input image is subjected to image processing in the order of raster scanning from the upper left to the lower right, and changed to a tint block image, the upper left is set as the initial position.

  Next, in step S204, the background threshold pattern 116, the latent image threshold pattern 114, and the latent image background area designation image 115 are arranged on the tile from the upper left of the input background image 112, respectively. Then, the following equation (1) is calculated for the pixels of the input background image 111 to be processed, and it is determined whether or not to write a pixel value corresponding to a dot at the time of printing. At this time, the pixel value corresponds to the input color information 111.

Here, the definition of the component of Formula (1) is shown below.
nCamouflage: 0 if the pixel is a camouflage area in the camouflage area designation image, otherwise 1
nSmallDotOn: 1 if the pixel value of the background threshold pattern is black, 0 if white
nLargeDotOn: 1 if the pixel value of the latent image threshold pattern is black, 0 if white
nHiddenMark: 1 for a pixel corresponding to a latent image portion in a latent image background region designation image, 0 for a pixel corresponding to a background portion
/ NHiddenMark: Denial of nHiddenMark. 0 in the latent image portion and 1 in the background portion.

  At this time, it may be determined whether or not to write a pixel value corresponding to a dot at the time of printing while referring to the pixel value of the input background image. In this case, the right side of Expression (1) is multiplied by an item (nBackground) obtained by referring to the input background image. This nBackground is set to 1 if the input background image has a specific pixel value (white background area), and 0 otherwise.

  Moreover, it is not necessary to calculate using all the elements of Formula (1) for each pixel to be processed. As described below, the processing speed can be increased by eliminating unnecessary calculations.

  For example, if nHiddenMark = 1, / nHiddenMark = 0, and if nHiddenMark = 0, / nHiddenMark = 1. Therefore, if nHiddenMark = 1, the value of equation (2) is the value of nLargeDotOn, and if nHiddenMark = 0, the value of equation (2) is the value of nSmallDotOn.

  Further, the value of nCamouflage is an integration over the whole. If nCamouflage = 0, nWriteDotOn = 0. Therefore, when nCamouflagage = 0, the calculation of equation (2) after nCamouflage can be omitted.

  In the generated tint block image, an image having a size of the least common multiple of the vertical and horizontal lengths of the background threshold pattern 116, the latent image threshold pattern 114, the latent image background area specifying image 115, and the camouflage area specifying image 117 is the minimum of repetition. Unit. For this reason, the copy-forgery-inhibited pattern image generation unit 101 generates only a part of the copy-forgery-inhibited pattern image, which is the minimum unit of repetition, and generates a copy-forgery-inhibited pattern image 118 by repeatedly arranging a part of the copy-forgery-inhibited pattern image in the size of the input background image. Processing time can be reduced.

  Next, in step S205, the calculation result in step S204 (the value of nWriteDotOn) is determined. If nWriteDotOn = 1, the process proceeds to step S206. If nWriteDotOn = 0, the process proceeds to step S207.

  In step S206, a process of writing pixel values corresponding to dots at the time of printing is performed. As will be described later, the pixel value can be changed depending on the color of the tint block image 118. When it is desired to create a black background pattern, the processing target pixel of the input background image 111 is set to black. As will be described later with reference to one embodiment of the present invention, for example, the latent image portion and the background portion are also represented in black, but one is represented in black and the other is a mixed color of cyan, magenta, and yellow. Is written, pixel values of different colors are written. In addition, if the color is set to cyan, magenta, yellow, or black in accordance with the color of the toner or ink of the printer, a color tint block image 118 can be created.

  When the input background image 112 is image data of 1 to several bits per pixel, the pixel value can be expressed using the index color. Index color is a method of expressing image data, and color information that frequently appears in the target color image is set in the table of contents (for example, index 0 is white, index 1 is cyan, etc.), and the value of each pixel is color information. It is expressed by the number of the listed table of contents. For example, the first pixel value is expressed as a value of index 1, the second pixel value is expressed as a value of index 2, and so on.

  In step S207, it is determined whether all the pixels in the processing target area of the input background image 112 have been processed. If all the pixels in the processing target area have not been processed, the process proceeds to step S208, an unprocessed pixel is selected, and the processes in steps S204 to S206 are repeatedly executed. If processing for all the pixels in the processing target area has been completed, the process proceeds to step S209, and the image processing in the tint block image generation unit 101 ends. Through the above-described processing, a tint block image 118 obtained by performing image processing on the input background image 111 can be generated.

  Next, the dot arrangement process for each of the latent image portion and the background portion in the present embodiment will be described. In the following, a case where the latent image portion is generated based on a dot concentration type dither matrix and the background portion is generated based on a dot dispersion type dither matrix will be described. A typical example of the dot concentration type dither matrix used when generating the latent image portion is a spiral dither matrix.

  FIG. 3 is a diagram illustrating an example of a 4 × 4 spiral dither matrix. The threshold values of the 4 × 4 spiral dither matrix are arranged in a spiral shape with numerical values increasing from the center.

  FIG. 4 is a diagram showing a threshold pattern (dot arrangement) obtained by performing threshold processing on a predetermined input image signal using the 4 × 4 spiral dither matrix shown in FIG. 4, reference numerals 401, 402, and 403 denote threshold patterns obtained by performing threshold processing on the signals having the input image signal values “3”, “6”, and “9”, respectively, using the dither matrix shown in FIG. Yes. The threshold pattern (dot arrangement) obtained here is a pattern in which each dot is arranged in a concentrated manner.

  On the other hand, as a representative of the dot dispersion type dither matrix constituting the background portion, there is a Bayer type dither matrix. The Bayer type N × N dither matrix is represented by the following equation.

Here, N power of 2, U _N is the N × N matrix of each element 1.

  FIG. 5 is a diagram illustrating an example of a 4 × 4 Bayer-type dither matrix. A threshold pattern generated by dithering an arbitrary input image signal with a Bayer-type dither matrix is designed so that each dot is dispersedly arranged.

  FIG. 6 is a diagram showing a threshold pattern (dot arrangement) obtained by performing threshold processing on a predetermined input image signal using the 4 × 4 Bayer-type dither matrix of FIG. In FIG. 6, reference numerals 601, 602, and 603 denote threshold patterns obtained by performing threshold processing on signals having input image signal values “2”, “4”, and “5”, respectively, using the dither matrix shown in FIG. Yes. The threshold pattern (dot arrangement) obtained here is a pattern in which each dot is arranged dispersedly. In the Bayer-type dither matrix, the elements of the threshold matrix are sequentially arranged at positions where they do not contact each other as much as possible, and the threshold pattern takes an isolated grid-like dot arrangement. In the Bayer type dither, when the size of the dither matrix is increased, a periodic texture due to the matrix may be conspicuous, but there is an advantage that a periodic and beautiful pattern can be obtained at a specific gradation.

  In the present embodiment, the case where a Bayer-type dither matrix is used as the dither matrix used for the background will be described below. However, the present invention is not limited to the Bayer-type dither matrix. Of course, other dot dispersion type dither matrices may be used.

  For example, a blue noise dither matrix is an example of a dot dispersion type dither matrix. In this blue noise dithermalyx, the threshold pattern of any gradation has all blue noise characteristics, the distribution of black pixels forming the threshold pattern is random but highly uniform, and the graininess is not noticeable And Here, the blue noise characteristic means that the output pattern of a point when set to an arbitrary gradation is locally aperiodic and isotropic and has low frequency components. To do. The threshold pattern obtained from the blue noise matrix has advantages in that a visually preferable output pattern can be obtained, for example, by preventing the occurrence of moire and making paper feeding unevenness inconspicuous.

  Further, instead of the blue noise matrix, a dot dispersion type dither matrix in which a threshold pattern of a specific or arbitrary gradation is periodic (or pseudo-periodic), is anisotropic, and has low frequency components can be used. Further, although not a method using a threshold pattern, a configuration of a background portion using an error diffusion method is also possible. When the background threshold pattern is generated using the Bayer dither matrix or the blue noise matrix already described, the value of nSmallDotOn in the equation (1) can be read by referring to the background threshold pattern. On the other hand, when the error diffusion method is used, the tone corresponding to the background density for each pixel and the sum of the error propagated from the surrounding pixels are compared with a predetermined threshold value, and the dot On in the pixel to be processed is turned on. / Off is determined and used as the value of nSmallDotOn. At this time, an error caused by dot On / Off is weighted and distributed to neighboring pixels. The pixel value of the unprocessed pixel is the sum of the original input pixel value corresponding to the background density and the distributed error.

  As in the case of the background threshold pattern, it is assumed that the gradation corresponding to the background darkness is prepared in advance. The error diffusion method has a demerit that takes a long time, but has an advantage that an image with good visual characteristics in which dots are uniformly dispersed can be obtained. Since the error diffusion method is already well known, detailed description is omitted here. Similarly, a method obtained by improving the error diffusion method is also applicable.

  Further, the threshold pattern for each gradation may not be generated based on the dither matrix. A background threshold pattern and a latent image threshold pattern may be independently generated for each gradation. In this case, there is an advantage that threshold patterns having good image quality can be collected for each gradation.

  FIG. 7 is a diagram for explaining a comparison of the area ratios of the black pixels of the background threshold pattern and the latent image threshold pattern. In FIG. 7, the horizontal and vertical sizes of the background dither matrix are represented by X_S and Y_S, respectively, and the gradation of the input image signal is represented by T_S. The horizontal and vertical sizes of the latent image dither matrix are represented by X_L and Y_L, respectively, and the gradation of the input image signal is represented by T_L. In this case, the ratio P_S occupied by black pixels in the background threshold pattern is P_S = T_S / (X_S * Y_S), and the ratio P_L occupied by black pixels in the latent image threshold pattern is P_L = T_L / (X_L * Y_L). It becomes.

  8A to 8C are diagrams showing the relationship between the area ratio of black pixels of a threshold pattern obtained by performing threshold processing on an input image signal with a dither matrix and the density when the threshold pattern is printed. . In the dither processing, the area ratio of the black pixels changes according to the gradation of the input image signal, so that the horizontal axis in FIG. 8 can be regarded as the gradation of the input image signal.

  Here, the dither matrix (background threshold pattern) of the background portion and the dither matrix (latent image threshold pattern) of the latent image portion need not have the same side size, as shown in FIG. For example, when the gradation characteristics of the background dither matrix and the latent image dither matrix are the same as those shown in FIG. 8A, the background dither matrix and the latent image portion dither matrix depend on the size of the dither matrix. It is sufficient that the values on the horizontal axis (area ratio of black pixels) are substantially equal. That is, if the values of the gradations T_S and T_L of the input image signal such that the black pixel ratios P_S and P_L are substantially equal to each other, the density of the background threshold pattern and the latent image threshold pattern are substantially equal. Thereby, a tint block image in which the latent image is not conspicuous can be generated.

  However, actually, the gradation characteristics obtained by the background dither matrix and the latent image dither matrix are not necessarily the same depending on the density characteristics of the printer. For example, the gradation characteristics obtained by the latent image dither matrix are represented by a gentle S-curve as shown in FIG. 8B, and the gradation characteristics obtained by the background dither matrix are as shown in FIG. It is assumed that it is represented by a steep S-shaped curve. In such a case, the density of the background portion and the latent image portion at the time of printing is not the same even if the area ratio of the black pixels of the background threshold pattern and the latent image threshold pattern is set to be approximately equal. For this reason, the density of the latent image portion and the background portion during printing is made as close as possible by appropriately adjusting the input image signal for the dither matrix of one or both of the background portion and the latent image portion. If the number of gradations that can be expressed by the background dither matrix or the latent image dither matrix is large, the density of the background portion or latent image portion can be finely adjusted by adjusting the gradation of the input image signal.

  When the latent image dither matrix is a dot concentration type dither matrix as shown in FIG. 3, when the gradation of the input image signal is below a certain level, it becomes close to an isolated dot state, and the latent image portion tends to disappear during copying. On the other hand, when the gradation of the input image signal exceeds a certain level, the dots are concentrated and the clustered dots constituting the latent image are easily recognized clearly by human eyes. Therefore, in the latent image dither matrix, it is better to keep the gradation of the possible input image signal within a certain range. Further, in the latent image dither matrix as shown in FIG. 3, even if the size of the dither matrix is changed, if the gradation of the input image signal is the same, substantially the same concentrated dot arrangement can be obtained. Therefore, the density per unit area can be changed by keeping the gradation of the input image signal with respect to the latent image dither matrix constant and changing the size of the dither matrix.

  On the other hand, when the background dither matrix is a dot dispersion type dither matrix as shown in FIG. 5, the density can be changed while forming dots uniformly on the whole by changing the gradation of the input image signal. Therefore, it can be said that the density of the background portion is excellent when the gradation of the background dither matrix is wide, that is, the size of the dither matrix is large.

  Note that when a copy-forgery-inhibited pattern image is output by a printer, an adjustment function for adjusting the density variation of the printer is necessary, which will be described later.

  FIGS. 9A to 9E are schematic diagrams showing how a tint block image is generated using the tint block synthesis printing apparatus shown in FIG. FIGS. 9A, 9B, and 9C show a latent image threshold pattern, a background threshold pattern, and a latent image background area designation image, respectively. FIG. 9 shows a copy-forgery-inhibited pattern image generated based on Expression (1). Note that the camouflage pattern is not introduced at the generation stage of the tint block image in FIG.

  In the copy-forgery-inhibited pattern image shown in FIG. 9D, as shown in a circled area 910, the dot pattern in which the latent image threshold pattern and the background threshold pattern are combined in the latent image and background switching portion of the latent image background area designation image. A lump has been generated. This cluster of dots tends to occur when the latent image and background switching of the latent image background area designation image 903 and the size of the latent image threshold pattern are not synchronized. In addition, since the cluster of dots appears concentratedly only at the portion where the latent image and the background of the latent image / background area designation image are switched, the outline of the latent image is conspicuous, and there is a demerit that the effect of the counterfeit suppression background pattern is diminished. Therefore, in order to generate a high-quality copy-forgery-inhibited pattern image, there is a process of preventing dot clumps from occurring when the latent image and background image of the latent image background area designation image are switched.

  Here, a process for preventing dot clumps from occurring when the latent image and the background of the latent image background area designation image are switched is referred to as “boundary processing”. An example of this boundary processing method is as follows. Only the pixel value of the repetitively arranged latent image background area designation image corresponding to the center of the repetitively arranged latent image threshold pattern is read as a HiddenMarkLattice value. Here, the pixel moved from the upper left by the amount corresponding to the pixel obtained by discarding half of one side of the latent image threshold pattern is set as the center. The pixels belonging to the same latent image threshold pattern are processed using the same HiddenMarkLattice value. This processing method is expressed as follows:

  When this method is used, the latent image threshold pattern is configured with a white background of the latent image threshold pattern around it unless it is at the edge of the image. Therefore, if a white background exists around the black pixels of the latent image threshold pattern, the white background becomes a buffer zone and the black pixels of the latent image threshold pattern do not contact the black pixels of the background threshold pattern, and the latent image background area designation The part where the latent image specified in the image and the background are switched does not stand out.

  FIG. 9E shows a copy-forgery-inhibited pattern image that has undergone boundary processing. In the figure, it can be seen that there is no cluster of dots in which the latent image threshold pattern and the background threshold pattern are merged at the switching portion between the latent image specified in the latent image background area specifying image and the background.

  As another example of the boundary processing, there is a method of pre-processing so that the switching between the latent image and the background in the input latent image background area designation image is synchronized with the size of the latent image threshold pattern. In this method, first, a latent image threshold area pattern is repeatedly arranged in the latent image background area designation image, the pixel value of the latent image background area designation image corresponding to the center of the latent image threshold pattern is read, and the subsampled latent image background is obtained. An area designation image is generated. Next, the subsampled latent image background region designation image is newly enlarged so that one pixel becomes an integer multiple of the size of the latent image threshold pattern, and a corrected latent image background region designation image is created. Finally, by generating a copy-forgery-inhibited pattern image based on the formula (1) for the modified latent image background region designation image, the copy-forgery-inhibited pattern image does not occur as in the region 910 in FIG. Can be generated.

  When the above-described “boundary processing” is added to the copy-forgery-inhibited pattern image generation unit 101, the latent image background area designating image is synchronized with the size of the latent image threshold pattern by synchronizing the latent image designated by the latent image background area designating image with the background switching portion. Since it is not necessary to create it, it is convenient for users.

  FIG. 12 is a diagram illustrating a part of the tint block image generated by the tint block image generation unit 101 in which the boundary processing is executed. In the example of generating the copy-forgery-inhibited pattern image shown in FIG. 12, the images shown in FIGS. 10A and 10B are used as the latent image background area designation image and the camouflage area designation image, respectively. Further, as the latent image threshold pattern and the background threshold pattern, images shown in FIGS. 11A and 11B are used. In FIGS. 10A and 10B and FIGS. 11A and 11B, broken lines surrounding these images indicate image boundaries and do not exist in actual images. Since the copy-forgery-inhibited pattern image shown in FIG. 12 is subjected to boundary processing, the phenomenon of dot solidification does not occur at the boundary between the latent image portion and the background portion, and the latent image portion is difficult to discriminate.

  Some embodiments of the present invention based on the basic structure of the tint block image composition described above will be described. In these embodiments, when printing the background portion and latent image portion of the same color constituting the copy-forgery-inhibited pattern image, one is represented by a mixed color of a plurality of color materials (such as toner and ink), and the other is represented by one color. It is expressed by a color material.

(First embodiment)
The first embodiment of the present invention provides an original document including a tint block image even when the density of the latent image portion and the background portion of the copied tint block image is substantially the same due to factors such as the type and setting of the copier. The copied image is cut by identification. That is, when the latent image portion and the background portion of the copy-forgery-inhibited pattern image are printed in the same black or gray, one of the latent image portion and the background portion is cyan (C), magenta (M), yellow (Y ) Is printed with process black using a color material such as toner. The other side is printed using only a black (K) color material.

  In general, a printer expresses a color image using K in addition to the three primary colors C, M, and Y by subtractive color mixing. In subtractive color mixing, C can be obtained by combining C, M, and Y. Black or gray generated from a plurality of color materials excluding K (for example, C, M, Y) is called process black, and is distinguished from black generated from a K color material. However, the spectral characteristics of the C, M, and Y color materials do not have ideal characteristics, and the densities of the color materials themselves are different. For this reason, even if equal amounts are actually mixed, it does not become gray. In order to obtain achromatic black or gray, it is necessary to adjust the ratio (gray balance) of a plurality of color materials.

Now, when generating a black or gray copy-forgery-inhibited pattern image, it is considered that the latent image portion is composed of process black and the background portion is composed of black. When the copy-forgery-inhibited pattern image is copied by a copying machine, it is assumed that the latent image portion of process black is reproduced in any of the following modes in the copying machine.
(1) Process black is reproduced with black color material only.
(2) Process black is reproduced with process black, but the gray balance is lost.
(3) Process black is accurately reproduced with process black.

  In the case of the mode (1), even if the latent image portion and the background portion of the copy image are almost equal in density, it is difficult to see the latent image. The original document and its copy image can be identified. However, when read by the scanner, each color is processed independently unless the respective color materials C, M, Y are overprinted or arranged very close to each other, so that only the black color material is used as described above. It is unlikely to be reproduced.

  In the case of the mode (2), the gray balance of the latent image portion of the copy image is lost, so that the color difference from the background portion reproduced in black can be visually identified.

  In the case of the mode (3), the process black latent image portion and the black background portion in the copy original cannot be identified. However, because there are various different factors in forming an image, such as the type of color material used in a printer that prints a copy-forgery-inhibited pattern image and a copying machine that copies it, color reproduction that maintains the gray balance of process black is not possible. It's not easy.

  As described above, when one of the latent image portion or the background portion of the copy-forgery-inhibited pattern image is configured with process black and the other is configured with black in the copying machine, when the copy-forgery-inhibited pattern image is copied, mode (2) The possibility of is increased. That is, there is a high possibility that one of the latent image portion and the background portion loses the gray balance of the process black and causes a color difference from the other black. One embodiment of the present invention makes it possible to distinguish between a latent image portion and a background portion in a copy image by utilizing such a gray balance collapse. In other words, when a copy-forgery-inhibited pattern image is printed, process black having a good gray balance, which is difficult to reproduce in a copy image, is applied to one of the latent image portion and the background portion. As a result, in the printed original document, the latent image portion and the background portion cannot be identified with the same color. However, in the copied image, a color difference occurs between the latent image portion and the background portion and the original document is copied. An image can be identified.

  Hereinafter, the configuration of the latent image threshold pattern when the latent image portion is configured by C, M, and Y will be specifically described.

  FIG. 19 is a diagram illustrating an example of a process black latent image threshold pattern. The latent image threshold pattern is internally divided into at least three regions, and at least one region is always assigned to C, M, and Y. In the example shown in FIG. 19, the area is divided into four areas, with Y at the upper left, C at the lower left, M at the upper right, and K at the lower right. However, an area may not be allocated to K, and any color material of C, M, or K may be allocated to the lower right area.

  The C, M, Y, and K regions divided into four in FIG. 19 represent the gradations of the respective colors in the concentrated dot arrangement that are dithered by the spiral dither. In the example shown in FIG. 19, the size of the C, M, and Y dots is 2 × 2, but in practice, the size of each color dot is adjusted according to the characteristics of the color material and the characteristics of the printer. A balanced latent image color gamut pattern is generated. In the example shown in FIG. 19, each color is expressed by a dot-concentrated dither in consideration of density stability. However, it is sufficient that the process black dots are finally concentrated, and each color is displayed by a dot-dispersed dither. May be expressed.

  In the above description, the dot On / Off value (nWriteDotOn) is calculated based on a logical expression in which each element is 1 or 0. However, when calculating the On / Of value (nWriteColorDotOn) of a dot in consideration of C, M, Y, and K colors, the color of the nWriteDotOn value of the calculation result is calculated for each area of the divided latent image threshold pattern. Calculate by multiplying the index value.

  As an example of nColorIndex values, index values 1, 2, 3, and 4 are assigned to K, C, M, and Y dots, respectively.

  A method for obtaining a process black having a desired density and adjusted gray balance will be described below.

  First, a gray balance chart in which a black having a desired density is used as a background, and a plurality of patches are arranged on the foreground by changing the gradation of each color is printed by a printer that prints a tint block image. Then, it is possible to visually select a patch closest in color to the background of the chart, and to determine a parameter for obtaining a process black having a desired density based on the selected patch.

  FIG. 21 is a diagram illustrating an example of a gray balance chart to be printed. A patch designated by 0 in each column of C, M, and Y is a patch printed with tone values having a predetermined balance for the color materials C, M, and Y. Then, a patch in which only the gradation value of that color is changed according to the corresponding number (from -2 to +2 in the figure) in each color column is printed. In this gray balance chart, the gray balance of the process black having a predetermined darkness can be adjusted by selecting a patch that is visually closest to the background and foreground colors and setting its parameters. Further, a background portion composed of black having the same density as the obtained latent image portion can be obtained by density calibration described later.

  When creating a copy-forgery-inhibited pattern image in which the latent image portion is composed of process black with a printer with unstable gray balance, the parameters for adjusting the gray balance and generating the process black of the latent image portion before generating the copy-forgery-inhibited pattern image It is good to decide.

  Next, an example in which the background portion is composed of process black and the latent image portion is composed of black, which is the reverse of the above example, will be described.

  In this case, the background threshold pattern is composed of three colors, C, M, and Y, but the dither matrix designed so that the dots of each color are low gradation and do not overlap. FIG. 20 shows an 8 × 8 background threshold pattern composed of three colors C, M, and Y, which is generated by synthesizing a background threshold pattern using a 4 × 4 Bayer-type dither matrix.

  Another method for obtaining a dispersed dot arrangement is to divide each threshold value of the dot-dispersed dither matrix by the number of colors (for example, 4), determine an area to be assigned to each color according to the remainder, and determine the dots in each area according to the quotient There is a method for determining the arrangement order. Various methods such as a method of preparing a dither matrix obtained by shifting the original dither matrix to the right or left by a predetermined number of pixels and using each of them for gradation representation of each color can be applied.

  The parameters of the background portion composed of process black having a desired density can be determined using a gray balance chart similar to the chart shown in FIG. That is, a gray balance chart is printed in which black having a desired density is arranged in the background and a plurality of patches are arranged in the foreground by changing the gradation of each color. Then, it is possible to visually select a patch that is closest in color to the background of the chart and determine parameters corresponding to the patch. Thereafter, a latent image portion composed of black having the same density as the obtained background portion can be obtained by density calibration described later. In a laser printer, since a latent image portion composed of a dot-concentrated binary pattern has high density stability, density calibration is often unnecessary. In this case, the background of the gray balance chart is a latent image portion composed of black having a desired density, and it is only necessary to determine the optimum parameters of the background portion from the gray balance chart, and density calibration can be omitted. However, if the gray balance of the background portion composed of process black is not stable, the optimum background portion parameters may be determined using a gray balance chart before the copy-forgery-inhibited pattern image is generated.

(Other embodiments)
In the above-described embodiment, the case where the process black is generated from C, M, and Y has been described, but the application of the present invention is not limited to this form. For example, there are printers having color materials such as red (R) and green (G). In this case, since it can be generally replaced with M + Y = R and C + Y = G, the process black may be generated with C and R or G and M without using all three colors of C, M, and Y.

  In addition, a copy-forgery-inhibited pattern image in which one of the latent image portion and the background portion is configured by G and the other is configured by C and Y, or one of the latent-image portion and the background portion is configured by R and the other is configured by M and Y. There may be. In this case, the copy image can be identified from the original image due to the loss of the color balance. In this specification, the above-described gray balance is also referred to as color balance.

  Further, in the above description, the background pattern image to be printed is described as having the same color in the latent image portion and the background portion, but it is not necessarily the same color. For example, even if the latent image is visually recognizable in different colors in the printed image, the latent image portion appears stronger than the background portion when the original image is copied. The difference may be easily discriminable. Also in this case, the present invention is applied, and in preparation for a situation in which the latent image does not appear more strongly when copied, one of the latent image portion and the background portion is expressed by a plurality of color materials, and the other one Use color materials.

  As an advanced embodiment, it is possible to embed one or more bits of information in one latent image threshold pattern by changing the assignment of C, M, Y, and K in the latent image threshold pattern. Thereby, a large number of latent image threshold patterns can be secured, and information having a long bit length can be embedded as watermark information. In a simple example, it is defined that the divided latent image threshold pattern whose upper left is blank indicates a watermark information embedding region. Then, for each of the latent image threshold patterns in the watermark information embedding area, the allocation position of each color C, M, and Y is changed and scanned from the upper left to the lower right in raster order, and the watermark information is added to each latent image threshold pattern. It can also be divided and embedded.

  As described above, the copy-forgery-inhibited pattern image generation unit 101 includes processing for expressing one of the same colors of the latent image portion and the background portion according to the embodiment of the present invention with one color material and expressing the other with a plurality of color materials. A tint block image is generated. Then, the copy-forgery-inhibited pattern image generated by the copy-forgery-inhibited pattern image generation unit 101 and the input original image (for example, a form or a certificate) are combined by the combining unit 102.

  FIG. 13 is a schematic diagram showing a composition process of an input document image and a tint block image. In FIG. 13, reference numeral 1301 denotes text attribute data, 1302 denotes graphic attribute data, and 1303 denotes an image attribute copy-forgery-inhibited pattern image.

  The synthesizing unit 102 superimposes the images of the data 1301 to 1303 by software according to the priority order (layer structure) regarding the arrangement, using the drawing interface of the OS. Then, like the image 1304, an image in which text attribute data, graphic attribute data, and image attribute copy-forgery-inhibited pattern image are combined is generated. This processing is almost the same as screen drawing (display drawing) in drawing software, which is a general application of a computer. Note that the composition unit 102 may independently perform image composition processing without depending on the OS drawing interface processing.

  In the example shown in FIG. 13, the copy-forgery-inhibited pattern image 1303 having the image attribute is superimposed as the lowest layer compared to the text attribute data 1301 and the graphic attribute data 1302. For example, in the position where the image attribute copy-forgery-inhibited pattern image 1303 and the text attribute data 1301 overlap, the text attribute data 1301 is preferentially drawn. Accordingly, the copy-forgery-inhibited pattern image is appropriately arranged on the background of the input document image, and the visibility of the text attribute data and the graphic attribute data is not deteriorated.

  In the example shown in FIG. 13, the copy-forgery-inhibited pattern image 1303 is an image having the same size as the input image. However, when a copy-forgery-inhibited pattern image is to be superimposed only on a partial area, an input background image having a size corresponding to the partial area is input by the copy-forgery-inhibited pattern image generation unit 101, and the copy-forgery-inhibited pattern image matching the input image size is input. And the composition unit 102 may compose the input document image. The processing in the tint block image generation unit 101 can be speeded up by the size of the tint block image to be generated.

  The copy-forgery-inhibited pattern output document image output by the combining unit 102 may be data expressed by an OS drawing interface, or may be a bitmap image as a result of combining. Then, the copy-forgery-inhibited pattern combined output original image generated by the combining unit 102 is sent to the print data processing unit 103.

  The print data processing unit 103 receives the copy-forgery-inhibited pattern synthesized output original image synthesized by the synthesis unit 102 as drawing information via the OS drawing interface, and sequentially converts it into a print command. At this time, image processing such as color matching processing, RGB-CMYK conversion, and halftone processing is executed as necessary. Then, the print data processing unit 103 uses a data format (for example, a data format described in a page description language or a data format developed in a print bitmap) that can be interpreted by the printing unit 104 as the copy-forgery-inhibited pattern output original image data. The data is sent to the subsequent printing unit 104.

  The printing unit 104 prints out the tint block composition output document according to the input tint block synthesis output document image data information.

  FIGS. 14A and 14B are schematic diagrams showing a process of synthesizing a tint block image with an input document image having no layer structure in which various images have already been synthesized. FIG. 14A shows an input original image having no layer structure in which various images have already been combined. Here, reference numeral 1402 denotes a copy-forgery-inhibited pattern image in an area having a specific pixel value (for example, a white background area). The area to be arranged is shown. Further, it is assumed that the other areas of the input document image do not have specific pixel values (for example, they are not white areas). As shown in FIG. 14B, an image in which the copy-forgery-inhibited pattern image 1404 is combined with this input image is obtained.

  FIG. 15 is a block diagram showing a configuration of a tint block synthesis printing apparatus for synthesizing a tint block image with an input document image having no layer structure in which various images have already been synthesized. The copy-forgery-inhibited pattern combination printing apparatus shown in FIG. 15 is suitable for combining a copy-forgery-inhibited pattern image with an image having no layer structure (for example, 1401) in which various images have already been combined.

  As shown in FIG. 15, this tint block composition printing apparatus includes a tint block image composition output document generation unit 1501, a print data processing unit 1502, and a printing unit 1503. First, an input original image, color information, processing area information, latent image threshold pattern, background threshold pattern, latent image background area designation image, and camouflage area designation image are input to the tint block image composition output original generation unit 1501. Generate and output a composite input document.

  The copy-forgery-inhibited pattern image output document generation unit 1501 detects a region (for example, a white background region) having a specific pixel value in the input document image, combines the copy-forgery-inhibited pattern image only in that region, and outputs a copy-forgery-inhibited pattern image input document image. To do. Specifically, whether or not to write the pixel value corresponding to the copy-forgery-inhibited pattern image to the pixels in the input document image using the following formula obtained by integrating the items (nBackground) that refer to the input document image with respect to Formula (3). Determine whether.

  Here, nBackground is set to 1 if the input document image is an area (white area) having a specific pixel value, and 0 otherwise.

  Similar to the copy-forgery-inhibited pattern image generation unit 101 shown in FIG. Since nBackground is an integration over the whole, Equation (3) is calculated only for the pixels where nBackground = 1, and it is determined whether or not to write a pixel value corresponding to the copy-forgery-inhibited pattern image. Except for referring to the pixel value of the input original image, the process is substantially the same as that of the tint block generation unit 101 shown in FIG.

  The tint block composition output document image generated by the tint block image composition output document generation unit 1501 is output to the print data processing unit 1502. The print data processing unit 1502 performs almost the same processing as the print data processing unit 103 in FIG. At this time, the image processing that has passed the color conversion process such as color matching is performed so that the area where the copy-forgery-inhibited pattern image is combined does not become a mixed-color dot because the pixel value of one pixel is expressed by a plurality of different inks or toners during printing Good to do.

  The print data processing unit 1502 further converts the data into a data format that can be interpreted by the printing unit 1503 (for example, a data format described in a page description language or a data format developed in a print bitmap), and outputs a copy-forgery-inhibited pattern original image data. To the subsequent printing unit 1503.

  The printing unit 1503 prints and outputs a copy-forgery-inhibited pattern composite output document according to the information of the input copy-forgery-inhibited pattern output document image data. As a result, the copy-forgery-inhibited pattern image can be synthesized and output to an area (for example, a white background area) having a specific pixel value of the input document image.

  By the way, when a copy-forgery-inhibited pattern image is actually output using a printer, the latent image portion and the background portion are not always output at the intended density due to various causes.

  This is due to differences in printer engine characteristics and dither matrices that output threshold patterns, printer differences, printing environment such as humidity and temperature, engine durability, paper differences, printer ink and toner differences, etc. It depends on concentration instability depending on various conditions. That is, the optimum input gradation for each of the background portion and latent image portion dither matrix may differ depending on the printer model, dither matrix, individual printer, printing environment, paper, ink, toner, and the like. .

  Therefore, even when the engine characteristics and the printing environment of the printer are different, it is necessary to generate a copy-forgery-inhibited pattern image after obtaining a background threshold pattern and a latent image threshold pattern having substantially the same density during printing. However, it is practically difficult to automatically calculate the optimum background threshold pattern and latent image threshold pattern in consideration of all the fluctuation factors including fluctuation due to the printing environment.

  For this reason, before executing the tint block synthesis printing apparatus, a function for obtaining a background threshold pattern and a latent image threshold pattern in which the density of the background portion and the latent image portion is almost the same for each printer, that is, a tint block density calibration function is executed. To do.

  As this copy-forgery-inhibited pattern density calibration function, a method of adjusting the density so that the densities are substantially equal by changing the gradation of the input image signal for one or both of the background dither matrix and the latent image dither matrix can be considered.

  FIGS. 16A to 16D are diagrams showing background threshold patterns obtained by performing threshold processing with a dither matrix on the latent image threshold patterns and the gradations of a plurality of input image signals. FIG. 16A shows a latent image threshold pattern obtained by inputting gradation 6 to a latent image dither matrix having 10 pixels on a side, and the area ratio of black pixels is 6%.

  On the other hand, FIGS. 16B to 16D show background threshold patterns obtained by inputting gradations 12, 16, and 20 to a background dither matrix of 16 pixels on each side, and the area ratio of black pixels is It is 4.69%, 6.25%, 7.81%. If the background dither matrix is 4 × 4 pixels, and the density adjustment is performed by changing the gradation of the input image signal with respect to the background dither matrix, the area ratio of the black pixels is a range of 4 × 4 + 1 = 17 steps. However, only a gradation change of about 6% step is given. For this reason, fine density adjustment cannot be performed.

  However, as shown in FIGS. 16B to 16D, the density of the background threshold pattern output from the dither matrix having a large number of expressible gradations can be finely adjusted by selecting the gradation of the input image signal. Yes, suitable for density calibration.

  In the following, the background pattern density test printing for executing the background pattern density calibration function will be described. The copy-forgery-inhibited pattern density test printing can be implemented by an application on a computer or a printer driver.

  FIG. 22 is a block diagram showing a configuration for executing the tint block density test printing. As shown in FIG. 22, the apparatus for executing the tint block density trial printing includes a setting information input unit 2201, a pattern generation unit 2202, a trial printing tint block image generation unit 2203, a print data processing unit 2204, and a printing unit 2205. Has been.

  First, the setting information input unit 2201 performs processing for reading setting information from an initial setting file in which setting information is stored. Alternatively, a process of receiving setting information input through the user interface is performed. Next, the pattern generation unit 2202 generates a pattern necessary for generating a tint block based on the setting information input from the setting information input unit 2201, and outputs the pattern to the test print tint block image generation unit. In the case of the present embodiment, patterns generated from input setting information are a background threshold pattern and a latent image threshold pattern. In the tint block density trial printing process, the pattern generation unit 2202 generates a plurality of background threshold patterns and latent image threshold patterns.

  The test print background pattern image generation unit 2203 generates a test print background pattern image based on the pattern input from the pattern generation unit 2202. Details of the trial-printed tint block image generated by the trial-printed tint block image generation unit 2203 will be described later.

  The print data processing unit 2204 performs necessary image processing on the test print tint block image generated by the test print tint block image generation unit 2203. However, if the pixel values of the tint block image (cyan, magenta, yellow, black) are one color pixel value, it is considered not to be a mixed color in which a plurality of inks or toners are mixed during printing. Image processing is performed on the copy-forgery-inhibited pattern output document image. The trial print copy-forgery-inhibited pattern image that has undergone the necessary image processing is converted into a data format that can be interpreted by the printer (for example, a data format described in a page description language or a data format that has been expanded into a print bitmap), and is printed later. Part 2204. The printing unit 2204 prints out a test printed tint block image according to the input data.

  Next, a description will be given of a test print sheet in which a plurality of copy-forgery-inhibited pattern images (patches) with different background densities generated by the test-printed copy-forgery-inhibited pattern image generation unit 2203 are arranged.

  FIG. 17 is a diagram illustrating an example of a test print sheet. A plurality of square copy-forgery-inhibited pattern images (patches) are arranged in one sheet. A rectangular area inside the patch is a latent image portion, and its periphery is a background portion. In FIG. 17, the density of the latent image portion is constant regardless of the patch, but the density of the background portion differs for each patch. In FIG. 17, the density of the background portion increases in order from the upper left to the lower right patches. By using this test printing sheet, it is possible to visually find a patch in which the latent image portion is not conspicuous.

  In FIG. 17, the density of the latent image portion is constant and the density of the latent image portion cannot be selected (that is, the default value), but the density is almost constant by another means not described in advance. It is assumed that a latent image threshold pattern is determined. However, although not shown in the figure, it is possible to mount the user by selecting the optimum density of the latent image portion and the background portion by changing the densities of both the latent image portion and the background portion in one test printing sheet. For this reason, in the following description, it is assumed that the user can specify the densities of both the latent image portion and the background portion.

  In FIG. 17, the density of the background portion of the background pattern is changed in order from the upper left to the lower right. However, as described above, as a method of changing the density of the background portion, as described above, the input image signal for the background portion dither matrix is changed. There is a method of changing the gradation.

  For example, when the size of the background dither matrix is 16 × 16 pixels, the gradation of the input image signal with respect to the background dither matrix is changed by four as shown in the background threshold patterns shown in FIGS. The area ratio of the black pixels of the threshold pattern changes by about 1.5%.

  In the present embodiment, hereinafter, the amount of change in the gradation of the input image signal with respect to the background dither matrix when changing the density of the background portion by trial printing is referred to as a “contrast step”, and the density adjustment unit of the background portion is large. This is an index that represents

  FIG. 23 is a diagram illustrating a tint block composition printing apparatus having a tint block density calibration function. A selection information input unit 2301 and a pattern generation unit 2302 are arranged in the preceding stage of the tint block composition printing apparatus (2303 in FIG. 23) shown in FIG. First, the configuration of a tint block composition printing apparatus having a tint block density calibration function will be described.

  The selection information input unit 2301 inputs information related to the patch determined to be optimal (for example, a number printed corresponding to each patch) as selection information through the user interface. At this time, the optimal tint block image patch has the density desired by the user, and the background portion and the latent image portion have substantially the same density. Further, when the test printing sheet is copied by a target copying machine, the latent image portion remains and the background portion disappears. If there is no target copying machine, copying may be performed with an available copying machine to investigate whether the latent image portion remains and the background portion disappears.

  The pattern generation unit 2302 generates a pattern necessary for generating a background pattern based on the selection information input from the selection information input unit 2301, and inputs the pattern to the background pattern synthesis printing apparatus 2303. In this embodiment, the patterns generated from the input selection information are the background threshold pattern and the latent image threshold pattern.

  Next, the tint block synthesis printing apparatus 2303 generates a tint block image based on the background threshold pattern and the latent image threshold pattern input from the pattern generation unit 2302, synthesizes the tint block image and the input document image, and prints out the output document. To do. Since the processing in the tint block composition printing apparatus 2303 has already been described in detail, the description thereof is omitted.

  Although the density of the background portion and the latent image portion is equal during printing, the latent image portion remains when the test printing sheet is copied by the target copying machine, but the background portion may not be completely lost.

  However, at this time, a patch whose density is greatly different from the density after copying of the latent image portion can be determined as an optimum patch. This is because if the latent image appears after copying, the effect as a forgery-suppressing tint block can be exhibited. In this embodiment, not only the patch in which the latent image portion remains and the background portion disappears after copying, but also a patch whose background portion after copying is sufficiently lower than the latent image portion is selected as the optimum patch. good.

  FIG. 18 is a flowchart showing the simplest test printing procedure. In accordance with an input from the user interface or the like, trial printing is started in step S1801. First, in step S1802, a process of reading setting information from an initial setting file in which setting information is stored or a process of receiving setting information input through a user interface is performed. In step S1803, a tint block density parameter for determining the print density of the latent image portion and the background portion when generating the tint block image is generated based on the setting information input in step S1802. In the present embodiment, the background pattern density pattern generated from the input setting information is a background threshold pattern and a latent image threshold pattern. In step S1804, a test print sheet as shown in FIG. 17 is generated based on the tint block density parameter input in step S1803, and is printed out by the printer.

  In step S1805, the density of the latent image portion and the background portion in each patch of the test printing sheet is visually compared. In the visual evaluation, the density of the latent image portion and the background portion of the test print sheet is almost equal, and when the test print sheet is copied by the target copying machine, the latent image portion remains and the background portion disappears (or Identify patches that have sufficient contrast compared to the latent image area. Then, the number associated with the patch is selected. The process in this step is a process performed by the user. For example, in the example shown in FIG. 17, patches with varying background densities are arranged from the upper left to the lower right of the paper, and a value representing the density of the background is written next to each patch. Has been. Here, it is assumed that there is a patch having a preferable density as the copy-forgery-inhibited pattern image, and the value representing the density of the background portion is 16. In that case, the patch can be selected as 16.

  As shown in FIG. 17, when the trial printing function that finds the optimum patch by one trial printing is realized, the darkness of the background portion and the latent image portion is almost equal in the trial printing sheet, and the latent image is visually observed. Inconspicuous patches need to be present in the proof sheet. In such a case, it is necessary to grasp the threshold pattern range in which the density of the background portion and the latent image portion are substantially equal as the initial device density parameter (device profile data) in consideration of the characteristics of the printer.

  Specific examples of the initial device density parameter include a latent image threshold pattern in which the latent image portion has a predetermined density, a background threshold pattern in which the background portion has a density substantially equal to the density of the latent image portion, and a change in the test printing sheet. For example, the density change width of the background portion. The density change width of the background portion is a contrast step parameter shown in FIG. The density change range of the background portion (the range in which the background threshold pattern in each column is changed; 0 to 30 in FIG. 17) can also be used as the initial parameter.

  In step S1806, the number (for example, 16) related to the patch selected in step S1805 is input as selection information through the user interface or the like. In step S1807, a tint block density parameter for determining the print density of the latent image portion and the background portion of the tint block image is generated based on the information input in step S1806. Specifically, the tint block density parameter corresponds to a latent image threshold pattern and a background threshold pattern in which the density of the background portion and the latent image portion are substantially equal and the background portion disappears during copying. At this time, as described above, the latent image portion and the background threshold pattern are generated so that one of the latent image portion and the background portion of the same color is formed with one color material and the other is formed with a plurality of color materials. .

  In step S1808, a copy-forgery-inhibited pattern image is generated based on the copy-forgery-inhibited pattern density parameter generated in step S1807, combined with the input document image, and printed out. The processing in this step is the same as that in the tint block synthesis printing apparatus described in FIG.

  When creating a threshold pattern using a Bayer-type dither, if the input gradation exceeds half the gradation 128, the generated threshold pattern has the effect that the dots touch each other and are not isolated dots, and the background portion disappears during copying. It is difficult to obtain. Therefore, for the purpose of searching for an optimum copy-forgery-inhibited pattern image, it is sufficient to cover the gradation value of the background portion from 0 to 128.

(Still another embodiment)
The tint block image composition apparatus according to the embodiment of the present invention can be implemented by a host computer such as a personal computer.

  FIG. 24 is a block diagram showing the basic configuration of this computer. For example, in this computer, when all functions except the printing unit (or the printer engine of the printing unit) in FIG. 1 of the first and second embodiments described above are executed, each functional configuration can be expressed by a program. By loading this into the computer, the above functions can be realized.

  In FIG. 24, reference numeral 2411 denotes a CPU, which controls the entire computer using programs and data stored in a RAM 2412 and ROM 2413, and performs each process described in the first embodiment and the second embodiment. The RAM 2412 includes an area for temporarily storing programs and data loaded from the external storage device 3308 and programs and data downloaded from other computer systems 5314 via an I / F (interface) 5313. Along with this, an area necessary for the CPU 2411 to perform various processes is provided.

  The ROM 2413 stores a computer function program, setting data, and the like. The display control device 2414 performs control processing for causing the display 3305 to display images, characters, and the like. A display 2415 displays images, characters, and the like. As a display, a CRT, a liquid crystal screen or the like can be applied.

  The operation input device 2416 includes a device that can input various instructions to the CPU 2411 such as a keyboard and a mouse. In addition, when manually inputting a latent image background area designation image or the like, these can be input via the operation input device 2416. Reference numeral 2417 denotes an I / O for notifying the CPU 2411 of various instructions input via the operation input device 2416.

  Reference numeral 2418 denotes an external storage device that functions as a large-capacity information storage device such as a hard disk. This is an OS (operating system), a program for causing the CPU 2411 to execute the processing of the first embodiment or the second embodiment, a background dither matrix, a latent image dither matrix, a generated tint block image, an input original image, and the like. Remember. In addition, writing of information to the external storage device 2418 and reading of information from the external storage device 2418 are performed via the I / O 2419.

  Reference numeral 5311 denotes a printer for outputting documents and images. Output data is sent from the RAM 2412 or the external storage device 2418 via the I / O 5312. Examples of printers for outputting documents and images include ink jet printers, laser beam printers, thermal transfer printers, and dot impact printers.

  Reference numeral 5320 denotes a bus for connecting the CPU 2411, ROM 2413, RAM 2412, I / O 5312, I / O 2419, display control device 2414, I / F 5313, and I / O 2417.

  In the present embodiment, the computer executes the processing except for the printing unit of the tint block synthesis printing apparatus and the tint block synthesis printing apparatus having a trial printing function. However, the processing is performed by the computer using a dedicated hardware circuit in the printer. You may act as a proxy.

  Even if the present invention is applied to a system constituted by a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), it is applied to an apparatus (for example, a copier, a facsimile machine, etc.) composed of a single device. It may be applied.

  In addition, a recording medium in which a program code of software for realizing the functions of the above-described embodiments is recorded is supplied to a system or the like, and a computer (CPU, MPU) such as the system reads and executes the program code stored in the recording medium. Can also be achieved.

  In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiment, and the recording medium storing the program code constitutes the present invention.

  As a recording medium for supplying the program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like is used. be able to.

  Further, the functions of the embodiments are not only realized by executing the program code read by the computer. This includes a case where an OS running on a computer performs part or all of the actual processing based on an instruction of the program code, and the functions of the above-described embodiments are realized by the processing.

  Furthermore, a form in which the program code read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer is also included. Then, based on the instruction of the program code, the CPU of the function expansion board or the like performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

1 is a block diagram illustrating a configuration of a tint block composition printing apparatus according to an embodiment of the present invention. FIG. It is a flowchart which shows the process sequence of the tint block image generation part shown in FIG. It is a figure which shows an example of a 4x4 spiral dither matrix. FIG. 4 is a diagram showing a threshold pattern (dot arrangement) obtained by performing threshold processing on a predetermined input image signal using the 4 × 4 spiral dither matrix of FIG. 3. It is a figure which shows an example of a 4x4 Bayer type dither matrix. FIG. 6 is a diagram showing a threshold pattern (dot arrangement) obtained by performing threshold processing on a predetermined input image signal using the 4 × 4 Bayer-type dither matrix of FIG. 5. It is a figure for comparing the area ratio of the black pixel of a background threshold value pattern and a latent image threshold value pattern. (A)-(c) is a figure showing the relationship between the area ratio of the black pixel of the threshold value pattern obtained by carrying out threshold processing of an input image signal with a dither matrix, and the density when a threshold value pattern is printed. (A)-(e) is a schematic diagram which shows a mode that a tint block image is produced | generated using the tint block synthesis printing apparatus of FIG. (A) And (b) is a figure which respectively shows an example of the latent image background area | region designation | designated image and camouflage area | region designation | designated image shown in FIG. (A) And (b) is a figure which respectively shows an example of the latent image threshold value pattern and background threshold value pattern which are shown in FIG. It is a figure which shows a part of tint block image produced | generated in the tint block image generation part by the boundary process. FIG. 6 is a schematic diagram illustrating a composition process of an input document image and a tint block image. (A) And (b) is a schematic diagram which shows the method of synthesize | combining a tint block image with the input original image which does not have a layer structure with which various images were already synthesize | combined. FIG. 2 is a block diagram showing a configuration of a tint block synthesis printing apparatus for synthesizing a tint block image with an input document image having no layer structure in which various images have already been synthesized. (A)-(d) is a figure which shows the background threshold value pattern obtained by threshold-processing with a dither matrix with respect to the latent image threshold value pattern and the gradation of several input image signal. FIG. 6 is a diagram illustrating an example of a test printing sheet in which a plurality of patches each including a latent image portion and a background portion are arranged while changing the background density. 10 is a flowchart showing a procedure of a trial print. It is a figure which shows an example of the latent image threshold value pattern comprised by C, M, and Y. It is a figure which shows an example of the background threshold value pattern comprised by C, M, and Y. It is a figure which shows an example of the gray balance adjustment sheet | seat of process black. It is a block diagram which shows the structure of the apparatus which performs a tint block density trial print. It is a figure which shows the tint block composition printing apparatus provided with the tint block density calibration function. It is a block diagram which shows the basic composition of the computer in other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Copy-forgery-inhibited pattern image generation part 102 Original data processing part 103 Composition part 104 Print data processing part 105 Printing part

Claims (16)

An information processing apparatus that generates print data of a tint block image including a latent image and a background,
The print data is generated so that either the latent image or the background is printed with only one color material and the other is printed with a plurality of color materials in a predetermined ratio. Information processing apparatus.   The information processing apparatus according to claim 1, wherein the means generates the print data so that the latent image and the background are printed in the same color.   The information processing apparatus according to claim 1, wherein the means generates the print data of the latent image by a dither process using a dot concentration type dither matrix.   The information processing apparatus according to claim 1, wherein the means generates the background print data by a dither process using a dot dispersion type dither matrix.   5. The information processing apparatus according to claim 1, wherein the predetermined ratio is determined visually with reference to an image composed of only one color material. 6.   5. The information processing apparatus according to claim 1, wherein the amount of the one color material is determined after the ratio of the plurality of color materials is determined.   7. The method according to claim 2, wherein the same color is black, the one color material is a black color material, and process black is formed using the plurality of color materials. The information processing apparatus described in 1. A tint block printing method for printing a tint block image including a latent image and a background,
One of the latent image and the background is printed with only one color material, and the other is printed with a plurality of color materials in a predetermined ratio.   9. The tint block printing method according to claim 8, wherein in the step, the latent image and the background are printed in the same color.   10. The tint block printing method according to claim 8, wherein in the step, the print data of the latent image is generated by dither processing using a dot concentration type dither matrix.   11. The tint block printing method according to claim 8, wherein in the step, the background print data is generated by a dither process using a dot dispersion type dither matrix.   12. The tint block printing method according to claim 8, wherein the predetermined ratio is determined visually with reference to an image composed of only one color material.   12. The tint block printing method according to claim 8, wherein the amount of the one color material is determined after determining the ratio of the plurality of color materials.   The same color is black, the one color material is a black color material, and process black is formed using the plurality of color materials. The tint block printing method described in 1.   A program causing a computer to function as the information processing apparatus according to any one of claims 1 to 7. A computer-readable recording medium storing a program that causes a computer to function as the information processing apparatus according to claim 1.

Images