JP4218727B2 - Image reproduction method, image reproduction apparatus, and image reproduction program - Google Patents

Description

  The present invention relates to an image data structure, an image recording method, an image recording apparatus, and an image recording program.

To represent a color image, three-channel image components such as R / G / B and Y / Cr / Cb are required. In addition, since image data has a large capacity, it is generally conveyed by a removable memory or a communication line in a compressed data format. As a compression processing method, the JPEG method is widely used. The compressed image data can be expanded at high speed by hardware processing using an expansion circuit corresponding to the compression method.
Conventionally, there has been known image data in which an α channel, which is a transmittance component for superimposing and synthesizing two images or clipping an image, is added to an image component of three channels (see, for example, Patent Document 1).

JP 2001-202504 A

  However, the image data decompression circuit is often designed exclusively for decompressing 3-channel image data. For example, a JPEG decompression circuit may not be able to decompress 4-channel image data even if it is JPEG format image data. In such a case, the transmittance component, or both the image component and the transmittance component, must be decompressed by software processing. As described above, the 4-channel image data composed of the 3-channel image component and the compressed transmittance component has a problem of low versatility.

  An object of the present invention is to provide an image reproducing method, apparatus, and program for reproducing versatile image data to which a transmittance component is added.

In order to achieve the above object, an image reproduction method according to the present invention is an image reproduction method for reproducing compressed image data having a three-channel image component and a one-channel transmittance component,
The compressed image data is the same as the image area in which the three-channel image component is recorded in the compression format, the transmission component in the same compression format as the image component, and the image area in which the two-channel pseudo component is recorded. An image area decoding stage for decoding the image area, a transparency area decoding stage for decoding the transparency area, and a three-channel decoded image decoded by the image area decoding stage. An image reproduction step of reproducing decoded image data having a component and a one-channel decoded transmittance component obtained by ignoring the two-channel pseudo channel from the transmittance region decoded by the transmittance region decoding step It is characterized by having.
By ignoring the decoded image component and the two-channel pseudo channel from the decoded transmittance region, a reproduction image similar to the conventional four-channel image can be obtained. Therefore, according to the image reproduction method according to the present invention, the image area in which the image components of the three channels are recorded in the compression format, the transmittance component in the same compression format as the image components, and the pseudo component of the two channels are recorded. Image data having an image area and a transmittance area having the same data structure can be reproduced in the same manner as normal 4-channel compressed image data.

Furthermore, in the image data structure according to the present invention, the structure of the image region and the transmittance region is a three-channel JPEG format. By adopting the 3-channel JPEG format, versatility can be further enhanced.
Further, the image data structure according to the present invention is characterized in that the image component, the transmittance component, and the pseudo component are recorded in one file. By recording the image component, the transmittance component, and the pseudo component in one file, the portability of the image data to which the transmittance component is added can be improved.

  The present invention can be specified not only as a method invention but also as a program invention, a recording medium recording the program, and a device invention. In addition, each function of the plurality of means provided in the present invention is realized by a hardware resource whose function is specified by the configuration itself, a hardware resource whose function is specified by a program, or a combination thereof. The functions of the plurality of means are not limited to those realized by hardware resources that are physically independent of each other.

Embodiments of the present invention will be described below based on a plurality of examples.
(First Example)
FIG. 2 is a block diagram showing an image recording apparatus according to the first embodiment of the present invention. This image recording apparatus is a computer system that records image data in the removable memory 18 by executing an image recording program described later. This computer system includes a CPU 10, a ROM 12, a RAM 14, a display 16, a keyboard 28, a mouse 26, a hard disk 24, a card controller 20, a network interface 22, and the like, and these components are connected to each other by a bus.

  The CPU 10 executes image data processing described later by executing an image recording program stored in the ROM 12, and controls the RAM 14, the display 16, the hard disk 24, the card controller 20, and the like via a device controller (not shown). The ROM 12 is a non-volatile memory in which a minimum control program and data necessary for the operation of the CPU 10 are stored in advance. The RAM 14 is a memory that temporarily stores various programs and data. The hard disk 24 is a nonvolatile memory that stores an OS and an image recording program. The image recording program and various data may be downloaded and input from a predetermined server via a network, or may be read from a computer-readable storage medium such as the removable memory 18 and input. The card controller 20 controls reading / writing of the removable memory 18. The network interface 22 is configured by a modem or a network interface card.

  The image data stored in the removable memory 18 and the image data transmitted through the network interface 22 are used in a playback device such as a printer, a display, or a projector. By using the image data according to the present embodiment in a playback device such as a printer, a display, or a projector, the image component of the image data is combined with other image data using the transmittance component added to the image component, and combined. Images can be played back.

  FIG. 3 is a schematic diagram showing an image 30 represented by image data according to the first embodiment of the present invention. The hatched area is a transparent area, and when another image 32 as shown in FIG. 4 is superimposed on the image 30, a composite image 34 in which the other image 32 is inserted into the area and synthesized as shown in FIG. Is formed.

  FIG. 6 is a schematic diagram for explaining image components and transmittance components included in image data according to the first embodiment of the present invention. The image component is composed of density information of three channels such as R / G / B and Y / Cb / Cr. The density information is composed of three gradation values recorded for each pixel. The number of levels of each gradation value is arbitrary, for example, 8 bits, and image components are recorded at 24 bits per pixel.

  The transmittance component is composed of transmittance information of one channel. The transmittance information is information that defines, for each pixel of the image component, the transmittance of the pixel by a gradation value. Hereinafter, the transmittance component is referred to as an α channel. The number of levels of the α channel is arbitrary, but is desirably the same as the number of levels of the image component. In the 8-bit α channel, for example, 0 is transparent and 255 is opaque to define the α channel. In the α channel, the weighting of two pixels in the process of forming one pixel of a composite image from two pixels can be defined. When the α channel is transparent, when the image represented by the image component to which the α channel is added and another image 32 as shown in FIG. 4 are superimposed and synthesized, the pixel of the other image 32 has priority. Is displayed. In the same case, the pixels in which the α channel is opaque are displayed with priority on the pixels of the image represented by the image component to which the α channel is added. In FIG. 6, the range in which the α channel is transparent is indicated by hatching. Note that alignment between the image represented by the image component to which the α channel is added and the image superimposed on the image is performed by separately specifying coordinates.

  FIG. 7 is a block diagram showing means for performing image recording processing in the image recording apparatus. Each means may be realized by hardware or software. In the following description, each means is realized by the process of the image recording program. The image recording process is a process of compressing the image component of three channels, the α channel, the first pseudo channel, and the second pseudo channel and outputting them to the removable memory 18, the hard disk 24, the communication line, and the like.

  In the DCT process P100, DCT (discrete cosine transform) is performed for each block. The DCT process P100 receives three channel image components such as Y / Cb / Cr, the α channel, the first pseudo channel, and the second pseudo channel, and the DCT process P100 outputs their DCT coefficients. The three-channel image components such as Y / Cb / Cr and the α channel are output from an image editing program different from the image recording program.

  The first pseudo channel and the second pseudo channel are output from the pseudo component forming process P110 of the image recording program to the DCT process P100, and have the same data structure as the α channel. That is, the pseudo component forming process P110 outputs two sets of gradation values having the same number of pixels and the same level as the α channel as the first pseudo channel and the second pseudo channel. In the pseudo component forming process P110, by setting all the pixels of the first pseudo channel and the second pseudo channel to the same value such as 0 and 255, the entropy of the first pseudo channel and the second pseudo channel is set to 0. Is desirable. Thereby, the compression efficiency of the pseudo component can be maximized, and the waste of the capacity of the removable memory 18 due to the pseudo component can be suppressed.

  In the quantization process P120, quantization is performed. The quantization process P120 is input with image components of three channels such as Y / Cb / Cr, DCT coefficients of the α channel, the first pseudo channel, and the second pseudo channel, and their quantized values (quantized DCT). Coefficient) is output. The quantization representative value is stored in the quantization table 36. In the quantization process P120, the address of the quantization table in which the quantized representative value is stored is obtained from the input DCT coefficient, and the quantized representative value stored in the obtained address is read and output as the quantized DCT coefficient. Thus, the input DCT coefficient is quantized. A different quantization table 36 is used for each channel, and in particular, the first pseudo channel and the second pseudo channel may have a larger quantization step width than that used for other channels. Thereby, the entropy of the first pseudo channel and the second pseudo channel can be significantly reduced as compared with other channels.

  In the run-length Huffman encoding process P130, encoding combining run-length encoding and Huffman encoding is performed. The run-length Huffman encoding process P130 receives three-channel image components such as Y / Cb / Cr, α channel, first pseudo channel, and quantized DCT coefficients of the second pseudo channel, for example, their run lengths. And a value (Huffman code) encoded by assigning a Huffman code to each set of values following the zero run is output. The Huffman code is determined by the Huffman table, and the Huffman table is determined by the value following the run length and zero run. In order to decode the Huffman code, the Huffman table used for encoding is required. In order to improve the portability of the Huffman table, by defining a protocol for uniquely identifying the Huffman table between the code processing device and the decoding processing device, the Huffman table used for encoding instead of passing the Huffman table itself It is desirable to pass information (Huffman table definition information) necessary for configuring the table to the decoding device.

  FIG. 1 is a data structure diagram showing the structure of image data according to the first embodiment. In the writing process P150, the image data is written in the removable memory 18 with the structure of FIG. In the following description, it is assumed that data is stored in the JPEG compression format in the image area and the transmission area. However, as long as the compression method and format of the data stored in the image area and the transmission area are the same, JPEG compression is used. It is not limited to the format. Specifically, for example, wavelet transform, predictive coding, Markov coding, or the like may be used for compression. The format may not be standardized.

  As described above, the image data of this embodiment is obtained by adding an α channel to the image components of three channels. It is desirable to store the image data in one file in order to improve portability. For example, the image component is stored in the compressed data area of the main image in the JFIF format file in the 3-channel JPEG compression format. As a result, the image component can be decoded as normal three-channel JPEG compressed data. The α channel is stored together with the first pseudo channel and the second pseudo channel in the JPEG compression format of 3 channels in the transmittance area in the file. The transparency area is stored in the compressed data area in the JFIF format APP7 in the same manner as the compressed data of the thumbnail image is stored in the JFIF format APP1, for example. Accordingly, the α channel, the first pseudo channel, and the second pseudo channel can be decoded as normal three-channel JPEG compressed data by cutting out only the APP7 portion. When the α channel is used, the decoded first pseudo channel and second pseudo channel may be ignored. The detailed data structure of the image area and the transmittance area is omitted because it is a 3-channel JPEG compression format.

  Since the image data having the structure according to the first embodiment is recorded in the same 3-channel JPEG compression format as the image component and the transmittance component, the image component and the transmittance component can be decoded by the same processing method. it can. Therefore, the image data structure according to this embodiment to which the transmittance component is added is highly versatile.

(Second embodiment)
The second embodiment of the present invention differs from the first embodiment in the processing of the first pseudo channel and the second pseudo channel, and is otherwise common to the first embodiment.
FIG. 8 is a block diagram showing means for performing image recording processing in the image recording apparatus. In the DCT process P105, DCT (discrete cosine transform) is performed for each block. Three-channel image components such as Y / Cb / Cr and α channel are input to the DCT process P105, and those DCT coefficients are output from the DCT process P105.

The first pseudo channel and the second pseudo channel are output from the pseudo component forming process P112 to the quantization process P120, and have the same data structure as the DCT coefficient of the α channel. That is, the pseudo component forming process P112 outputs two sets of gradation values having the same number of pixels and the same level as the α channel as the first pseudo channel and the second pseudo channel. In the pseudo component formation process P112, the entropy of the first pseudo channel and the second pseudo channel is set to 0 by setting all the pixels of the first pseudo channel and the second pseudo channel to the same value such as 0 and 255. Is desirable. Thereby, the compression efficiency of the pseudo component can be maximized, and the waste of the capacity of the removable memory 18 due to the pseudo component can be suppressed.
Since the quantization process P120, the run-length Huffman encoding process P130, the Huffman encoding process P140, and the writing process P150 are the same as those in the first embodiment, description thereof is omitted.

(Third embodiment)
The third embodiment of the present invention differs from the first embodiment in the processing of the first pseudo channel and the second pseudo channel, and is otherwise common to the first embodiment.
FIG. 9 is a block diagram showing means for performing image recording processing in the image recording apparatus. Since the DCT process P105 is the same as that of the second embodiment, the description thereof is omitted.

  In the quantization process P125, quantization is performed. The quantization process P125 receives three-channel image components such as Y / Cb / Cr and α-channel DCT coefficients, and outputs their quantized values (quantized DCT coefficients). The quantization representative value is stored in the quantization table 36. In the quantization process P125, the address of the quantization table in which the quantized representative value is stored is obtained from the input DCT coefficient, the quantized representative value stored in the obtained address is read and output as the quantized DCT coefficient. Thus, the input DCT coefficient is quantized.

The first pseudo channel and the second pseudo channel are output from the pseudo component forming process P114 of the image recording program to the run-length Huffman encoding process P130, and have the same data structure as the quantized DCT coefficient of the α channel. That is, the pseudo component forming process P114 outputs two sets of gradation values having the same number of pixels and the same number of levels as the α channel as the first pseudo channel and the second pseudo channel. In the pseudo component formation process P114, the entropy of the first pseudo channel and the second pseudo channel is set to 0 by setting all the pixels of the first pseudo channel and the second pseudo channel to the same value such as 0 and 255. Is desirable. Thereby, the compression efficiency of the pseudo component can be maximized, and the waste of the capacity of the removable memory 18 due to the pseudo component can be suppressed. The quantization table for decoding the first pseudo channel and the second pseudo channel may be output from the pseudo component forming process to the writing process. The first pseudo channel and the second pseudo channel are not useful even if they are decoded. Therefore, the decoding process of the first pseudo channel and the second pseudo channel need not be performed in correspondence with the code process, and may be performed in a random manner. For this reason, as long as the quantization table of the first pseudo channel and the second pseudo channel matches the quantization table of the α channel, the contents themselves may be anything.
Since the run-length Huffman encoding process P130, the Huffman encoding process P140, and the writing process P150 are the same as those in the first embodiment, description thereof is omitted.

(Fourth embodiment)
The fourth embodiment of the present invention differs from the first embodiment in the processing of the first pseudo channel and the second pseudo channel, and is otherwise common to the first embodiment.
FIG. 10 is a block diagram showing means for performing image recording processing in the image recording apparatus. Since the DCT process P105 and the quantization process P125 are the same as those in the third embodiment, description thereof will be omitted.

  In the run-length Huffman encoding process P135, encoding combining run-length encoding and Huffman encoding is performed. The run-length Huffman encoding process P135 receives three channels of image components such as Y / Cb / Cr and the α channel, and assigns a Huffman code to each set of values following the run length and zero run, for example. The encoded value (Huffman code) is output. The Huffman code is determined by the Huffman table, and the Huffman table is determined by the value following the run length and zero run. In order to decode the Huffman code, the Huffman table used for encoding is required. In order to improve the portability of the Huffman table, by defining a protocol for uniquely identifying the Huffman table between the code processing device and the decoding processing device, the Huffman table used for encoding instead of passing the Huffman table itself It is desirable to pass information (Huffman table definition information) necessary for configuring the table to the decoding device.

The first pseudo channel and the second pseudo channel are output from the pseudo component forming process P118 of the image recording program to the writing process P150, and have the same data structure as the Huffman code of the α channel. In the pseudo component forming process P118, the first pseudo channel is output by outputting a Huffman code of a run length code in which the length of 0 run matches the number of pixels of one block of the first pseudo channel and the second pseudo channel for each block. It is desirable to minimize the data amount of the second pseudo channel. The quantization table and the Huffman table definition information for decoding the first pseudo channel and the second pseudo channel may be output from the pseudo component forming process P118 to the writing process P150. The quantization table and Huffman table definition information of the first pseudo channel and the second pseudo channel may be anything as long as the format matches the quantization table and Huffman table definition information of the α channel.
Since the writing process P150 is the same as that of the first embodiment, the description thereof is omitted.

It is a data structure figure which shows the structure of the image data by a 1st Example. 1 is a block diagram illustrating an image recording apparatus according to a first embodiment. It is a schematic diagram which shows an image. It is a schematic diagram which shows an image. It is a schematic diagram which shows a synthesized image. It is a schematic diagram regarding a 1st Example. It is a block diagram regarding the first embodiment. It is a block diagram regarding the second embodiment. It is a block diagram regarding the third embodiment. It is a block diagram regarding the fourth embodiment.

Explanation of symbols

  P100 ... DCT process, P105 ... DCT process, P110 ... Pseudo component formation process, P112 ... Pseudo component formation process, P114 ... Pseudo component formation process, P116 ... Pseudo component formation process, P118 ... Pseudo component formation process, P120 ... Quantization process , P125 ... quantization process, P130 ... run-length Huffman encoding process, P135 ... run-length Huffman encoding process, P140 ... Huffman encoding process, P145 ... Huffman encoding process, P150 ... write process.

Claims (9)

An image reproduction method for reproducing compressed image data,
The compressed image data is the same as the image area in which the image components of the three channels are recorded in the compression format, the transmittance component in the same compression format as the image components, and the image area in which the pseudo components of the two channels are recorded. Including the transparency region of the data structure,
An image region decoding stage for decoding the image region;
A transmittance region decoding step of decoding the transmittance region;
One channel decoded transmission obtained by ignoring the two-channel pseudo channel from the three-channel decoded image component decoded by the image region decoding step and the transmittance region decoded by the transmittance region decoding step. An image reproduction stage for reproducing decoded image data having a rate component;
An image reproduction method comprising:   The image reproducing method according to claim 1, wherein the image region decoding step and the transmittance region decoding step perform decoding by the same processing method.   3. The image reproducing method according to claim 1, wherein the structure of the image area and the transmittance area is a three-channel JPEG format.   The image reproducing method according to claim 1, wherein the image component, the transmittance component, and the pseudo component are recorded in one file. An image reproduction device for reproducing compressed image data,
The compressed image data is the same as the image area in which the image components of three channels are recorded in a compressed format, the transmittance component in the same compression format as the image components, and the image region in which the pseudo components of two channels are recorded. Including the transparency region of the data structure,
Image region decoding means for decoding the image region;
A transmittance region decoding means for decoding the transmittance region;
One channel decoded transmission obtained by ignoring the two-channel pseudo channel from the three-channel decoded image component decoded by the image region decoding unit and the transmittance region decoded by the transmittance region decoding unit. Image reproduction means for reproducing decoded image data having a rate component;
An image reproducing apparatus comprising:   6. The image reproduction apparatus according to claim 5, wherein the image area decoding unit and the transmittance area decoding unit perform decoding by the same processing method.   7. The image reproducing apparatus according to claim 5, wherein the structure of the image area and the transmittance area is a three-channel JPEG format.   The image reproducing apparatus according to claim 5, wherein the image component, the transmittance component, and the pseudo component are recorded in one file. An image reproduction program for reproducing compressed image data,
The compressed image data is the same as the image area in which the image components of three channels are recorded in a compressed format, the transmittance component in the same compression format as the image components, and the image region in which the pseudo components of two channels are recorded. Including the transparency region of the data structure,
Image region decoding means for decoding the image region;
A transmittance region decoding means for decoding the transmittance region;
One channel decoded transmission obtained by ignoring the two-channel pseudo channel from the three-channel decoded image component decoded by the image region decoding unit and the transmittance region decoded by the transmittance region decoding unit. An image reproduction program that causes a computer to function as image reproduction means for reproducing decoded image data having a rate component.

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