JP3987425B2 - Image decompression apparatus, program, storage medium, and image decompression method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image expansion device, a program, a storage medium, and an image expansion method.
[0002]
[Prior art]
Today, image compression methods that divide image data into blocks (also called tiles), perform independent encoding for each block, and compress and encode image data are widely used in JPEG, JPEG2000, FlashPix, etc. Yes.
[0003]
By the way, in the compression encoding method as described above, various compression methods have been proposed for the purpose of shortening the decompression time. For example, in JPEG, a compression method called a block comparison technique (BCT: Block Comparator Technique) has been proposed. The BCT in JPEG is a block having the same pixel value at the time of compression as a representative block (a block subjected to the first compression) and the same block (a block having the same pixel value as the representative block). The object is to record the same relationship of the same block in a table (BCT table), incorporate it into a compressed file, and encode only the representative block to improve the compression rate. Also, at the time of decompression, the purpose is to shorten the decompression time by performing decompression processing only on the representative block and omitting decompression processing on the same block.
[0004]
[Problems to be solved by the invention]
However, the BCT in JPEG has a problem that since the compression format changes, it is necessary to implement functions dedicated to the method on the compression processing side and the decompression processing side.
[0005]
An object of the present invention is to provide an image decompression apparatus, a program, a storage medium, and an image decompression method capable of increasing the speed of decompression processing without changing the compression format.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 is an image decompression apparatus for decompressing code data obtained by subjecting pixel values to discrete wavelet transform and hierarchical compression coding for each rectangular area obtained by dividing an image into one or a plurality of areas. A cache unit that caches decompressed data obtained by decompressing data, a data determination unit that acquires the code data for each rectangular area, and determines whether the size of the acquired code data is equal to or less than a threshold value; When it is determined that the size of the code data is equal to or less than a threshold value, the data comparison means for determining whether other code data that matches the acquired code data is cached, and the data comparison means When it is determined that other matching code data is not cached, the acquired code data and this code data are expanded. Data cache means for caching the decompressed data and the decompressed data of the code data obtained by obtaining the decompressed data of the other matched code data when it is determined that the matched code data is cached by the data comparing means Decompression data alternative means for transferring as
[0007]
Therefore, when the size of the code data acquired for each rectangular area is equal to or smaller than the threshold value and other code data matching the code data is not cached, the code data and the code data are expanded. When the decompressed data is cached and other code data that matches the code data is cached, the decompressed data of the other code data that matches is transferred as the decompressed data of the code data. As a result, when the same code data appears for code data having a small size, such as blank image data, the decompressed data of the same code data that has been decompressed first is used without performing the decompression process. This makes it possible to increase the speed of the decompression process without changing the compression format.
[0008]
According to a second aspect of the present invention, there is provided an image decompressing apparatus for decompressing code data obtained by subjecting pixel values to discrete wavelet transform and hierarchical compression coding for each rectangular area obtained by dividing an image into one or a plurality of areas. A cache unit that caches decompressed data obtained by decompressing data; obtains the code data for each rectangular area; and the size of the obtained code data is equal to or less than a threshold value, and the appearance rate of the obtained code data is When it is determined that the size of the acquired code data is equal to or less than the threshold and the appearance rate of the acquired code data is equal to or greater than the threshold, the data determination unit that determines whether or not the threshold is equal to or greater than A data comparison means for determining whether or not other code data matching the acquired code data is cached, and the data comparison means When it is determined that other code data to be cached is not cached, the data cache means for caching the acquired code data and the decompressed data obtained by decompressing the code data, and the code data matched by the data comparison means are cached. And decompressed data substitution means for transferring decompressed data of other matching code data as decompressed data of the acquired code data when it is determined that the data is matched.
[0009]
Therefore, when it is determined that the size of the code data acquired for each rectangular area is equal to or smaller than the threshold and the appearance rate of the acquired code data is equal to or higher than the threshold, other codes that match the code data If the data is not cached, the code data and the decompressed data obtained by decompressing the code data are cached. If other code data that matches the code data is cached, the other code data that matches the code data The decompressed data is transferred as decompressed data of the code data. As a result, when the same code data appears for code data that appears at a certain ratio or more and has a small size, such as image data of a blank part, the same code that has been previously decompressed without performing the decompression process By using the decompressed data, it is possible to increase the speed of the decompression process without an overhead and without changing the compression format.
[0010]
According to a third aspect of the present invention, in the image expansion device according to the first or second aspect, the data comparison means is performed using a hash function.
[0011]
Therefore, it is possible to speed up verification of data identity.
[0012]
The invention according to claim 4 is installed in a computer that causes a computer to execute a process of decompressing code data obtained by performing discrete wavelet transform on pixel values and hierarchically compression-coding each rectangular area obtained by dividing an image into one or a plurality of rectangular areas. Or a program that is interpreted and executed, the cache function for caching the code data and decompressed data obtained by decompressing the code data in the computer, and obtaining the code data for each rectangular area, A data determination function for determining whether or not the size of the acquired code data is equal to or smaller than a threshold value, and when it is determined that the size of the acquired code data is equal to or smaller than the threshold value, it matches the acquired code data A data comparison function that determines whether other code data is cached, and this data comparison function When it is determined that the other code data that matches is not cached, the data cache function that caches the acquired code data and the decompressed data obtained by decompressing the code data, and the code data that matches by the data comparison function are When it is determined that the data is cached, a decompressed data substitution function for transferring the decompressed data of the matching other code data as the decompressed data of the acquired code data is executed.
[0013]
Therefore, when the size of the code data acquired for each rectangular area is equal to or smaller than the threshold value and other code data matching the code data is not cached, the code data and the code data are expanded. When the decompressed data is cached and other code data that matches the code data is cached, the decompressed data of the other code data that matches is transferred as the decompressed data of the code data. As a result, when the same code data appears for code data having a small size, such as blank image data, the decompressed data of the same code data that has been decompressed first is used without performing the decompression process. This makes it possible to increase the speed of the decompression process without changing the compression format.
[0014]
According to the fifth aspect of the present invention, a process for expanding code data obtained by subjecting pixel values to discrete wavelet transform and hierarchical compression encoding for each rectangular area obtained by dividing an image into one or a plurality of areas is installed in a computer or interpreted. A cache function that caches the code data and decompressed data obtained by decompressing the code data in the computer, and obtains the code data for each rectangular area, and obtains the code A data determination function for determining whether the size of the data is equal to or less than a threshold and the appearance rate of the acquired code data is equal to or greater than the threshold; and the size of the acquired code data is equal to or less than the threshold; and When it is determined that the appearance rate of the acquired code data is equal to or higher than a threshold, another code that matches the acquired code data The data comparison function for determining whether or not the data is cached, and the code comparison data and the code data acquired when it is determined by the data comparison function that the other matched code data is not cached. Data cache function that caches decompressed decompressed data and decompression of the code data obtained by obtaining decompressed data of other matched code data when it is determined by the data comparison function that the matched code data is cached And a decompression data substitution function to transfer as data.
[0015]
Therefore, when it is determined that the size of the code data acquired for each rectangular area is equal to or smaller than the threshold and the appearance rate of the acquired code data is equal to or higher than the threshold, other codes that match the code data If the data is not cached, the code data and the decompressed data obtained by decompressing the code data are cached. If other code data that matches the code data is cached, the other code data that matches the code data The decompressed data is transferred as decompressed data of the code data. As a result, when the same code data appears for code data that appears at a certain ratio or more and has a small size, such as image data of a blank part, the same code that has been previously decompressed without performing the decompression process By using the decompressed data, it is possible to increase the speed of the decompression process without an overhead and without changing the compression format.
[0016]
According to a sixth aspect of the present invention, in the program according to the fourth or fifth aspect, the data comparison function is performed using a hash function.
[0017]
Therefore, it is possible to speed up verification of data identity.
[0018]
A storage medium according to a seventh aspect stores the program according to any one of the fourth to sixth aspects.
[0019]
Therefore, by installing or interpreting the program stored in the storage medium in the computer, it is possible to obtain the same operation as that of the invention according to any one of claims 4 to 6.
[0020]
The invention according to claim 8 is an image decompression method for decompressing code data obtained by subjecting a pixel value to discrete wavelet transform and hierarchical compression coding for each rectangular area obtained by dividing an image into one or a plurality of rectangular areas. A data determination step of acquiring code data and determining whether or not the size of the acquired code data is equal to or less than a threshold value, and acquiring when it is determined that the size of the acquired code data is equal to or less than a threshold value The data comparison step for determining whether or not other code data that matches the code data is cached, and when the data comparison step determines that the other code data that matches is not cached. The data cache process that caches the encoded data and the decompressed data obtained by decompressing the encoded data matches the data comparing process. If the code data is judged to be cached, including the decompressed data alternative process of transferring the decompressed data of the other code data that matches the decompressed data of the encoded data acquired, the.
[0021]
Therefore, when the size of the code data acquired for each rectangular area is equal to or smaller than the threshold value and other code data matching the code data is not cached, the code data and the code data are expanded. When the decompressed data is cached and other code data that matches the code data is cached, the decompressed data of the other code data that matches is transferred as the decompressed data of the code data. As a result, when the same code data appears for code data having a small size, such as blank image data, the decompressed data of the same code data that has been decompressed first is used without performing the decompression process. This makes it possible to increase the speed of the decompression process without changing the compression format.
[0022]
The invention according to claim 9 is an image decompression method for decompressing code data obtained by subjecting a pixel value to discrete wavelet transform and hierarchical compression coding for each rectangular area obtained by dividing an image into one or a plurality of rectangular areas. A data determination step of acquiring code data, determining whether the size of the acquired code data is equal to or less than a threshold value, and whether the appearance rate of the acquired code data is equal to or greater than a threshold value, and the acquired code Whether or not other code data that matches the acquired code data is cached when the size of the data is equal to or smaller than the threshold and the appearance rate of the acquired code data is determined to be equal to or higher than the threshold The data comparison process for determining the code data obtained when the data comparison process determines that the other code data that matches is not cached. In addition, when it is determined by the data cache step that caches the decompressed data obtained by decompressing the code data and the code data that is matched by the data comparison step, the decompressed data of the other code data that matches is acquired. A decompression data substitution step of transferring the data as decompressed data of the code data.
[0023]
Therefore, when it is determined that the size of the code data acquired for each rectangular area is equal to or smaller than the threshold and the appearance rate of the acquired code data is equal to or higher than the threshold, other codes that match the code data If the data is not cached, the code data and the decompressed data obtained by decompressing the code data are cached. If other code data that matches the code data is cached, the other code data that matches the code data The decompressed data is transferred as decompressed data of the code data. As a result, when the same code data appears for code data that appears at a certain ratio or more and has a small size, such as image data of a blank part, the same code that has been previously decompressed without performing the decompression process By using the decompressed data, it is possible to increase the speed of the decompression process without an overhead and without changing the compression format.
[0024]
According to a tenth aspect of the present invention, in the image expansion method according to the eighth or ninth aspect, the data comparison step is performed using a hash function.
[0025]
Therefore, it is possible to speed up verification of data identity.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
First, an outline of the “hierarchical encoding algorithm” and the “JPEG2000 algorithm” that are the premise of the present embodiment will be described.
[0027]
FIG. 1 is a functional block diagram of a system that implements a hierarchical encoding algorithm that is the basis of the JPEG2000 system. This system includes color space transform / inverse transform unit 101, two-dimensional wavelet transform / inverse transform unit 102, quantization / inverse quantization unit 103, entropy encoding / decoding unit 104, and tag processing unit 105. It is configured.
[0028]
One of the biggest differences between this system and the conventional JPEG algorithm is the conversion method. In JPEG, discrete cosine transform (DCT) is used. In this hierarchical coding algorithm, the two-dimensional wavelet transform / inverse transform unit 102 uses discrete wavelet transform (DWT). ing. DWT has the advantage of better image quality in the high compression region than DCT, and this is one of the main reasons why DWT is adopted in JPEG2000, which is a successor algorithm of JPEG.
[0029]
Another major difference is that in this hierarchical encoding algorithm, a functional block of the tag processing unit 105 is added in order to perform code formation at the final stage of the system. The tag processing unit 105 generates compressed data as code string data during an image compression operation, and interprets code string data necessary for decompression during the decompression operation. And JPEG2000 can realize various convenient functions by code string data. For example, the compression / decompression operation of a still image can be freely stopped at an arbitrary layer (decomposition level) corresponding to octave division in block-based DWT (see FIG. 3 described later).
[0030]
In many cases, color space conversion / inverse conversion 101 is connected to the input / output portion of the original image. For example, the RGB color system composed of R (red) / G (green) / B (blue) components of the primary color system and the Y (yellow) / M (magenta) / C (cyan) components of the complementary color system This corresponds to the part that performs conversion or reverse conversion from the YMC color system consisting of the above to the YUV or YCbCr color system.
[0031]
Next, the JPEG2000 algorithm will be described.
[0032]
As shown in FIG. 2, in a color image, each component 111 (RGB primary color system here) of an original image is generally divided by a rectangular area. This divided rectangular area is generally called a block or a tile. In JPEG2000, it is generally called a tile. Therefore, such a divided rectangular area is hereinafter referred to as a tile. (In the example of FIG. 2, each component 111 is divided into a total of 16 rectangular tiles 112, 4 × 4 in length and breadth). When such individual tiles 112 (R00, R01,..., R15 / G00, G01,..., G15 / B00, B01,..., B15 in the example of FIG. 2) execute the image data compression / decompression process. It becomes the basic unit. Therefore, the compression / decompression operation of the image data is performed independently for each component and for each tile 112.
[0033]
At the time of encoding image data, the data of each tile 112 of each component 111 is input to the color space conversion / inverse conversion unit 101 in FIG. A dimensional wavelet transform (forward transform) is applied to divide the space into frequency bands.
[0034]
FIG. 3 shows subbands at each decomposition level when the number of decomposition levels is three. In other words, the tile original image (0LL) (decomposition level 0) obtained by tile division of the original image is subjected to two-dimensional wavelet transform, and the subbands (1LL, 1HL, 1LH shown in the decomposition level 1) , 1HH). Subsequently, the low-frequency component 1LL in this hierarchy is subjected to two-dimensional wavelet transformation to separate the subbands (2LL, 2HL, 2LH, 2HH) indicated by the decomposition level 2. Similarly, the low-frequency component 2LL is also subjected to two-dimensional wavelet transform to separate subbands (3LL, 3HL, 3LH, 3HH) shown in the decomposition level 3. In FIG. 3, the subbands to be encoded at each decomposition level are indicated by shading. For example, when the number of decomposition levels is 3, the subbands (3HL, 3LH, 3HH, 2HL, 2LH, 2HH, 1HL, 1LH, 1HH) indicated by shading are the encoding targets, and the 3LL subband is encoded. It is not converted.
[0035]
Next, the bits to be encoded are determined in the specified encoding order, and the context is generated from the bits around the target bits by the quantization / inverse quantization unit 103 shown in FIG.
[0036]
The wavelet coefficients that have undergone the quantization process are divided into non-overlapping rectangles called “precincts” for each subband. This was introduced to use memory efficiently in implementation. As shown in FIG. 4, one precinct consists of three rectangular regions that are spatially coincident. Further, each precinct is divided into non-overlapping rectangular “code blocks”. This is the basic unit for entropy coding.
[0037]
The coefficient value after wavelet transform can be quantized and encoded as it is, but in JPEG2000, in order to increase the encoding efficiency, the coefficient value is decomposed into “bit plane” units, and each pixel or code block is divided. Ranking can be performed on “bitplanes”.
[0038]
Here, FIG. 5 is an explanatory diagram showing an example of a procedure for ranking the bit planes. As shown in FIG. 5, this example is a case where the original image (32 × 32 pixels) is divided into four 16 × 16 pixel tiles, and the size of the precinct and code block at the composition level 1 is Each is 8 × 8 pixels and 4 × 4 pixels. The numbers of the precinct and the code block are assigned in raster order. In this example, the number of assigns is assigned from numbers 0 to 3, and the code block is assigned from numbers 0 to 3. A mirroring method is used for pixel expansion outside the tile boundary, wavelet transform is performed with a reversible (5, 3) filter, and a wavelet coefficient value of decomposition level 1 is obtained.
[0039]
An explanatory diagram showing an example of the concept of a typical “layer” configuration for tile 0 / precinct 3 / code block 3 is also shown in FIG. The converted code block is divided into subbands (1LL, 1HL, 1LH, 1HH), and wavelet coefficient values are assigned to the subbands.
[0040]
The layer structure is easy to understand when the wavelet coefficient values are viewed from the horizontal direction (bit plane direction). One layer is composed of an arbitrary number of bit planes. In this example, layers 0, 1, 2, and 3 are made up of bit planes of 1, 3, 1, and 3, respectively. A layer including a bit plane closer to LSB (Least Significant Bit) is subject to quantization first. Conversely, a layer closer to MSB (Most Significant Bit) is quantized to the end. It will remain without being. A method of discarding from a layer close to the LSB is called truncation, and the quantization rate can be finely controlled.
[0041]
The entropy encoding / decoding unit 104 illustrated in FIG. 1 performs encoding on the tile 112 of each component 111 by probability estimation from the context and the target bit. In this way, encoding processing is performed in units of tiles 112 for all components 111 of the original image. Finally, the tag processing unit 105 performs a process of combining all the encoded data from the entropy encoding / decoding unit 104 into one code string data (code stream) and adding a tag thereto.
[0042]
FIG. 6 shows a schematic configuration of a JPEG2000 code format. The code format starts with an SOC (Start of Codestream) marker indicating the start of code data. The SOC marker is followed by a main header which is tag information describing coding parameters, quantization parameters, and the like, followed by actual code data. The actual code data starts with an SOT (Start of Tile-part) marker, and is composed of a tile header (Tile Header), an SOD (Start of data) marker, and tile data (code: bit stream) as tag information. After the code data corresponding to the entire image, an EOC (End of Codestream) marker which is tag information indicating the end of the code is added.
[0043]
On the other hand, at the time of decoding, the image data is generated from the code string data of each tile 112 of each component 111, contrary to the case of encoding the image data. In this case, the tag processing unit 105 interprets tag information added to the code string data input from the outside, decomposes the code string data into code string data of each tile 112 of each component 111, and Decoding processing (decompression processing) is performed for each code string data of each tile 112. At this time, the positions of the bits to be decoded are determined in the order based on the tag information in the code string data, and the quantization / inverse quantization unit 103 determines the peripheral bits of the target bit position (already decoded). Context is generated from the sequence of The entropy encoding / decoding unit 104 performs decoding by probability estimation from the context and code string data, generates a target bit, and writes it in the position of the target bit. Since the data decoded in this way is spatially divided for each frequency band, the two-dimensional wavelet transform / inverse transform unit 102 performs two-dimensional wavelet inverse transform on each of the components of the image data. The tile is restored. The restored data is converted to original color system image data by the color space conversion / inverse conversion unit 101.
[0044]
The above is the outline of the “JPEG2000 algorithm”.
[0045]
Hereinafter, an embodiment of the present invention will be described. Although an example relating to an image compression / decompression technique represented by JPEG2000 will be described here, it goes without saying that the present invention is not limited to the contents of the following description.
[0046]
7 is a system configuration diagram showing a system including the image processing apparatus 1 to which the present invention is applied, and FIG. 8 is a functional block diagram schematically showing the image processing apparatus 1. As shown in FIG. 7, an image processing apparatus 1 to which the present invention is applied is, for example, a personal computer, and can be connected to a server computer S that stores various image data via a network 5 that is the Internet. . In the present embodiment, the image data stored and held in the server computer S is code string data compressed and generated according to the “JPEG2000 algorithm”. As shown in FIG. 8, the image processing apparatus 1 displays an image based on the image decompression apparatus 2 that decompresses (decodes) the code string data received from the server computer S into image data and the decompressed image data. An image display device 3 and a code string storage unit 4 that stores code string data received from the server computer S are provided. The code string storage unit 4 functions as a general buffer, or functions as a storage for code string data of an image over a long period of time, and is used depending on the application.
[0047]
Next, the hardware configuration of the image processing apparatus 1 will be described with reference to FIG. As shown in FIG. 9, an image processing apparatus 1 includes a central processing unit (CPU) 6 that performs information processing by centrally controlling each unit, a read only memory (ROM) that stores information, and a random access memory (RAM). A memory 7 comprising: a HDD (Hard Disk Drive) 10 constituting a code string storage unit 4 for storing code string data (see FIG. 6) downloaded from the server computer S via the network 5; CD-ROM drive 12 for distributing information and obtaining information from the outside, communication control device 13 for communicating information with other external computers via the network 5, operating the process and results A display device 15 such as a CRT (Cathode Ray Tube) or LCD (Liquid Crystal Display) constituting the image display device 3 to be displayed to the user, and an operator gives commands and information to the CPU 6. It comprises an input device 14 such as a keyboard and mouse for input, a logic circuit 8 and the like. The bus controller 9 operates by arbitrating data transmitted and received between these units.
[0048]
In the present embodiment, the memory 7 and the HDD 10 also function as a cache unit that caches some data.
[0049]
In such an image processing apparatus 1, when the user turns on the power, the CPU 6 activates a program called a loader in the memory 7, loads a program for managing computer hardware and software called an operating system from the HDD 10 into the memory 7, Start this operating system. Such an operating system starts a program, reads information, and performs storage according to a user operation. As typical operating systems, Windows (registered trademark), UNIX (registered trademark), and the like are known. An operation program running on these operating systems is called an application program.
[0050]
Here, the image processing apparatus 1 stores an image processing program in the HDD 10 as an application program. In this sense, the HDD 10 functions as a storage medium that stores an image processing program.
[0051]
In general, an operation program installed in the HDD 10 of the image processing apparatus 1 is recorded on an optical information recording medium such as a CD-ROM 11 or DVD-ROM, a magnetic medium such as an FD, and the like. A program is installed in the HDD 10. For this reason, portable storage media such as optical information recording media such as the CD-ROM 11 and magnetic media such as the FD can also be storage media for storing the image processing program. Furthermore, the image processing program may be imported from the outside via, for example, the communication control device 13 and installed in the HDD 10.
[0052]
In the image processing apparatus 1, when an image processing program that operates on an operating system is started, the CPU 6 executes various arithmetic processes according to the image processing program and controls each unit intensively. Here, the operation of each part of the image processing apparatus 1 executed by the CPU 6 will be briefly described. The code string data (JPEG2000 data) output from the server computer S to the image processing apparatus 1 via the network 5 is output to the code string storage unit 4 and stored in the HDD 10, and is decompressed by the image decompressing apparatus 2. The Then, the image data generated by the decompression process by the image decompression device 2 is output to the image display device 3, and an image based on the decompressed image data is displayed on the display device 15. Various functions in these units are realized by processing performed by the CPU 6 in accordance with the above-described image processing program. In addition, when real-time property is regarded as important, it is necessary to speed up the processing. For this purpose, it is desirable to realize various functions in each unit by the operation of the logic circuit 8.
[0053]
Next, characteristic processing of the present embodiment among various types of arithmetic processing executed by the CPU 6 of the image processing apparatus 1 will be described below. Here, the image expansion process in the image expansion apparatus 2 which is a main part of the present invention will be described.
[0054]
Here, FIG. 10 is a flowchart schematically showing the flow of the image expansion processing. As shown in FIG. 10, the image decompression process according to the present embodiment is obtained by adding a cache control process in which some data is cached in the memory 7 or the HDD 10 to the conventional image decompression process.
[0055]
First, for the first tile of the code string data (JPEG2000 data) input to the image decompression device 2 (N in step S1), whether the code data of the tile (tile data shown in FIG. 6) can be cached or not. (Step S2: data determination means).
[0056]
Here, the determination as to whether or not the cache is possible is made based on whether or not the cache conditions (size and appearance rate) are met. Here, the condition for caching the code data will be described. For example, when the size of the code data is about several hundred bytes, it is highly possible that the code data is blank image data, and it is considered that there are other similar tiles. Therefore, by setting the condition that the size of the code data is equal to or smaller than the threshold (about several hundred bytes) as a cache condition, it is possible to easily extract data for similar tiles. Even if the size of the code data is about several hundred bytes, the code data may be cached only when tiles having the same size appear in a certain ratio (about 5%) or more. . This is because even if the code data is accommodated in the cache, if the number of similar tiles is small, there is some overhead, and the cache processing does not work efficiently.
[0057]
If it is determined that the code data can be cached (Y in step S2), the process proceeds to step S3. If it is not determined that the code data is cacheable (N in step S2), the process proceeds to step S4, and the code data of the tile is decompressed according to the “JPEG2000 algorithm”. For decompression processing (decoding processing) in accordance with the “JPEG2000 algorithm” of code data, the spatial transform / inverse transform unit 101, the two-dimensional wavelet transform / inverse transform unit 102, and the quantization / inverse quantization unit shown in FIG. 103, the description of the entropy encoding / decoding unit 104 and the tag processing unit 105 has been described above, and a description thereof will be omitted here.
[0058]
In step S3, it is determined whether or not the same code data as the code data of the tile is cached. In this determination, a hash function is used instead of comparing all codes. By using the hash function in this way, it is possible to speed up verification of data identity. Here, the function of the data comparison means is executed.
[0059]
When it is determined that the same code data as the code data of the tile is not cached (N in step S3), after the code data of the tile is expanded (step S5), the code data and the code data are The expanded tile data is stored in the cache (step S6: data cache unit), and the process returns to step S1 to process the next tile.
[0060]
If it is determined that the same code data as the code data of the tile is cached (Y in step S3), tile data expanded before the code data match is transferred from the cache (step S7: Decompressed data alternative means).
[0061]
Here, when the size of the code data acquired for each rectangular area is equal to or smaller than the threshold value, and other code data matching the code data is not cached, the code data and the code data are decompressed. When the decompressed data is cached and other code data that matches the code data is cached, the decompressed data of the other code data that matches is transferred as the decompressed data of the code data. As a result, when the same code data appears for code data having a small size, such as blank image data, the decompressed data of the same code data that has been decompressed first is used without performing the decompression process. This makes it possible to increase the speed of the decompression process without changing the compression format.
[0062]
In the present embodiment, the code data and the tile data obtained by decompressing the code data are cached in the memory 7 or the HDD 10, but the present invention is not limited to this. For example, the CPU 6 or the logic circuit 8 may be provided with a cache memory in advance, and the code data and tile data obtained by decompressing the code data may be accommodated in the cache memory.
[0063]
In the present embodiment, the case where the tile division process is performed on the original image has been described. However, the present invention is not limited to this. Even when tile division is not performed on the original image, a precinct or a code block in the JPEG2000 algorithm can be used as a rectangular area (block).
[0064]
【The invention's effect】
According to the first aspect of the present invention, in the image decompression device for decompressing code data obtained by subjecting pixel values to discrete wavelet transform and hierarchical compression coding for each rectangular region obtained by dividing an image into one or a plurality of regions, the code data and A cache unit that caches decompressed data obtained by decompressing the code data; a data determination unit that acquires the code data for each rectangular area and determines whether the size of the acquired code data is equal to or less than a threshold; A data comparison unit that determines whether or not other code data that matches the acquired code data is cached when it is determined that the size of the acquired code data is equal to or less than a threshold; When it is determined by the means that other code data that matches is not cached, the acquired code data and the code data Data cache means for caching the decompressed data obtained by decompressing the data, and when the code comparison data is judged to be cached by the data comparison means, A decompressed data alternative means for transferring as decompressed data, and the size of the code data acquired for each rectangular area is equal to or smaller than a threshold value, and other code data matching the code data is not cached The code data and the decompressed data obtained by decompressing the code data are cached, and when other code data that matches the code data is cached, the decompressed data of the other code data that matches the code data By transferring the data as decompressed data, it is possible to reduce If the same code data appears for the data, the decompression process can be accelerated without changing the compression format by using the decompressed data of the same code data that has been decompressed before the decompression process. Can be achieved.
[0065]
According to the second aspect of the present invention, in the image decompression apparatus for decompressing code data obtained by subjecting pixel values to discrete wavelet transform and hierarchical compression coding for each rectangular region obtained by dividing an image into one or a plurality of regions, the code data and A cache unit that caches decompressed data obtained by decompressing the code data, obtains the code data for each rectangular area, and the size of the obtained code data is equal to or smaller than a threshold, and the appearance of the obtained code data Data determination means for determining whether the rate is equal to or greater than a threshold value, when the size of the acquired code data is equal to or less than the threshold value, and the appearance rate of the acquired code data is determined to be equal to or greater than the threshold value A data comparison means for determining whether or not other code data that matches the acquired code data is cached, and the data comparison means Data cache means for caching the acquired code data and the decompressed data obtained by decompressing the code data when it is determined that other code data that matches the data is not cached, and the code data matched by the data comparison means Code data acquired for each rectangular area, and decompressed data alternative means for transferring the decompressed data of the other code data that coincides as the decompressed data of the code data when it is determined that the data is cached Is smaller than the threshold, and it is determined that the appearance rate of the acquired code data is greater than or equal to the threshold, and other code data that matches the code data is not cached, The code data and the decompressed data obtained by decompressing the code data are cached, and other codes that match the code data If the data is cached, the decompressed data of the other code data that matches is transferred as the decompressed data of the code data, so that it appears at a certain ratio or more like the image data of the blank portion and the size is small. When the same code data appears for the code data, the compression format is changed without any overhead by using the decompressed data of the same code data that has been decompressed before the decompression process. It is possible to speed up the decompression process without any problem.
[0066]
According to a third aspect of the present invention, in the image decompression apparatus according to the first or second aspect, the data comparison unit can perform a high-speed verification of data identity by using a hash function. it can.
[0067]
According to the fourth aspect of the present invention, the image processing apparatus is installed in a computer that causes the computer to execute a process of decompressing code data obtained by performing discrete wavelet transform on pixel values and hierarchically compression-coding each rectangular area obtained by dividing an image into one or more. Or a program that is executed after being interpreted, the computer having the cache function for caching the code data and decompressed data obtained by decompressing the code data, and obtaining the code data for each rectangular area A data determination function for determining whether or not the size of the acquired code data is equal to or smaller than a threshold value, and when the size of the acquired code data is determined to be equal to or smaller than the threshold value, A data comparison function for determining whether or not other matching code data is cached, and the data comparator The data cache function that caches the acquired code data and the decompressed data obtained by decompressing the code data when it is determined that other code data that matches is not cached, and the code data that matches by the data comparison function Code is obtained for each rectangular area by executing the decompressed data substitution function for transferring the decompressed data of the other code data that matches with the decompressed data of the code data obtained when the data is cached. If the data size is equal to or smaller than the threshold value and other code data matching the code data is not cached, the code data and the decompressed data obtained by decompressing the code data are cached, and the code data If other code data that matches is cached, the other code that matches By transferring the decompressed data of the data as decompressed data of the code data, when the same code data appears for the code data having a small size such as the image data of the blank portion, the decompression process is not performed. By using decompressed data of the same code data that has undergone decompression processing, it is possible to speed up the decompression processing without changing the compression format.
[0068]
According to the invention described in claim 5, is a computer installed with a process of decompressing code data obtained by performing discrete wavelet transform on pixel values and hierarchically compression-coding each rectangular area obtained by dividing an image into one or a plurality of areas, Alternatively, the program is interpreted and executed, and the computer acquires the code data and the cache function for caching the decompressed data obtained by decompressing the code data, and obtains the code data for each rectangular area. A data determination function for determining whether the size of the code data is equal to or smaller than a threshold and the appearance rate of the acquired code data is equal to or larger than the threshold; and the size of the acquired code data is equal to or smaller than the threshold. In addition, when it is determined that the appearance rate of the acquired code data is equal to or greater than a threshold value, The data comparison function for determining whether or not the code data is cached, and when it is determined by the data comparison function that other code data that matches is not cached, the acquired code data and the code data are Data cache function that caches decompressed decompressed data and decompression of the code data obtained by obtaining decompressed data of other matched code data when it is determined by the data comparison function that the matched code data is cached When the decompressed data substitution function to transfer as data is executed, the size of the code data acquired for each rectangular area is determined to be less than or equal to the threshold value, and the appearance rate of the acquired code data is determined to be equal to or greater than the threshold value. If other code data that matches the code data is not cached, the code Data and the decompressed data obtained by decompressing the code data are cached, and when other code data that matches the code data is cached, the decompressed data of the other code data that matches the decompressed data of the code data When the same code data appears for code data with a small size that appears at a certain ratio or more like the image data of the blank part, the decompression process was performed first without performing the decompression process. By using decompressed data of the same code data, it is possible to increase the speed of decompression processing without overhead and without changing the compression format.
[0069]
According to a sixth aspect of the invention, in the program according to the fourth or fifth aspect, the data comparison function is performed using a hash function, so that verification of data identity can be speeded up.
[0070]
According to the storage medium of the invention described in claim 7, by storing the program according to any one of claims 4 to 6, the program stored in the storage medium is installed in the computer or interpreted. By doing so, it is possible to obtain the same effects as the invention according to any one of claims 4 to 6.
[0071]
According to an eighth aspect of the present invention, in the image decompression method for decompressing code data obtained by subjecting a pixel value to discrete wavelet transform and hierarchical compression coding for each rectangular area obtained by dividing an image into one or a plurality of rectangular areas, A data determination step of acquiring the code data and determining whether or not the size of the acquired code data is equal to or smaller than a threshold; and when it is determined that the size of the acquired code data is equal to or smaller than the threshold A data comparison step for determining whether or not other code data that matches the acquired code data is cached, and when it is determined by the data comparison step that other code data that matches is not cached A data cache step for caching the acquired code data and decompressed data obtained by decompressing the code data, and the data comparison step A decompression data substitution step that transfers the decompressed data of the other code data that matches with the decompressed data of the code data acquired when it is determined that matching code data is cached. When the size of the acquired code data is equal to or smaller than the threshold value and other code data matching the code data is not cached, the code data and the decompressed data obtained by decompressing the code data are cached, If other code data that matches the code data is cached, the decompressed data of the other code data that matches is transferred as decompressed data of the code data, so that the size of the image data in the blank portion If the same code data appears for code data with a small size, the decompression process is performed first without performing the decompression process. Was by using the extension data of the same coded data, it is possible to increase the speed of expansion processing without changing the compression format.
[0072]
According to the ninth aspect of the present invention, in the image decompression method for decompressing code data obtained by subjecting pixel values to discrete wavelet transform and hierarchical compression coding for each rectangular region obtained by dividing an image into one or a plurality of regions, each rectangular region A data determination step of acquiring the code data, determining whether the size of the acquired code data is equal to or less than a threshold value, and whether the appearance rate of the acquired code data is equal to or greater than the threshold value; Whether other code data matching the acquired code data is cached when the size of the code data is less than or equal to the threshold and the appearance rate of the acquired code data is determined to be greater than or equal to the threshold The data comparison step for determining whether or not the code code obtained when it is determined that the other code data that matches the data comparison step is not cached. Data and a data cache step for caching the decompressed data obtained by decompressing the code data, and when the matching data is determined to be cached by the data comparison step, A decompression data substitution step for transferring as decompressed data of the acquired code data, the size of the code data acquired for each rectangular area is equal to or less than a threshold value, and the appearance rate of the acquired code data is equal to or greater than the threshold value If other code data that matches the code data is not cached, the code data and the decompressed data obtained by decompressing the code data are cached, and other data that matches the code data is stored. If the code data of the other code data is cached, the decompressed data of the other code data that matches is sent to the code data. If the same code data appears for code data with a small size that appears at a certain ratio or more, such as blank image data, the decompression process is performed first without performing the decompression process. By using the decompressed data of the same code data that has been subjected to the above, it is possible to increase the speed of the decompression process without an overhead and without changing the compression format.
[0073]
According to a tenth aspect of the present invention, in the image decompression method according to the eighth or ninth aspect, the data comparison step is performed using a hash function, thereby speeding up verification of data identity. it can.
[Brief description of the drawings]
FIG. 1 is a functional block diagram of a system that realizes a hierarchical encoding algorithm that is the basis of the JPEG2000 system that is a premise of the present invention.
FIG. 2 is an explanatory diagram showing a divided rectangular area of each component of the original image.
FIG. 3 is an explanatory diagram showing subbands at each decomposition level when the number of decomposition levels is 3. FIG.
FIG. 4 is an explanatory diagram showing a precinct.
FIG. 5 is an explanatory diagram showing an example of a procedure for ranking bit planes;
FIG. 6 is an explanatory diagram showing a schematic configuration of a JPEG2000 code format.
FIG. 7 is a system configuration diagram showing a system including an image processing apparatus according to an embodiment of the present invention.
FIG. 8 is a functional block diagram schematically showing an image processing apparatus.
FIG. 9 is a block diagram schematically illustrating a hardware configuration of the image processing apparatus.
FIG. 10 is a flowchart schematically showing a flow of image expansion processing.
[Explanation of symbols]
2 Image expansion device
10,11 Storage media

Claims (10)

In an image decompression device for decompressing code data obtained by subjecting pixel values to discrete wavelet transform and hierarchical compression coding for each rectangular region obtained by dividing an image into one or more,
A cache unit for caching the code data and the extension data extended the code data,
Data determination means for acquiring the code data for each rectangular area and determining whether the size of the acquired code data is equal to or less than a threshold;
A data comparison means for determining whether or not other code data that matches the acquired code data is cached when it is determined that the size of the acquired code data is equal to or less than a threshold;
And data cache means other code data matching by said data comparing means for caching the extension data extended if it is determined not to be cached, the code data and the code data acquired,
Decompressed data substitution means for transferring, as the decompressed data of the code data, the decompressed data of the other matched code data, when the data comparing means determines that the matched code data is cached;
An image expansion apparatus comprising: In an image decompression device for decompressing code data obtained by subjecting pixel values to discrete wavelet transform and hierarchical compression coding for each rectangular region obtained by dividing an image into one or more,
A cache unit for caching the code data and the extension data extended the code data,
Data determination means for acquiring the code data for each rectangular area, and determining whether the size of the acquired code data is equal to or less than a threshold and whether the appearance rate of the acquired code data is equal to or greater than the threshold When,
When it is determined that the size of the acquired code data is equal to or smaller than the threshold and the appearance rate of the acquired code data is equal to or higher than the threshold, other code data that matches the acquired code data is cached. Data comparison means for determining whether or not
And data cache means other code data matching by said data comparing means for caching the extension data extended if it is determined not to be cached, the code data and the code data acquired,
Decompressed data substitution means for transferring, as the decompressed data of the code data, the decompressed data of the other matched code data, when the data comparing means determines that the matched code data is cached;
An image expansion apparatus comprising: The image expansion apparatus according to claim 1 or 2, wherein the data comparison means is performed using a hash function. Installed in or interpreted by a computer that causes the computer to execute processing for decompressing code data obtained by performing discrete wavelet transform on pixel values for each rectangular area obtained by dividing an image into one or a plurality of images and hierarchically compression-coding the image data A program for the computer,
A cache function for caching the code data and the extension data extended the code data,
A data determination function for acquiring the code data for each rectangular area and determining whether the size of the acquired code data is equal to or less than a threshold;
A data comparison function for determining whether other code data that matches the acquired code data is cached when it is determined that the size of the acquired code data is equal to or less than a threshold;
When the other code data matching by said data comparing function is judged not to be cached, the data cache function for caching the extension data extended the code data and the code data acquired,
A decompressed data substitution function for transferring, as the decompressed data of the encoded data, the decompressed data of the matched other code data, when the matched code data is determined to be cached by the data comparison function;
A program characterized by having executed. This is a program that is installed in a computer, or is interpreted and executed by a computer to perform processing for decompressing code data obtained by subjecting pixel values to discrete wavelet transform and hierarchical compression encoding for each rectangular area obtained by dividing an image into one or more. And the computer
A cache function for caching the code data and the extension data extended the code data,
A data determination function that acquires the code data for each rectangular area, determines whether the size of the acquired code data is equal to or less than a threshold value, and whether the appearance rate of the acquired code data is equal to or greater than a threshold value When,
When it is determined that the size of the acquired code data is equal to or smaller than the threshold and the appearance rate of the acquired code data is equal to or higher than the threshold, other code data that matches the acquired code data is cached. Data comparison function to determine whether or not
When the other code data matching by said data comparing function is judged not to be cached, the data cache function for caching the extension data extended the code data and the code data acquired,
A decompressed data substitution function for transferring, as the decompressed data of the encoded data, the decompressed data of the matched other code data, when the matched code data is determined to be cached by the data comparison function;
A program characterized by having executed. 6. The program according to claim 4, wherein the data comparison function is performed using a hash function. A storage medium storing the program according to any one of claims 4 to 6. In an image decompression method for decompressing code data obtained by subjecting pixel values to discrete wavelet transform and hierarchically compression-encoding for each rectangular region obtained by dividing an image into one or a plurality of regions,
A data determination step of acquiring the code data for each rectangular area and determining whether the size of the acquired code data is equal to or less than a threshold;
A data comparison step of determining whether other code data that matches the acquired code data is cached when it is determined that the size of the acquired code data is equal to or less than a threshold;
A data cache process other code data matching by said data comparing step to cache the decompressed data extended if it is determined not to be cached, the code data and the code data acquired,
When it is determined that the matching code data is cached by the data comparison step, a decompression data substitution step of transferring the decompression data of the other matching code data as the decompressed data of the obtained code data;
An image decompression method comprising: In an image decompression method for decompressing code data obtained by subjecting pixel values to discrete wavelet transform and hierarchically compression-encoding for each rectangular region obtained by dividing an image into one or a plurality of regions,
A data determination step of acquiring the code data for each rectangular area, and determining whether the size of the acquired code data is equal to or less than a threshold and whether the appearance rate of the acquired code data is equal to or greater than the threshold. When,
When it is determined that the size of the acquired code data is equal to or smaller than the threshold and the appearance rate of the acquired code data is equal to or higher than the threshold, other code data that matches the acquired code data is cached. A data comparison process to determine whether or not
A data cache process other code data matching by said data comparing step to cache the decompressed data extended if it is determined not to be cached, the code data and the code data acquired,
When it is determined that the matching code data is cached by the data comparison step, a decompression data substitution step of transferring the decompression data of the other matching code data as the decompressed data of the obtained code data;
An image decompression method comprising: 10. The image expansion method according to claim 8, wherein the data comparison step is performed using a hash function.

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