JP2006352214A - Coding device, decoding device, coding method, decoding method and their programs - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coding device and a decoding device capable of efficiently coding and decoding a document to such a degree that an alteration mark can be detected. <P>SOLUTION: In a coding program 4, a view image generating section 42 allows a binary threshold to vary depending on the concentration of a pixel value within a predetermined range for input multivalue image to apply binarization processing to the multivalue image, thereby generating a binary image for viewing. A detection image generating section 44 buries data for detecting alteration, for example, into the base of an input multivalue image to generate a multivalue image different from the input multivalue image. A viewing image coding section 460 applies text region coding defined in JBIG2 to code the binary image. A detection image coding section 462 applies halftone region coding to code the multivalue image. A code generating section 46 generates code data including each of the coded data. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an encoding device and a decoding device that detect tampering of an encoded document.

The document is required to be appropriately compressed while maintaining the legibility so that the content of the document can be confirmed, so that the user can easily handle the document. On the other hand, it is required to prevent falsification of documents including company information and personal information. For this reason, it is important to achieve both readability and prevention of tampering.
Patent Document 1 discloses a method for removing an unnecessary image portion such as a background color or show-through while suppressing deterioration of an image with respect to a color input image.
Patent Document 2 discloses a method of removing a background without leaving an isolated point even when the background is a halftone dot region.
However, none of these methods considers the detection of tamper marks.
Patent Document 3 discloses a method for authorizing an electronic document provided by a user using a cryptographic function and creating a document fingerprint.
However, the background portion necessary for tampering detection is likely to disappear when encoded at a high compression rate.

JP 2001-094804 A JP 2002-354253 A JP-A-11-338780

  The present invention has been made from the above-described background, and an object thereof is to provide an encoding device and a decoding device that effectively encode and decode a document to such an extent that tampering can be detected.

  In order to achieve the above object, a first encoding apparatus according to the present invention is generated by a binary image generating unit that generates a binary image from an input multi-valued image, and the binary image generating unit. Code generation means for generating code data by encoding a binary image and a multi-value image using different methods.

Preferably, the code generation means includes: a binary image encoding means for encoding the binary image generated by the binary image generation means; and a multi-value image encoding means for encoding a multi-value image. Have.
Preferably, the binary image encoding means applies text region encoding or generic region encoding defined in JBIG2.
Preferably, the multi-level image encoding means applies halftone region encoding defined in JBIG2 to the multi-level image.

  The second encoding device according to the present invention includes a binary image generating unit that generates a binary image from an input multi-valued image, and generates a multi-valued image different from the multi-valued image from the multi-valued image. The multi-value image generation means, the binary image generated by the binary image generation means, and the multi-value image generated by the multi-value image generation means are encoded using different methods to generate code data. Code generation means for generating.

  The third encoding apparatus according to the present invention includes a binary image generating means for generating a binary image from an input multi-valued image, and a multi-value binary conversion for converting the multi-valued image into a binary image. Code generation for generating code data by encoding the binary image generated by the means, the binary image generation means, and the binary image converted by the multi-value binary conversion means using different methods Means.

Preferably, the code generation unit generates a code data by converting the binary image converted by the multi-level binary conversion unit into a multi-level image and then encoding the binary image.
Preferably, the code generation unit converts the binary image converted by the multi-level binary conversion unit into the same multi-level image as the multi-level image before the binary image is converted.

  A fourth encoding device according to the present invention includes a binary image generating means for generating a binary image from an input multi-valued image, and generates a multi-valued image different from the multi-valued image from the multi-valued image. In the multi-value image generating means and the image composed of a plurality of layers, the binary image generated by the binary image generating means is assigned to the first layer, and the multi-value image generated by the multi-value image generating means An assigning means for assigning a value image to the second layer, a binary image assigned to the first layer by the assigning means, and a multi-value image assigned to the second layer by the assigning means are different. And code generation means for generating code data by encoding using.

  A first decoding apparatus according to the present invention includes: a receiving unit that receives code data including a binary image and a multi-valued image that are encoded by applying different methods; and the code data received by the receiving unit. Image generating means for decoding at least a multi-valued image among the included images and generating image data.

  Preferably, the image generation means decodes a multi-valued image by applying halftone region decoding defined in JBIG2.

  A second decoding apparatus according to the present invention includes: a receiving unit that receives code data including a binary image and a multi-valued image that are encoded by applying different methods; and the code data received by the receiving unit. An image generating unit that decodes a multi-valued image included and generates a binary image based on the multi-valued image, and a binary multi-value that converts the binary image generated by the image generating unit into a multi-valued image Value means.

  The third decoding apparatus according to the present invention comprises a plurality of layers, accepting means for accepting code data of an image including a binary image and a multivalued image in different layers, and accepted by the accepting means. Image generating means for decoding at least the multi-valued image of the images included in the encoded data and generating multi-valued image data.

  Preferably, the image generation further generates a binary image data by further decoding a binary image among the images included in the code data received by the receiving unit.

  A first encoding method according to the present invention generates a binary image from an input multi-valued image, encodes the generated binary image and the multi-valued image using different methods, and performs encoding. Generate data.

  The second encoding method according to the present invention generates a binary image from an input multi-value image, generates a multi-value image different from the multi-value image from the multi-value image, and generates the generated multi-value image. Code data is generated by encoding the binary image and the generated multi-value image using different methods.

  A third encoding method according to the present invention generates a binary image from an input multi-valued image, converts the multi-valued image to a binary image, and generates the generated binary image and the converted image. The binary image is encoded using a different method to generate code data.

  A fourth encoding method according to the present invention generates a binary image from an input multi-value image, generates a multi-value image different from the multi-value image from the multi-value image, and includes a plurality of layers. In the configured image, the generated binary image is assigned to a first layer, the generated multi-valued image is assigned to a second layer, and the binary image assigned to the first layer; The multi-valued image assigned to the second layer is encoded using a different method to generate code data.

  A first decoding method according to the present invention receives code data including a binary image and a multi-value image that are encoded by applying different methods, and includes at least one of images included in the received code data. The multi-valued image is decoded to generate image data.

  The second decoding method according to the present invention receives code data including a binary image and a multi-value image encoded by applying different methods, and receives a multi-value image included in the received code data. Decoding is performed to generate a binary image based on the multi-valued image, and the generated binary image is converted into a multi-valued image.

  A third decoding method according to the present invention includes a plurality of layers, accepts code data of an image including a binary image and a multi-value image in different layers, and stores the image data included in the received code data. Of these, at least the multi-value image is decoded to generate multi-value image data.

  A first program according to the present invention includes: a binary image generation step of generating a binary image from an input multivalued image in the encoding device including a computer; the generated binary image; and the multivalued image And a code generation step of generating code data by encoding using different methods.

  The second program according to the present invention includes a binary image generation step of generating a binary image from an input multivalued image in an encoding device including a computer, A multi-value image generation step for generating different multi-value images; a code generation step for generating code data by encoding the generated binary image and the generated multi-value image using different methods; Is executed by the encoding device.

  A third program according to the present invention includes a binary image generation step for generating a binary image from an input multilevel image and a multi-level image for converting the multilevel image into a binary image in an encoding device including a computer. A value binary conversion step, and a code generation step for generating code data by encoding the generated binary image and the converted binary image using different methods are executed in the encoding device. Let

  According to a fourth program of the present invention, in a coding apparatus including a computer, a binary image generating step for generating a binary image from an input multivalued image, and the multivalued image from the multivalued image are: In a multi-value image generation step for generating different multi-value images and an image composed of a plurality of layers, the generated binary image is assigned to a first layer, and the generated multi-value image is assigned to a second layer A code for generating code data by encoding a binary image assigned to the first layer and a multi-valued image assigned to the second layer using different methods; And generating the encoding step.

  A fifth program according to the present invention includes a receiving step of receiving code data including a binary image and a multi-valued image encoded by applying different methods in a decoding device including a computer, and the receiving The decoding apparatus is caused to execute an image generation step of decoding at least a multi-value image among images included in the encoded data and generating image data.

  In addition, a sixth program according to the present invention includes a receiving step of receiving code data including a binary image and a multi-valued image encoded by applying different methods in a decoding device including a computer, and the receiving An image generation step of decoding a multi-value image included in the encoded data and generating a binary image based on the multi-value image; and a binary for converting the generated binary image into a multi-value image A multi-value step is executed by the decoding device.

  Furthermore, a seventh program according to the present invention is a decoding step that includes a computer, and includes a reception step of receiving code data of an image that includes a plurality of layers and includes a binary image and a multi-value image in different layers; The decoding apparatus is caused to execute an image generation step of decoding at least a multi-value image among images included in the received code data to generate multi-value image data.

  According to the encoding device and the decoding device of the present invention, it is possible to effectively encode and decode a document to such an extent that tampering can be detected.

An encoding device 2 and a decoding device 3 according to the first embodiment of the present invention will be described.
FIG. 1 is a diagram illustrating a hardware configuration of an encoding device 2 and a decoding device 3 to which an encoding method and a decoding method according to the present invention are applied, centering on a control device 20.
As illustrated in FIG. 1, the encoding device 2 or the like includes a control device 20 including a CPU 202 and a memory 204, a communication device 22, a recording device 24 such as an HDD / CD device, an LCD display device or a CRT display device, and a keyboard. A user interface device (UI device) 26 including a touch panel and the like is included.

  The encoding device 2 and the decoding device 3 are, for example, general-purpose computers in which an encoding program 4 and a decoding program 5 described later are installed as a part of the printer driver. The encoding device 2 performs predetermined encoding processing on the multi-valued image data input via the communication device 22 or the recording device 24, and generates code data that can detect tampering. Whether the decoding device 3 acquires code data from the communication device 22 via a network (not shown), or acquires code data stored in the recording device 24, performs a decoding process, and has the document been falsified? Extract data that can detect whether or not.

FIG. 2 is a diagram showing a functional configuration of the encoding program 4 that is executed by the control device 20 and realizes the encoding method according to the present invention.
As shown in FIG. 2, the encoding program 4 includes a multi-value image receiving unit 40, a browsing image generation unit 42, a detected image generation unit 44, and a code generation unit 46. The code generation unit 46 includes a browsing image encoding unit. 460 and a detected image encoding unit 462.
Note that all or some of the functions of the encoding program 4 may be realized by hardware such as an ASIC provided in the printer apparatus 10. Further, the subsequent programs can be realized in the same manner.

  In the encoding program 4, the multi-value image receiving unit 40 inputs multi-value image data acquired via the communication device 22 or the recording device 24. The multi-value image receiving unit 40 converts the image data of the received input image into raster data (color component image) of each color component, performs screen processing on the raster data, and generates a browsing image generation unit 42 and a detection image generation Output to the unit 44.

  The browsing image generation unit 42 generates a binary image from the multi-value image input from the multi-value image reception unit 40. For example, the browsing image generation unit 42 changes the binarization threshold according to the density (gradation value) of the pixel value within a predetermined range of the multi-value image, and floats the multi-value image. Binarization processing is performed. The browsing image generation unit 42 binarizes each pixel value into black or white according to the changed threshold value, and generates a binary image. The browsing image generation unit 42 varies the threshold value up and down based on, for example, the pixel values of pixels included in an image region of 5 × 5 pixels. The browsing image generation unit 42 outputs the generated binary image to the code generation unit 46.

The browsing image generation unit 42 may generate a binary image from the multi-valued image according to a fixed threshold value, or 2 according to the density of pixel values within a predetermined range of the multi-valued image. A halftone dot image may be generated.
Further, the binarization processing by the browsing image generation unit 42 will be described in detail later.

  The detection image generation unit 44 generates a multi-value image different from the multi-value image from the multi-value image input from the multi-value image reception unit 40. The detected image generation unit 44 embeds, for example, time stamp information indicating the image creation date and time in the multi-valued image. The detection image generation unit 44 generates an image pattern that is not visible to humans based on the time stamp information, and embeds it in the background of a multi-valued image as tampering detection data. The detected image generation unit 44 outputs the generated multilevel image to the code generation unit 46.

  The detected image generation unit 44 may output the multi-value image input from the multi-value image reception unit 40 to the code generation unit 46 as it is. Further, the multi-value image receiving unit 40 may directly output the input multi-value image directly to the code generation unit 46 without using the detected image generation unit 44.

The code generation unit 46 encodes the binary image generated by the browsing image generation unit 42 and the multi-value image generated by the detection image generation unit 44 using different methods. More specifically, the code generation unit 46 encodes a binary image by applying text region coding or generic region coding defined in JBIG2, and applies halftone region coding defined in JBIG2. Then, the multi-valued image is encoded. The code generation unit 46 generates code data from these encoded data and outputs the code data to the communication device 22 or stores it in the recording device 24.
Text area coding, halftone area coding, etc. will be described in detail later.

The browsing image encoding unit 460 of the code generation unit 46 encodes a binary image by applying text region encoding or generic region encoding specified in JBIG2.
The detected image encoding unit 462 encodes the multi-level image by applying the halftone area encoding specified in JBIG2.

FIG. 3 is a diagram for explaining the binarization processing performed by the browsing image generation unit 42. FIG. 3A illustrates the relationship between the input pixel value, the floating threshold value, and the fixed threshold value. FIG. 3B illustrates a binary image generated when a fixed threshold value is used, and FIG. 3C illustrates a binary image generated when a floating threshold value is used. For example, FIG. 3D illustrates a binary image that is generated when the binary halftone processing is performed.
As illustrated in FIG. 3A, in the case of a fixed threshold value, the browsing image generation unit 42 compares the pixel value with the fixed threshold value and binarizes the pixel value. In the case of the floating threshold value, the browsing image generation unit 42 varies the threshold value up and down according to the pixel value input according to the scanning direction. In this case, the browsing image generation unit 42 changes the floating threshold value according to, for example, the average value of the pixel values included in the predetermined range, so that the floating threshold value follows the brightness of the input pixel value. To fluctuate up and down.

As illustrated in FIG. 3B, in the case of a fixed threshold value, slight brightness and dark lines, thin lines, and the like of pixel values are removed.
On the other hand, as illustrated in FIG. 3C, in the case of the floating threshold value, a thin line or the like is left, and a slight contrast of the pixel value is also expressed by black and white.

  As illustrated in FIG. 3D, when the binary halftone processing is used, the browsing image generation unit 42 corresponds to a predetermined range of density values (tone values) of the multi-valued image. Based on the binary halftone image, a binary halftone image that can be expressed in a pseudo gradation from the multivalued image is constructed to generate a binary image. Here, the size of the halftone dot corresponds to the density value.

FIG. 4 is a diagram for explaining the encoding process of the text area performed by the browsing image encoding unit 460. FIG. 4A illustrates a binary image input to the browsing image encoding unit 460. 4B illustrates an image dictionary created by the browsing image encoding unit 460, and FIG. 4C illustrates data after text region encoding.
As illustrated in FIG. 4A, the binary image is composed of binary values of black and white, and fine lines and the like are removed.

As illustrated in FIG. 4B, the browsing image encoding unit 460 registers typical patterns included in the binary image in the image dictionary, and sets an index for identifying these patterns for each pattern. To complete the image dictionary.
As illustrated in FIG. 4C, the browsing image encoding unit 460 compares the registered pattern with the pattern included in each color component image of the binary image, and associates the index with the position. Generate and encode data.

  Moreover, the browsing image encoding part 460 may encode the binary image illustrated by FIG. 4 (A) by the generic area encoding prescribed | regulated to JBIG2. Generic region coding is a method of coding a binary image without creating an image dictionary or the like. More specifically, generic region encoding encodes an input image using local pixel array statistics (for example, context).

FIG. 5 is a diagram for explaining the encoding process of the halftone region, FIG. 5A illustrates a multi-value image to be encoded, and FIG. 5B illustrates the halftone region encoding process. FIG. 5C illustrates code data generated using this image dictionary.
As illustrated in FIG. 5A, the encoding device 2 according to the present invention directly encodes a multilevel image. The browsing image encoding unit 460 registers and encodes the density value (gradation value) for each pixel of the multilevel image in the image dictionary.

As illustrated in FIG. 5B, the browsing image encoding unit 460 registers the density value of the multi-valued image in the image dictionary in association with the index. The index is identification information that uniquely identifies each density value.
When a multi-valued image is encoded using this image dictionary, code data as illustrated in FIG. 5C is generated. The code data is composed of density values (that is, indexes) of the respective areas in the multi-valued image and position information indicating positions where the density values exist.

FIG. 6 is a flowchart showing the encoding process (S10) by the encoding program 4.
As shown in FIG. 6, in step 100 (S100), when multi-value image data is input, the multi-value image receiving unit 40 converts the multi-value image data into raster data of each color component, and converts the raster data into this raster data. Screen processing is performed and output to the browsing image generation unit 42 and the detection image generation unit 44.
For the multi-valued image input from the multi-valued image receiving unit 40, the browsing image generation unit 42 varies the threshold value for binarization according to the density of pixel values within a predetermined range, for example. A binarization process is performed on the value image to generate a binary image. The browsing image generation unit 42 outputs the generated browsing binary image to the browsing image encoding unit 460 of the code generation unit 46.

  In step 102 (S102), the detection image generation unit 44 embeds time stamp information in the background of the multi-value image input from the multi-value image reception unit 40, and is different from the input multi-value image. Is generated. The detected image generation unit 44 outputs the generated multilevel image to the detected image encoding unit 462 of the code generation unit 46. The detected image generation unit 44 may output the multi-value image input from the multi-value image receiving unit 40 to the detected image encoding unit 462 as it is.

In step 104 (S104), the browsing image encoding unit 460 encodes a binary image by applying text region encoding or generic region encoding.
In step 106 (S106), the detected image encoding unit 462 encodes the multilevel image by applying halftone region encoding.
In step 108 (S108), the code generation unit 46 generates code data including the data encoded by the browsing image encoding unit 460 and the detected image encoding unit 462, and outputs the code data to the communication device 22. Or stored in the recording device 24.

FIG. 7 is a diagram showing a functional configuration of the decryption program 5 that is executed by the control device 20 and implements the decryption method according to the present invention.
As illustrated in FIG. 7, the decoding program 5 includes a code data reception unit 50 and an image generation unit 52, and the image generation unit 52 includes a browsing image decoding unit 520 and a detected image decoding unit 522.

  In the decoding program 5, the code data receiving unit 50 receives code data including a binary image and a multi-value image encoded by applying different methods via the communication device 22 or the recording device 24. These image data are output to the generation unit 52. More specifically, the code data receiving unit 50 outputs a binary image to the browsing image decoding unit 520 of the image generation unit 52 and outputs a multi-value image to the detected image decoding unit 522. Here, the binary image is an image encoded in a text region or a generic region defined in JBIG2, and the multi-valued image is an image encoded in a halftone region.

The image generation unit 52 generates image data by decoding at least the multi-valued image among the images input from the code data receiving unit 50. The image generation unit 52 decodes a binary image by applying text region decoding or generic region decoding, and decodes a multi-value image by applying halftone region decoding.
Note that the image generation unit 52 may decode only a binary image or may decode both a binary image and a multi-valued image in accordance with image browsing, falsification detection, and the like.

  The browsing image decoding unit 520 of the image generation unit 52 decodes the binary image input from the code data reception unit 50 by applying text region decoding or generic region decoding under the control of the image generation unit 52. To do. The browsing image decoding unit 520 outputs the decoded binary image to the communication device 22 or stores it in the recording device 24.

  The detected image decoding unit 522 decodes the multi-value image by applying halftone region decoding under the control of the image generation unit 52. The detected image decoding unit 522 outputs the multi-value image directly to the communication device 22 or stores it in the recording device 24.

FIG. 8 is a flowchart showing the decryption process (S20) by the decryption program 5.
As shown in FIG. 8, in step 200 (S200), the code data receiving unit 50 receives code data including an encoded binary image and a multi-valued image, and provides 2 to the browsing image decoding unit 520. A value image is output, and a multi-value image is output to the detected image decoding unit 522.

In step 202 (S202), the browsing image decoding unit 520 applies text region decoding or generic region decoding, decodes the binary image input from the code data reception unit 50, and stores it in the recording device 24 or the like. On the other hand, a binary image is output.
In step 204 (S204), the detected image decoding unit 522 applies halftone region decoding, decodes the multi-valued image, and outputs a confirmation image to the recording device 24 and the like.

  As described above, the encoding device 2 according to the present embodiment generates a binary image from an input multilevel image, and encodes the multilevel image and the generated binary image using different methods. Therefore, it is possible to efficiently encode a document having document readability and falsification detection. In addition, since the encoding device 2 generates code data by generating a multi-value image different from the multi-value image from the input multi-value image, it can generate code data with improved tamper detection. Can do. In particular, since the encoding device 2 embeds the time stamp information in the multi-valued image, it can generate code data for which effective tampering detection is performed. Furthermore, the encoding device 2 applies text region encoding or generic region encoding specified in JBIG2, encodes a binary image, applies halftone region encoding, and encodes a multi-value image. Therefore, the encoding process can be performed efficiently and at high speed.

  In addition, the decoding device 3 according to the present embodiment receives code data including a binary image and a multi-value image encoded by applying different methods, and at least multi-value among images included in the code data. Since the image data is generated by decoding the image, the processing speed at the time of tampering detection can be improved. Further, since the decoding device 3 may generate image data by encoding only a binary image among images included in the encoded data, the processing speed at the time of browsing can be improved. In addition, the decoding device 3 decodes the binary image and the multi-value image included in the received code data, generates a binary image with excellent readability, and generates a multi-value image that can be tampered with. Therefore, both readability and tampering detection can be achieved. Furthermore, the decoding device 3 decodes a binary image by applying text region decoding or generic region decoding specified in JBIG2, and decodes a multi-value image by applying halftone region decoding. Therefore, the decoding process can be performed efficiently and at high speed.

Next, an encoding device 2 and a decoding device 3 according to the second embodiment of the present invention will be described.
FIG. 9 is a diagram illustrating a functional configuration of the encoding program 6 that realizes the encoding method according to the present embodiment.
As shown in FIG. 9, the encoding program 6 includes a multi-value image receiving unit 40, a browse image generating unit 42, a detected image generating unit 44, a multi-value binary converting unit 60 and a code generating unit 66. The code generation unit 66 includes a browsing image encoding unit 460 and a detected image encoding unit 660. The detected image encoding unit 660 includes a binary multilevel conversion unit 662, a multilevel image encoding unit 664, and a binary pattern code. Including a conversion unit 666. The encoding program 6 according to the present embodiment is different from the encoding program 4 according to the first embodiment in that encoding is performed after converting a multi-value image for falsification detection into a binary image.
9 that are substantially the same as those shown in FIG. 2 are denoted by the same reference numerals.

The multilevel binary conversion unit 60 converts the multilevel image input from the detected image generation unit 44 into a binary image and outputs the binary image to the code generation unit 66. The multi-value binary conversion unit 60 converts the multi-value image into a binary image by replacing each pixel of the multi-value image with a predetermined binary pattern corresponding to the pixel value. For example, the multilevel binary conversion unit 60 replaces each pixel of the multilevel image with a binary pattern of 4 × 4 pixels.
The multi-value image receiving unit 40 directly outputs a multi-value image to the multi-value binary conversion unit 60 without using the detection image generation unit 44, and the multi-value binary conversion unit 60 The multi-valued image input from the receiving unit 40 may be converted into a binary image.

  The code generation unit 66 encodes the binary image generated by the browsing image generation unit 42 and the binary image converted by the multi-level binary conversion unit 60 using different methods to generate code data. . More specifically, the code generation unit 66 encodes the binary image generated by the browsing image generation unit 42 by applying text region encoding or generic region encoding specified in JBIG2, and specifies it in JBIG2. The binary image converted by the multilevel binary conversion unit 60 is encoded by applying the halftone region encoding. The code generation unit 66 generates code data from these encoded data and outputs the code data to the communication device 22 or stores it in the recording device 24.

The detected image encoding unit 660 encodes the binary image by applying the halftone area encoding specified in JBIG2. More specifically, the detected image encoding unit 660 generates code data by converting the binary image converted by the multi-level binary conversion unit 60 into a multi-level image and encoding the binary image. The detected image encoding unit 660 converts the binary image into a multi-value image that is the same as the multi-value image before the binary image is converted, and encodes the multi-value image and the multi-value parameter. Turn into.
The halftone area encoding process performed by the detected image encoding unit 660 will be described in detail later.

  The binary multi-value conversion unit 662 of the detected image encoding unit 660 converts the binary image input from the multi-value binary conversion unit 60 into the same multi-value as the multi-value image before the binary image is converted. Convert to image. For example, the binary multi-value conversion unit 662 converts a binary pattern in a predetermined range into a multi-value determined according to the binary pattern. The detected image encoding unit 660 outputs the converted multi-value image to the multi-value image encoding unit 664, and outputs a combination of the binary pattern and the multi-value to the binary pattern encoding unit 666 ( Multi-value parameter) is output.

The multilevel image encoding unit 664 encodes the multilevel image input from the binary multilevel conversion unit 662 by applying halftone region encoding.
The binary pattern encoding unit 666 encodes the multi-value parameter by entropy encoding or the like (Huffman encoding, arithmetic encoding, LZ encoding, or the like).

FIG. 10 is a diagram for explaining the encoding process of the halftone area. FIG. 10A illustrates an image dictionary created in the halftone area encoding process, and FIG. 10B illustrates this image. The code data produced | generated using the dictionary and its decoded image are illustrated.
As illustrated in FIG. 10A, in a binary image, when a predetermined binary pattern exists within a predetermined range, each binary pattern is associated with an index (density value) in the image dictionary. Registered in

  When an image is encoded using this image dictionary, code data as illustrated in FIG. 10B is generated. The code data is composed of density values (that is, indexes) of respective regions in the binary image and position information (grid-like positions) indicating positions where the density values exist. When this code data is decoded, the image dictionary is referred to and a decoded image is generated. More specifically, based on the density value decoded from the code data, a binary pattern registered in the image dictionary is selected, and the selected binary pattern is converted into position information decoded from the code data. Accordingly, the decoded image is generated.

FIG. 11 is a flowchart showing the encoding process (S30) by the encoding program 6. Of the processes shown in FIG. 11, processes that are substantially the same as the processes shown in FIG. 6 are denoted by the same reference numerals.
As shown in FIG. 11, a binary image for browsing and a multi-value image for tampering detection are generated from the input multi-value image in the processing of S100 to S104. The generated binary image is encoded by the browse image encoding unit 460 of the code generation unit 66 by applying text region encoding or generic region encoding. Further, the generated multi-value image is output to the multi-value binary conversion unit 60. Note that the input multi-value image may be output to the multi-value binary conversion unit 60 by the multi-value image receiving unit 40.

In step 300 (S300), the multi-value binary conversion unit 60 converts the multi-value image input from the detected image generation unit 44 into a binary image and outputs the binary image to the code generation unit 66.
In step 306 (S306), the detected image encoding unit 660 of the code generation unit 66 applies the halftone region encoding to encode the binary image input from the multi-level binary conversion unit 60. More specifically, the binary multi-value conversion unit 662 converts the binary image input from the multi-value binary conversion unit 60 into the same multi-value image as the multi-value image before the binary image is converted. And output to the multi-valued image encoding unit 664. In addition, the binary multilevel conversion unit 662 outputs a multilevel parameter to the binary pattern encoding unit 666. The multilevel image encoding unit 664 encodes the multilevel image to generate multilevel image code data, and the binary pattern encoding unit 666 encodes the multilevel parameter to generate binary pattern code data. .

  In step 308 (S308), the code generation unit 66 includes the binary image code data generated by the browsing image encoding unit 460, the multi-value image code data generated by the multi-value image encoding unit 664, and the binary pattern. Code data including the binary pattern code data generated by the encoding unit 666 is generated and output to the communication device 22 or stored in the recording device 24.

FIG. 12 is a diagram showing a functional configuration of the decryption program 7 for realizing the decryption method according to the present embodiment.
As illustrated in FIG. 12, the decoding program 7 includes a code data reception unit 50, an image generation unit 72, and a binary multi-value conversion unit 74. The image generation unit 72 includes a browsing image decoding unit 520 and a detection image decoding unit 720. The detection image decoding unit 720 includes a multi-value image decoding unit 722, a binary pattern decoding unit 724, and a binary image decoding unit 726. including.
12 that are substantially the same as those shown in FIG. 7 are denoted by the same reference numerals.

  In the decoding program 7, the image generation unit 72 decodes the multilevel image included in the code data input from the code data reception unit 50, generates a binary image based on the multilevel image, The value is output to the multivalue conversion unit 74. More specifically, the detected image decoding unit 720 of the image generation unit 72 applies halftone region decoding under the control of the image generation unit 72 to decode and encode the encoded multi-valued image. The binary pattern thus decoded is decoded, and a binary image is generated based on the decoded data.

The multi-value image decoding unit 722 of the detected image decoding unit 720 decodes the encoded multi-value image, extracts correspondence data between the binary pattern and the position, and outputs the data to the binary image decoding unit 726. To do.
The binary pattern decoding unit 724 decodes the encoded multilevel parameter, extracts the image dictionary shown in FIG. 10A, and outputs the extracted image dictionary to the binary image decoding unit 726.
The binary image decoding unit 726 refers to the image dictionary, arranges a binary pattern at each position of the image, generates a binary image, and outputs the binary image to the binary multi-value conversion unit 74.

  The binary multi-value conversion unit 74 converts the binary image input from the detected image decoding unit 720 into a multi-value image. The binary multi-value conversion unit 74 performs substantially the same processing as the binary multi-value conversion unit 662 (FIG. 9) of the encoding program 6, thereby generating a multi-value image generated by the multi-value image decoding unit 722. The same multi-valued image is generated. The binary multi-value conversion unit 74 outputs the generated multi-value image to the communication device 22 or stores it in the recording device 24.

FIG. 13 is a flowchart showing the decryption process (S40) by the decryption program 7. Of the processes shown in FIG. 13, processes that are substantially the same as those shown in FIG. 8 are denoted by the same reference numerals.
As shown in FIG. 13, code data is received in the processes of S200 to S202, and the browsing image decoding unit 520 of the image generation unit 72 applies text area decoding or generic area decoding to code data. The included binary image is decoded, and the binary image is output to the recording device 24 or the like.

In step 400 (S400), the detected image decoding unit 720 of the image generation unit 72 applies halftone region decoding to decode a multi-value image included in the code data, and based on this multi-value image. Thus, a binary image is generated and output to the binary multi-value conversion unit 74.
In step 402 (S402), the binary multi-value conversion unit 74 converts the binary image input from the detected image decoding unit 720 into a multi-value image, and outputs a confirmation image to the recording device 24 or the like. To do.

As described above, the encoding device 2 according to the present embodiment generates a binary image from an input multivalued image, converts the input multivalued image into a binary image, and generates the generated binary value. Code data is generated by encoding the image and the binary image converted by the multi-value binary conversion means using different methods. For this reason, the encoding device 2 can efficiently perform the encoding process of the halftone area defined in JBIG2.
In addition, the decoding device 3 according to the present embodiment receives code data including a binary image and a multi-value image that are encoded by applying different methods, and receives the multi-value image included in the received code data. Decoding is performed, a binary image is generated based on the multi-valued image, and the binary image is converted into a multi-valued image. For this reason, the decoding apparatus 3 can efficiently perform the decoding process of the halftone area defined in JBIG2.

Next, an encoding device 2 and a decoding device 3 according to the third embodiment of the present invention will be described.
FIG. 14 is a diagram showing a functional configuration of the encoding program 8 that realizes the encoding method according to the present embodiment.
As shown in FIG. 14, the encoding program 8 includes a multi-value image receiving unit 40, a browsing image generation unit 42, a detection image generation unit 44, an allocation unit 80, and a code generation unit 86. An image encoding unit 860 and a detected image encoding unit 862 are included. The encoding program 8 according to the present embodiment assigns the generated binary image to the first layer of an image composed of a plurality of layers, assigns the generated multi-valued image to the second layer, It differs from the encoding program 4 according to the first embodiment in that each layer image is encoded using a different method.
14 that are substantially the same as those shown in FIG. 2 are denoted by the same reference numerals.

  In the encoding program 8, the assigning unit 80 assigns the binary image generated by the browsing image generating unit 42 to the first layer in the image composed of a plurality of layers, and is generated by the detected image generating unit 44. A multi-valued image is assigned to the second layer. The image composed of a plurality of layers is an MRC (Mixed Raster Content) format image, and the assigning unit 80 generates an MRC format image from the input image and outputs the generated image to the code generation unit 86. .

The code generator 86 encodes the binary image assigned to the first layer of the MRC format image by the assigning unit 80 and the multi-valued image assigned to the second layer by using different methods. Generate data.
The browsing image encoding unit 860 applies, for example, text region encoding or generic region encoding specified in JBIG2 under the control of the code generation unit 86 to encode the binary image assigned to the first layer. Turn into.
The detected image encoding unit 862 encodes a multi-valued image assigned to the second layer by applying an encoding method based on, for example, JPEG2000 under the control of the code generation unit 86.

FIG. 15 is a flowchart showing the encoding process (S50) by the encoding program 8. Note that among the processes shown in FIG. 15, processes that are substantially the same as the processes shown in FIG. 6 are denoted by the same reference numerals.
As shown in FIG. 15, in the processes of S <b> 100 to S <b> 102, a browsing binary image and a tampering detection multi-value image are generated from the input multi-value image. Each of the generated images is output to the assigning unit 80. Note that the input multi-value image may be directly output to the assigning unit 80 by the multi-value image receiving unit 40.

In step 500 (S500), the assigning unit 80 assigns a binary image to the first layer, assigns a multi-valued image to the second layer, generates an image in the MRC format, and sends it to the code generating unit 86. Output.
In step 504 (S504), the browse image encoding unit 860 of the code generation unit 86 is assigned to the first layer by applying, for example, text region encoding or generic region encoding specified in JBIG2. The value image is encoded.
In step 506 (S506), the detected image encoding unit 862 of the code generation unit 86 encodes the multilevel image assigned to the second layer by applying an encoding method based on, for example, JPEG2000.

  In step 508 (S508), the code generation unit 86 generates code data including the binary image code data generated by the browsing image encoding unit 860 and the multi-value image code data generated by the detected image encoding unit 862. The data is output to the communication device 22 or stored in the recording device 24.

FIG. 16 is a diagram illustrating a functional configuration of the decryption program 9 that realizes the decryption method according to the present embodiment.
As illustrated in FIG. 16, the decoding program 9 includes a code data receiving unit 50, an image generation unit 92, and a synthesis unit 90. The image generation unit 92 includes a browsing image decoding unit 920 and a detected image decoding unit 922. Including.
16 that are substantially the same as those shown in FIG. 7 are denoted by the same reference numerals.

  In the decoding program 9, the image generation unit 92 is code data composed of a plurality of layers, and at least many of the images included in the code data of an image including a binary image and a multilevel image in different layers. A multi-valued image is generated by decoding the value image. Furthermore, the image generation unit 92 may generate a binary image by further decoding a binary image among images included in the code data. The image generation unit 92 may generate only a binary image when the image is browsed, or may generate only a multi-valued image when alteration of the image is detected. The image generation unit 92 outputs the generated binary image and multi-valued image to the synthesis unit 90, and further outputs them to the communication device 22 or stores them in the recording device 24.

The browsing image decoding unit 920 decodes the binary image by applying, for example, text region decoding or generic region decoding specified in JBIG2 under the control of the image generation unit 92.
The detected image decoding unit 922 decodes the multi-valued image by applying a decoding method based on, for example, JPEG2000 under the control of the image generation unit 92.

  The synthesizing unit 90 assigns the binary image and the multi-valued image input from the image generating unit 92 to different layers of the MRC format image to generate an MRC format image (synthesized image), and the communication device 22. Or stored in the recording device 24.

FIG. 17 is a flowchart showing the decryption process (S60) by the decryption program 9. Of the processes shown in FIG. 17, processes that are substantially the same as the processes shown in FIG. 8 are denoted by the same reference numerals.
As shown in FIG. 17, in the process of S <b> 200, code data is accepted and output to the image generation unit 92.

In step 602 (S602), the browsing image decoding unit 920 of the image generation unit 92 decodes the binary image by applying, for example, text region decoding or generic region decoding defined in JBIG2. The image generating unit 92 outputs the generated binary image to the synthesizing unit 90, and further outputs it to the communication device 22 or stores it in the recording device 24.
In step 604 (S602), the detected image decoding unit 922 of the image generation unit 92 decodes the multi-valued image by applying a decoding method based on, for example, JPEG2000. The image generation unit 92 outputs the generated multi-value image to the synthesis unit 90, and further outputs it to the communication device 22 or stores it in the recording device 24.

In step 606 (S606), the synthesizing unit 90 assigns the binary image and the multi-valued image input from the image generating unit 92 to different layers of the MRC format image, and the MRC format image (synthesized image). Generated and output to the communication device 22 or stored in the recording device 24.
In addition, when each image is stored in the recording device 24, the image is appropriately read and displayed on the UI device 26 of the decoding device 3, or output to the printer device 10 and printed on a recording medium.

As described above, the encoding device 2 according to the present embodiment generates a binary image from the input multi-value image, generates a multi-value image different from the multi-value image from the multi-value image, In an image composed of a plurality of layers, the generated binary image is assigned to the first layer, the generated multi-valued image is assigned to the second layer, and the binary image assigned to the first layer The multilevel image assigned to the second layer is encoded using a different method to generate code data. For this reason, the encoding device 2 can generate code data that can be processed at high speed during browsing and when tampering is detected.
In addition, the decoding device 3 according to the present embodiment includes a plurality of layers, receives code data of an image including a binary image and a multi-value image in different layers, and stores the image data included in the received code data. Among them, since at least the multi-valued image is decoded to generate the multi-valued image, it is possible to perform processing at the time of tampering detection at high speed. Furthermore, since the decoding device 3 generates a binary image by decoding only the binary image among the images included in the code data, the processing during browsing can be performed at high speed.

It is a figure which illustrates the hardware constitutions of the encoding apparatus 2 and the decoding apparatus 3 to which the encoding method and decoding method concerning this invention are applied centering on the control apparatus 20. FIG. It is a figure which shows the function structure of the encoding program 4 which implement | achieves the encoding method concerning the 1st Embodiment of this invention. FIG. 3A illustrates a binarization process performed by the browsing image generation unit 42. FIG. 3A illustrates the relationship between an input pixel value, a floating threshold value, and a fixed threshold value. B) illustrates a binary image generated when a fixed threshold is used, and FIG. 3C illustrates a binary image generated when a floating threshold is used. 3 (D) exemplifies a binary image generated when a binary halftone dot conversion process is performed. FIG. 4A is a diagram illustrating a text area encoding process performed by the browsing image encoding unit 460. FIG. 4A illustrates a binary image input to the browsing image encoding unit 460, and FIG. B) illustrates an image dictionary created by the browsing image encoding unit 460, and FIG. 4C illustrates data after text region encoding. FIGS. 5A and 5B are diagrams illustrating a halftone area encoding process. FIG. 5A illustrates a multi-value image to be encoded, and FIG. 5B is created in the halftone area encoding process. An image dictionary is illustrated, and FIG. 5C illustrates code data generated using the image dictionary. It is a flowchart which shows the encoding process (S10) by the encoding program 4. It is a figure which shows the function structure of the decoding program 5 which implement | achieves the decoding method concerning the 1st Embodiment of this invention. It is a flowchart which shows the decoding process (S20) by the decoding program 5. FIG. It is a figure which shows the function structure of the encoding program 6 which implement | achieves the encoding method concerning the 2nd Embodiment of this invention. FIG. 10A illustrates an image dictionary created in the halftone area encoding process, and FIG. 10B uses this image dictionary. The generated code data and its decoded image are illustrated. It is a flowchart which shows the encoding process (S30) by the encoding program 6. FIG. It is a figure which shows the function structure of the decoding program 7 which implement | achieves the decoding method concerning the 2nd Embodiment of this invention. It is a flowchart which shows the decoding process (S40) by the decoding program 7. FIG. It is a figure which shows the function structure of the encoding program 8 which implement | achieves the encoding method concerning the 3rd Embodiment of this invention. It is a flowchart which shows the encoding process (S50) by the encoding program 8. FIG. It is a figure which shows the function structure of the decoding program 9 which implement | achieves the decoding method concerning the 3rd Embodiment of this invention. It is a flowchart which shows the decoding process (S60) by the decoding program 9. FIG.

Explanation of symbols

2 ... Encoding device 10 ... Printer device 20 ... Control device 202 ... CPU
204 ... Memory 22 ... Communication device 24 ... Recording device 26 ... UI device 3 ... Decoding device 4 ... Encoding program 40 ... Multi-valued image receiving unit 42 ... Browsing image generation unit 44... Detection image generation unit 46... Code generation unit 460 .. browsing image encoding unit 462... Detection image encoding unit 5. Reception unit 52 ... Image generation unit 520 ... Browsing image decoding unit 522 ... Detected image decoding unit 6 ... Encoding program 60 ... Multi-level binary conversion unit 66 ... Code generation 660... Detected image encoding unit 662... Binary multilevel conversion unit 664... Multilevel image encoding unit 666... Binary pattern encoding unit 7. Image generation unit 720 ... Detected image decoding unit 722 Multi-level image decoding unit 724 ... Binary pattern decoding unit 726 ... Binary image decoding unit 74 ... Binary multi-level conversion unit 8 ... Encoding program 80 ... Allocation unit 86 ... Code generation unit 860 ... browsing image encoding unit 862 ... detected image encoding unit 9 ... decoding program 90 ... synthesis unit 92 ... image generation unit 920 ... browsing image decoding 922... Detected image decoding unit

Claims (28)

Binary image generating means for generating a binary image from the input multi-valued image;
An encoding apparatus comprising: a code generation unit that encodes a binary image generated by the binary image generation unit and a multi-level image using different methods to generate code data. The code generation means includes
Binary image encoding means for encoding the binary image generated by the binary image generation means;
The encoding apparatus according to claim 1, further comprising: a multi-level image encoding unit that encodes the multi-level image. The encoding apparatus according to claim 2, wherein the binary image encoding means applies text region encoding or generic region encoding specified in JBIG2. The encoding device according to claim 2 or 3, wherein the multi-level image encoding means applies halftone region encoding defined in JBIG2 to the multi-level image. Binary image generating means for generating a binary image from the input multi-valued image;
A multi-value image generating means for generating a multi-value image different from the multi-value image from the multi-value image;
Code generation means for generating code data by encoding the binary image generated by the binary image generation means and the multi-value image generated by the multi-value image generation means using different methods. Encoding device. Binary image generating means for generating a binary image from the input multi-valued image;
Multi-value binary conversion means for converting the multi-value image into a binary image;
Code generation means for generating code data by encoding the binary image generated by the binary image generation means and the binary image converted by the multi-value binary conversion means using different methods. An encoding device having. The encoding device according to claim 6, wherein the code generation unit generates code data by encoding the binary image converted by the multi-level binary conversion unit after converting the binary image into a multi-level image. The code generation means converts the binary image converted by the multi-value binary conversion means into a multi-value image identical to the multi-value image before the binary image is converted. Encoding device. Binary image generating means for generating a binary image from the input multi-valued image;
A multi-value image generating means for generating a multi-value image different from the multi-value image from the multi-value image;
In an image composed of a plurality of layers, the binary image generated by the binary image generating means is assigned to the first layer, and the multi-value image generated by the multi-value image generating means is assigned to the second layer. Assigning means to assign;
Code generation for generating code data by encoding the binary image assigned to the first layer by the assigning means and the multi-valued image assigned to the second layer by the assigning means using different methods And a coding device. Receiving means for receiving code data including a binary image and a multi-value image encoded by applying different methods;
A decoding apparatus comprising: an image generation unit configured to decode at least a multi-valued image among images included in the code data received by the reception unit and generate image data. The decoding device according to claim 10, wherein the image generation means decodes a multi-valued image by applying halftone region decoding defined in JBIG2. Receiving means for receiving code data including a binary image and a multi-value image encoded by applying different methods;
Image generating means for decoding a multi-valued image included in the code data received by the receiving means, and generating a binary image based on the multi-valued image;
A decoding apparatus comprising: binary multi-value means for converting the binary image generated by the image generation means into a multi-value image. A receiving unit configured to receive code data of an image including a plurality of layers and including a binary image and a multi-valued image in different layers;
A decoding device comprising: image generation means for decoding at least a multi-value image among images included in the code data received by the reception means to generate multi-value image data. The decoding apparatus according to claim 13, wherein the image generation further generates a binary image data by further decoding a binary image among images included in the code data received by the receiving unit. Generate a binary image from the input multi-valued image,
An encoding method for generating code data by encoding the generated binary image and the multi-valued image using different methods. Generate a binary image from the input multi-valued image,
From this multi-value image, a multi-value image different from the multi-value image is generated,
An encoding method for generating code data by encoding the generated binary image and the generated multi-valued image using different methods. Generate a binary image from the input multi-valued image,
Convert this multi-valued image into a binary image,
An encoding method for generating code data by encoding the generated binary image and the converted binary image using different methods. Generate a binary image from the input multi-valued image,
From this multi-value image, a multi-value image different from the multi-value image is generated,
In an image composed of a plurality of layers, the generated binary image is assigned to a first layer, the generated multi-valued image is assigned to a second layer,
An encoding method for generating code data by encoding a binary image assigned to the first layer and a multi-value image assigned to the second layer using different methods. Accepts encoded data including a binary image and a multi-valued image encoded by applying different methods;
A decoding method for generating image data by decoding at least a multi-valued image of images included in the received code data. Accepts encoded data including a binary image and a multi-valued image encoded by applying different methods;
Decoding a multi-value image included in the received code data, and generating a binary image based on the multi-value image;
A decoding method for converting the generated binary image into a multi-valued image. Accepts code data of an image composed of a plurality of layers and including a binary image and a multi-value image in different layers,
A decoding method for generating multi-value image data by decoding at least a multi-value image among images included in the received code data. In an encoding device including a computer,
A binary image generation step of generating a binary image from the input multi-valued image;
A program that causes the encoding apparatus to execute a code generation step of generating code data by encoding the generated binary image and multi-valued image using different methods. In an encoding device including a computer,
A binary image generation step of generating a binary image from the input multi-valued image;
A multi-value image generation step for generating a multi-value image different from the multi-value image from the multi-value image,
A program that causes the encoding device to execute a code generation step of generating code data by encoding the generated binary image and the generated multi-valued image using different methods. In an encoding device including a computer,
A binary image generation step of generating a binary image from the input multi-valued image;
A multi-value binary conversion step for converting the multi-value image into a binary image;
A program that causes the encoding apparatus to execute a code generation step of generating code data by encoding the generated binary image and the converted binary image using different methods. In an encoding device including a computer,
A binary image generation step of generating a binary image from the input multi-valued image;
A multi-value image generation step for generating a multi-value image different from the multi-value image from the multi-value image,
An assigning step of assigning the generated binary image to a first layer and assigning the generated multi-valued image to a second layer in an image composed of a plurality of layers;
A code generation step of generating code data by encoding the binary image assigned to the first layer and the multi-value image assigned to the second layer using different methods; A program to be executed by a device. In a decoding device including a computer,
A reception step of receiving code data including a binary image and a multi-value image encoded by applying different methods;
A program that causes the decoding device to execute an image generation step of decoding at least a multi-value image among images included in the received code data to generate image data. In a decoding device including a computer,
A reception step of receiving code data including a binary image and a multi-value image encoded by applying different methods;
An image generation step of decoding a multi-valued image included in the received code data and generating a binary image based on the multi-valued image;
A program that causes the decoding device to execute a binary multi-value step of converting the generated binary image into a multi-value image. In a decoding device including a computer,
An accepting step for receiving code data of an image composed of a plurality of layers and including a binary image and a multi-valued image in different layers;
A program that causes the decoding apparatus to execute an image generation step of decoding at least a multi-value image among images included in the received code data to generate multi-value image data.

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