JP6158576B2 - Image compression apparatus, image decompression apparatus, image compression program, image decompression program, and data structure - Google Patents

Description

  The present invention relates to an image compression apparatus, an image decompression apparatus, an image compression program, an image decompression program, and a data structure.

  Conventionally, in order to efficiently store or transmit medical image data such as X-ray images and CT images, it is required to compress the images at high speed. For example, Patent Document 1 discloses a method of compressing image data indicating an image captured using radiation. In order to speed up the compression of image data, a method of compressing block data which is a part of a plurality of image data by a plurality of processors is known. For example, Patent Document 2 discloses a method of performing Huffman coding for each of a plurality of block data.

JP 2011-130880 A JP 2004-104677 A

By the way, the compression process using Huffman coding has a problem that it takes a long time to process the frequency of pixel values in image data.
In image data with a large background area, such as medical image data, the same pixel values are often continuous in both the vertical and horizontal directions. For example, many medical image data have a feature that the pixel value is 0 in many pixels of the image data because the pixel value at a position where a part of the body is not projected is 0. Therefore, an image compression apparatus capable of compressing image data at high speed by utilizing such characteristics of image data is desired.

The present invention has been made in view of these points, and an object thereof is to provide an image compression apparatus, an image compression program, and a data structure capable of compressing image data at high speed.
It is another object of the present invention to provide an image decompression apparatus and an image decompression program that can restore compressed image data created by an image compression apparatus and an image compression program.

  In the first aspect of the present invention, an image data acquisition unit that acquires image data, and block data that is a part of the image data, a plurality of sub-block data including a plurality of pixel information indicating pixel values of pixels in the image data A compressing unit that compresses sub-block data to create compressed sub-block data, and a combining unit that combines compressed sub-block data to create compressed image data. The unit includes a specifying unit that specifies a minimum value from pixel values of a plurality of pixel information, a subtraction unit that subtracts the minimum value from pixel values of the plurality of pixel information, and pixel information whose pixel value is other than a predetermined value. A pressure including effective pixel information, a pixel value after the minimum value is subtracted by the subtracting unit, compressed pixel information that associates information specifying the pixel position of the pixel value, and information indicating the minimum value. A creation unit for creating a finished sub-block data, to provide an image compression device comprising a.

  In the above image compression apparatus, each of the plurality of pieces of pixel information has a predetermined data length, the specifying unit specifies the maximum value from the pixel values of the plurality of pieces of pixel information, and the creating unit has the predetermined data length. The compressed sub-block data may be created by changing the data length to the pixel value obtained by subtracting the minimum value from the maximum value.

  In the above image compression device, the specifying unit specifies the number of effective pixel information based on the pixel values of the plurality of pixel information, and the creating unit includes a plurality of pixels when the number of effective pixel information is within a predetermined range. Information indicating whether each piece of information is effective pixel information, map data for storing the order of the plurality of pixel information in the sub-block, pixel values of effective pixel information after subtracting the minimum value by the subtracting unit, Compressed sub-block data including may be created. In the above image compression apparatus, a plurality of compression units are provided, and a plurality of sub-block data may be compressed in parallel.

  In the second aspect of the present invention, the computer includes an image data acquisition unit that acquires image data, block data that is a part of the image data, and a plurality of pixel information that includes a plurality of pixel information indicating pixel values of the pixels in the image data. Functions as a division unit that divides into sub-block data, a compression unit that compresses sub-block data to create compressed sub-block data, and a combining unit that combines compressed sub-block data to create compressed image data The compression unit includes a specifying unit that specifies the minimum value from the pixel values of the plurality of pixel information, a subtraction unit that subtracts the minimum value from the pixel values of the plurality of pixel information, and a pixel having a pixel value other than the predetermined value. The compressed pixel information in which the pixel value after the minimum value is subtracted by the subtraction unit of the effective pixel information, which is information, and the information specifying the pixel position of the pixel value, and the minimum A creation unit that creates a zipped subblock data including information indicating to provide an image compression program including.

  In the third aspect of the present invention, an image data acquisition unit that acquires compressed image data obtained by compressing image data, and the compressed image data are divided into compressed block data that is a part of the compressed image data. A dividing unit that acquires compressed sub-block data to be configured; and a sub that includes a plurality of pieces of pixel information indicating pixel values of pixels in the image data that constitutes block data that is a part of the image data by decompressing the compressed sub-block data A decompression unit that restores block data; and a concatenation unit that restores image data by combining a plurality of sub-block data restored by the decompression unit. The compressed sub-block data includes a plurality of pixels included in the sub-block data. The minimum value and the pixel value after subtraction of the minimum value of the effective pixel information of the pixel value other than the predetermined value in the image data, And compressed pixel information associated with information specifying the pixel position of the pixel value, the decompression unit includes a minimum value acquisition unit that acquires a minimum value from the compressed image data, and compressed sub-block data Based on the compressed pixel information included in the pixel block, the pixel restoration unit that restores the pixel information included in the sub-block data, and the minimum value are added to each of the pixel values of the pixel information restored by the pixel restoration unit. An image decompression device comprising: a pixel value restoration unit that restores a pixel value before compression.

  In the fourth aspect of the present invention, the computer includes an image data acquisition unit that acquires compressed image data obtained by compressing image data, and a compressed image that is a part of the compressed image data by dividing the compressed image data. A division unit that obtains compressed sub-block data constituting block data, and pixel information that indicates pixel values of pixels in the image data that constitutes block data that is a part of the image data by decompressing the compressed sub-block data The compressed sub-block data is included in the sub-block data. The decompressing unit restores the sub-block data including the plurality of sub-block data and the combining unit restores the image data by combining the sub-block data restored by the decompressing unit. The minimum value of the effective pixel information of a pixel value other than the minimum value of a plurality of pixel values and the pixel value in the image data is A compressed pixel information that associates the calculated pixel value and information specifying the pixel position of the pixel value, and the decompression unit acquires the minimum value from the compressed image data. Based on the compressed pixel information included in the compressed sub-block data, a pixel restoration unit that restores the pixel information included in the sub-block data, and a pixel value of the pixel information restored by the pixel restoration unit An image decompression program including a pixel value restoration unit that restores a pixel value before compression by adding a minimum value to each is provided.

  According to a fifth aspect of the present invention, there is provided a data structure of compressed sub-block data constituting compressed image data obtained by compressing image data, the pixel value of pixel information indicating the pixel value of a pixel included in the image data. Provided is a data structure including compressed pixel information in which a minimum value, a pixel value after the minimum value is subtracted from the pixel value of the pixel information, and information specifying the position of the pixel of the pixel value are associated with each other.

  According to the present invention, it is possible to compress image data at high speed.

It is a figure which shows the outline | summary of the image processing system of this embodiment. It is a block diagram which shows the function structure of the image compression apparatus which concerns on this embodiment. It is a flowchart of the image compression process of the image compression apparatus which concerns on this embodiment. It is a flowchart of the subblock data compression process which concerns on this embodiment. It is a flowchart of the sub block data creation processing according to the present embodiment. It is a figure which shows the structure of the compressed image data which concerns on this embodiment. It is a figure which shows the structure of the compressed subblock data which concern on this embodiment. It is a figure which shows the state before the subblock data which concern on this embodiment are compressed. It is a figure which shows the example by which the minimum value was subtracted by the subtraction part which concerns on this embodiment. It is a figure which shows the body part of the subblock data produced by the process of the process pattern 1 which concerns on this embodiment. It is a figure which shows the body part of the subblock data produced by the process of the process pattern 2 which concerns on this embodiment. It is a figure which shows the body part of the subblock data produced by the process of the process pattern 3 which concerns on this embodiment. It is a figure which shows the body part of the subblock data produced by the process of the process pattern 4 which concerns on this embodiment. It is a block diagram which shows the function structure of the image decompression | decompression apparatus which concerns on this embodiment. It is a flowchart which shows the flow of the image decompression process of the image decompression | decompression apparatus which concerns on this embodiment. It is a flowchart of the decompression | decompression process by the decompression | decompression part which concerns on this embodiment.

FIG. 1 is a diagram showing an overview of the image processing system S of the present embodiment.
The image processing system S includes an image compression device 1 that compresses image data and creates compressed image data, and an image decompression device that restores medical image data from the compressed image data created by the image compression device 1 2 is provided.

  The image compression apparatus 1 divides image data into a plurality of block data, and divides the block data into sub-block data including a plurality of pieces of pixel information indicating pixel values of pixels in the image data. Then, the image compression apparatus 1 compresses the sub-block data and creates compressed image data. Here, the image data is medical image data, such as CT (Computed Tomography) image data or MRI (Magnetic Resonance Imaging) image data.

Details of the image compression apparatus 1 will be described below.
FIG. 2 is a block diagram illustrating a functional configuration of the image compression apparatus 1 according to the present embodiment.
As shown in FIG. 2, the image compression apparatus 1 includes a display unit 11, an input unit 12, a storage unit 13, a control unit 14, and a plurality of compression units 15.

The display unit 11 is configured by, for example, a liquid crystal display or an organic EL (Electro-Luminescence) display. The display unit 11 displays, for example, an operation screen for image data compression processing under the control of the control unit 14.
The input unit 12 is configured by, for example, a keyboard and a mouse. The input unit 12 receives an operation input from the user of the image compression apparatus 1.

  The storage unit 13 includes, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk, and an external storage device connected to the image compression apparatus 1. Here, the external storage device may be directly connected to the image compression device 1 or may be connected to be communicable via a communication network (not shown). The storage unit 13 stores, for example, medical image data as image data to be compressed. The storage unit 13 also stores an image compression program for causing the computer to function as an image data acquisition unit 141, a size adjustment unit 142, a division unit 143, a combining unit 144, an output unit 145, and a compression unit 15 described later.

The control part 14 is comprised by CPU (Central Processor Unit), for example. The control unit 14 comprehensively controls functions related to the image compression device 1 by executing various programs stored in the storage unit 13 for causing the image compression device 1 to function. The control unit 14 includes an image data acquisition unit 141, a size adjustment unit 142, a division unit 143, a combining unit 144, and an output unit 145.
Hereinafter, description of each function will be made with reference to flowcharts as appropriate. FIG. 3 is a flowchart showing a flow of image compression processing of the image compression apparatus 1 according to the present embodiment. FIG. 4 is a flowchart of sub-block data compression processing according to the present embodiment. FIG. 5 is a flowchart of compressed sub-block data creation processing according to this embodiment.

First, the overall flow of image compression processing will be described with reference to FIG.
The image data acquisition unit 141 acquires image data (S1). Specifically, the image data acquisition unit 141 acquires image data stored in the storage unit 13 in response to the input unit 12 receiving an image data acquisition operation. Note that the image data acquisition unit 141 may acquire image data by receiving image data from an external device connected to the image compression apparatus 1 via a communication network.

  The size adjustment unit 142 adjusts the size of the image data acquired by the image data acquisition unit 141 (S2). Specifically, the size adjustment unit 142 adds a pixel having a pixel value of 0 to the image data so that the number of pixels in the row direction and the number of pixels in the column direction of the acquired image data are multiples of 4, respectively. To do.

  The dividing unit 143 divides block data which is a part of the acquired image data into a plurality of sub-block data including a plurality of pieces of pixel information indicating pixel values of pixels in the image data (S3). Specifically, first, the image data acquisition unit 141 determines the number of block data constituting the image data, and divides the block data. Here, the number of block data in the row direction is bh, and the number of rows in the column direction is bw. Subsequently, the image data acquisition unit 141 determines the number of sub-block data constituting the block data. For example, when the number of pixels in the row direction of the sub-block data is sh and the number of pixels in the column direction is sw, the dividing unit 143 determines the number of sub-block data so that sw × sh is 16 to 128. The sub-block data is divided into this number.

  Subsequently, the dividing unit 143 secures a buffer area for each data (S4). Specifically, the dividing unit 143 secures a buffer area for compressed block data, which is compressed data of each block data, in the storage unit 13. The capacity of this buffer area is, for example, sh × sw × 396 + 4. Further, the dividing unit 143 determines the size of the buffer area for the compressed image data from the number of compressed block data, and secures the buffer area for the compressed image data.

  Here, the configuration of the compressed image data will be described. FIG. 6A is a diagram illustrating a configuration of compressed image data. FIG. 6B is a diagram illustrating a configuration of compressed sub-block data included in compressed image data.

  The compressed image data is composed of a header part and a body part as shown in FIG. 6A. The header portion of the compressed image data includes the number of compressed block data included in the body portion, the number of the compressed sub-block data, and pixels in the row direction of the image data before size adjustment by the size adjustment unit 142 The number and the number of pixels in the column direction are stored. For example, 1 to 8 bytes in the header portion of the compressed image data include the number bh of block data in the row direction, the number bw in the column direction, the number of pixels sh in the row direction of the sub-block data, and the number of pixels sw in the column direction. Is remembered. In the 9 to 12 bytes of the header portion, the number of pixels in the column direction before the size adjustment of the image data and the number of pixels in the row direction are stored. The body portion of the compressed image data stores one or more block data.

  As shown in FIG. 6A, the compressed block data is composed of a header portion and a body portion. The header portion of the compressed block data stores an address indicating the position of the block data in the image data and the size of the body portion. The body portion of the compressed block data stores one or more compressed sub-block data.

As shown in FIG. 6B, the compressed sub-block data is composed of a header part and a body part. The header part of the compressed sub-block data is divided into a plurality of areas.
Specifically, 1 to 16 bits store the address indicating the position of the sub-block data in the block data and the data length of the compressed sub-block data. More specifically, the address of sub-block data is stored in 1 to 7 bits. In 8 to 16 bits, the data length of the compressed sub-block data is stored.
In the 17th to 29th bits, information indicating the minimum value among the pixel values of the pixel information included in the sub-block data is stored.

  In 30 to 32 bits, pattern information indicating the data length of the pixel information after compression is stored. The data length after compression is, for example, 0 bit, 4 bits, 6 bits, 8 bits, 10 bits, or 12 bits. That is, 30 to 32 bits store binary pattern information for distinguishing these bit lengths.

The number of effective pixel information is stored in 33 to 41 bits.
The number of valid unit data is stored in 42 to 48 bits. Effective pixel information and effective unit data will be described later.
In 49 to 64 bits, the pixel value of invalid pixel information is stored.
Unit data or effective pixel information is stored in the body portion of the compressed sub-block data.

  The dividing unit 143 inputs the sub-block data to the compressing unit 15. Here, the pixel values of the plurality of pieces of pixel information included in the sub-block data are represented by binary numbers, for example. Each of the plurality of pieces of pixel information has a predetermined data length (for example, 12 bits).

  The plurality of compression units 15 are configured by, for example, a GPU (Graphics Processing Unit) including a plurality of cores. Each of the plurality of compression units 15 corresponds to one of a plurality of cores constituting the GPU. Each of the plurality of compression units 15 performs sub-block data compression processing, which is processing for compressing sub-block data and creating compressed sub-block data (S5). The plurality of compression units 15 create compressed sub-block data by compressing the plurality of sub-block data input from the control unit 14 in parallel. The processing of the compression unit 15 will be described later.

The combining unit 144 combines compressed sub-block data and creates compressed image data.
Specifically, the combining unit 144 calculates the size of the compressed block data based on the size of the compressed sub-block data created by the compression unit 15 (S6). The combining unit 144 stores the calculated compressed block data size and the plurality of compressed sub-block data in the compressed block data buffer to create compressed block data (S7). Here, the combining unit 144 stores the compressed sub-block data in the buffer based on the position of the compressed sub-block data before compression.

  Subsequently, the combining unit 144 generates compressed image data by combining a plurality of compressed block data (S8).

  The output unit 145 outputs the compressed image data created by the combining unit 144. The output unit 145 transmits the compressed image data to the image decompression device 2 via, for example, a communication line, or stores the compressed image data in a storage medium.

  Next, details of the processing of the compression unit 15 will be described. Each of the plurality of compression units 15 includes a specifying unit 151, a subtraction unit 152, and a creation unit 153. 7A and 7B are diagrams illustrating a process in which sub-block data is generated. FIG. 7A is a diagram illustrating a state before sub-block data is compressed. In order to simplify the description, in FIGS. 7A and 7B, it is assumed that the sub-block data includes pixel information of 16 pixels p1 to p16. 7A and 7B, the combined length of the white bar and the black bar represents the data length (predetermined data length) of the pixel information, and the black bar represents the pixel value of the pixel. It shall be. For example, when the black bar is short, the pixel value is small, and when the black bar is long, the pixel value is large.

  The details of the sub-block data compression processing in the compression unit 15 will be described below with reference to FIG. The specifying unit 151 specifies the minimum value and the maximum value from the pixel values included in the plurality of pixel information included in the sub-block data (S51). In the example illustrated in FIG. 7A, the specifying unit 151 specifies the pixel values of the pixels p1 to p6 as the minimum value, and specifies the pixel value of the pixel p9 as the maximum value. The identifying unit 151 stores information indicating the minimum value among the minimum value and the maximum value in 17 to 29 bits of the header portion of the sub-block data.

  Subsequently, the specifying unit 151 specifies effective pixel information from a plurality of pieces of pixel information included in the sub-block data (S52). The effective pixel information is pixel information whose pixel value is other than a predetermined value. The invalid pixel information is pixel information having a predetermined pixel value. Here, the predetermined value is the minimum value specified by the specifying unit 151. For example, in FIG. 7A, the specifying unit 151 specifies the pixels p1 to p6 as invalid pixel information pixels, and specifies the pixels p7 to p16 as valid pixel information pixels. The identifying unit 151 stores the number of valid pixel information in the 33 to 41 bits of the header portion of the compressed sub-block data. In the present embodiment, the predetermined value is the minimum value, but the present invention is not limited to this. For example, instead of the minimum value, a pixel value having the highest appearance frequency among a plurality of pieces of pixel information may be set as the predetermined value.

  Subsequently, the specifying unit 151 specifies the data length after compression of the pixel information included in the sub-block data (S53). Specifically, the specifying unit 151 specifies the data length after compression of the data length (predetermined data length) of the pixel information as the data length corresponding to the pixel value obtained by subtracting the minimum value from the maximum value. . For example, the specifying unit 151 associates the pixel value with the pixel value, and stores the smallest bit among the predetermined number of bits that is greater than the number of bits required when the pixel value is represented in binary. Specify the data length corresponding to the number. Here, the predetermined number of bits is 0 bit, 4 bits, 6 bits, 8 bits, 10 bits, or 12 bits.

The identifying unit 151 stores pattern information indicating the data length after compression in 30 to 32 bits of the header portion of the sub-block data.
The specifying unit 151 may specify the first data length obtained by subtracting the data length corresponding to the minimum value from the data length of the pixel information as the compressed data length.

Subsequently, the number of effective unit data included in the sub-block data is specified (S54). Here, effective unit data is data constituting sub-block data, and includes effective pixel information after a minimum value is subtracted by a subtracting unit 152 described later. When the data length after compression is 8 bits, or when the number of effective pixel information included in the compressed sub-block data is 32 or more, effective unit data is not created.
Subsequently, the specifying unit 151 calculates the number of effective pixel information in each effective unit data (S55).

  The subtracting unit 152 subtracts the minimum value specified by the specifying unit 151 from the pixels included in the plurality of pieces of pixel information included in the sub-block data (S56). For example, FIG. 7B is a diagram illustrating an example in which the minimum value is subtracted from the pixel values of the pixels p1 to p16 by the subtraction unit 152.

  The creation unit 153 executes compressed sub-block data creation processing to create compressed sub-block data (S57). Specifically, the creation unit 153 performs the compressed sub-block data creation process, and thereby the pixel value after the pixel value is subtracted by the subtraction unit 152 from the effective pixel information that is pixel information other than the predetermined value. And compressed sub-block data including the compressed pixel information that associates the information specifying the pixel position of the pixel value with the information indicating the minimum value. Hereinafter, the information specifying the pixel position of the pixel value after the subtraction is also referred to as index information.

  Here, the creating unit 153 creates the compressed sub-block data by changing the data length (predetermined data length) of the pixel information to the data length (compressed data length) specified by the specifying unit 151. Note that the creation unit 153 may subtract the data length corresponding to the minimum value specified by the specification unit 151 from the predetermined data length to change the data length to create the compressed sub-block data.

The details of the compressed sub-block data creation process will be described below with reference to FIG.
First, the creation unit 153 determines the value of the compressed data length specified by the specification unit 151, performs branch processing (S571), and creates compressed sub-block data.

  When the data length after compression is 0 bit or 4 bits, the creation unit 153 performs processing of the processing pattern 1 (S572). FIG. 8A is a diagram illustrating a body portion of compressed sub-block data created by the processing pattern 1. The creation unit 153 performs different processing depending on the number of effective pixel information from 0 to 31, from 32 to 191, and from 192 to 256, and creates a body portion of compressed sub-block data.

  Specifically, the creation unit 153 creates valid unit data when the number of valid pixel information is 0 to 31, and stores the created valid unit data in the body portion of the compressed sub-block data. One effective unit data includes pixel information of 4 rows and 4 columns. The data length of the header portion of the effective unit data is 8 bits. The creation unit 153 stores information specifying the position of the effective unit data in the sub-block data in 1 to 4 bits of the header unit of the effective unit data, and stores the number of effective pixel information in 5 to 8 bits. .

  The creation unit 153 stores an address indicating the position of the pixel information in the effective unit data in 1 to 4 bits of the plurality of effective pixel information included in the body portion of the effective unit data, and in 5 to 8 bits. The pixel value after subtraction by the subtraction unit 152 is stored. Here, invalid pixel information, that is, pixel information with a pixel value of 0 after being subtracted by the subtraction unit 152 is not stored in the body portion of the effective unit data.

  For example, the pixels p1 to p16 illustrated in FIG. 7B are assumed to be stored in four unit data including pixel information of 2 rows and 2 columns in order. Here, although the pixels p1 to p4 can be stored in the body portion of the first unit data, since the pixels p1 to p4 are not effective pixel information, the first unit data is not effective unit data and is compressed. Not stored in sub-block data. Similarly, although the pixels p5 to p8 can be stored in the body portion of the second unit data, the pixels p5 and p6 are not effective pixel information, so the body portion of the second unit data includes the pixels p7 and p7. The pixel value of p8 and index information are stored. When the number of pieces of pixel information included in the unit data is 4, the index information is, for example, 2-bit information.

  When the number of valid pixel information is 32 to 191, the creation unit 153 creates compressed sub-block data including the map data and the pixel value of the valid pixel information after the minimum value is subtracted by the subtraction unit 152. That is, the creation unit 153 creates compressed sub-block data including the map data and the pixel value of the valid pixel information after subtracting the minimum value by the subtraction unit 152 when the number of valid pixel information is within a predetermined range. To do.

  The map data stores information indicating whether each of the plurality of pieces of pixel information is effective pixel information in the order of arrangement of the plurality of pieces of pixel information in the sub-block, and is a bit of the number of pieces of pixel information included in the sub-block data. Consists of. For example, when the sub-block data includes 16 × 16 pixel information, the map data is 256-bit binary information. Each bit of the map data indicates the state of the pixel value at the position of the pixel information included in the body part of the sub-block data. In the map data, a bit whose bit value is 0 indicates invalid pixel information, and a bit whose bit value is 1 indicates valid pixel information.

The creation unit 153 stores the map data and the pixel value (4 bits) of the effective pixel information in the body portion of the compressed sub-block data. Here, when n is an odd number, the creation unit 153 inserts 4 bits of dummy data (pixel information with a pixel value of 0) into the body portion of the compressed sub-block data.
When the number of valid pixel information is 192 to 256, the creation unit 153 stores the pixel values (4 bits) of all the pixel information in the body portion of the compressed sub-block data in the order of the pixel information.

  Returning to FIG. If the data length after compression is 6 bits, the creation unit 153 performs processing pattern 2 (S573). FIG. 8B is a diagram illustrating a body portion of compressed sub-block data created by the processing pattern 2. The creation unit 153 performs different processing depending on the number of effective pixel information from 0 to 31, from 32 to 212, and from 213 to 256, and creates a body portion of compressed sub-block data.

  Specifically, the creation unit 153 creates valid unit data when the number of valid pixel information is 0 to 31, and stores the created valid unit data in the body portion of the compressed sub-block data. One effective unit data includes pixel information of 2 rows and 2 columns. The data length of the header portion of the effective unit data is 8 bits. The creation unit 153 stores an address indicating the position of the effective unit data in the sub-block data in 1 to 6 bits of the header unit of the effective unit data, and stores the number of effective pixel information in 7 to 8 bits. .

  The creation unit 153 stores an address indicating the position of the pixel information in the effective unit data in 1 to 2 bits of the plurality of effective pixel information included in the body portion of the effective unit data, and in 3 to 8 bits. The pixel value after subtraction by the subtraction unit 152 is stored. Here, invalid pixel information is not stored in the body portion.

When the number of effective pixel information is 32 to 212, the creation unit 153 creates map data in the same manner as described above. The creation unit 153 stores the map data and the pixel value (6 bits) of the effective pixel information in the body portion of the compressed sub-block data. Here, the creation unit 153 inserts k bits of dummy data (pixel information with a pixel value of 0) into the body portion so that n × 6 + k = 24.
When the number of effective pixel information is 213 to 256, the creation unit 153 stores the pixel values (6 bits) of all the pixel information in the body portion of the compressed sub-block data in the order of the pixel information.

  Returning to FIG. When the data length is 8 bits, the creation unit 153 performs processing pattern 3 (S574). FIG. 8C is a diagram illustrating a body portion of the compressed sub-block data created by the processing pattern 3. The creation unit 153 performs different processing depending on the number of effective pixel information from 0 to 31, from 32 to 223, and from 224 to 256, and creates a body portion of compressed sub-block data.

  Specifically, when the number of effective pixel information is 0 to 31, the creation unit 153 stores the pixel information of effective pixels in the body portion of the compressed sub-block data. The creation unit 153 stores the address indicating the position of the pixel information in the sub-block data in 1 to 8 bits of the body portion, and the effective pixel information after subtraction by the subtraction unit 152 in 9 to 16 bits. Stores pixel values.

The creation unit 153 creates map data in the same manner as described above when the number of valid pixel information is 32 to 223. The creation unit 153 stores the map data and the pixel value (8 bits) of the effective pixel information in the body portion of the compressed sub-block data.
When the number of effective pixel information is 224 to 256, the creation unit 153 stores the pixel values (8 bits) of all the pixel information in the body portion of the compressed sub-block data in the order of the pixel information.

  Returning to FIG. When the data length is 10 bits or 12 bits, the creation unit 153 performs processing of the processing pattern 4 (S575). FIG. 8D is a diagram illustrating a body portion of the compressed sub-block data created by the processing pattern 4. The creation unit 153 performs different processing depending on the number of valid pixel information from 0 to 31, from 32 to 234, and from 235 to 256, and creates a body portion of compressed sub-block data.

  Specifically, the creation unit 153 creates valid unit data when the number of valid pixel information is 0 to 31, and stores the created valid unit data in the body portion of the compressed sub-block data. One effective unit data stores pixel information of 4 rows and 4 columns. The data length of the header portion of the effective unit data is 8 bits. The creation unit 153 stores an address indicating the position of the effective unit data in the sub-block data in 1 to 4 bits of the header unit of the effective unit data, and stores the number of effective pixel information in 5 to 8 bits. . The creation unit 153 stores an address indicating the position of the pixel information in the effective unit data in 1 to 4 bits of the plurality of effective pixel information included in the body portion of the effective unit data, and in 5 to 16 bits. The pixel value of the effective pixel information after subtraction by the subtraction unit 152 is stored.

When the number of effective pixel information is 32 to 234, the creation unit 153 creates map data in the same manner as described above. The creation unit 153 stores the map data and the pixel value (12 bits) of the effective pixel information in the body portion of the compressed sub-block data. Here, when n is an odd number, the creation unit 153 inserts 12 bits of dummy data (pixel information with a pixel value of 0) into the body portion.
When the number of valid pixel information is 235 to 256, the creation unit 153 stores the pixel values (12 bits) of all the pixel information in the body portion of the compressed sub-block data.

Next, details of the image decompression device 2 will be described.
FIG. 9 is a block diagram showing a functional configuration of the image decompression apparatus 2 according to the present embodiment.
As shown in FIG. 9, the image decompression device 2 includes a display unit 21, an input unit 22, a storage unit 23, a control unit 24, and a plurality of decompression units 25.

The display unit 21 is configured by, for example, a liquid crystal display device or an organic EL display. The display unit 21 displays, for example, an operation screen for decompression processing in accordance with the control of the control unit 24.
The input unit 22 is configured by, for example, a keyboard and a mouse. The input unit 22 receives an operation input from the user of the image decompression device 2.

  The storage unit 23 includes, for example, a ROM, a RAM, a hard disk, and an external storage device connected to the image decompression device 2. Here, the external storage device may be directly connected to the image decompression device 2 or may be connected to be communicable via a communication network. The storage unit 23 may store compressed image data obtained by compressing image data. Further, the storage unit 23 stores an image decompression program for causing the computer to function as an image data acquisition unit 241, a division unit 242, a combination unit 243, a size adjustment unit 244, an output unit 245, and a decompression unit 25, which will be described later.

The control unit 24 is configured by a CPU, for example. The control unit 24 comprehensively controls functions related to the image decompression device 2 by executing various programs stored in the storage unit 23 for causing the image decompression device 2 to function. The control unit 24 includes an image data acquisition unit 241, a dividing unit 242, a combining unit 243, a size adjusting unit 244, and an output unit 245.
Hereinafter, description of each function will be made with reference to flowcharts as appropriate. FIG. 10 is a flowchart showing a flow of image decompression processing of the image decompression apparatus 2 according to the present embodiment.

  The image data acquisition unit 241 acquires compressed image data obtained by compressing the image data (S11). Specifically, the image data acquisition unit 241 receives the compressed image data from an external device such as the image compression device 1 connected to the image decompression device 2 via a communication network, thereby obtaining the compressed image data. get. The image data acquisition unit 241 receives the compressed image data from the image compression apparatus 1 and stores the compressed image data in the storage unit 23. In response to the input unit 22 receiving an operation for acquiring compressed image data, The compressed image data stored in the storage unit 23 may be acquired.

  The dividing unit 242 divides the compressed image data acquired by the image data acquiring unit 241 into a plurality of compressed block data. Then, the dividing unit 242 further divides the compressed image data to obtain a plurality of compressed sub-block data constituting the compressed block data that is a part of the compressed image data (S12). The dividing unit 242 inputs the acquired plurality of compressed sub-block data to the plurality of decompressing units 25.

  The plurality of decompression units 25 are configured by a GPU, for example. The plurality of decompression units 25 include a plurality of pieces of pixel information indicating pixel values of pixels in the image data, which decompress the compressed sub-block data to form block data that is a part of the image data by executing decompression processing. The sub-block data is restored (S13). The plurality of decompressing units 25 decompress the plurality of compressed sub-block data input from the control unit 24 in parallel. The processing of the decompression unit 25 will be described later.

  The combining unit 243 combines a plurality of sub-block data restored by the decompressing unit 25 to restore the image data (S14). Specifically, the combining unit 243 combines the plurality of restored sub-block data based on the address of the sub-block data stored in the header part of the compressed sub-block data, and restores the block data. Then, based on the block data address stored in the header portion of the compressed block data, the combining unit 243 combines the plurality of restored block data to restore the image data.

The size adjustment unit 244 adjusts the size of the restored image data (S15). Specifically, the size adjustment unit 244 restores an image restored based on the number of pixels in the column direction width and the number of pixels in the row direction before the size adjustment of the image data stored in the header portion of the compressed image data. Adjust the size of the data.
The output unit 245 outputs the image data after the size adjustment unit 244 has adjusted the size. The output unit 245 displays image data on the display unit 21, for example.

  Next, details of the processing of the decompression unit 25 will be described. Each of the plurality of decompression units 25 includes a minimum value acquisition unit 251, a pixel restoration unit 252, and a pixel value restoration unit 253. FIG. 11 is a flowchart of the decompression process by the decompression unit 25 according to the present embodiment. Hereinafter, the processing of the decompression unit 25 when decompressing the compressed sub-block data compressed in the image compression apparatus 1 will be described with reference to FIG.

First, the minimum value acquisition unit 251 acquires information indicating the minimum value stored in the header portion of the compressed sub-block data (S131).
The pixel restoration unit 252 restores pixel information included in the sub-block data based on the compressed pixel information included in the compressed sub-block data. Subsequently, the pixel restoration unit 252 changes the data length of the pixel information to a predetermined data length (S132). Since the storage format of the compressed pixel information differs depending on the data length after compression and the number of effective pixel information, the pixel restoration unit 252 performs different processing based on the data length after compression and the number of effective pixel information, and performs sub-block data The pixel information included in is restored.

  Specifically, when the data length after compression is 0 or 4 bits and the number of valid pixel information is 0 to 31, the pixel restoration unit 252 stores the unit data stored in the compressed sub-block data. The position of the pixel of the effective pixel information included in the unit data is specified based on the body part. The pixel restoration unit 252 specifies that the pixel value of the pixel information whose pixel position cannot be specified is 0.

  Also, the pixel restoration unit 252 restores pixel information based on the map data when the compressed data length is 0 or 4 bits and the number of effective pixel information is 32 to 191. When the bit value is 0 in the map data, the pixel information at the position corresponding to the bit value corresponds to the bit value based on the pixel value of the invalid pixel information included in the header portion of the compressed sub-block data. The pixel information of the position is restored. When the bit value is 1 in the map data, the pixel information at the position corresponding to the bit value is restored based on the pixel value of the effective pixel information included in the body portion of the compressed sub-block data.

  In addition, when the data length after compression is 0 bit or 4 bits and the number of effective pixel information is 192 to 256, the pixel restoration unit 252 stores the pixel information included in the body portion of the compressed sub-block data. The pixel information of the sub-block data is restored based on the pixel value.

  In addition, when the data length after compression is 6 bits and the number of valid pixel information is 0 to 31, the pixel restoration unit 252 performs unit based on the body portion of the unit data stored in the compressed sub-block data. The pixel position of the effective pixel information included in the data is specified. In addition, the pixel restoration unit 252 specifies that the pixel value of the pixel information in which the position of the pixel cannot be specified is 0.

  Further, the pixel restoration unit 252 restores pixel information based on map data when the compressed data length is 6 bits and the number of effective pixel information is 32 to 212. Further, when the data length after compression is 6 bits and the number of effective pixel information is 213 to 256, the pixel restoration unit 252 calculates the pixel value of the pixel information included in the body portion of the compressed sub-block data. Based on this, the pixel information of the sub-block data is restored.

  Further, when the data length after compression is 8 bits and the number of valid pixel information is 0 to 31, the pixel restoration unit 252 is based on the valid pixel information stored in the body portion of the compressed sub-block data. Perform restoration. In addition, the pixel restoration unit 252 specifies that the pixel value of the pixel information in which the position of the pixel cannot be specified is 0. Further, the pixel restoration unit 252 restores pixel information based on the map data when the compressed data length is 8 bits and the number of effective pixel information is 32 to 223. In addition, when the data length after compression is 8 bits and the number of effective pixel information is 224 to 256, the pixel restoration unit 252 calculates the pixel value of the pixel information included in the body portion of the compressed sub-block data. Based on this, the pixel information of the sub-block data is restored.

  In addition, when the data length after compression is 10 bits or 12 bits and the number of effective pixel information is 0 to 31, the pixel restoration unit 252 is a body part of unit data stored in the compressed sub-block data. The position of the pixel of the effective pixel information included in the unit data is specified based on the above. In addition, the pixel restoration unit 252 specifies that the pixel value of the pixel information in which the position of the pixel cannot be specified is 0. Further, when the data length after compression is 10 bits or 12 bits and the number of effective pixel information is 32 to 234, the pixel restoration unit 252 restores the pixel information based on the map data. In addition, when the data length after compression is 10 bits or 12 bits and the number of valid pixel information is 235 to 256, the pixel restoration unit 252 stores the pixel information included in the body portion of the compressed sub-block data. The pixel information of the sub-block data is restored based on the pixel value.

  The pixel value restoration unit 253 adds the minimum value to each of the pixel values of the pixel information restored by the pixel restoration unit 252 based on the information indicating the minimum value acquired by the minimum value acquisition unit 251, and before compression. The pixel value is restored (S133).

  As described above, according to the present embodiment, the compression unit 15 of the image compression device 1 subtracts the minimum value from the pixel value of the plurality of pixel information and the specifying unit 151 that specifies the minimum value from the plurality of pixel information. The subtracting unit 152, the effective pixel information whose pixel value is pixel information other than the predetermined value, the pixel value after the minimum value is subtracted by the subtracting unit 152, and the information specifying the pixel position of the pixel value A creation unit 153 that creates compressed sub-block data including the associated compressed pixel information and information indicating the minimum value.

  By doing in this way, the image compression apparatus 1 can reduce the conditional branch process in process, and can reduce the processing amount in an image compression process with respect to other compression systems, such as Huffman encoding. Therefore, the image compression apparatus 1 can compress medical images at high speed. Further, the block data of medical image data has few gradations, and the minimum value and the maximum value of the pixel values of the pixel information included in the sub-block data tend to be close. For this reason, the image compression apparatus 1 can efficiently compress medical image data.

  Further, the compression unit 15 of the image compression apparatus 1 causes the creation unit 153 to use a data length corresponding to a pixel value obtained by subtracting a predetermined data length, which is a data length of a plurality of pieces of pixel information, from a maximum value and a minimum value. To create compressed sub-block data. By doing in this way, the image compression apparatus 1 can delete unnecessary data length and can compress efficiently. In addition, a plurality of compression units 15 of the image compression apparatus 1 are provided, and a plurality of sub-block data are compressed in parallel, so that the compression can be performed at high speed.

  Further, the compression unit 15 of the image compression apparatus 1 causes the creation unit 153 to obtain information indicating whether each of the plurality of pieces of pixel information is effective pixel information when the number of effective pixel information is within a predetermined range. Compressed sub-block data including map data stored in the arrangement order of a plurality of pieces of pixel information and pixel values of effective pixel information after subtracting the minimum value by the subtraction unit 152 is created. By doing in this way, the image compression apparatus 1 can express efficiently whether the pixel information contained in subblock data is expressed by the minimum data number, whether it is effective pixel information in map data.

  Further, the decompression unit 25 of the image decompression apparatus 2 obtains the minimum value from the compressed image data by the minimum value acquisition unit 251, and the compressed pixel information included in the compressed sub-block data by the pixel restoration unit 252 Based on the above, the pixel information included in the sub-block data is restored, and the pixel value restoration unit 253 restores the pixel value before compression by adding the minimum value to each of the restored pixel information. Then, the combining unit 243 combines a plurality of restored sub-block data to restore the image data. By doing so, the image decompression device 2 can restore the compressed image data compressed by the image compression device 1 to image data at high speed.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. In addition, it will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention. For example, the present embodiment can be applied to other types of image data different from medical image data.

DESCRIPTION OF SYMBOLS 1 ... Image compression apparatus, 2 ... Image decompression | decompression apparatus, 11, 21 ... Display part, 12, 22 ... Input part, 13, 23 ... Memory | storage part, 14, 24 ... Control 15, compression unit 25, decompression unit 141, 241 image data acquisition unit 142 244 size adjustment unit 143 242 division unit 144 243 ..Combining unit, 145, 245 ... Output unit, 151 ... Specifying unit, 152 ... Subtracting unit, 153 ... Creating unit, 251 ... Minimum value obtaining unit, 252 ... Pixel restoration , 253... Pixel value restoration unit, S... Image processing system

Claims (6)

A specifying unit that specifies a minimum value of pixel values based on a plurality of pieces of pixel information indicating pixel values of pixels in image data;
A subtraction unit that subtracts the minimum value from pixel values of the plurality of pixel information;
The pixel value after the minimum value is subtracted by the subtracting unit of the effective pixel information in which the pixel value does not include invalid pixel information that is pixel information of a predetermined value and the pixel value is pixel information other than the predetermined value And a creation unit that creates compressed data including compressed pixel information associated with information specifying the pixel position of the pixel value, and information indicating the minimum value;
An image compression apparatus comprising: Each of the plurality of pixel information has a predetermined data length,
The specifying unit specifies a maximum value from pixel values of the plurality of pixel information,
The creation unit creates the compressed data by changing the predetermined data length to a data length corresponding to a pixel value obtained by subtracting the minimum value from the maximum value.
The image compression apparatus according to claim 1. The specifying unit specifies the number of effective pixel information based on pixel values of the plurality of pixel information,
When the number of the effective pixel information is within a predetermined range, the creation unit displays information indicating whether each of the plurality of pieces of pixel information is the effective pixel information in the order of arrangement of the plurality of pieces of pixel information in the image data. Creating the compressed data including map data to be stored and a pixel value of the effective pixel information after the minimum value is subtracted by the subtraction unit;
The image compression apparatus according to claim 1 or 2. Computer
A specifying unit that specifies a minimum pixel value based on a plurality of pieces of pixel information indicating pixel values of pixels in the image data;
A subtractor that subtracts the minimum value from pixel values of the plurality of pixel information; and
The pixel value after the minimum value is subtracted by the subtracting unit of the effective pixel information in which the pixel value does not include invalid pixel information that is pixel information of a predetermined value and the pixel value is pixel information other than the predetermined value And a creation unit that creates compressed data including compressed pixel information associated with information specifying the pixel position of the pixel value, and information indicating the minimum value,
Image compression program that functions as Among the plurality of pieces of pixel information indicating the minimum value of the plurality of pixel values included in the image data and the pixel values of the plurality of pixels constituting the image data, invalid pixel information in which the pixel value is pixel information having a predetermined value. The compressed pixel pixel is not associated with the pixel value after the minimum value is subtracted from the effective pixel information that is pixel information other than the predetermined value, and the compressed pixel information is associated with the information specifying the pixel position of the pixel value. A minimum value acquisition unit that acquires the minimum value from the compressed data of the image data including pixel information;
A pixel restoration unit that restores the pixel information included in the image data based on the compressed pixel information included in the compressed data;
A pixel value restoring unit that restores a pixel value before compression by adding the minimum value to each of the pixel values of the pixel information restored by the pixel restoring unit;
An image decompression apparatus comprising: Computer
Among the plurality of pieces of pixel information indicating the minimum value of the plurality of pixel values included in the image data and the pixel values of the plurality of pixels constituting the image data, invalid pixel information in which the pixel value is pixel information having a predetermined value. The compressed pixel pixel is not associated with the pixel value after the minimum value is subtracted from the effective pixel information that is pixel information other than the predetermined value, and the compressed pixel information is associated with the information specifying the pixel position of the pixel value. A minimum value acquisition unit for acquiring the minimum value from compressed data of the image data including pixel information;
Based on the compressed pixel information included in the compressed data, a pixel restoration unit that restores the pixel information contained in the image data, and a pixel value of the pixel information restored by the pixel restoration unit A pixel value restoration unit that restores the pixel value before compression by adding the minimum value to each,
An image decompression program that functions as

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