JP2016025420A - Image processing system, image processing method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing system capable of generating an information-embedded image without annoying a user and damaging the format or appearance of a document.SOLUTION: An image processing system which embeds information into an image comprises output image generation means which generates an achromatic color object out of objects included in the image by using monochrome gray or mixed color gray. An achromatic color object generated by using the monochrome gray has first data assigned thereto, and an achromatic color object generated by using the mixed color gray has second data different from the first data assigned thereto.SELECTED DRAWING: Figure 5

Description

  The present invention relates to image processing for generating an image in which information is embedded without losing the format or appearance of a document, printing the generated image, and reading the embedded information from the printed paper.

  In recent years, the function of an image forming apparatus that performs image copying by an image reading process and an image forming process has been improved, and the image copying accuracy has been improved, so that an original image such as a document can be copied easily and with high accuracy. it can. By using such a high-function image forming apparatus, it is possible to easily create illegal copies by copying documents that should not be copied, and to produce highly accurate copies that are indistinguishable from the original. Can be obtained. Therefore, in order to prevent unauthorized copying of a document image, a technique for combining a copy prevention pattern or a watermark character with a document image that should be prohibited from being copied has been realized. In general, a document is copied and used by a multifunction machine or the like having a copy function. However, due to the development of the copy function, it is difficult to distinguish the original from a copy. In addition, it is difficult to clarify the origin of the document while it is being copied, and it is necessary to apply some ingenuity to the document. Desirable to ensure reliable recognition.

  Patent Document 1 discloses a technique for generating a latent image having low visibility under visible light.

  Further, Patent Document 2 discloses a technique for generating an image for obtaining a printed material that guarantees an original or a printed material that can trace the source without using a special color material. Yes.

JP 2013-223144 A JP 2013-225843 A

  The technique described in Patent Document 1 outputs a sample image of single color gray and mixed color gray, reads the output image or accepts a selection based on the output image, and determines the density of each color constituting the mixed color gray. It has a configuration to determine. Therefore, there is a problem that it is troublesome for the user because the user has to present a sample of single color gray and mixed color gray and select the designation that matches the color.

  In the technique described in Patent Document 2, a background image is generated using a color component different from the color component used by the latent image, and the latent image and the background image have the same color when the print image is printed. It is necessary to use each color component in the form printed in For this reason, since two images, a latent image and a background image, are required, there is a problem that it is difficult to embed information in a document image or the like consisting only of characters.

  The present invention is an image processing apparatus for embedding information in an image, comprising output image generation means for generating an achromatic object among the objects included in the image in either a single color gray or a mixed color gray, First data is assigned to the achromatic object generated with the single gray, and second data different from the first data is assigned to the achromatic object generated with the mixed gray. It is characterized by.

  According to the present invention, since it is possible to embed information in the character part of a document image, it is possible to generate an image in which information is embedded without bothering the user and without losing the format or appearance of the document. Further, according to the present invention, it is possible to embed information in an image without using a special color material.

1 is an overview diagram of a system according to Embodiment 1. FIG. 1 is a block diagram illustrating a hardware configuration of a terminal device according to Embodiment 1. FIG. FIG. 2 is a block diagram illustrating a functional configuration of an image processing unit according to the first embodiment. 3 is a flowchart illustrating a flow of output image generation processing according to the first embodiment. 3 is a flowchart illustrating a flow of information embedding processing according to the first embodiment. 3 is a flowchart illustrating a flow of information reading processing according to the first embodiment. 6 is a flowchart illustrating a flow of information reading processing according to the first embodiment. 12 is a flowchart illustrating a flow of information embedding processing according to the second embodiment. 12 is a flowchart illustrating a flow of information reading processing according to the second embodiment. 12 is a flowchart illustrating a flow of information embedding processing according to a third embodiment. It is a figure which shows the outline | summary which embeds information in a character. It is a figure which shows the example which calculated | required the circumscribed rectangle with respect to each character, and was made into the circumscribed rectangle. It is a figure which shows the example which performed the blurring process with respect to the binary image. 14 is a flowchart illustrating a flow of information embedding processing according to a fourth embodiment. FIG. 10 is a diagram illustrating print settings at an end portion of a mixed color gray character according to a fourth embodiment. 14 is a flowchart illustrating a flow of information reading processing according to the fourth embodiment. 10 is a flowchart illustrating a flow of information embedding processing according to a fifth embodiment. 10 is a flowchart illustrating a flow of an information reading process according to Embodiment 5. It is a figure which shows the outline | summary which allocates the information which concerns on Example 5 to a character.

  Preferred embodiments of the present invention will be described below with reference to the drawings. However, the configuration described below is merely an example, and the present invention is not limited to the illustrated configuration. In addition, the same code | symbol is attached | subjected to the same element over all the figures.

  FIG. 1 is an overview of a system according to the present embodiment. The system includes a terminal device 1 and an image processing device 2. The terminal device 1 is an information processing device including a display unit 11 and an operation unit 12, and is specifically a general-purpose PC. Alternatively, the terminal device 1 may be a portable information terminal device such as a mobile phone or a smartphone. The image processing apparatus 2 is a multifunction machine having a general scan function, a printer function, and the like. The image processing apparatus 2 includes an ADF (Auto Document Feeder) unit 21, an operation unit 22, and a laser printer 23. The image processing apparatus 2 may be a single printer.

  The terminal device 1 and the image processing device 2 are connected to a network, and an image read by the image processing device 2 can be transmitted to the terminal device 1 via the network. In addition, an image generated by the terminal device 1 can be transmitted to the image processing device 2 via the network and printed by the image processing device 2.

  In the present embodiment, the terminal device 1 embeds information in the received input image and transmits it to the image processing device 2, and the image processing device 2 prints the transmitted image in which the information is embedded. The embedded information embedded in the image on the printed paper is expressed by switching between printing characters in single color gray or mixed color gray. The embedded information is usually not visible to the user on the printed paper. However, when the image processing apparatus 2 acquires and analyzes the read image using the scan function, the embedded information can be recognized.

  In the following description, for the sake of convenience, the image processing apparatus 2 uses the laser printer 23 to print on paper using toners of C (cyan), M (magenta), Y (yellow), and K (black) color components. However, it may be printed by an ink jet method. In that case, the image processing apparatus 2 executes printing using ink of each color component of CMYK.

(Hardware configuration of terminal device 1)
A hardware configuration of the terminal device 1 will be described. FIG. 2 is a block diagram illustrating a hardware configuration of the terminal device 1. In addition to the display unit 11 and the operation unit 12 described above, the terminal device 1 includes a CPU 101, a memory device 102, a network I / F 103, an external media I / F 104, and an image processing unit 105.

  The CPU 101 executes processing according to a program stored in the memory device 102. The memory device 102 includes a ROM, a RAM, and / or an HDD, and stores programs executed by the CPU 101 and various data. The display unit 11 is a display such as a liquid crystal display screen or a CRT, and displays information to be embedded in the input image, a read image received from the scanner, and information related to the operation of the terminal device 1. The operation unit 12 is an operation device such as a keyboard and a mouse, and accepts user operations. The network I / F 103 is a network interface to which the terminal device 1 is connected, and mediates communication between the terminal device 1 and the image processing device 2. The external media I / F 104 is an interface with external media, and specifically, is a removable external media drive such as a DVD or CD. For example, when executing a program recorded on a DVD, the program is executed via the external media I / F 104.

  The image processing unit 105 performs predetermined image processing on the input image received by the terminal device 1. As image processing unique to the present embodiment, the image processing unit 105 executes processing for embedding information in the input image, which will be described in detail later. Note that the image processing unit 105 is actually realized by the CPU 101 executing a program stored in the memory device 102. The program is installed in the memory device 102 of the terminal device 1 as, for example, a printer driver, a mobile phone application, a smartphone application, or the like. Alternatively, the image processing apparatus 2 can be used as the terminal apparatus 1 by installing the program in the image processing apparatus 2.

(Configuration of the image processing unit 105)
The function of the image processing unit 105 will be described. FIG. 3 is a block diagram illustrating a functional configuration of the image processing unit 105. The image processing unit 105 includes an information acquisition unit 1051, an embedded information generation unit 1052, an input image acquisition unit 1053, and an output image generation unit 1054.

  In this embodiment, the terminal device 1 generates an output image that is an information-embedded image by determining whether each character is generated in single color gray or mixed color gray based on the embedded information. The generated output image is transmitted to the image processing apparatus 2 via the network I / F 103 and printed by the image processing apparatus 2.

  The information acquisition unit 1051 acquires information. Information acquired by the information acquisition unit 1051 is information indicating that the document is genuine (genuine), and may be input by the user via the operation unit 12. Information indicating that a document is genuine is used in a workflow for proceeding to the next procedure if the document itself is genuine after identifying whether the document itself is genuine as a procedure of the document procedure. If the document is not authentic, stop subsequent procedures or return to the previous procedure. Specifically, when an approval mark is stamped or an approval sign is applied to a document, the document is checked for authenticity (authentic) and then the document is stamped or signed. The embedding information generated by the embedding information generation unit 1052 is printed on paper in a state of being embedded in characters by the image processing apparatus 2. Then, the image processing apparatus 2 reads and analyzes the printed sheet using the scan function, and if the information indicating that the document is genuine is embedded, the read document is assumed to be genuine, and embedded. If not, it is not genuine.

  As another example, the information acquired by the information acquisition unit 1051 is ID information or information indicating “time” (that is, information indicating “when a document was created”) or the like, which is input by the user via the operation unit 12 Alternatively, it may be acquired from information added to the image data of the input image.

  The embedded information generating unit 1052 encodes the information acquired by the information acquiring unit 1051 to generate bit-structured embedded information.

  The input image acquisition unit 1053 acquires the input image received by the terminal device 1. The input image may be acquired in advance stored in the memory device 102, or may be acquired via a network via the network I / F 103.

  The output image generation unit 1054 generates a character part of the document image using each color component of CMYK based on the embedded information generated by the embedded information generation unit 1052 and the input image acquired by the input image acquisition unit 1053. Then, an output image that is an information-embedded image is generated.

  In this embodiment, information is embedded in characters. Specifically, 0 (zero) is assigned as the first data to the single-color gray character, 1 is assigned to the mixed-color gray character as the second data, and the single-color gray character is generated using only the K color component. Gray characters are generated using CMY color components. An information embedding image is generated by generating each character using either a single color gray character or a mixed color gray character in accordance with the embedding information. Here, if the color of the single-color gray character is different from the color of the mixed-color gray character when printed on paper, it is not desirable because the generated image is recognized by the naked eye. For this reason, in this embodiment, adjustment is performed so that the colors of the single-color gray character and the mixed-color gray character cannot be distinguished with the naked eye. FIG. 11 shows an outline of embedding information in characters. In the example shown in FIG. 11, the embedding information “101” is embedded in the three characters “Shimomaruko”. The “lower” and “child” characters to which bit 1 is assigned are generated using CMY color components, and the “circle” character to which bit 0 is assigned are generated using K color components. In this example, as described above, data is assigned to characters. However, the object to which data is assigned is not limited to characters, and data can be assigned to objects composed of lines such as symbols. is there.

  It is known that when the C color component, the M color component, and the Y color component are added together at the same ratio, it looks the same as the K color component to the naked eye. However, when viewed in units of one pixel, one pixel having CMY color components is printed without the CMY toners completely overlapping each other. Therefore, when one pixel having the same color as the K color component is printed by adding the CMY color components, the one pixel may appear to be the same color as the one pixel printed with only the K toner. The multifunction device detects each color component of CMY and does not detect the color component of K. On the other hand, when one pixel having a K color component is printed, the K color component is printed with K toner, so the multifunction peripheral detects the K color component for each pixel.

  In the present embodiment, a mixed-color gray character is generated by using a CMY color component obtained by adding each CMY density value corresponding to the K color component to each CMY density value of the mixed-color gray character. Further, by adjusting the brightness, hue, and saturation of the pixels constituting the mixed-color gray character, the colors of the single-color gray character and the mixed-color gray character pixel are matched. As a result, even when a single-color gray character and a mixed-color gray character are adjacent to each other in the printed matter, an information-embedded image that cannot be recognized by the naked eye as the appearance of the character can be generated.

  Specifically, the density of the K color component is set to 0 among the CMYK color components included in the pixels constituting the mixed color gray character. Then, the density of each CMY color component is increased by the same density (that is, minus) as the density of the K color component before being set to 0, and each of the CMY included in one pixel of the mixed color gray characters is increased. Temporarily obtain the density of the color component. Next, in consideration of the non-linearity of lightness that occurs when the color components of CMY are added, the density of the color components of CMY is adjusted (corrected) to obtain the final density of the color components of CMY. The technique shown here is an example of a technique for matching the color of characters.

  As a specific method for adjusting (correcting) the density of the color components of the CMY pixels constituting the mixed gray character, for example, the following method can be considered. In other words, the correction amount of the density of each color component is previously determined by experiments or the like for all possible combinations (condition information) of the density of each color component of CMYK included in one of the pixels constituting the monochromatic gray character. It can be stored in a table. Alternatively, the correction amount of the density of each color component with respect to the combination (condition information) for each constant density range (step) of each color component may be obtained in advance and stored in the table. In that case, the correction accuracy can be improved by performing linear approximation or the like for combinations of density values at constant density steps.

  In the above-described example, a single-color gray character generated using only the K color component and a mixed-color gray character generated without using the K color component are printed with an apparently equivalent color. Therefore, in the mixed color gray character, the CMY color component is increased by the amount corresponding to the reduction of the K color component. However, the present embodiment is not limited to this example.

  Conversely, in order to print a single color gray character generated using only the K color component and a mixed color gray character generated without using the K color component in the same color, The CMY color components may be reduced, and the K color component may be increased accordingly. In this case, similarly to the above-described example, the density of the CMY color components is reduced to 0 by reducing the density of the CMYK color components in the monochromatic gray character. Then, the K color component is increased by the reduced density. In this way, the density of the K color component included in the single-color gray character is provisionally obtained. Next, in consideration of the non-linearity of the brightness that occurs when the K color components are added, the density of the K color component is adjusted (corrected) to obtain the final density of the K color component. The technique shown here is an example of a technique for matching the color of characters, and the density of the K color component can be adjusted (corrected) using the table data as in the above-described example.

(Output image generation processing)
The output image generation process will be described with reference to FIG. FIG. 4 is a flowchart showing the flow of output image generation processing.

  In step S41 (hereinafter, “step S41” is abbreviated as “S41” and other steps are also abbreviated in the same manner), the information acquisition unit 1051 acquires information (raw data) to be embedded in the input image.

  In S42, the embedding information generation unit 1052 generates embedding information (binary data) that can be embedded in the input image from the information acquired in S41.

  In step S <b> 43, the input image acquisition unit 1053 acquires an input image from the memory device 102.

In S44, the output image generation unit 1054 generates an output image by embedding the embedding information generated in S42 in the character portion of the input image acquired in S43.
(Information embedding process)
The process of embedding the embedding information described in S44 of FIG. 4 in the input image will be described with reference to FIG. FIG. 5 is a flowchart showing the flow of the embedding process.

  In S51, the output image generation unit 1054 converts the color space (RGB space) of the input image into a space (Lab space) indicating luminance and chromaticity. Although the description will be made here assuming that the color space of the input image is the RGB space, the color space of the input image is not limited to the RGB space.

  In S52, the output image generation unit 1054 determines whether each pixel constituting the image expressed in the Lab space by the processing in S51 is a chromatic color or an achromatic color, and extracts an achromatic pixel.

  In S53, the output image generation unit 1054 executes the binarization process on the pixels determined to be achromatic in S52 and generates a binary image, thereby acquiring the character part.

  In S54, the output image generation unit 1054 executes arrangement processing of the single color gray character and the mixed color gray character based on the embedding information generated in S42. In S54, 0 (zero) is assigned to a single-color gray character, and bit assignment is performed to assign 1 to a mixed-color gray character. With this processing, an information-embedded image in which embedded information is embedded in a document image can be generated. Become.

(Information reading process)
A flow of information reading processing executed by the image processing apparatus 2 will be described with reference to FIG. FIG. 6 is a flowchart showing the flow of the information reading process.

  In S61, the image processing apparatus 2 performs image reading by scanning the printed paper using a scanner. In the case where the terminal device 1 is a portable information terminal device such as a mobile phone or a smartphone, an image is read by photographing the printed paper using a built-in camera, and the read image is transmitted to the image processing device 2. It is also possible.

  In S <b> 62, the image processing apparatus 2 executes information reading processing for the read image. Details of the information reading process will be described later.

  In S63, the image processing apparatus 2 displays the information read in S62. The information read by the image processing device 2 may be transmitted to the terminal device 1, and the display unit 11 of the terminal device 1 may display the information.

(Information reading process)
The information reading process described in S62 of FIG. 6 will be described with reference to FIG. FIG. 7 is a flowchart showing the flow of the information reading process.

  In S71, the image processing apparatus 2 converts the color space (RGB space) of the image data read in S61 into a space (Lab space) indicating luminance and chromaticity. Although the description will be made here assuming that the color space of the read image is the RGB space, the color space of the read image is not limited to the RGB space. Further, the color space after conversion is not limited to the Lab space.

  In S <b> 72, the image processing apparatus 2 determines whether each pixel constituting the image expressed in the Lab space by the process in S <b> 71 is a chromatic color or an achromatic color, and extracts an achromatic pixel.

  In S73, the image processing apparatus 2 executes a binarization process on the pixels determined to be achromatic in S72, generates a binary image, and extracts a character part.

  In S74, the image processing apparatus 2 determines whether each character is a single color gray character or a mixed color gray character with respect to the character portion extracted by the binarization processing in S73.

  In S75, the image processing apparatus 2 executes the information decoding process from the bit arrangement obtained from the arrangement of the single-color gray character and the mixed-color gray character acquired by the determination in S74.

  According to the present embodiment, since the information is embedded by generating each character of the character portion of the document image as either a single color gray character or a mixed color gray character, the information embedded image is not changed without changing the format or appearance of the document. Can be generated.

  In this embodiment, the characters for embedding information are narrowed down. Hereinafter, the present embodiment will be described by paying attention to different points from the first embodiment. However, in the following description of the embodiment, the description common to the above-described embodiment is simplified or omitted.

(Information embedding process)
A process for narrowing down characters to be embedded according to the present embodiment will be described with reference to FIG. FIG. 8 is a flowchart illustrating a flow of processing for embedding information in characters while narrowing down characters for embedding information according to the present embodiment.

  The processing from S51 to S53 is the same as that in the first embodiment (see FIG. 5).

  In S81, the output image generation unit 1054 executes a labeling process for searching only the parent outline (outer outline) of the character with respect to the character part extracted by the binarization process of S53. The reason for searching only the parent contour here is that even if the child contour is found by the search, the region surrounded by the child contour exists above the region surrounded by the parent contour. This is because it can be determined that there is a high possibility that a ground exists.

  In S82, the output image generation unit 1054 analyzes the result of the labeling process in S81, and determines whether information can be embedded for each character according to the square condition, the size condition, and the density condition. . FIG. 12 shows an example in which a circumscribed rectangle is obtained for each character and converted into a circumscribed rectangle. For example, the narrowing-down process according to the square condition is performed on each circumscribed rectangular character as shown in FIG.

  The square condition is used to pick up characters that are easy to find even if the reading process is blurred or the resolution is reduced. The size condition is used to pick up characters that are neither too big nor too small. If the characters are too large, mixed color gray characters are likely to be noticeable and toner consumption increases when printing with CMY toner. In addition, if the character is too small, the number of pixels is reduced and the determination accuracy at the time of reading may be reduced. The density condition is used in order not to pick up a character having a density that is too high, because if the density of the character is too high, there is a possibility that the mixed color gray character may be crushed.

  The process of S54 is the same as that of the first embodiment (see FIG. 5).

  As described above, information is embedded while narrowing down characters to be embedded. When the information embedding is completed, the terminal device 1 transmits the information embedded image to the image processing device 2. The image processing apparatus 2 prints the transmitted information-embedded image on paper, and executes a reading process on the printed paper (see FIG. 6).

(Information reading process)
Processing for reading information from the information embedded image according to the present embodiment will be described with reference to FIG. FIG. 9 is a flowchart illustrating the flow of the information reading process according to the present embodiment.

  The processing from S71 to S73 is the same as that in the first embodiment (see FIG. 7).

  In S91, the image processing apparatus 2 executes a labeling process for searching only the parent outline of the character for the character part extracted by the binarization process in S73. This process is the same as S81 in FIG.

  In S92, the image processing apparatus 2 analyzes the result of the labeling process in S91, and determines whether or not the information can be embedded with information according to the square condition, the size condition, and the density condition. Then, characters that can be embedded are extracted.

  In S <b> 74, the image processing apparatus 2 determines whether each character extracted in S <b> 92 is a single color gray character or a mixed color gray character.

  The process of S75 is the same as that of the first embodiment (see FIG. 7).

  According to the present embodiment, information is embedded in the character after executing a process of determining whether or not each character is suitable for embedding information in the character portion of the document image. Thereby, information can be read more reliably on the reading side.

  The present embodiment is the same as the second embodiment in that the characters for embedding information are narrowed down. Hereinafter, the present embodiment will be described by focusing on differences from the above-described second embodiment.

  In the present embodiment, the characters to embed information are narrowed down on the embedding side so that the reading side can easily perform the reading process. Specifically, when reading information on the reading side, considering the possibility of blurring in the character part of the document image, only characters that can be read accurately even if blurring occurs. Then, embed the information on the embedding side. FIG. 10 is a flowchart illustrating a flow of processing for embedding information in characters while narrowing down characters for embedding information according to the present embodiment.

  The processing from S51 to S53 is the same as that in the first embodiment (see FIG. 5).

  In S101, the output image generation unit 1054 executes a fattening process on the character part extracted as a result of the process in S53. This fattening process allows the embedded information to be accurately read from the characters even when blurring occurs in consideration of the possibility of blurring in the character part of the document image when reading the information on the reading side. To be executed. Control is performed so as not to embed information for characters that come in contact with surrounding characters as a result of the fattening process. Here, the “thickening process” is a process of thickening lines constituting each character of the character part. As an alternative to the fattening process, a trapping process may be executed. Also, by executing the blurring process, an image similar to the fattening process can be obtained, and any image processing that can reproduce the blurring of characters can be used in this step.

  FIG. 13 is a diagram illustrating an example in which the blurring process is performed on the binary image after the binarization process. In the upper example of FIG. 13, the characters “lower”, “circle”, and “child” are arranged apart from each other, so that when the blurring process is performed, adjacent characters are not in contact with each other. However, in the lower example of FIG. 13, since the space between the adjacent characters “lower” and “circle” is narrow, the characters “lower” and “circle” are in contact when the blurring process is performed. . When characters touch each other in this way, even if information is embedded in each character on the embedding side, a plurality of adjacent characters are recognized as one character on the reading side, so that information can be read accurately. Can not. For this reason, in this embodiment, characters that will be in contact with surrounding characters due to the blurring process are excluded from the information embedding targets.

  The processing subsequent to S101 is the same as that in the above-described embodiment (see FIGS. 5 and 8).

  According to the present embodiment, information is embedded in the character after executing a process of determining whether or not each character is suitable for embedding information in the character portion of the document image. Thereby, information can be read more reliably on the reading side.

  In the first embodiment, a method of embedding information in a character by generating each character as either a single color gray character or a mixed color gray character, and assigning 0 (zero) to the single color gray character and 1 to the mixed color gray character. explained. When an image in which information is embedded according to the first embodiment is printed out, if the image processing apparatus 2 includes a high-resolution scanner such as 600 dpi, the difference between the single color gray character and the mixed color gray character in the image reading process Can be easily determined. However, when images are acquired using a low-resolution device or a device with unstable color, such as when using a camera equipped with a smartphone or mobile phone, or using a digital camera, color mixing with monochromatic gray characters in the image reading process The difference from gray letters cannot be easily determined. Therefore, in this embodiment, a mixed gray character printing method is devised in order to improve information reading accuracy when reading information on the reading side.

(Information embedding process)
Information embedding processing according to the present embodiment will be described with reference to FIGS. FIG. 14 is a flowchart showing the flow of the information embedding process according to the present embodiment, and FIG. 15 is a diagram showing the print setting at the end of the mixed color gray character according to the present embodiment.

  The processing from S51 to S54 is the same as that in the first embodiment (see FIG. 5).

  In step S141, the output image generation unit 1054 executes end pixel detection processing for the character that has been changed to the mixed color gray character in step S54. The edge pixel detection process will be described with reference to FIG. For the binary image acquired by the binarization process in S53, the pixel values of the pixels in the range of 1 row and 2 columns (that is, the pixel at the position (x, y) and the pixel at the position (x + 1, y)) are acquired. . If the pixel at the position (x, y) is a black pixel and the pixel at the position (x + 1, y) is a white pixel, it is determined that the pixel at the position (x, y) is the right end of the character. To do. On the other hand, when the pixel at the position (x, y) is a white pixel and the pixel at the position (x + 1, y) is a black pixel, it is determined that the pixel at the position (x + 1, y) is the left end of the character. To do. Further, when the pixel value of the pixel in the range of 2 rows and 1 column is acquired, the pixel at the position (x, y) is a black pixel, and the pixel at the position (x, y + 1) is a white pixel. You may judge that the pixel of (x, y) is the upper end part of a character. If the pixel at the position (x, y) is a white pixel and the pixel at the position (x, y + 1) is a black pixel, it is determined that the pixel at the position (x, y + 1) is the lower end of the character. May be.

  In S142, when it is determined in S141 that the pixel at the position (x, y) is the right end of the character, the pixel (white pixel) at the position (x + 1, y) is printed in one of CMY colors. Set. In the example of FIG. 15, the bitmap is generated so that the pixel at the position (x + 1, y) is printed in Y (yellow). In the example of FIG. 15, the bitmap is generated so that a pixel printed with one color Y (yellow) is added to the right end of the character “A”, but the same applies to the left end, upper end, and lower end. Processing is possible. In addition, on the right side of the right end of the character “A”, a bitmap is generated so that only one pixel is printed in Y (yellow), but a plurality of pixels including pixels on the right side are further printed. You may do it. Further, the color used for one-color printing is not limited to Y (yellow), and M (magenta) or C (cyan) may be used.

  As described above, in this embodiment, in the information embedding process, a bit map is generated so as to detect the end of the mixed color gray character and add a pixel to be printed with one color at the detected end of the mixed color gray character. To do.

(Information reading process)
A process of reading information from the information embedded image according to the present embodiment will be described with reference to FIG. FIG. 16 is a flowchart illustrating the flow of the information reading process according to the present embodiment.

  The processing from S71 to S73 is the same as that in the first embodiment (see FIG. 7).

  In S161, the image processing apparatus 2 performs the edge pixel detection process similar to S141 in FIG. 14 described above on the single color gray character and the mixed color gray character included in the character part extracted by the binarization process in S73. .

  In S162, the image processing apparatus 2 determines whether each character is a single color gray character or a mixed color gray character by analyzing the printing state at the end of each character. Specifically, the signal value of the pixel adjacent to the end detected in S161 is acquired. As an example, consider a case where the pixel at the position (x, y) is the right end of the character and the pixel at the position (x + 1, y) is printed in Y (yellow). In this case, the luminance values (R (red), G (green), B (blue)) of the pixel at the position (x + 1, y) are acquired. Such luminance value acquisition is executed for all right ends of one character, and the acquired luminance values are cumulatively added. If Y (yellow) is not printed on the right side of the right end, that is, the pixel at the position (x + 1, y), the result of cumulative addition of luminance values is that the pixel on the right side of the right end is achromatic. R≈G≈B. However, in this example, the pixel at the position (x + 1, y) immediately adjacent to the right end portion is printed in Y (yellow). Therefore, as a result of cumulative addition of the luminance values, the signal value of the B (blue) signal that is a complementary color of Y (yellow) becomes larger than the signal values of the other colors, and R≈G <B. Thus, by accumulatively adding the luminance values of the pixels adjacent to the end of the character, it is possible to easily determine whether each character is a single color gray character or a mixed color gray character.

  In the above-described example, 0 (zero) is assigned to a single-color gray character, 1 is assigned to a mixed-color gray character, and one color is printed at a pixel adjacent to the end of the mixed-color gray character. I was able to read. However, the present embodiment is not limited to the example described above. For example, using only a mixed-color gray character without using a single-color gray character, 0 (zero) or 1 is assigned to a mixed-color gray character in which a pixel adjacent to the right end is printed in one color, and a pixel adjacent to the left end is one color. You may assign 1 or 0 (zero) to the mixed color gray character printed.

  In addition, this embodiment can be implemented in combination with the second embodiment or the third embodiment. For example, when the present embodiment is combined with the second embodiment, after narrowing down the character in which information is to be embedded, for a mixed-color gray character of the narrowed-down character, one color pixel is printed adjacent to the edge. Control. Similarly, when combining the present embodiment with the third embodiment, after narrowing down the characters to embed information after the fattening process, for mixed-color gray characters of the narrowed-down characters, one pixel adjacent to the end portion is one color. Control to print.

  According to the present embodiment, even when the image processing apparatus 2 that executes image reading is a low-resolution device or a device with unstable color, information can be read more reliably.

  In the fourth embodiment, in order to make it possible to read information more reliably on the reading side, one color of the pixel adjacent to the end of the mixed color gray character is printed, but either 0 (zero) or 1 is printed on each character. Therefore, the capacity of information that can be embedded in one character is 1 bit. In the present embodiment, the information embedding method and reading method are changed so that information of a plurality of bits can be embedded in one character.

(Information embedding process)
Information embedding processing according to the present embodiment will be described with reference to FIG. FIG. 17 is a flowchart illustrating the flow of the information embedding process according to the present embodiment.

  The processing from S51 to S54 is the same as that in the first embodiment (see FIG. 5).

  In step S171, the output image generation unit 1054 performs a four-direction end pixel detection process on the character that is a mixed-color gray character in step S54. The four-direction ends are ends in the vertical and horizontal directions in one character, and refer to the right end, the left end, the upper end, and the lower end.

  The four-direction end pixel detection process will be described. For the binary image acquired by the binarization process in S53, the pixel values of the pixels in the range of 1 row and 2 columns (that is, the pixel at the position (x, y) and the pixel at the position (x + 1, y)) are acquired. . When the pixel at the position (x, y) is a black pixel and the pixel at the position (x + 1, y) is a white pixel, the pixel at the position (x, y) is the right end of the character part. to decide. If the pixel at position (x, y) is a white pixel and the pixel at position (x + 1, y) is a black pixel among the pixels in the range of 1 row and 2 columns, the pixel at position (x + 1, y) It is determined that the pixel is the left edge of the character. Similarly, the pixel value of the pixel in the range of 2 rows and 1 column (that is, the pixel at the position (x, y) and the pixel at the position (x, y + 1)) is acquired. If the pixel at the position (x, y) is a black pixel and the pixel at the position (x, y + 1) is a white pixel, it is determined that the pixel at the position (x, y) is the upper end of the character. To do. When the pixel at the position (x, y) is a white pixel and the pixel at the position (x, y + 1) is a black pixel among the pixels in the 2 rows and 1 column range, the pixel at the position (x, y + 1) is Judged as the lower end of the character.

  In step S172, the output image generation unit executes end pixel print setting processing for embedding the embedding information generated in step S42 in each character.

  For example, a character to which 0 (zero) is assigned is set to a monochrome gray character. The character to which 1 is assigned is set to a mixed color gray character and a character in which a pixel adjacent to the right end is printed in one color. The character to be assigned 2 is set to a mixed color gray character and a character in which a pixel adjacent to the left end is printed in one color. The character to which 3 is assigned is set to a mixed color gray character and a character in which a pixel adjacent to the upper end is printed in one color. The character to which 4 is assigned is set to a character in which a mixed color gray character and a pixel adjacent to the lower end are printed in one color. By performing the above switching, information of 0 (zero) or 1 can be embedded in one character in the fourth embodiment, whereas any information from 0 (zero) to 4 is embedded in one character in the present embodiment. (See FIG. 19).

  Furthermore, the character to which 5 is assigned is set to a character in which a mixed color gray character, a pixel adjacent to the right end portion, and a pixel adjacent to the upper end portion are printed in one color. The character to which 6 is assigned is set to a character in which a mixed color gray character and a pixel adjacent to the right end and a pixel adjacent to the lower end are printed in one color. The character to which 7 is assigned is set to a character in which one color is printed in a mixed color gray character and a pixel adjacent to the left end and a pixel adjacent to the upper end. The character to which 8 is assigned is set to a character in which a mixed color gray character and a pixel adjacent to the left end and a pixel adjacent to the lower end are printed in one color. By performing the above switching, any information from 0 (zero) to 8 can be embedded in one character.

  Furthermore, the character to which 9 is assigned is set to a mixed color gray character and a character in which a pixel adjacent to the left end and a pixel adjacent to the right end are printed in one color. The character to which 10 is assigned is set to a character in which a mixed color gray character and a pixel adjacent to the upper end and a pixel adjacent to the lower end are printed in one color. The character to which 11 is assigned is set to a character in which a mixed color gray character and a pixel adjacent to the right end, a pixel adjacent to the upper end, and a pixel adjacent to the lower end are printed in one color. The character to which 12 is assigned is set to a character in which a mixed color gray character and a pixel adjacent to the left end, a pixel adjacent to the upper end, and a pixel adjacent to the lower end are printed in one color. The character to which 13 is assigned is set to a character in which a mixed color gray character and a pixel adjacent to the upper end, a pixel adjacent to the right end, and a pixel adjacent to the left end are printed in one color. The character assigned 14 is set to a character in which a mixed color gray character and a pixel adjacent to the lower end, a pixel adjacent to the right end, and a pixel adjacent to the left end are printed in one color. The character to which 15 is assigned is set to a character in which a mixed color gray character and a pixel adjacent to the upper end, a pixel adjacent to the lower end, a pixel adjacent to the left end, and a pixel adjacent to the right end are printed in one color. By performing the above switching, any information (4 bits) from 0 (zero) to 15 can be embedded in one character.

(Information reading process)
Processing for reading information from the information embedded image according to the present embodiment will be described with reference to FIG. FIG. 18 is a flowchart illustrating the flow of the information reading process according to the present embodiment.

  The processing from S71 to S73 is the same as that in the first embodiment (see FIG. 7).

  In S181, the image processing apparatus 2 executes the four-direction end pixel detection process similar to S171 in FIG. 17 on the single color gray character and the mixed color gray character included in the character part extracted by the binarization process in S73. .

  In S <b> 182, the image processing apparatus 2 determines whether a pixel adjacent to the pixel detected as the end of the character in S <b> 181 is printed in one color. The processing in this step is the same as S162 in FIG. For example, when Y (yellow) is printed on the pixel at the position (x + 1, y) right next to the pixel at the right end position (x, y), the luminance value (R (red (red)) of the pixel at the position (x + 1, y) is printed. ), G (green), B (blue)). Such luminance value acquisition is executed for all right ends of one character, and the acquired luminance values are cumulatively added. If the pixel at the position (x + 1, y) right next to the right end is not printed in Y (yellow), the result of cumulative addition of the luminance values is that the right adjacent pixel at the right end is achromatic. R≈G≈B. However, in this example, the pixel at the position (x + 1, y) immediately adjacent to the right end portion is printed in Y (yellow). Therefore, as a result of cumulative addition of the luminance values, the signal value of the B (blue) signal that is a complementary color of Y (yellow) becomes larger than the signal values of the other colors, and R≈G <B. Thus, by accumulatively adding the luminance values of the pixels adjacent to the right end portion of the character, it is possible to determine whether or not one color is printed on the pixels adjacent to the right end portion. This process is executed in the four directions, up, down, left, and right, and the printing state of the end portion of the mixed color gray character is analyzed to determine at which end the one-color printing is being executed.

  In this embodiment, by using a single color gray character and a mixed color gray character that can be printed in one color with pixels adjacent to the end portions in the four directions, any one of 0 (zero) to 15 is assigned to each character. It is possible. In the above-described example, the case where one color can be printed in all four directions of the mixed color gray character is shown. However, the present embodiment is not limited to this example. It is possible to change such that only one direction can be printed in one direction.

(Other embodiments)
The object of the present invention can also be achieved by executing the following processing. That is, a storage medium in which a program code of software that realizes the functions of the above-described embodiment is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus is stored in the storage medium. Is a process of reading.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

Claims (14)

An image processing apparatus for embedding information in an image,
An output image generating means for generating an achromatic object among the objects included in the image in either a single color gray or a mixed color gray;
First data is assigned to the achromatic object generated in the single color gray,
2. An image processing apparatus according to claim 1, wherein second data different from the first data is assigned to the achromatic object generated in the mixed color gray.   The image processing apparatus according to claim 1, wherein the achromatic color object generated by the single color gray is a single color gray character, and the achromatic color object generated by the mixed color gray is a mixed color gray character. When printed out,
The mixed color gray character is printed in C (cyan), M (magenta), and Y (yellow),
3. The image processing according to claim 2, wherein a pixel adjacent to an end portion of the mixed-color gray character is printed in one color in any of C (cyan), M (magenta), and Y (yellow). apparatus.   The output image generation means executes a labeling process for searching a parent contour of the achromatic object, and uses the image obtained by the labeling process to determine whether the achromatic object can be embedded with information. The image processing apparatus according to claim 1, wherein the determination is performed.   The output image generation unit executes a fattening process on the achromatic color object, and when the achromatic color object touches by the thickening process, the touching achromatic color object is excluded from information embedding targets. The image processing apparatus according to claim 1, wherein: The end portions are an upper end portion, a lower end portion, a left end portion, and a right end portion,
The image according to claim 3, wherein the output image generation unit sets which one of the end portions is to be subjected to one-color printing in accordance with data assigned to each character. Processing equipment. An image processing apparatus that reads information from an image,
Means for determining whether an achromatic color object among the objects included in the image is generated in a single color gray or a mixed color gray;
First data is assigned to the achromatic color object generated in the single color gray,
2. An image processing apparatus according to claim 1, wherein second data different from the first data is assigned to the achromatic color object generated in the mixed color gray.   The image processing according to claim 7, wherein the achromatic color object generated in the single color gray is a single color gray character, and the achromatic color object generated in the color mixture gray is a mixed color gray character. apparatus. The mixed color gray character is printed in C (cyan), M (magenta), and Y (yellow),
9. The image processing apparatus according to claim 8, wherein a pixel adjacent to an end portion of the mixed color gray character is printed in any one of C (cyan), M (magenta), and Y (yellow).   A means for executing a labeling process for searching for a parent contour of the achromatic object and determining whether or not the achromatic object can be embedded with information using an image obtained by the labeling process; The image processing apparatus according to claim 7. The end portions are an upper end portion, a lower end portion, a left end portion, and a right end portion,
The image processing apparatus according to claim 9, wherein a determination is made as to which one of the ends is subjected to one-color printing. An image processing method for embedding information in an image,
An output image generation step of generating an achromatic object among the objects included in the image in either a single-color gray or a mixed-color gray;
First data is assigned to the achromatic object generated in the single color gray,
An image processing method, wherein second data different from the first data is assigned to the achromatic object generated in the mixed color gray. An image processing method for reading information from an image,
A step of determining whether an achromatic color object among the objects included in the image is generated in a single color gray or a mixed color gray,
First data is assigned to the achromatic color object generated in the single color gray,
2. An image processing method according to claim 1, wherein second data different from the first data is assigned to the achromatic color object generated in the mixed color gray.   The program for functioning a computer as an image processing apparatus as described in any one of Claims 1 thru | or 11.