JPH08317225A - Image data compression and expansion device - Google Patents

Abstract

PURPOSE: To provide an image data compression/expansion device which can perform the fast extractive output and rotary output of a single area of an image without deteriorating the reduction effect of the memory capacity that is caused by compression of the image data. CONSTITUTION: The image data equivalent to one page is divided into plural rectangular blocks with the image data equivalent to (n×n) pixels defined as a single unit. A compression code is generated in each of divided rectangular blocks, and these compression codes are stored in a compression code buffer 57. At the same time, the address of the storage area occupied by every compression code in the buffer 57 is stored in a compression code table 58 in response to the number given to every rectangular block. In such a constitution of an image data compression/expansion device, only a desired compression code can be read out and expanded. Thus it is possible to perform the fast extractive output and rotary output of a single area of an image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data compression / expansion device, and more particularly to an image data compression / expansion device such as a printer or an image filing device for compressing and storing image data.

[0002]

2. Description of the Related Art An apparatus for handling image data, such as a printer, a display device or an image filing apparatus, is provided with a memory called a page memory or a frame memory for storing image data. If such an apparatus is configured so that the image data is stored in the page memory as it is, a large-capacity memory is required as the page memory, which increases the manufacturing cost of the apparatus. Further, when the device is in operation, a process of reading all data and a process of writing all data are performed on the large-capacity page memory, which causes a problem that the operation speed is slow.

In order to deal with such a problem, a method of compressing and storing image data has been conventionally used. For example, run-length compression (MH, MR, MM) is normally applied to binary image data.
R) is adopted and the image data is compressed,
A reduction in memory capacity and an increase in speed of memory access have been achieved.

[0004]

As described above, in the apparatus for compressing and storing the image data, although the memory capacity can be reduced and the memory access can be speeded up, for example, it is stored. When outputting image data, even if the image to be output is only a part of the stored image, the compression code is sequentially expanded to obtain the image data for each line, and then the part that is requested to be output There is a need for a process of extracting and outputting image data corresponding to.

As described above, in the conventional technique, it is necessary to output one area of the stored image to a time substantially equal to the time required to output the entire area. There was a problem that

Further, when the image data is rotated by 90 degrees and outputted, all the compression codes must be expanded in order to obtain the first raster data of the image data to be outputted. There was a problem that it took a lot of time to output the output.

In order to solve the above-mentioned problem, Japanese Patent Laid-Open No. 60-16767 discloses a compression code in which image data is normally compressed and a compression code in which the image data is compressed by rotating 90 degrees. Although a technique using a method of storing and is disclosed, this method requires the provision of a memory having a double capacity. That is, with this technique, although the time required for rotating and outputting the image data can be shortened, the original purpose of reducing the memory capacity will not be achieved.

Therefore, an object of the present invention is to extract an area of an image and output the image, or rotate and output the image at high speed without reducing the effect of reducing the memory capacity by compressing the image data. It is to provide a data compression / decompression device.

[0009]

According to the first aspect of the present invention,
(B) The image data of a pixels x b pixels input in the raster format is divided into a plurality of rectangular blocks each having n pixels x n pixels of image data as one unit, and each rectangular block has a pixels of a pixels. Dividing / allocating means for allocating block position information indicating a position in the image data of × b pixels,
(B) The image data for n pixels × n pixels in each rectangular block divided by the dividing means is converted into a data line for one line according to a predetermined rule, and the converted data line is compressed. A compression means for generating a compression code, (c) a compression code storage means for storing the compression code generated by this compression means, and (d) a storage position of each compression code stored in this compression code storage means are shown. Correspondence storage means for storing the correspondence between the storage position information and the block position information assigned by the dividing / assigning means to the rectangular block that is the source of each compressed code, and (e) an image to be output A range designating means for designating a range of data and (f) block position information of a rectangular block corresponding to the image data of the range designated by the range designating means is obtained and obtained. Based on the block position information and the correspondence relationship stored in the correspondence relationship storage means, the specification means for specifying the storage position information for the compression code for each rectangular block, and the specification means from the (g) compression code storage means. Decompression means for decompressing and decompressing each compressed code stored in the memory location corresponding to the memory location information, and (h) performing inverse conversion of conversion according to a predetermined rule on the decompression result of this decompression means. The image data for n pixels × n pixels created by is arranged according to the block position information of the original rectangular block and is output as image data in a raster format.

That is, according to the first aspect of the present invention, the image data for a pixel × b pixel is divided into a plurality of rectangular blocks each having image data for n pixels × n pixels as one unit, and each rectangular block is divided into a plurality of rectangular blocks. The image data compression / decompression device is configured so that the compression code is generated / stored in block units.
As a result, it becomes possible to perform processing such as reading out only the necessary compressed code and expanding it, and as a result, processing such as outputting only one area of the image for one page can be performed at high speed.

According to a second aspect of the present invention, (a) a plurality of rectangular blocks in which image data for a pixels × b pixels input in a raster format is used as one unit for image data for n pixels × n pixels And each rectangular block has a pixel ×
A dividing / assigning means for assigning block position information indicating a position in the image data for b pixels, and (b) a predetermined number of image data for n pixels × n pixels in each rectangular block divided by this dividing means. And a conversion means for converting the converted data string into a data string for one line and compressing the converted data string using a compression method selected from several compression methods to generate a compressed code. (C) Compressed code storage means for storing the compressed code generated by this compression means, (d) Storage position information indicating the storage position of each compressed code stored in this compressed code storage means, and each compressed code. The compression attribute, which is information for identifying the compression method used when generating, and the division / allocation means assigned to the rectangular block that is the source of each compression code. Correspondence storage means for storing the correspondence relationship with the block position information, (f) range designation means for designating the range of image data to be output, and (g) image data within the range designated by this range designation means. Obtaining the block position information of the corresponding rectangular block, based on the obtained block position information and the correspondence stored in the correspondence storage unit,
Specifying means for specifying the storage position information and compression attribute for the compression code for each rectangular block; and (h) each compression stored from the compression code storage means at the storage position corresponding to the storage position information specified by the specifying means. Decompressing means for reading the code and decompressing the read compressed code according to the compression attribute specified by the specifying means; and (i) inverse conversion of the decompression result of this decompressing means according to a predetermined rule. The image data for n pixels × n pixels created by performing the above process is arranged according to the block position information of the original rectangular block and is output as raster-format image data.

That is, according to the second aspect of the present invention, the image data of a pixel × b pixel is divided into a plurality of rectangular blocks each having image data of n pixels × n pixels as one unit, and each rectangular block is divided. An image data compression / expansion device is configured so that a compression code is generated / stored in block units and a different compression method can be selected for each rectangular block. As a result, the processing of outputting only one area of the image for one page can be performed at high speed, and the storage capacity required for storing the compressed code can be reduced.

According to a third aspect of the present invention, (a) a plurality of rectangular blocks in which image data for a pixels × b pixels input in a raster format are image data for n pixels × n pixels as one unit And each rectangular block has a pixel ×
A dividing / assigning means for assigning block position information indicating a position in the image data for b pixels, and (b) a predetermined number of image data for n pixels × n pixels in each rectangular block divided by this dividing means. According to the rule of (1), a compression means for converting a data string for one line and compressing the converted data string to generate a compression code, and (c) a compression code storage for storing the compression code generated by this compression means. Means, and (d) storage position information indicating the storage position of each compressed code stored in the compressed code storage means, and the rectangular block that is the source of each compressed code is assigned by the dividing / assigning means. Correspondence storage means for storing the correspondence with the block position information, and (e) Range / angle that specifies the range of image data to be output and the angle to rotate at the time of output. (F) The block position information of the rectangular block corresponding to the image data in the range specified by the range / angle specifying means is obtained, and the obtained block position information and the correspondence relationship stored in the correspondence storage means are obtained. Based on the above, specifying means for specifying storage position information for the compressed code for each rectangular block, and (g) each compression code stored in the storage position corresponding to the storage position information specified by the specifying means from the compression code storage means. Decompression means for reading and decompressing, and (h) for the decompression result of this decompression means,
The image data for n pixels × n pixels created by performing the inverse conversion of the conversion according to the predetermined rule is rotated by the angle designated by the range / angle designating unit, and the rotated image data is used as the original. And output means for arranging the rectangular blocks according to the block position information and outputting as image data in a raster format.

That is, according to the third aspect of the present invention, the image data of a pixel × b pixel is divided into a plurality of rectangular blocks each having image data of n pixels × n pixels as one unit, and each rectangular block is divided. An image data compression / expansion device is configured so that a compression code is generated / stored in block units and a rotation process can be performed on a rectangular block. Thereby, the rotation output of the image data can be performed without using the memory for the rotation processing.

[0015]

EXAMPLES The present invention will be described in detail below with reference to examples.

FIG. 1 shows the arrangement of an image data compression / decompression device according to an embodiment of the present invention. As shown in the figure, the image data compression / expansion device of the embodiment has a switch 51, two image data expansion units 52 ₁ and 52 ₂ , a switch 54, a byte pack & swap 55, a compression / expansion circuit 56, and a compression code buffer 57. It comprises a compression code table 58, a block scan generator 59 and a clipping rotate count circuit 60.

The switch 51 is a circuit that connects an external device that handles image data to either one of the two image data expansion units 52. The control of the switch 51 is performed by the clipping rotate count circuit 60. . Each image data decompression unit 52 compresses the input image data (n dots × n) during compression (when inputting image data).
This is a circuit that divides into line rectangular image data (hereinafter referred to as a rectangular block), converts the data in each rectangular block into a one-dimensional data string, and outputs the data string. Function as a circuit for performing. In the image data compression / expansion apparatus of the embodiment, the image data expansion unit 52
Is used to divide the image data into rectangular blocks of n = 64.

For example, as schematically shown in FIG.
Image data 1 for 13248 dots x 18688 lines
00 indicates 60444 (2) including image data of 64 dots × 64 lines by the image data developing unit 52.
(07 × 292) rectangular blocks 200 are divided.
Note that, in FIG. 2, each frame shows one rectangular block, and “0” to “6044” described in each frame.
The numerical value “3” indicates the block number given to each rectangular block when the image data is expanded into the rectangular block.

Further, each image data expansion unit 52 can use four different expansion methods when converting the data of 64 × 64 pixels in each rectangular block into a one-dimensional data string. There is. In each expansion method, the image data is converted into 0, 90, 180, 270 degrees (rotational direction:
It is used when compressing / storing in a rotated form (counterclockwise). For example, when compressing / storing by converting 0 ° or 90 °, the following expansion method is used. .

In FIG. 3, the image data decompression unit uses the decompression method used when scanning the data in the rectangular block at the time of normal compression and the compression / compression of the input image data rotated by 90 degrees. The expansion method used when storing is shown.

As shown in FIG. 3A, during normal compression (when data is stored without being rotated), data regarding each pixel in the rectangular block 200 is left as indicated by an arrow. Is converted into a one-dimensional data string by repeating the scan from the top to the bottom. And FIG.
As shown in (b), when compressing and storing the input image data in a state of being rotated by 90 degrees, the data regarding each pixel in the rectangular block 200 is displayed as indicated by an arrow. From the left to the right in the form of repeating the scan from top to bottom (when the inverse transformation of the transformation shown in FIG. 3A is applied to the transformed one-dimensional data string, an image rotated by 90 degrees is obtained. It is converted into a one-dimensional data string.

Further, when rotating 180 degrees and 270 degrees, FIG.
The deployment method 300 _c 300 _d , as shown in FIG. It should be noted that in this figure, the unfolding methods 300 _a and 300 _b shown in FIG.
Is also shown.

Returning to FIG. 1, the image data compression and
The description of the structure of the extension device will be continued.

The two image data expansion units 52 are also connected to a switch 54, respectively.
Is controlled by the clipping rotate count circuit 60 so as to connect either one of the image data expanding section 52 and the byte pack & swap 55.

As shown in FIG. 5, the byte pack & swap 55 is a circuit which is composed of a plurality of flip-flops (F / F) and packs data in byte units, and is schematically shown in FIG. As shown, by swapping the data input order (numerical values in the solid line frame) and the data output order 400 (expressed as "byte 0" and "byte 1" on the right side of the figure), the data can be swapped during rotation. It can also be done.

The compression / decompression circuit 56 is a circuit for compressing and decompressing image data.
In the decompression device, the compression / decompression circuit 56 uses the MH (Modif
A circuit called one-dimensional compression (expansion) called ied Huffman) is used.

The compression code buffer 57 is a buffer for storing the rectangular block data compressed by the compression / expansion circuit 56, and the compression code table 58 stores which rectangular block is stored in which part of the compression code buffer 57. It is a table for storing whether or not. Information is stored in the compressed code buffer 57 and the compressed code table 58 in the following manner.

FIG. 7 shows the correspondence relationship between the compressed code buffer and the information stored in the compressed code table. As shown in the figure, the compression code table 58 has data (“block 0”, “block 1”, ..., “b” corresponding to the maximum number of blocks of image data to be processed by the image data compression / decompression device.
lock 60443 ") is composed of a memory that can store the data for each block in the compressed code table 57.
"0", "code 1", ..., "Code 60443") are stored in the compressed code buffer 57 and indicate the start address of the storage area.

The reading / writing control of the compressed code buffer 57 and the compressed code table 58 is performed by the clipping rotate count circuit 60, and the control of the image data expansion unit 52 and the byte pack & swap 55 is performed by the block scan generator 59. Be seen.

The operation of the image data compression / decompression device of the embodiment will be specifically described below with reference to the drawings. First, FIG.
The operation in the case of compressing and storing the image data without rotating will be described using.

When compressing and storing the image data as shown in FIG. 2, the image data compression / expansion device has a switch 51.
To one of the image data developing units 52 (for convenience of explanation, the image data developing unit 52 ₁ is input), the image data relating to the top line of the block 0, the block 1 The data is input in the order of the image data for the first line of ..., The image data for the second line of the block 207.

The image data development unit 52 ₁ obtains 64 × 64 dots of image data in each block when 64 lines of data, that is, 207 blocks of data from block 0 to block 206 are gathered. , Blocks 0, 1, ..., 206 in this order to the switch 54. At this time, as shown in FIG. 3A, the image data for 64 × 64 dots in each block is, as shown in FIG.
The data regarding each pixel is output in the form of raster scan.

The data string of 64 × 64 dots for each block output from the image data expansion unit 52 ₁ is compressed / compressed.
The decompression circuit 56 compresses the compressed code to generate a compressed code for each block. Then, under the control of the clipping rotate count circuit 60, the compression code “code 0” for the block 0 is stored in the compression code buffer 57, and “code 0” is stored in the storage area corresponding to the block number 0 of the compression code table 58. The head address "block 0" of the compressed code buffer 57 in which is stored is stored (see FIG. 7). Next, the compression code “code1” for the block 1 is stored in the storage area of the compression code buffer 57 subsequent to the storage area of the compression code “code 0”, and is stored in the storage area corresponding to the block number 1 of the compression code table 58. The head address "block 1" of the compressed code buffer 57 in which "code 1" is stored is stored.

It should be noted that the switch 51 is switched when 64 lines of data are supplied to the image data decompression unit 52 ₁ , and these compression processes are performed on the image data of the 65th and subsequent lines. This will proceed in parallel with the input processing to the data expansion unit 52 ₂ .

When the storage of the compressed code relating to the block 206 is completed, the switch 54 and the switch 51 are switched, and the image data from the 65th line to the 128th line stored in the image data decompression unit 52 _2. The compression and the storage of the compressed data are started, and the supply of the image data from the 129th line to the image data expansion unit 52 ₁ is started.

By repeating such processing up to block 60243, compression / storing of image data for one page is completed.

Next, the operation of outputting a part of the image data compressed and stored in this way will be described with reference to FIGS. 8 and 9. Note that FIG. 8 is a diagram showing a division state of the image data used for the description into rectangular blocks and a block number given to each rectangular block. Here, from the block 203 shown in the upper right of FIG. Image data range 40 for 20 blocks up to block 1033
It is assumed that 0 is output as it is (without performing the rotation process) to the external device. Further, FIG. 9 is a diagram showing an outline of a process performed by the image data expanding unit in the output process.

In this case, first, the compression code table 58
The start address of the storage area in which the compressed code for the block 203 is stored is specified based on the content of the block 203, and the compressed code buffer 57 from the start address "block 203" is specified.
The data within is supplied to the compression / expansion circuit 56, where it is expanded. Then, the decompressed data string relating to the block 203 passes through the byte pack & swap 55 and is written in the image data expanding unit 52 ₁ according to the address from the block scan generator 59. For the conversion of each one-dimensional data string into an n × n rectangular block, a development method 300 _a for 0 ° rotation is used, as schematically shown in FIG.

Such processing is repeated up to the block 206, and as shown in FIG.
After 4 blocks of data have been collected in 2, the image data rasterizing unit 52 ₁ starts the process of outputting the internally stored data in raster units to the outside via the switch 51.

When the data up to the block 206 is input to the image data expansion unit 52 ₁ , the switch 5 is activated.
4 is performed, and block 410 is executed in the same procedure.
Through 413, the decompression result of the compressed code is
When the data up to the block 413 is supplied to the image data expansion unit 52 ₂ and is internally stored, the image data expansion unit 5
2 ₂ is a switch 51 for those data in raster units.
The process of outputting to the outside via the. Then, the same processing is repeated up to the block 1033, so that the output for 20 blocks is completed.

As described above, the image data compression / decompression device of the embodiment is capable of outputting an image for one area without performing decompression processing on all data.

Next, the operation when the image data area 400 in the range shown in FIG. 8 is rotated by 90 degrees and output is described.

In this case, of the rectangular blocks included in the image data area 400, the rectangular blocks to be processed first are blocks 206, 413, 620, 827, and 1.
Since it is composed of 5 blocks 033, the clipping rotate count circuit 60 includes the compression / expansion circuit 56.
First to perform decompression processing of the compressed code for block 206, and then blocks 413, 620, 8
Decompress the compressed code for 27 and 1033.

The decompression result for each rectangular block is shown in FIG.
As shown in FIG. 6, the image data is written in the image data developing unit 52 according to the 90-degree rotation developing method 300 _b . Output in raster units.

Then, such processing is executed by alternately using the two image data developing units 52, and the image of 20 blocks rotated by 90 degrees is output.

The operation at the time of 180-degree rotation and 270-degree rotation output is the same, and as shown in FIG. 11, when performing 180-degree rotation output, blocks 1033, 1032,
The compressed code is decompressed in the order of 1031 and 1030, and each decompression result is written in the image data decompression unit 52 in accordance with the decompression method 300 _c for 180 degrees, and the image data decompression unit 52 stores four blocks. When all the data are collected, output in raster units is started.

Further, in the case of performing the rotation by 270 degrees and outputting the data, as shown in FIG.
The compressed code is decompressed in the order of 24, 617, 410, 203, and each decompression result is written in the image data decompression unit 52 according to the decompression method 300 _d for 270 degrees. Then, the image data rasterization unit 52 starts outputting in raster units when the data for 5 blocks are gathered.

As described above, in the image data compression / expansion device of the embodiment, since the compression code is generated and stored in the unit of rectangular block, only the compression code relating to the required rectangular block is read and expanded. Can be done. Therefore, as compared with a conventional apparatus that stores image data by performing compression, a process of expanding image data of only one part or a process of expanding while rotating one or all image data is faster. You can do it.

Modification

The image data compression / decompression device of the embodiment is 2
Although the configuration is such that two image data rasterizing sections are operated alternately, even if the apparatus is configured to have only one image data rasterizing section, an apparatus having an average operating speed higher than that of the conventional apparatus can be used. Obtainable. Further, in the image data compression / decompression device of the embodiment, one block is treated as one-dimensional and compressed, but two-dimensional compression such as MR and MMR is performed using one block as a two-dimensional compressed area. The device can also be configured as follows.

A compression / expansion circuit that can perform compression by a plurality of methods is used, and a storage area for attribute information indicating which compression method is used for each block is provided in the compression code table. In this case, the total amount of compressed code generated from each rectangular block can be further reduced.

For example, in a halftone image or the like, the compressed data may be larger than the original image data. However, as described above, the image data is compressed so that the compression method can be selected for each rectangular block. -By configuring the decompression device, only the halftone image part can be stored without compression, and as a result, the storage capacity required for storing image data can be reduced. Become.

Further, the image data compression / expansion apparatus of the embodiment is configured so that only the rotation processing for the image data can be carried out, but the mirror image processing (mirror) is performed only by slightly changing the operation contents of the image data expansion section. It can also be made possible.

[0054]

As described above, in the inventions according to claims 1 to 3, the compressed code is generated and stored in units of rectangular blocks, so that only the necessary compressed code is read out. As a result, the processing of outputting only one area of the image for one page can be performed at high speed.

When the image data compression / expansion device is configured so that each rectangular block can be compressed by a different compression method as in the second aspect of the invention, it is necessary to store the compression code. It is also possible to reduce the required memory capacity.

When the function of performing rotation processing is added to each rectangular block as in the third aspect of the invention, the rotation output of image data is performed without using a memory for rotation processing. An image data compression / decompression device capable of performing the above is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image data compression / decompression device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a procedure of dividing image data into rectangular blocks by the image data compression / decompression device according to the embodiment.

FIG. 3 is an explanatory diagram showing an outline of an expansion method for 0 ° rotation and 90 ° rotation used by an image data decompression unit provided in the image data compression / decompression device of the embodiment for image data decompression. is there.

FIG. 4 is an explanatory diagram showing an outline of four types of decompression methods used by an image data decompression unit provided in the image data compression / decompression device according to the embodiment.

FIG. 5 is a block diagram showing a configuration of a byte pack & swap provided in the image data compression / decompression device according to the embodiment.

FIG. 6 is an explanatory diagram showing an example of a byte pack & swap operation provided in the image data compression / decompression device of the embodiment.

FIG. 7 is an explanatory diagram schematically showing information stored in a compression code buffer and a compression code table provided in the image data compression / decompression device of the embodiment.

FIG. 8 is an explanatory diagram showing an outline of image data used for explaining the operation of the image data compression / decompression device of the embodiment.

FIG. 9 is an explanatory diagram showing the operation content of the image data compression unit when outputting one area of image data in the image data compression / decompression device of the embodiment.

FIG. 10 is an explanatory diagram showing the operation content of the image data compression unit when rotating one region of image data by 90 degrees and outputting the image data in the image data compression / decompression device according to the embodiment.

FIG. 11 is an explanatory diagram showing the operation content of the image data compression unit when rotating one region of image data by 180 degrees and outputting the image data in the image data compression / decompression device of the embodiment.

FIG. 12 is an explanatory diagram showing the operation content of the image data compression unit when rotating one region of image data by 270 degrees and outputting the image data in the image data compression / decompression device according to the embodiment.

[Explanation of symbols]

51, 53 ... Switch, 52 ... Image data expansion section, 55
… Byte pack & swap, 56… Compression / expansion circuit, 5
7 ... compressed code buffer, 58 ... compressed code table,
59 ... Block scan generator, 60 ... Clipping rotate count circuit

Claims (3)

[Claims] 1. Image data for a pixels × b pixels, which is input in a raster format, and image data for n pixels × n pixels is 1
While dividing into a plurality of rectangular blocks as a unit,
Dividing / assigning means for allocating block position information indicating a position in the image data of a pixels × b pixels to each rectangular block, and n in each rectangular block divided by this dividing means.
The image data of pixels × n pixels is converted according to a predetermined rule.
A compression unit that converts the data string for one line and compresses the converted data string to generate a compression code, a compression code storage unit that stores the compression code generated by the compression unit, and a compression code storage unit. The correspondence relationship between the storage position information indicating the storage position of each compressed code stored in the means and the block position information assigned by the dividing / assigning means to the rectangular block that is the source of each compressed code is stored. Corresponding correspondence storage means, range specifying means for specifying the range of image data to be output, and the block position information of the rectangular block corresponding to the image data in the range specified by the range specifying means,
Based on the obtained block position information and the correspondence relationship stored in the correspondence relationship storage means, specifying means for specifying storage position information for the compressed code for each rectangular block, and from the compression code storage means by the specifying means Decompressing means for decompressing and decompressing each compressed code stored in the memory location corresponding to the stored memory location information, and decompressing the decompressed result of this decompressing means by performing inverse conversion of conversion according to the predetermined rule. Created n pixels x n
An image data compression / expansion device, comprising: an output unit configured to arrange image data for pixels in accordance with block position information of a rectangular block which is a source of the image data and output the image data in a raster format. 2. Image data for a pixels × b pixels input in a raster format, and image data for n pixels × n pixels is 1
While dividing into a plurality of rectangular blocks as a unit,
Dividing / assigning means for allocating block position information indicating a position in the image data of a pixels × b pixels to each rectangular block, and n in each rectangular block divided by this dividing means.
The image data of pixels × n pixels is converted according to a predetermined rule.
A compression unit for converting the data string into one line and compressing the converted data string using a compression method selected from several compression methods to generate a compression code, and the compression unit. Compression code storage means for storing the compressed code generated by the compression code storage means, storage location information indicating the storage location of each compression code stored in the compression code storage means, and the compression method used when generating each compression code. And a correspondence storage unit that stores the correspondence between the compression attribute that is information for identifying the block and the block position information that is assigned to the rectangular block that is the source of each compression code by the dividing / assigning unit. , Range specifying means for specifying a range of image data to be output, and the block of the rectangular block corresponding to the image data in the range specified by the range specifying means. Seek position information,
Based on the obtained block position information and the correspondence relationship stored in the correspondence relationship storage means, specifying means for specifying the storage position information and the compression attribute for the compression code for each rectangular block, and from the compression code storage means, Decompression means for reading each compression code stored in the storage position corresponding to the storage position information specified by the specifying means, and expanding the read compression code in accordance with the compression attribute specified by the specifying means, The decompression result of the decompression means is subjected to an inverse conversion of the conversion according to the predetermined rule to create n pixels × n.
An image data compression / expansion device, comprising: an output unit configured to arrange image data for pixels in accordance with block position information of a rectangular block which is a source of the image data and output the image data in a raster format. 3. Image data for a pixels × b pixels, which is input in a raster format, and image data for n pixels × n pixels is 1
While dividing into a plurality of rectangular blocks as a unit,
Dividing / assigning means for allocating block position information indicating a position in the image data of a pixels × b pixels to each rectangular block, and n in each rectangular block divided by this dividing means.
The image data of pixels × n pixels is converted according to a predetermined rule.
A compression unit that converts the data string for one line and compresses the converted data string to generate a compression code, a compression code storage unit that stores the compression code generated by the compression unit, and a compression code storage unit. The correspondence relationship between the storage position information indicating the storage position of each compressed code stored in the means and the block position information assigned by the dividing / assigning means to the rectangular block that is the source of each compressed code is stored. Corresponding correspondence storage means, a range / angle designating means for designating a range of image data to be output and an angle to be rotated at the time of output, and the rectangle corresponding to the image data in the range designated by the range / angle designating means. The block position information of the block is obtained, and each rectangular block is calculated based on the obtained block position information and the correspondence relationship stored in the correspondence relationship storage means. Specifying means for specifying storage position information for the compressed code relating to the lock; and reading and expanding each compression code stored in the storage position corresponding to the storage position information specified by the specifying means from the compression code storage means. Decompression means and n pixels × n created by subjecting the decompression result of this decompression means to inverse conversion of the conversion according to the predetermined rule.
Image data in pixels is rotated by the angle designated by the range / angle designating means, and the rotated image data is arranged in accordance with the block position information of the original rectangular block to form a raster format image. An image data compression / decompression device, comprising: an output unit for outputting as data.