JP2009284092A - Image encoding device, image encoding method, image encoding program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image encoding device which significantly reduces data capacity while minimizing deterioration in picture quality in encoding an image, and to provide an image encoding method, an image encoding program, and a recording medium. <P>SOLUTION: A first mask image is generated by enlarging a first area including a predetermined element in an area-separated image, and a select image is generated including a first area obtained by reducing the first area in the first mask image and a second area other than the reduced area in the first mask image. A second mask image is generated by enlarging the second area in the select image; and a first reproduction image is generated by using an image which corresponds to the first area in the first mask image among images to be processed, and a second reproduction image is generated using an image which corresponds to the second area in the second mask image among images to be processed, thereby generating first encoded data generated by encoding the first reproduction image and second encoded data generated by encoding the second reproduction image. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image encoding device, an image encoding method, an image encoding program, and a recording medium, and in particular, an image encoding device, an image encoding method, an image encoding program, and a recording medium that process an image for each of a plurality of layers. It relates to the medium.

  In recent years, many techniques for efficiently reducing the volume of image data in which a plurality of different elements such as characters and photographs are arranged have been disclosed. In the following, for example, an area in an image where elements such as characters and photographs are displayed is also referred to as an image area.

  Japanese Patent Laid-Open No. 2004-187000 (Patent Document 1) describes ITU-T Recommendation T.30. 44, a technique based on MRC (Mixed Raster Content) (hereinafter also referred to as a first prior art) is disclosed.

  In MRC, image data composed of a plurality of different image areas indicating characters, lines, photographs, and the like is separated into a total of three planes: a foreground plane, a background plane, and a mask plane. Here, the mask plane is a plane indicating which of the foreground plane and the background plane is selected. In MRC, a method for individually coding three-layer planes is defined.

  In general, in an image encoding apparatus that uses MRC, a mask plane that is information for selecting a foreground plane representing characters and lines and a background plane representing a photograph or the like is configured in units of pixels.

In addition, in an image encoding apparatus using MRC, holding of shape information of characters and lines at high resolution is left to a mask plane to perform lossless encoding at high resolution. In many cases, the foreground plane that holds the color information of characters and lines and the background plane such as a photograph in which deterioration due to a decrease in resolution is not noticeable are irreversibly encoded at a lower resolution than the mask plane.
JP 2004-187000 A

  In the first prior art, retention of character and line shape information is left to the mask plane. Therefore, when coding a mask plane, it is necessary to have high resolution and reversibility, and thus a large amount of data capacity is required to hold the mask plane.

  The present invention has been made to solve the above-described problems, and its object is to significantly reduce the data capacity while minimizing the deterioration of image quality in the image encoding process. An image encoding device, an image encoding method, an image encoding program, and a recording medium are provided.

  In order to solve the above-described problem, an image encoding device according to an aspect of the present invention includes a processing target image, a first region where a predetermined element in the processing target image exists, and a predetermined element in the processing target image. An acquisition unit that acquires a region separation image indicating a second region that does not exist, and a first mask that generates a first mask image that is an image obtained by expanding the first region in the region separation image at a first predetermined ratio. The first area in the first mask image is reduced to a first area in the first mask image, and the area other than the reduced first area in the first mask image is the second area. Select image generation means for generating a select image that is an image as an area, and second mask generation means for generating a second mask image that is an image obtained by expanding the second area in the select image at a second predetermined ratio Among the images to be processed, A first reproduction image generating means for generating a first reproduction image for reproducing the image, the image generated using an image corresponding to the first region in the image, and among the processing target images A second reproduction image generating means for generating a second reproduction image for reproducing the image, the image being generated using an image corresponding to the second region in the second mask image; By performing an encoding process for encoding the reproduction image, the second reproduction image, and the select image, the first encoded data obtained by encoding the first reproduction image and the second encoded image obtained by encoding the second reproduction image. Encoding means for generating 2 encoded data and 3rd encoded data obtained by encoding the select image. In the image obtained by decoding the first encoded data, the image quality of the image corresponding to the first region in the select image is the same as that in the select image in the image obtained by decoding the second encoded data. Higher than the image quality of the image corresponding to the second region. When an image is reproduced using the first encoded data and the second encoded data, an image of a portion corresponding to the first region in the select image in the image obtained by decoding the first encoded data Then, in the image obtained by decoding the second encoded data, the image is reproduced by using the portion of the image corresponding to the second area in the select image.

  Preferably, the encoding process performed on each of the first reproduction image and the second reproduction image is an irreversible encoding process.

  Preferably, the encoding unit performs the encoding process with a compression rate for the second reproduction image higher than that for the first reproduction image.

  Preferably, the first mask generation unit eliminates the second region included in the first region in the region separation image when the second region is included in the first region in the region separation image. Is generated.

  Preferably, the image processing apparatus further includes resolution conversion means for converting the resolution of at least one of the first reproduction image and the second reproduction image.

Preferably, the predetermined element is a character.
According to another aspect of the present invention, an image encoding method executed by an image encoding apparatus includes a processing target image, a first region where a predetermined element in the processing target image exists, and a predetermined element in the processing target image. Obtaining a region separation image indicating a second region in which no image exists, generating a first mask image that is an image obtained by expanding the first region in the region separation image by a first predetermined ratio, An image in which the first area in the first mask image is defined as the first area, and the area other than the reduced first area in the first mask image is defined as the second area. Generating a select image, generating a second mask image that is an image obtained by expanding the second region in the select image at a second predetermined ratio, and out of the processing target images, the first mask The image corresponding to the first area in the image Using the image corresponding to the second region in the second mask image of the processing target image, and a step of generating a first reproduction image for reproducing the image. A step of generating a second reproduction image for reproducing the image and an encoding process for encoding the first reproduction image, the second reproduction image, and the select image. Generating first encoded data obtained by encoding the first image for reproduction, second encoded data obtained by encoding the second image for reproduction, and third encoded data obtained by encoding the select image; Is provided. In the image obtained by decoding the first encoded data, the image quality of the image corresponding to the first region in the select image is the same as that in the select image in the image obtained by decoding the second encoded data. Higher than the image quality of the image corresponding to the second region. When an image is reproduced using the first encoded data and the second encoded data, an image of a portion corresponding to the first region in the select image in the image obtained by decoding the first encoded data Then, in the image obtained by decoding the second encoded data, the image is reproduced by using the portion of the image corresponding to the second area in the select image.

  According to still another aspect of the present invention, an image encoding program executed by a computer includes a processing target image, a first region in which a predetermined element in the processing target image exists, and a predetermined element in the processing target image. Obtaining a region separation image indicating a second region that is not to be performed; generating a first mask image that is an image obtained by expanding the first region in the region separation image at a first predetermined ratio; This is an image in which the first area in the mask image is defined as an area reduced at a first predetermined ratio as the first area, and an area other than the reduced first area in the first mask image is set as the second area. A step of generating a select image; a step of generating a second mask image that is an image obtained by expanding a second region in the select image at a second predetermined ratio; In the first area of An image generated using the corresponding image, the step of generating a first reproduction image for reproducing the image, and an image corresponding to the second region in the second mask image among the processing target images A second reproduction image for reproducing the image, and an encoding process for encoding the first reproduction image, the second reproduction image, and the select image. By performing, the first encoded data obtained by encoding the first reproduction image, the second encoded data obtained by encoding the second reproduction image, and the third encoded data obtained by encoding the select image are generated. And a step of performing. In the image obtained by decoding the first encoded data, the image quality of the image corresponding to the first region in the select image is the same as that in the select image in the image obtained by decoding the second encoded data. Higher than the image quality of the image corresponding to the second region. When an image is reproduced using the first encoded data and the second encoded data, an image of a portion corresponding to the first region in the select image in the image obtained by decoding the first encoded data Then, in the image obtained by decoding the second encoded data, the image is reproduced by using the portion of the image corresponding to the second area in the select image.

  According to still another aspect of the present invention, the recording medium is a medium on which an image encoding program is recorded.

  An image encoding device, an image encoding method, an image encoding program, and a recording medium according to the present invention generate a first mask image in which a first region in which a predetermined element in a region separation image is present is expanded, A select image is generated in which a region obtained by reducing the first region in the mask image is defined as a first region, and a region other than the reduced first region in the first mask image is defined as a second region, and a second image in the select image is generated. A second mask image in which the region is expanded is generated, and a first reproduction image is generated using an image corresponding to the first region in the first mask image among the processing target images, and among the processing target images, A second reproduction image is generated using an image corresponding to the second region in the second mask image, and the first encoded data obtained by encoding the first reproduction image and the second reproduction image are encoded. The second encoded data is generated. In the image obtained by decoding the first encoded data, the image quality of the image corresponding to the first area in the select image is the same as the second area in the select image in the image obtained by decoding the second encoded data. It is higher than the image quality of the part corresponding to. When the image is reproduced, in the image obtained by decoding the first encoded data, in the image corresponding to the first area in the select image and in the image obtained by decoding the second encoded data, the select image The image is reproduced by using the portion corresponding to the second region in the image.

  Therefore, it is possible to greatly reduce the data capacity while minimizing the deterioration of the image quality in the image encoding process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<First Embodiment>
FIG. 1 is a block diagram showing an internal configuration of an image coding apparatus 500 in the first embodiment. The image coding apparatus 500 is a PC (Personal Computer). Note that the image coding apparatus 500 is not limited to a PC and may be any apparatus as long as it has an arithmetic function.

  FIG. 1 also shows a recording medium 555 for explanation. A recording medium 555 stores a program 180 described later. That is, the program 180 is recorded on a medium or the like and distributed as a program product. The recording medium 555 is also distributed as a program product.

  Referring to FIG. 1, image coding apparatus 500 includes a display unit 530, a control unit 510, and a storage unit 520.

  The display unit 530 has a function of displaying characters, images, and the like. Display unit 530 is provided with a display surface for displaying characters, images, and the like. The display unit 530 is a device using an LCD panel (Liquid Crystal Display Panel). Note that the display unit 530 may be a device using a panel of a display method other than the above. The resolution of the display surface of the display unit 530 is horizontal 480 (dots) × vertical 640 (dots). Note that the resolution of the display surface of the display unit 530 is not limited to horizontal 480 (dots) × vertical 640 (dots), and may be other resolutions.

  The storage unit 520 is a memory that stores data in a nonvolatile manner. The storage unit 520 is accessed by the control unit 510. The storage unit 520 is, for example, a flash memory or a hard disk. The storage unit 520 stores a program 180 and other various data.

  Control unit 510 has a function of performing various types of processing, arithmetic processing, and the like for each unit in image coding apparatus 500 in accordance with program 180 stored in storage unit 520. Control unit 510 is a CPU (Central Processing Unit). Control unit 510 is not limited to a CPU, and may be another circuit having an arithmetic function.

  Control unit 510 performs data communication with display unit 530. Control unit 510 causes display unit 530 to display the generated image.

The image encoding device 500 further includes a recording medium access unit 550.
The recording medium access unit 550 can access data to the recording medium 555 when the recording medium 555 is inserted (attached) to the image encoding device 500. As a result, the recording medium access unit 550 can read the program 180 from the recording medium 555 on which the program 180 is recorded.

  The program 180 stored in the recording medium 555 is read by the recording medium access unit 550 by the installation process of the control unit 510, and the control unit 510 stores the program 180 in the storage unit 520.

  The recording medium 555 is an SD (Secure Digital) memory card. Note that the recording medium 555 is not limited to the SD memory card, and may be another medium capable of recording data in a nonvolatile manner.

The image encoding device 500 further includes a communication unit 560.
Communication unit 560 performs data communication with control unit 510. Further, the communication unit 560 has a function of performing data communication with the external device 600 in a wired or wireless manner.

  FIG. 2 is a functional block diagram of the control unit 510 according to the first embodiment. For the sake of explanation, FIG. 2 also shows the external device 600, the storage unit 520, and data stored in the storage unit 520 by an image encoding process to be described later.

  Referring to FIG. 2, control unit 510 includes acquisition unit 511, first mask generation unit 512A, select image generation unit 513, second mask generation unit 512B, first reproduction image generation unit 514A, A second reproduction image generation unit 514B and an encoding unit 515 are included.

  An acquisition unit 511, a first mask generation unit 512A, a select image generation unit 513, a second mask generation unit 512B, a first reproduction image generation unit 514A, a second reproduction image generation unit 514B, and a code included in the control unit 510 All or part of the conversion unit 515 may be configured by independent hardware (for example, an arithmetic circuit). Also included in the control unit 510 are an acquisition unit 511, a first mask generation unit 512A, a select image generation unit 513, a second mask generation unit 512B, a first reproduction image generation unit 514A, and a second reproduction image generation unit 514B. All or part of the encoding unit 515 may be a module of a program executed by the control unit 510.

  An acquisition unit 511, a first mask generation unit 512A, a select image generation unit 513, a second mask generation unit 512B, a first reproduction image generation unit 514A, a second reproduction image generation unit 514B, and a code included in the control unit 510 The processing performed by each of the conversion units 515 will be described later.

(Encoding process)
Next, specific processing contents of the image coding apparatus 500 according to the first embodiment will be described. In the image encoding device 500, the following image encoding process is performed. Hereinafter, an image to be processed by the image coding apparatus 500 is also referred to as a processing target image. Further, the processing target image data is also referred to as processing target image data. Here, it is assumed that the external device 600 stores processing target image data (hereinafter also referred to as processing target image data). When there is a request for processing target image data, the external device 600 transmits the processing target image data to the device that issued the request.

  FIG. 3 is a flowchart of the image encoding process. Referring to FIG. 3, in the image encoding process, first, the process of step S111 is performed.

  In step S111, an image data acquisition process is performed. In the image data acquisition process, the acquisition unit 511 requests the external device 600 for processing target image data. The external device 600 transmits the processing target image data to the image encoding device 500 in response to the request for the processing target image data. The acquisition unit 511 receives the processing target image data. Here, it is assumed that the processing target image indicated by the received processing target image data is the following processing target image G100. Then, the acquisition unit 511 stores the received processing target image data in the storage unit 520. And the process of step S111 is complete | finished.

  FIG. 4 is a diagram illustrating an image used or generated in the image encoding process. With reference to FIG. 4, the processing target image G <b> 100 is an image showing characters and buildings as an example. Hereinafter, an area where characters exist in an image is also referred to as a character area. The character area in the image is represented by an area composed of a plurality of black pixels. In the following, a region where no character exists in the image is also referred to as a non-character region. The non-character area in the image is expressed by an area composed of a plurality of white pixels.

  In the following, an image showing a character region and a non-character region in the processing target image is referred to as a region separation image. The region separation image is a binary image expressed in binary (for example, “0”, “1”). Note that the region separation image is not limited to characters, and may be an image showing regions where elements other than characters exist and regions where elements other than characters exist. When the processing target image is the processing target image G100, the region separation image is the region separation image RG100.

  The region separation image RG100 shows a character region CR10 in the corresponding processing target image G100 and a non-character region BR10 in the corresponding processing target image G100. The resolution of the region separation image RG100 is the same as the resolution of the processing target image G100. The plurality of pixels constituting the region separation image RG100 correspond to the plurality of pixels constituting the processing target image G100, respectively. Note that the resolution of the region separation image RG100 may be lower than the resolution of the processing target image G100.

  Of the plurality of pixels in the character region CR10, the color of the pixels excluding some pixels is expressed in black. The black pixel value in the character region CR10 is “0”. The color of the pixel in the non-character region BR10 is expressed in white. The white pixel value in the non-character region BR10 is “1”. A region composed of a plurality of white pixels in the character region CR10 is a non-character region.

  The region separation image may be an image in which the user sets a character region and a non-character region by operating the mouse or the like. Further, the region separation image may be an image generated by a method for determining whether or not a character exists, which is disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-129456.

  It is assumed that data of the region separation image (hereinafter also referred to as region separation image data) is stored in the external device 600. When there is a request for region separation image data, the external device 600 transmits the region separation image data to the device that issued the request.

  The data format of the region separation image data is not limited as long as it is not data indicating a region separation image but data indicating a character region and a non-character region. The area separation image data may be data indicating a character area and a non-character area by coordinates, for example.

Referring to FIG. 3 again, after the process of step S111, the process proceeds to step S112.
In step S112, region separation image data acquisition processing is performed. In the region separation image data acquisition process, the acquisition unit 511 requests the external device 600 for region separation image data. The external device 600 transmits the region separated image data to the image encoding device 500 in response to the request for the region separated image data. Then, the acquisition unit 511 receives the region separation image data. Here, it is assumed that the image indicated by the received region separated image data is the region separated image RG100 in FIG.

  Then, the acquisition unit 511 causes the storage unit 520 to store the received region separation image data. Then, the process proceeds to step S113. Note that the processing target image data and the region separation image data may be received from two different devices.

  In step S113, a first mask generation process is performed. In the first mask generation process, the first mask generation unit 512A reads the region separation image data from the storage unit 520. Then, the first mask generation unit 512A generates an image (hereinafter also referred to as a first mask image) obtained by expanding the character region in the region separation image indicated by the region separation image data at a first predetermined ratio. The first mask image is a binary image expressed in binary (for example, “0”, “1”). The first predetermined ratio is assumed to be 10%, for example. Note that the character region in the region separation image is expanded in a state where the center position of the character region is fixed.

  When a non-character area is included in the character area in the area separation image, if the non-character area is smaller than a predetermined size, the non-character area in the character area is eliminated by the extension process by the first mask generation process It will be. In the present embodiment, it is assumed that the non-character area in the character area CR10 is smaller than a predetermined size. In this case, the non-character region in the region CR10 disappears due to the extension process by the first mask generation process, and the first mask image RG101 is generated.

  The first mask generation unit 512A eliminates the non-character area regardless of the size of the non-character area in the character area when the non-character area is included in the character area in the area separation image. One mask image may be generated.

  Then, the first mask generation unit 512A causes the storage unit 520 to store the generated first mask image data (hereinafter also referred to as first mask image data). And the process of step S113 is complete | finished.

  Here, it is assumed that the region separation image indicated by the region separation image data is the region separation image RG100 in FIG. In this case, the first mask image generated by the first mask generation process is the first mask image RG101 in FIG. The resolution of the first mask image RG101 is the same as the resolution of the processing target image G100. The plurality of pixels constituting the first mask image RG101 correspond to the plurality of pixels constituting the processing target image G100, respectively. Note that the resolution of the first mask image RG101 may be lower than the resolution of the processing target image G100.

  First mask image RG101 shows character region CR10A in which character region CR10 in region separation image RG100 is expanded at the first predetermined ratio. Note that the first mask image RG101 generated by the first mask generation processing shows a character region CR10A in which the non-character region included in the character region CR10A in the region separation image RG100 is eliminated.

  Further, by expanding the character region CR10 in the region separation image RG100, the first mask image RG101 shows a non-character region BR10A in which the non-character region BR10 in the region separation image RG100 is reduced.

Referring to FIG. 3 again, after the process of step S113, the process proceeds to step S114.
In step S114, select image data generation processing is performed. In the select image data generation process, the select image generation unit 513 reads the first mask image data from the storage unit 520. Then, the select image generation unit 513 sets the character area in the first mask image indicated by the first mask image data as the character area as the area reduced by the first predetermined ratio, and the first mask image data indicates the first area. A select image in which an area other than the reduced character area in the mask image is a non-character area is generated. The select image is a binary image expressed in binary (eg, “0”, “1”). Note that the character area in the first mask image is reduced with the center position of the character area fixed.

  Then, the select image generation unit 513 stores the generated select image data (hereinafter also referred to as select image data) in the storage unit 520. The select image data is data for reproducing an image from encoded data by a process described later. Then, the process of step S114 ends.

  Here, it is assumed that the first predetermined ratio is the same as the first predetermined ratio used in the process of step S113. When the first predetermined ratio used in the process of step S113 is 10%, the first predetermined ratio used in step S114 is 10%.

  Here, it is assumed that the first mask image indicated by the first mask image data is the first mask image RG101 in FIG. In this case, the select image generated by the select image data generation process is the select image RG100SL in FIG. In addition, the size of the character region CR10SL in the select image RG100SL is the same as the size of the character region CR10 in the region separation image RG100. Further, by reducing the character area CR10A in the first mask image RG101, the select image RG100SL shows a non-character area BR10SL in which the non-character area BR10A in the first mask image RG101 is expanded.

Referring to FIG. 3 again, after the process of step S114, the process proceeds to step S115.
In step S115, a second mask generation process is performed. In the second mask generation process, the second mask generation unit 512B reads select image data from the storage unit 520. Then, the second mask generation unit 512B generates an image (hereinafter also referred to as a second mask image) obtained by expanding the non-character area in the select image indicated by the select image data at a second predetermined ratio. The second mask image is a binary image expressed in binary (for example, “0”, “1”). The second predetermined ratio is assumed to be 15%, for example. The first predetermined ratio and the second predetermined ratio described above may be the same value (for example, 10%). Note that the non-character area in the select image is expanded in a state where the center position of the non-character area is fixed.

  Then, the second mask generation unit 512B causes the storage unit 520 to store the generated second mask image data (hereinafter also referred to as second mask image data). And the process of step S115 is complete | finished.

  Here, it is assumed that the select image indicated by the select image data is the select image RG100SL in FIG. In this case, the second mask image generated by the second mask generation process is the second mask image RG102 of FIG. The resolution of the second mask image RG102 is the same as the resolution of the processing target image G100. The plurality of pixels constituting the second mask image RG102 correspond to the plurality of pixels constituting the processing target image G100, respectively. Note that the resolution of the second mask image RG102 may be lower than the resolution of the processing target image G100.

  Second mask image RG102 shows non-character region BR10B in which non-character region BR10SL in select image RG100SL is expanded at a second predetermined ratio. Note that, by expanding the non-character region BR10B in the select image RG100SL, the second mask image RG102 shows a character region CR10B in which the character region CR10SL in the select image RG100SL is reduced.

Referring again to FIG. 3, after the process of step S115, the process proceeds to step S116. In step S116, a first reproduction image generation process is performed. In the first reproduction image generation process, the first reproduction image generation unit 514A reads the processing target image data and the first mask image data from the storage unit 520.

  Then, the first reproduction image generation unit 514A generates a first reproduction image for reproducing the processing target image. Specifically, the first reproduction image generation unit 514A includes, among the processing target images indicated by the processing target image data, an image corresponding to a character area in the first mask image indicated by the read first mask image data; A first reproduction image is generated using an image in which a plurality of pixels in a region other than the character region (non-character region) in the first mask image is white. The generated first reproduction image is an image showing characters.

  Then, the first reproduction image generation unit 514A causes the storage unit 520 to store the generated first reproduction image data (hereinafter also referred to as first reproduction image data).

  Note that an image in which a plurality of pixels in a region other than the character region in the first mask image have a color other than white (for example, black) may be used for generating the first reproduction image. And the process of step S116 is complete | finished.

  Here, it is assumed that the processing target image indicated by the processing target image data is the processing target image G100 in FIG. 4, and the first mask image indicated by the first mask image data is the first mask image RG101 in FIG. In this case, the first reproduction image generated by the first reproduction image generation process is the first reproduction image REG200A in FIG.

Referring to FIG. 3 again, after the process of step S116, the process proceeds to step S117.
In step S117, second reproduction image generation processing is performed. In the second reproduction image generation process, the second reproduction image generation unit 514B reads out the processing target image data and the second mask image data from the storage unit 520.

  Then, the second reproduction image generation unit 514B generates a second reproduction image for reproducing the processing target image. Specifically, the second reproduction image generation unit 514B includes an image corresponding to a non-character region in the second mask image indicated by the read second mask image data among the processing target images indicated by the processing target image data. Then, a second reproduction image is generated using an image in which a plurality of pixels in a region (character region) other than the non-character region in the second mask image is white. Then, the second reproduction image generation unit 514B causes the storage unit 520 to store the generated second reproduction image data (hereinafter also referred to as second reproduction image data).

  Note that an image in which a plurality of pixels in an area other than the non-character area in the second mask image is a color other than white (for example, black) may be used for generating the second reproduction image. Then, the process of step S117 ends.

  Here, it is assumed that the processing target image indicated by the processing target image data is the processing target image G100 in FIG. 4, and the second mask image indicated by the second mask image data is the second mask image RG102 in FIG. In this case, the second reproduction image generated by the second reproduction image generation process is the second reproduction image REG200B in FIG.

Referring to FIG. 3 again, after the process of step S117, the process proceeds to step S118.
In step S118, an encoding process is performed. In the encoding process, the encoding unit 515 reads select image data, first reproduction image data, and second reproduction image data from the storage unit 520.

  The encoding unit 515 obtains encoded data (hereinafter also referred to as first encoded data) by irreversibly encoding the first reproduction image indicated by the read first reproduction image data. The encoding unit 515 obtains encoded data (hereinafter also referred to as second encoded data) by irreversibly encoding the second reproduction image indicated by the read second reproduction image data. As a lossy encoding method, a JPEG (Joint Photographic Coding Experts Group) method is used. The lossy encoding method is not limited to the JPEG method, and may be another encoding method.

  The first reproduction image is an image showing characters. Therefore, when irreversible encoding is performed on the first reproduction image, the encoding unit 515 performs the first compression at a compression rate (hereinafter, also referred to as a first compression rate) that can sufficiently distinguish characters. The reproduction image is lossy encoded. When lossy encoding is performed on the second reproduction image, the encoding unit 515 performs the second reproduction image at a compression rate higher than the first compression rate (hereinafter also referred to as the second compression rate). Is lossy encoded. The first compression rate is assumed to be 1/2, for example. It is assumed that the second compression rate is 1/20, for example.

  The encoding unit 515 obtains encoded data (hereinafter also referred to as third encoded data) by performing lossless encoding on the select image indicated by the read select image data. The lossless encoding method may be any encoding method such as MR (Modified Read), MMR (Modified Modified Read), or JBIG (Joint Bi-level Image Coding Expert Group).

  Here, it is assumed that the first reproduction image indicated by the first reproduction image data is the first reproduction image REG200A in FIG. Further, it is assumed that the second reproduction image indicated by the second reproduction image data is the second reproduction image REG200B in FIG. The select image indicated by the select image data is the select image RG100SL in FIG.

  In this case, the image quality of the portion corresponding to the character region CR10SL in the select image RG100SL in the first reproduction image obtained by decoding the first encoded data by performing the above process is the second image. In the second reproduction image obtained by decoding the encoded data, the image quality is higher than the image quality of the portion corresponding to the non-character region BR10SL in the select image RG100SL.

  Then, the encoding unit 515 causes the storage unit 520 to store the first encoded data, the second encoded data, and the third encoded data. For example, the encoding unit 515 may transmit the first encoded data, the second encoded data, and the third encoded data to the external device 600 without storing them in the storage unit 520. Then, this image encoding process ends.

(Image playback processing)
Next, processing for reproducing an image (hereinafter also referred to as image reproduction processing) in the first embodiment will be described. Here, it is assumed that the first encoded data, the second encoded data, and the third encoded data are stored in the storage unit 520 by the image encoding process of FIG.

  FIG. 5 is a flowchart of the image reproduction process. Referring to FIG. 5, in the image reproduction process, first, the process of step S211 is performed.

  In step S211, a decoding process is performed. In the decoding process, control unit 510 reads first encoded data, second encoded data, and third encoded data from storage unit 520. Then, control unit 510 decodes each of the first encoded data, the second encoded data, and the third encoded data based on the corresponding encoding scheme.

  A first reproduction image is obtained by decoding the first encoded data. A second reproduction image is obtained by decoding the second encoded data. A select image is obtained by decoding the third encoded data. Then, the process of step S211 ends.

  FIG. 6 is a diagram illustrating an image used or generated in the image reproduction process. Referring to FIG. 6, it is assumed that first reproduction image REG200A is an image obtained by decoding the first encoded data by the decoding process. The second reproduction image REG200B is assumed to be an image obtained by decoding the second encoded data by the decoding process. The select image RG100SL is assumed to be an image obtained by decoding the third encoded data by the decoding process.

  Here, it is assumed that the first reproduction image REG200A, the second reproduction image REG200B, and the select image RG100SL have the same resolution. The plurality of pixels constituting the select image RG100SL correspond to the plurality of pixels constituting the first reproduction image REG200A. The plurality of pixels constituting the select image RG100SL correspond to the plurality of pixels constituting the second reproduction image REG200B, respectively.

  Note that the resolution of the select image RG100SL may be lower than the resolution of the first reproduction image REG200A and the second reproduction image REG200B. In this case, the select image RG100SL is enlarged so as to have the same resolution as that of the first reproduction image REG200A and the second reproduction image REG200B.

Referring to FIG. 5 again, after the process of step S211, the process proceeds to step S212.
In step S212, image composition processing is performed. In the image composition processing, the control unit 510 controls the image of the portion corresponding to the character area in the select image in the first reproduction image and the portion corresponding to the non-character area in the select image in the second reproduction image. The image is reproduced by combining the image.

  Here, it is assumed that the first reproduction image is the first reproduction image REG200A in FIG. Further, it is assumed that the second reproduction image is the second reproduction image REG200B in FIG. The select image is assumed to be the select image RG100SL in FIG. In this case, in the first reproduction image REG200A, an image of a portion corresponding to the character region CR10SL in the select image RG100SL and an image of a portion corresponding to the non-character region BR10SL in the select image RG100SL in the second reproduction image REG200B. And the image G100 is reproduced.

  Then, control unit 510 causes display unit 530 to display generated image G100. Then, this image reproduction process ends.

  As described above, according to the processing according to the first embodiment, when irreversible encoding is performed on the first reproduction image indicating characters, the first compression is such that the characters can be sufficiently distinguished. At a rate, the first playback image is lossy encoded. When lossy encoding is performed on the second reproduction image, the second reproduction image is lossy encoded at a second compression rate higher than the first compression rate. Therefore, it is possible to greatly reduce the data capacity while minimizing the deterioration of the image quality of the character portion.

  Further, according to the processing according to the first embodiment, when a non-character region is included in the character region in the region separation image, the non-character region included in the character region in the region separation image is eliminated. One mask image is generated. In the image encoding process, a select image is generated using the first mask image. Therefore, even if a non-character area is included in the character area in the area separation image, the non-character area is not included in the character area in the select image generated in the image encoding process. Therefore, the data amount of the select image can be reduced. That is, the data amount of the third encoded data obtained by encoding the select image can be reduced.

  As described above, according to the processing according to the first embodiment, it is possible to significantly reduce the data capacity while minimizing the deterioration of the image quality in the image encoding processing.

<Second Embodiment>
Next, processing when the resolution of the display surface of the image display device (hereinafter also referred to as an image display device) and the resolution of the processing target image are different will be described. The image display device is, for example, the display unit 530.

  Since the image coding apparatus in the second embodiment is similar to the image coding apparatus 500 in the first embodiment, detailed description will not be repeated.

  FIG. 7 is a functional block diagram of the control unit 510 according to the second embodiment. For the sake of explanation, FIG. 7 also shows the external device 600, the storage unit 520, and data stored in the storage unit 520 by the image encoding process A described later.

  Referring to FIG. 7, control unit 510 in the second embodiment is different from control unit 510 in the first embodiment in FIG. 2 in that it further includes a resolution conversion unit 516. Since other than that is the same as that of the control unit 510 in the first embodiment, detailed description will not be repeated.

  An acquisition unit 511, a first mask generation unit 512A, a select image generation unit 513, a second mask generation unit 512B, a first reproduction image generation unit 514A, a second reproduction image generation unit 514B, a code included in the control unit 510 All or part of the conversion unit 515 and the resolution conversion unit 516 may be configured by independent hardware (for example, an arithmetic circuit).

  Also included in the control unit 510 are an acquisition unit 511, a first mask generation unit 512A, a select image generation unit 513, a second mask generation unit 512B, a first reproduction image generation unit 514A, and a second reproduction image generation unit 514B. All or part of the encoding unit 515 and the resolution conversion unit 516 may be a module of a program executed by the control unit 510.

  An acquisition unit 511, a first mask generation unit 512A, a select image generation unit 513, a second mask generation unit 512B, a first reproduction image generation unit 514A, a second reproduction image generation unit 514B, a code included in the control unit 510 The processing performed by each of the conversion unit 515 and the resolution conversion unit 516 will be described later.

(Encoding process)
Next, specific processing contents of the image coding apparatus 500 according to the second embodiment will be described. In the image encoding device 500, the following image encoding process A is performed. It is assumed that the processing target image processed in the image encoding device 500 is the processing target image G100 in FIG.

  FIG. 8 is a flowchart of the image encoding process A. The image encoding process A is different from the image encoding process of FIG. 3 in that the process of step S117A is further performed. The other processes are the same as the image encoding process. In the image encoding process A, the process having the same step number as the step number of the image encoding process is performed in the same manner as the process described in the first embodiment, and therefore detailed description will not be repeated.

  In the image encoding process A, the process from step S111 to step S117 is performed as in the first embodiment, and thus detailed description will not be repeated. Through these processes, the storage unit 520 stores processing target image data, region separation image data, first mask image data, select image data, second mask image data, first reproduction image data, and second reproduction image data. Is memorized. Then, the process proceeds to step S117A.

  In step S117A, resolution conversion processing is performed. In the resolution conversion process, the resolution conversion unit 516 reads the first reproduction image data and the second reproduction image data from the storage unit 520. Then, the resolution conversion unit 516 converts the resolution of the first reproduction image indicated by the first reproduction image data and the resolution of the second reproduction image indicated by the second reproduction image data on the image display surface of the image display device. Convert to the same resolution as the resolution.

  Then, the resolution conversion unit 516 uses the first reproduction image data whose resolution is converted and the second reproduction image data whose resolution is converted as the first reproduction image data and the second reproduction image data, respectively. The first reproduction image data and the second reproduction image data stored in the storage unit 520 are overwritten and stored respectively.

  Here, the image display surface of the image display device is assumed to be the display surface of the display unit 530 as an example. Here, the resolution of the display surface of the display unit 530 is, for example, 480 (dots) × 640 (dots) in width. Further, as an example, the resolution of the processing target image is assumed to be 240 horizontal (dots) × 320 vertical (dots). In this case, the resolution of the first playback image and the resolution of the second playback image are 240 horizontal (dots) × 320 vertical (dots). That is, the resolution of the display surface of the display unit 530 is higher than the resolution of the processing target image.

  In this case, in the resolution conversion process, the resolution conversion unit 516 enlarges the first reproduction image and the second reproduction image, thereby changing the resolution of the first reproduction image and the second reproduction image to the display unit. Conversion to the same resolution as that of the display surface 530 is performed.

  When the resolution of the display surface of the image of the image display device is lower than the resolution of the processing target image, the resolution conversion unit 516 reduces the first reproduction image and the second reproduction image in the resolution conversion process. The resolution of the first playback image and the resolution of the second playback image are converted to the same resolution as the resolution of the image display surface of the image display device.

  In the resolution conversion process, if the resolution of the image display surface of the image display device is different from the resolution of the processing target image, only one of the first reproduction image and the second reproduction image is subjected to resolution conversion. Also good. In this case, when the image is reproduced, the image that has not been subjected to resolution conversion in the resolution conversion process among the first reproduction image and the second reproduction image is set as the resolution of the image display surface of the image display device. What is necessary is just to perform resolution conversion so that it may become the same resolution.

  Then, as in the first embodiment, the image encoding process A ends when the process of step S118 is performed.

  In order to reproduce an image from the data encoded by the image encoding process A, the image reproduction process of FIG. 5 may be performed as in the first embodiment.

  As described above, according to the processing according to the second embodiment, in addition to the effects achieved by the first embodiment, the display of the image of the device that displays the image reproduced using the encoded data. It is possible to generate encoded data corresponding to the surface resolution.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is the block diagram which showed the internal structure of the image coding apparatus in 1st Embodiment. It is a functional block diagram of a control part in a 1st embodiment. It is a flowchart of an image encoding process. It is a figure which shows the image used or produced | generated by an image coding process. It is a flowchart of an image reproduction process. It is a figure which shows the image used or produced | generated by an image reproduction process. It is a functional block diagram of a control part in a 2nd embodiment. It is a flowchart of the image encoding process A.

Explanation of symbols

  500 image encoding device, 510 control unit, 520 storage unit, 530 display unit.

Claims (9)

Acquisition means for acquiring a processing target image, and a region separation image indicating a first region in which the predetermined element in the processing target image exists and a second region in which the predetermined element in the processing target image does not exist;
First mask generating means for generating a first mask image that is an image obtained by expanding the first region in the region separation image at a first predetermined ratio;
A region obtained by reducing the first region in the first mask image at the first predetermined ratio is defined as the first region, and a region other than the reduced first region in the first mask image is defined. Select image generation means for generating a select image which is an image as the second region;
Second mask generation means for generating a second mask image that is an image obtained by expanding the second region in the select image at a second predetermined ratio;
First reproduction for generating a first reproduction image for reproducing an image generated using an image corresponding to the first region in the first mask image among the processing target images. Image generating means;
Second reproduction for generating a second reproduction image for reproducing an image generated using an image corresponding to the second region in the second mask image among the processing target images. Image generating means;
First encoded data obtained by encoding the first reproduction image by performing an encoding process for encoding the first reproduction image, the second reproduction image, and the select image, and the second reproduction Encoding means for generating second encoded data obtained by encoding an image for use and third encoded data obtained by encoding the select image,
In the image obtained by decoding the first encoded data, the image quality of the image corresponding to the first area in the select image is the image obtained by decoding the second encoded data. , Higher than the image quality of the image corresponding to the second region in the select image,
When an image is reproduced using the first encoded data and the second encoded data, in the image obtained by decoding the first encoded data, in the first area in the select image The image is reproduced by using the image of the corresponding part and the image of the part corresponding to the second area in the select image in the image obtained by decoding the second encoded data. , Image encoding device.   The image encoding device according to claim 1, wherein the encoding process performed on each of the first reproduction image and the second reproduction image is an irreversible encoding process.   3. The image encoding apparatus according to claim 1, wherein the encoding unit performs the encoding process with a compression rate for the second reproduction image being higher than a compression rate for the first reproduction image. 4. .   The first mask generation means eliminates the second region included in the first region in the region separation image when the second region is included in the first region in the region separation image. The image coding apparatus according to claim 1, wherein the first mask image is generated.   5. The image encoding device according to claim 1, further comprising a resolution conversion unit configured to convert at least one resolution of the first reproduction image and the second reproduction image.   The image encoding device according to claim 1, wherein the predetermined element is a character. An image encoding method executed by an image encoding device,
Obtaining a processing target image, a first region where a predetermined element in the processing target image is present, and a region separation image indicating a second region where the predetermined element is not present in the processing target image;
Generating a first mask image that is an image obtained by expanding the first region in the region separation image at a first predetermined ratio;
A region obtained by reducing the first region in the first mask image at the first predetermined ratio is defined as the first region, and a region other than the reduced first region in the first mask image is defined. Generating a select image which is an image as the second region;
Generating a second mask image that is an image obtained by expanding the second region in the select image at a second predetermined ratio;
Generating an image for reproduction, which is an image generated using an image corresponding to the first region in the first mask image among the processing target images, and for reproducing the image;
A step of generating a second reproduction image for reproducing the image, the image being generated using an image corresponding to the second region in the second mask image among the processing target images;
First encoded data obtained by encoding the first reproduction image by performing an encoding process for encoding the first reproduction image, the second reproduction image, and the select image, and the second reproduction Generating second encoded data obtained by encoding an image for use, and third encoded data obtained by encoding the select image,
In the image obtained by decoding the first encoded data, the image quality of the image corresponding to the first area in the select image is the image obtained by decoding the second encoded data. , Higher than the image quality of the image corresponding to the second region in the select image,
When an image is reproduced using the first encoded data and the second encoded data, in the image obtained by decoding the first encoded data, in the first area in the select image An image is reproduced by using a corresponding part image and an image obtained by decoding the second encoded data by using a part image corresponding to the second area in the select image. , Image coding method. An image encoding program executed by a computer,
Obtaining a processing target image, a first region where a predetermined element in the processing target image is present, and a region separation image indicating a second region where the predetermined element is not present in the processing target image;
Generating a first mask image that is an image obtained by expanding the first region in the region separation image at a first predetermined ratio;
A region obtained by reducing the first region in the first mask image at the first predetermined ratio is defined as the first region, and a region other than the reduced first region in the first mask image is defined. Generating a select image which is an image as the second region;
Generating a second mask image that is an image obtained by expanding the second region in the select image at a second predetermined ratio;
Generating an image for reproduction, which is an image generated using an image corresponding to the first region in the first mask image among the processing target images, and for reproducing the image;
Generating an image for reproduction, which is an image generated using an image corresponding to the second region in the second mask image among the processing target images, and for reproducing the image;
First encoded data obtained by encoding the first reproduction image by performing an encoding process for encoding the first reproduction image, the second reproduction image, and the select image, and the second reproduction Generating second encoded data obtained by encoding an image for use, and third encoded data obtained by encoding the select image,
In the image obtained by decoding the first encoded data, the image quality of the image corresponding to the first area in the select image is the image obtained by decoding the second encoded data. , Higher than the image quality of the image corresponding to the second region in the select image,
When an image is reproduced using the first encoded data and the second encoded data, in the image obtained by decoding the first encoded data, the first region in the select image is stored in the first area. An image is reproduced by using a corresponding part image and an image obtained by decoding the second encoded data by using a part image corresponding to the second area in the select image. , Image coding program.   A computer-readable recording medium on which the image encoding program according to claim 8 is recorded.

Images