JPH11205613A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor with which multilevel image data can be compressed/extended at high speed by a simple compression/extension method. SOLUTION: Concerning the image processor provided with a means for compressing/extending the multilevel image data, this device is provided with a group extracting means 11 for extracting the image data of a group composed of N pieces of adjacent pixels, a sub-grouping means 12 for collecting image data having the same value of a high-order bit among the image data of the extracted group for each equal value and sub-grouping the image data, an encoding means 13 for encoding the average values of image data in respective sub-groups and the codes of sub-groups, to which the respective pixels belong, as compressed image data (encoded data) while having an average value calculating means for finding the average value of image data concerning each sub- group, and an extending means for decoding and extending image data by turning the average value of image data in the sub-groups, to which the respective pixels belong, into image data of the said pixels according to the held said compressed image data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus such as a copying machine or a printer for compressing and recording digital image data and then expanding and outputting the digital image data. Hereinafter, abbreviated as multi-valued image data) is easily encoded and compressed and stored.
The present invention relates to an image processing device for decoding and decompressing and outputting.

[0002]

2. Description of the Related Art Generally, image data is composed of image data of an enormous number of pixels constituting an image, so that the data amount becomes extremely large. Therefore, when storing or transferring image data, when encoding and compressing and then performing storage and transfer, and when outputting the encoded and compressed image data as a real image,
Techniques for decoding and decompressing are conventionally known. For example, in a facsimile apparatus that handles binary image data, MH
Encoding and compression are performed by a method or an MR method.
In the case of multi-valued image data, for example, the image data of the first pixel is left as the original image data, and the image data of the subsequent pixel is encoded as a change from the preceding image data. And compression. In this case, the amount of change in image data between adjacent pixels is generally a small value, so that the number of bits for one pixel is reduced, and thus the data amount is reduced. In addition, JP-A-9-
In the image processing system disclosed in Japanese Patent No. 83809, the data amount is reduced by dividing the image data into blocks each including a plurality of pixels and expressing the image data in the blocks with a small number of approximate colors, such as two or four. The approximate color is statistically obtained from the color signals in the block.

[0003]

However, in the prior art for compressing multi-valued image data using the above-mentioned change, processing corresponding to the case where the change is large becomes complicated and a long processing time is required. Therefore, it is not suitable for a copier or the like that requires real-time properties. Also, JP-A-9-8380
The prior art disclosed in Japanese Patent Publication No. 9 also requires a complicated process to calculate the approximate color data value. Is not suitable. An object of the present invention is to provide an image processing apparatus that solves the above-described problem of the real-time property of the conventional technology and enables high-speed compression and decompression of multi-valued image data by an easy compression and decompression method that requires less processing time. Is to do.

[0004]

In order to solve the above-mentioned problems, according to the present invention, there is provided a compression storage means for compressing and storing multi-valued image data after encoding, and the compressed and stored multi-valued image data. In an image processing apparatus provided with a decompression means for decoding and decompressing image data, the most significant bit of the image data of the image data of each pixel in a group of N adjacent pixels has the same value. Sub-grouping means for collecting image data for each of the same values and sub-grouping the image data; average value calculating means for calculating an average value of image data in each of the sub-groups; Compressed data storage means for storing, as compressed image data, an average value of image data and a code of a subgroup to which the image data belongs in each pixel; Decoding means for decoding the average value of the image data of the subgroup to which each pixel belongs in accordance with the compressed image data obtained from the storage means as the image data of the pixel. The average value of the image data and the code of the subgroup to which each pixel belongs are stored as compressed image data, and the average value of the image data of the subgroup to which each pixel belongs according to the stored compressed image data is the image data of the pixel. Is decrypted. Further, in the invention according to claim 2, the sub-grouping means determines whether or not the most significant bits of all the image data in the original group to be sub-grouped have the same value, or if the most significant bits are all If they are the same, it is determined in order from the most significant bit side whether or not the next most significant bit has the same value, and all the image data of the same digit from the most significant bit side in the group have the same value (0 Or the value of the most significant bit sequence after deleting one or more bits until it is no longer 1) is 1 or 0
In this case, one or more bits are deleted from the most significant bit side until the most significant bits of all the image data in the group are not all 0s or 1s. They are subgrouped by 1 or 0. Further, in the invention according to claim 3, the group is a two-dimensional N pixel set including pixels adjacent to each other in a plurality of adjacent lines as well as a case where N pixels adjacent to each other on the same line are regarded as one group. As a group, and a two-dimensional pixel set including pixels on a plurality of adjacent lines is regarded as one group including N adjacent pixels. Further, in the invention according to claim 4, the sub-grouping means further sub-groups the larger sub-group when the number of image data belonging to one of the sub-groups is larger than the other. Sub-grouping is repeated until the number of image data belonging to the two sub-groups becomes the same, and the number of image data belonging to the two sub-groups becomes the same in the last sub-grouping of the sub-grouping means. In this case, the maximum image data value in the image data of the sub-group with the smaller image data value or the minimum image data value in the image data of the sub-group with the larger image data value is replaced with the average value calculating means. 1 and the number of image data belonging to the two sub-groups is the same in the last sub-grouping by the sub-grouping means. If not, the same value of the image data belonging to the sub-group with the larger number of image data is taken as the second representative value, and the image data belonging to the two sub-groups in the last sub-grouping by the sub-grouping means. One of the first and second representative values depending on whether the number of
A representative value extracting unit that replaces the average value calculating unit with the third representative value, wherein the compressed data storage unit stores the average value in the compressed image data instead of the third representative value. 3. The method according to claim 2, wherein the decoding means decodes the average value in the image data of the pixel in place of the third representative value. When the number of image data belonging to one of the divided sub-groups is larger than that of the other, the larger sub-group is further sub-grouped,
When the number of image data belonging to the two sub-groups is the same or when they are the same, the maximum image data value in the image data of the sub-group with the smaller image data value,
Alternatively, the smallest image data value in the image data of the sub-group having the larger image data value is regarded as the representative value, and if the values of the image data belonging to the sub-group having the larger number of image data are all the same, the image data value Is a representative value, the representative value of each subgroup and the sign of the subgroup to which each pixel belongs are stored as compressed image data,
According to the stored compressed image data, the representative value of the image data of the sub-group to which each pixel belongs is set as the image data of the pixel, and thus the image is decoded. In the invention according to claim 5, the image processing apparatus further includes a representative value acquisition unit that acquires a maximum value or a minimum value in the image data of each of the subgroups as a fourth representative value instead of the average value calculation unit, The compressed data storage means stores the average value in the compressed image data in place of the fourth representative value, and the compounding means stores the average value in the image data of the pixel in the fourth representative value. Characterized by decoding instead,
The maximum value or the minimum value of the image data of each subgroup and the code of the subgroup to which each pixel belongs are stored as compressed image data, and the image data of the subgroup to which each pixel belongs according to the stored compressed image data. The decoding is performed by setting the maximum value or the minimum value as the image data of the pixel. Further, in the invention according to claim 6, the representative value acquiring means sets a maximum value as a fourth representative value in a subgroup having a larger value of image data belonging to the subgrouping, The sub-group having the smaller value of the image data is characterized by using the minimum value as the representative value, the sub-group having the larger value of the image data to which the sub-group belongs has the maximum value as the representative value, For the subgroup, the minimum value is set as the representative value. Further, in the invention according to claim 7, the representative value acquiring means sets a minimum value as a fourth representative value in a subgroup having a larger value of image data belonging to the subgrouping, and The sub-group having a smaller value of the image data is characterized by the maximum value as a representative value,
A sub-group having a large value of the image data to which it belongs has a minimum value as a representative value, and a sub-group having a small value of the image data has a maximum value as a representative value. Further, in the invention according to claim 8, for each of the subgroups, the average value by the average value calculating means or any of the first to fourth representative values by the representative value extracting means and the representative value obtaining means is set to the fifth value. A second representative value obtaining means obtainable as a representative value;
And a representative value designating means capable of designating in advance which value of the representative value acquiring means is the fifth representative value. Are used as representative values. In the invention according to claim 9, the sub-grouping means can add a group code for identifying a group to each of the groups, and the compressed data storage means stores the compressed image data in the group code. When the image data of the same line is included in a plurality of groups, the decoding unit can store the compressed image data of one line including the image data in the group code and the image data. Characterized in that it is obtained from the compressed data storage means and decoded based on the line number or pixel number of the data,
When image data of the same one line is included in a plurality of groups, by specifying a group code and a line number or a group code and a pixel number, the compressed image data of the one line is acquired and decoded. You.

[0005]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing an overall configuration of a main part of an image processing apparatus according to the present invention. As shown in the figure, the image processing apparatus includes an image input unit 1 for reading an image from a document or the like and inputting image data, a compression unit 2 for encoding and compressing the image data, and a compression storage for storing the compressed image data. A memory 3 as a means, an expansion means 4 for decoding and expanding the compressed and stored image data, an image data output means 5 for outputting the expanded image data to a recording paper or the like are provided. FIG. 2 is a block diagram showing the configuration of the first embodiment of the compression means of the image processing apparatus of the present invention. As shown in the figure, the compression unit 2 of this embodiment includes a group extraction unit 11 for extracting image data in a group including N adjacent pixels as one group, and a sub-group for extracting the image data in one group. And an encoding unit 13 that encodes and compresses the image data by including an average value calculating unit that calculates an average value of the sub-grouped image data. The operation of this embodiment will be described below with reference to FIGS. First, the image data input unit 1 sequentially reads, for example, images on a document from the first line. Then, the read image data is grouped by the group extracting means 11 into image data of, for example, 16 pixels as shown in FIG. In FIG. 3, the number (No) in the left column is a pixel number for each group. For example, the first pixel or the 17th pixel in one line is pixel number 1, and the second pixel in one line is And the 18th pixel is pixel number 2.
Also, since the image data is shown in an example of an 8-bit configuration, bit 7, bit 6, bit 5, bit 4, bit 3,
The contents of bit 2, bit 1, bit 0 and 8 bits are shown, and the rightmost column shows the values of the first to sixteenth image data in decimal. When the group extracting means 11 extracts the image data as shown in FIG. 3, the sub-grouping means 12 determines whether the value of the column of bit 7 which is the most significant bit (hereinafter referred to as MSB) is the same value for all the image data. Determine whether or not. In the illustrated example, all the values in the column of bit 7 are all 0. In this case, if the values are the same, the MSB of the column is deleted to change the effective bit to 7 bits.
The sub-grouping means 12 determines whether or not the values of all 6 are the same.

In the example of FIG. 3, there are a pixel having a value of 0 and a pixel having a value of 1 in bit 6, and in such a case, the subgrouping means 12 converts one group into a subpixel having a value of 0. It is divided into a group G0 (9 pieces of image data) and a subgroup G1 (7 pieces of image data) having a value of 1 (see FIG. 4).
Subsequently, the subgrouping means 12 compares bit 5 to further subgroup the subgroup G0, and compares the subgroup G00 with the value of 0 (the number of image data is 3) with the subgroup G01 with the value of 1 (3). (The number of image data is 6).
Also, to further subgroup the subgroup G1
When bit 5 is compared, since all in the subgroup are 1, bit 4 is compared next, and subgroup G10 (the number of image data is 5) having a value of 0 and subgroup G11 (the number of image data is 5) having a value of 1 The image data is divided into two (the number of image data is two) (see FIG. 5).
Subsequently, the average value calculating means in the encoding means 13 calculates the average value of the image data belonging to each of the subgroups G00, G01, G10, G11, and calculates the average value as the representative value of the image data of each subgroup. And Further, a 2-bit pixel code (subgroup number) indicating which subgroup each pixel in the group belongs to is determined from the content of the compared bits, and the plurality of pixel codes and the representative value corresponding to the pixel code are calculated. Together, the encoded data (compressed image data) of the group is set (see FIG. 6). As a result, in the case of the example shown in the figure, the data amount per group is halved from the original 128 bits (8 bits × 16 pixels) to 64 bits (2 bits × 16 pixels + 8 bits × 4 subgroups). The data is compressed, and the compressed encoded data is written to the memory 3 and held. After that, the decompression means 4 acquires the corresponding representative value (average value) from the pixel code of each pixel in the order of the pixel number, and outputs it to the image data output means as approximate decoded data, for example (see FIG. 7). Thus, according to the first embodiment, multi-valued image data can be compressed and the approximate value can be decoded by simple processing, so that real-time high-speed encoding and decoding can be realized. can do. In the above description, the case of dividing into four subgroups has been described, but the number of subgroups is not limited to four.

FIG. 8 is an explanatory diagram showing a second embodiment of the present invention. This is an example in which each image data has a 4-bit configuration and the number of pixels in one group is 4, and a mismatch detection circuit is provided for each bit as shown in FIG. As shown in FIG. 9, the non-coincidence detection circuit is a four-input AND gate 21 which is a four-input AND gate that inverts all inputs and outputs one when all inputs are zeros, and all inputs are ones. When the input side is all 0's or all 1's, it outputs 0 (Low level), and when not, it outputs 0 (Low level). Time) 1 is output. In this way, in the case of the image data shown in FIG. 8, since the bits other than bit 3 do not match, the mismatch detection result of each bit becomes “0, 1, 1, 1” as shown in FIG. Also, referring to FIG. 8, it is easy to see that the bit closest to the MSB among the mismatched bits is bit 2. However, in the second embodiment,
This is identified by a comparison bit determination circuit as shown in FIG. AND becomes 1 when both inputs are 1
Three gates 24 are provided, and one input of each is inverted and input as shown in FIG. When four mismatch detection result signals are input as shown in the figure, a comparison bit signal of 1 is output to one of the four output terminals. The bit (n) that outputs the comparison bit signal of 1 is the mismatch bit closest to the MSB (see FIG. 8).

Next, a bit (n) for outputting a comparison bit signal of 1 is used as a determination bit for subgrouping, a group whose bit is 1 is one subgroup, and a group whose bit is 0 is another subgroup. Sub-grouping is performed by grouping. Thus, according to the second embodiment, a higher speed subgrouping can be achieved with a simple circuit. In the above description, the bit configuration and the case where the number of pixels in one group is small have been described. However, even when the number of constituent bits is large or the number of pixels is large, sub-grouping can be performed by a similar circuit. In addition, by providing the decoder 25 as shown in FIG. 11, for example, by decoding the bit (n) and the bit (n-1) as an input, the signal is divided into four instead of two as described above. It is also possible to generate four subgroups. In the above-described first and second embodiments, one group is a one-dimensional group in which one group is included in one line as shown in FIG. 12 (a). However, in the third embodiment, FIG. 12 (b) As shown in (1), one group is formed over several lines. For this reason, in the third embodiment, as shown in FIG. 13A, a line buffer 31 capable of inputting and outputting to the group extracting means 11 is provided, and the group extracting means 11 converts the input image data for a plurality of lines ( After the image data is stored in the line buffer 31, the image data in the group extending over a plurality of lines is sequentially read from the corresponding address and passed to the sub-grouping means 12. Hereinafter, the processing after the subgrouping is performed in the same manner as in the first or second embodiment. As shown in FIG. 13 (b), a predetermined area in the memory 3 provided so as to be able to input and output to and from the group extracting means 11 may be used as a line buffer.

As described above, according to the third embodiment, since pixels at closer positions are grouped into the same group, the correlation of the image data in the group is increased, and therefore, the quality of the expanded image data ( Approximation with the original image). In the fourth embodiment of the present invention, a method of using a representative value close to the average value (pseudo average value) calculated by the first embodiment in subgrouping in the first embodiment is described. Find in a similar way. For example, the first
The four subgroups G00, G01, G shown in the embodiment of FIG.
10, G11 will be described as an example. First, in the case of the subgroup G00, as shown in FIG. 14, the MSB (bit 2, hatched portion shown) excluding the common upper bit 00011 is 0 or 1, Divide into G000 and G001. Further, the image data is divided into subgroups G0010 and G0011 according to whether the lower bit (bit 1 in the illustrated example) of the lower value of the image data of the subgroup G001 having the larger number of image data is 0 or 1. Thus, the number of image data belonging to each of the subgroups becomes one. In such a case, any of the above is set as the representative value of the subgroup G00.

Similarly, in the case of subgroup G01, FIG.
As shown in the last subgrouping, subgroup G0
10010 and G010011 are obtained, and the number of image data belonging to each of the above subgroups becomes one.
One of the above is set as a representative value of the subgroup G01. Also, when the subgroup is divided into two, as shown in FIG. 15, if the number of image data belonging to each of the two subgroups is the same, the maximum image data value in the image data of the subgroup having the smaller image data value Or the smallest image data value in the image data of the sub-group having the larger image data value is set as the representative value. That is, in the example of FIG.
100 or 00110100 is set as a representative value. As shown in FIG. 14, the case where the number of image data belonging to each subgroup is one is a special case of the same number, and also in this case, the representative value is determined according to the above rule. If the values of the image data belonging to the sub-group with the larger number of image data are all the same, the image data value is set as the representative value. Thus, according to the fourth embodiment, since the representative value can be obtained without calculating the average value, the dividing means is not required, and the circuit for obtaining the representative value is simplified.

The maximum image data value or the minimum image data value belonging to each subgroup may be used as a representative value of each subgroup. For example, in the sub-group G00 shown in FIG.
10, maximum image data value 0011 in subgroup G01
Set 1100 as the representative value. Alternatively, in the subgroup G00, the minimum image data value 00011001, the subgroup G0
In 1, the minimum image data value 00100000 is set as a representative value. In a subgroup to which a large image data value belongs, the maximum image data value in the image data to which the subgroup belongs is set as a representative value, and in a subgroup to which a small image data value belongs, the minimum image data in the image data to which the subgroup belongs. The value may be used as the representative value. For example, the subgroup shown in FIG.
G00 has the minimum image data value 00011001, subgroup G01 has the minimum image data value 00100000, subgroup G10 has the maximum image data value 01101110,
In the subgroup G11, the maximum image data value is 0111100.
Set 0 as the representative value. With such a representative value, an image with high contrast can be restored. In a subgroup to which a large image data value belongs, the minimum image data value in the image data to which the image data belongs is set as a representative value. In a subgroup to which a small image data value belongs, the maximum image data in the image data to which the image data belongs. The value may be used as the representative value. For example, in the sub-group G00 shown in FIG. 5, the maximum image data value is 0111110, in the sub-group G01 is the maximum image data value 001111100, and in the sub-group G10.
Is the minimum image data value 01100010, subgroup
In G11, the minimum image data value 01110100 is set as the representative value. With such a representative value, an image with low contrast can be restored.

FIG. 16 is a block diagram of a main part of an image processing apparatus according to a fifth embodiment of the present invention. In the image processing apparatus of this embodiment, various first
A plurality of means for obtaining the representative value and the average value described in the fourth to fourth embodiments are provided, and the means for obtaining the representative value can be specified by the representative value specifying means. That is, the representative value designating means of the fifth embodiment includes, for example, the system control unit 6, the operation unit 7, the representative value acquisition method storage unit 8 shown in FIG. From 7, the representative value acquisition method is input. For example, the system control unit 6 displays guidance as shown in FIG. 17 on the display unit, and instructs a desired representative value acquisition method using a cursor key or the like in the operation unit 7. FIG. 17
In the above, the pseudo average value of the displayed guidance is the representative value shown in the fourth embodiment. When a desired representative value acquisition method is instructed by the user, the system control unit 6 sets a numerical value indicating the representative value acquisition method in the representative value acquisition method storage unit 8 configured by a flash memory or the like. After that, when the image data is input, the encoding unit 13
Refers to the representative value obtaining method set in the representative value obtaining method storage unit 8 and obtains a representative value according to the representative value obtaining method. Thus, according to this embodiment, an image output according to the user's request can be obtained. Note that a configuration including only a part of the representative value obtaining method illustrated in FIG. 17 is also possible.

FIG. 18 is an explanatory view showing a sixth embodiment of the present invention. In FIG. 18A, in the third embodiment in which one group extends over a plurality of lines, if the group has a 4 × 4 two-dimensional configuration as illustrated, the image data is decoded in the order indicated by numerals. It is shown that In other words, in the example shown in the figure, the decoding results of all the groups of up to four lines cannot be output to the image data output means 5 unless they are once stored in another area of the memory 3 or a line buffer. . On the other hand, in the sixth embodiment, as shown in FIG. 18B, decoding can be performed in line order and output in decoding order. That is, in this embodiment, a group code for identifying the group is added to each group, and the group code and the line number or the group code and the pixel number are specified to obtain one line of the compressed image data. And decrypt it. For example, the decompression unit 4 as a decoding unit obtains a representative value of each subgroup from the compressed data area corresponding to the first group code in the memory 3, and obtains the first to fourth pixel codes. (See FIG. 6) are sequentially read out and replaced with corresponding representative values and output. Next, a representative value of each sub-group is acquired from the compressed data area associated with the second group code, and the first to fourth pixel codes (see FIG. 6) of the group are sequentially read out and read. The data is replaced with the corresponding representative value and output as the fifth to eighth image data of the first line. Subsequently, the representative value of each subgroup is obtained from the compressed data area associated with the third group code, and the first to fourth representative values of the group are obtained.
The pixel codes up to the first pixel are sequentially read and replaced with the corresponding representative values, and are output as the ninth to twelfth image data of the first line. When outputting the first part of the second line, that is, the thirteenth to sixteenth image data shown in FIG. 18B, the fifth part of the compressed data area associated with the first group code is output. , The addresses where the pixel codes (see FIG. 6) are stored are calculated, and the fifth to eighth pixel codes are sequentially read out and replaced with the corresponding representative values. Output. Hereinafter, the same applies. As described above, according to the sixth embodiment, the buffer memory is not required for the decompression means, and the hardware can be reduced in size accordingly.

[0014]

As described above, according to the present invention,
According to the first aspect of the present invention, the average value of the image data of each subgroup and the code of the subgroup to which each pixel belongs are stored as compressed image data, and the subgroup to which each pixel belongs according to the stored compressed image data. Since the image data is decoded by setting the average value of the image data as the image data of the pixel, the multi-valued image data can be compressed and decompressed at high speed. Further, in the invention according to claim 2, in the invention according to claim 1, one or more bits are deleted from the most significant bit side until the most significant bits of all the image data in the group are not all 0 or all 1. Since the most significant bit after the sub-grouping is sub-grouped according to whether it is 1 or 0, sub-grouping can be easily realized. According to the third aspect of the present invention, in the first or second aspect of the present invention, a two-dimensional pixel set consisting of pixels on a plurality of adjacent lines is a group consisting of N adjacent pixels. Thus, the correlation of the image data is increased, and an image close to the original image can be restored. In the invention according to claim 4, further sub-grouping is performed by the method according to claim 2, and when the number of image data belonging to one of the sub-groups is larger than that of the other sub-group, the larger one is used. Are further sub-grouped, and when the number of image data belonging to the two sub-groups is the same or becomes the same, the maximum image data value in the image data of the sub-group having the smaller image data value Or the smallest image data value in the image data of the sub-group having the larger image data value is set as the representative value, and if the values of the image data belonging to the sub-group having the larger number of image data are all the same, the image data The representative value of each subgroup and the sign of the subgroup to which each pixel belongs are stored as compressed image data, Since the representative value of the image data of the subgroup to which each pixel belongs is determined as the image data of the pixel according to the compressed image data thus decoded, the division is unnecessary as in the case where the average value is used as the representative value. , Thus simplifying the circuit.

According to the fifth aspect of the present invention, the maximum value or the minimum value of the image data of each subgroup and the code of the subgroup to which each pixel belongs are stored as compressed image data, and the stored compressed image data is stored. The decoding is performed by setting the maximum value or the minimum value of the image data of the sub-group to which each pixel belongs as the image data of the pixel according to the data. Is unnecessary, and the circuit is simplified. According to a sixth aspect of the present invention, in the invention of the fifth aspect, a subgroup having a large value of the image data to which the image data belongs has a maximum value as a representative value, and a subgroup having a small value of the image data has a minimum value. Is a representative value, so that an image with high contrast can be obtained. According to a seventh aspect of the present invention, in the invention of the fifth aspect, a subgroup having a large image data value has a minimum value as a representative value, and a subgroup having a small image data value has a maximum value. Is a representative value, an image with low contrast is obtained. Also, in the invention according to claim 8, in the invention according to claim 1, 2, 3, or 4, a specified one of an average value, a maximum value, a minimum value, and the like is used as a representative value. Since it is used, various images can be obtained depending on the situation. According to the ninth aspect of the present invention,
When one line extends over a plurality of groups, if a group code and a line number or a group code and a pixel number are designated, the compressed image data for the one line is acquired and decoded, so that a buffer memory for image output is obtained. Can be reduced in size.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a main part of an image processing apparatus according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of a first embodiment of a compression unit of the image processing apparatus according to the present invention.

FIG. 3 is an explanatory diagram illustrating grouping according to the first embodiment of this invention.

FIG. 4 is an explanatory diagram showing sub-grouping according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing further sub-grouping of the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing pixel codes and representative values according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram showing decoding according to the first embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a second embodiment of the present invention in which each image data has a 4-bit configuration and the number of pixels in one group is four.

FIG. 9 is a block diagram of a mismatch detection circuit according to a second embodiment of the present invention.

FIG. 10 is a block diagram of a comparison bit determination circuit according to a second embodiment of the present invention.

FIG. 11 is a block diagram of a decoder according to the second embodiment of the present invention.

12A and 12B are explanatory diagrams of a third embodiment of the present invention in which one group extends over a plurality of lines.

FIGS. 13A and 13B are block diagrams of main parts of an image processing apparatus according to a third embodiment of the present invention.

FIG. 14 is an explanatory diagram of how to obtain a representative value according to the fourth embodiment of the present invention.

FIG. 15 is an explanatory diagram of a method of obtaining a general representative value according to the fourth embodiment of the present invention.

FIG. 16 is a block diagram illustrating a main part of an image processing apparatus according to a fifth embodiment of the present invention including a plurality of representative value obtaining units.

FIG. 17 is a screen view of guidance on a display unit according to the fifth embodiment of the present invention.

FIGS. 18 (a) and (b) are explanatory views of a sixth embodiment of the present invention.

[Explanation of symbols]

1 ... image data input means, 2 ... compression means, 3 ...
..Memory, 4 ... Expansion means, 5 ... Image data output means, 6 ... System control unit, 7 ... Operation unit, 8
... Representative value acquisition method storage unit, 11 ... Group extraction means, 12 ... Subgrouping means, 13 ... Encoding means, 14, 21 ... All zero detection circuit, 15, 22, ..All 1 detection circuits,

Claims (9)

[Claims] 1. An image processing apparatus comprising: compression storage means for compressing and storing multi-valued image data after being stored; and decompression means for decoding and decompressing the compressed and stored image data. Sub-grouping means for collecting, for each same value, image data in which the most significant bit of the image data in the image data of each pixel in the group of adjacent pixels as one group is the same, and sub-grouping the image data; Average value calculating means for calculating an average value of the image data in each of the sub-groups, and compressing the average value of the image data in each of the sub-groups and the code of the sub-group to which the image data belongs in each pixel. A compressed data storage means for storing the compressed image data obtained from the compressed data storage means, Decoding means for decoding by setting the average value of the image data as the image data of the pixel. 2. The method according to claim 1, wherein the sub-grouping unit determines whether the most significant bits of all image data in the original group to be sub-grouped have the same value or if all the most significant bits are the same. Determines in order from the most significant bit side whether or not the next most significant bit has the same value, and all the image data of the same digit from the most significant bit side in the group are not all the same value (0 or 1). 2. The image processing apparatus according to claim 1, wherein sub-grouping is performed based on whether the value of the most significant bit string after removing one or more bits is 1 or 0. 3. The group includes not only a case where N pixels adjacent on the same line are grouped into one group, but also a group of two-dimensional N pixels including adjacent pixels on a plurality of adjacent lines. The image processing apparatus according to claim 1, further comprising a case. 4. When the number of image data belonging to one of the sub-groups is larger than that of the other sub-group, the sub-grouping means further sub-groups the larger sub-group to form two sub-groups. The sub-grouping is repeated until the number of image data belonging to the same sub-group becomes equal. If the number of image data belonging to the two sub-groups becomes the same in the last sub-grouping by the sub-grouping means, a small image The maximum image data value in the image data of the sub-group with the data value or the minimum image data value in the image data of the sub-group with the larger image data value is used as the first representative value instead of the average value calculating means. When the number of image data belonging to the two sub-groups is not the same in the last sub-grouping of the sub-grouping means, Is the same as the second representative value of the image data belonging to the subgroup having the larger number of image data, and the number of image data belonging to the two subgroups is the same in the last subgrouping by the subgrouping means. A representative value extracting unit that replaces the average value calculating unit with one of the first and second representative values as a third representative value depending on whether or not the compressed data storage unit stores the compressed data. The average value in the image data is stored in place of the third representative value, and the decoding unit decodes the average value in the image data of the pixel in place of the third representative value. The image processing device according to claim 2 or 3, wherein 5. A representative value acquiring unit for acquiring a maximum value or a minimum value in the image data of each of the subgroups as a fourth representative value instead of the average value calculating unit, wherein the compressed data storage unit includes And storing the average value in the compressed image data in place of the fourth representative value, and decoding the image data in place of the average value in the image data of the pixel in place of the fourth representative value. The image processing apparatus according to claim 1, wherein: 6. The representative value acquisition unit, wherein a subgroup having a larger value of image data belonging to the subgrouping as a fourth representative value has a maximum value as a representative value,
6. The image processing apparatus according to claim 5, wherein a sub-group having a smaller value of the image data sets a minimum value as a representative value. 7. The representative value acquiring means, wherein a subgroup having a larger value of image data belonging to the subgrouping as a fourth representative value has a minimum value as a representative value,
6. The image processing apparatus according to claim 5, wherein the sub-group having a smaller value of the image data sets a maximum value as a representative value. 8. A fifth representative value may be obtained for each of the subgroups as an average value by the average value calculating means or any of the first to fourth representative values by the representative value extracting means and the representative value obtaining means. A second representative value obtaining unit, and a representative value specifying unit that can specify in advance which value obtainable by the second representative value obtaining unit is the fifth representative value. The image processing apparatus according to claim 4. 9. The sub-grouping unit can add a group code for identifying a group to each group, and the compressed data storage unit can store the group code as compressed image data. In the case where the image data of the same line is included in a plurality of groups, the combining unit converts the compressed image data of one line including the image data into the group code and the line number of the image data or The image processing apparatus according to any one of claims 3 to 8, wherein the image processing apparatus obtains the data from the compressed data storage unit and decodes the data based on the pixel number.