JP2002262098A - Picture compressing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a picture compressing device by which hardware conversion is easily performed with a simple algorism at high processing speed. SOLUTION: The device is provided with a memory 5 for storing input picture data 101 for the portion of one line and an encoding mean 7 for permitting the prescribed bit number of the picture data in the memory 5 to be one unit picture word, encoding the picture word to be compressed to have a prescribed code length in relation to the picture word compressed in the past, outputting it, permitting the picture word to be compressed at present to have the prescribed code length unless relating is possible and outputting it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image compression apparatus capable of reducing the transmission speed and the capacity of a storage medium by utilizing digital compression technology for a large amount of image data, and an office automation device having a semiconductor memory. The present invention relates to an image compression device suitable for personal devices in general.

[0002]

2. Description of the Related Art In general, when handling images in digital equipment such as office automation equipment and personal equipment, there is an increasing demand for color and multiple gradations due to the demand for higher image quality. With the demand for such colorization, multi-gradation, and high image quality, digital devices need to process image data of an enormous amount of data, and a storage medium for storing the image data is required. Techniques for compressing image data are now indispensable due to the need to reduce the capacity and the transmission speed of image data. The technology related to such image compression is described in detail in, for example, Japanese Patent Application Laid-Open No. Hei 10-13688. According to this technique, image data is separated by type according to data contents, each separated information is encoded, and these are converted into serial data using a multiplexer and transmitted. Thereby, the required amount of memory at the time of decoding can be reduced, and the management of code data can be simplified. By the way, when the image data is data that is difficult to compress, even if the image data is encoded, the data cannot be compressed, but may be several times larger than the input image data capacity. In order to solve such inconveniences, there has been proposed a solution which can be performed with the same data capacity as the original image data even if the image data which is difficult to compress is encoded.

[0003]

However, the above-mentioned prior art has a drawback that the algorithm for compressing the image data is complicated, so that it is difficult to implement hardware and the processing speed is slow.

A first object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to simplify the encoding by associating a previously input image word with the image word to be encoded. It is an object of the present invention to provide an image compression apparatus which has a simple algorithm, can be easily implemented in hardware, and has a high processing speed. A second object of the present invention is to solve the problem that the compression ratio is not very good even when the image data is easily compressible data, and to perform encoding that does not increase the data amount by using the characteristics of the output data. It is an object of the present invention to provide an image compression apparatus which enables the image compression. A third object of the present invention is to provide an image compression apparatus that can further compress data.

[0005]

According to the first aspect of the present invention, in an image data processing apparatus for encoding and compressing input image data, a memory capable of storing one line of input image data is provided. The predetermined number of bits of the image data is defined as one unit of an image word, and the image word to be compressed is coded into a predetermined code length in association with the previously compressed image word and output. The first object is achieved by providing encoding means for outputting an image word to be compressed (at present) with a predetermined code length. According to a second aspect of the present invention, in the image compressing apparatus according to the first aspect, code words of data serially output and encoded using a half of the predetermined number of bits output from the encoding means as one unit. And a determination means capable of determining whether or not the same value is continuous between the currently captured code word and the previously captured code word and holding the determination result, and a command from the determination means. A counter capable of starting a count operation and outputting the count value, and causing the counter to perform a count operation when the determination means determines that the same value has been repeated in the code word for a predetermined number of times or more, and counting the count value of the counter. Output as a word, otherwise output the current code word input to the determination means as a code word By providing a force means, to achieve the second object. According to a third aspect of the present invention, in the image compression apparatus according to the second aspect, code words output from the output unit are successively captured, and a code word between a currently captured code word and a previously captured code word is read. To determine whether or not the specific value is continuous, and to retain the determination result.
Determination means, a counter capable of starting a count operation in response to a command from the second determination means and outputting the count value, and determining that the specific value of the code word has continued for a predetermined number of times by the second determination means. When the counter is operated, the counter performs a count operation, outputs the count value of the counter as a code word, and otherwise outputs the current code word input to the second determination means as a code word. With the provision of the output means, the third object is achieved.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. [First Embodiment] FIGS. 1 to 5 illustrate a first embodiment of the present invention. Here, FIG.
FIG. 1 is a block diagram illustrating an image compression device according to a first embodiment of the present invention. An image compression apparatus 1 according to a first embodiment of the present invention is an apparatus that performs compression processing on image data that encodes and compresses input image data, and is an apparatus that can compress digital image data. This image compression device 1
Are a central processing unit (CPU) and a main storage device (RA
M), an office automation device or a personal device equipped with a read-only storage device (RAM) and various interfaces. Image compression device 1 described above
When roughly classified, a correction circuit 3 for correcting image data so that post-processing can be easily performed, a memory 5 capable of storing image data, and an encoding unit capable of compressing and outputting the image data stored in the memory 5 7 and a control means 9 for controlling the operation of each means in accordance with the timing signal TG. More specifically, in the present invention, the input image data 1
Reference numeral 01 denotes an apparatus (not shown) in which one line of analog data obtained by raster scanning is digitally converted and provided as digital data.

In the present invention, the input image data is handled by the image word GW in which a predetermined number of bits (for example, 32 bits) is defined as one unit, so that one line of the input image data is not a multiple of 32. In addition, the correction circuit 3
Dummy data is added to the last image data for one line of the original input image data to make it 32 bits, and correction is made so that the entirety of one line of the input image data 101 is a multiple of 32. The memory 5 stores one line of image data 1 including the image word WG corrected by the correction circuit 3.
01 can be stored. The digital data for one line is successively stored in the memory 5 as input image data 101 in accordance with the processing timing.
The encoding means 7 sets a predetermined number of bits (for example, 32 bits) of the image data in the memory 5 as one unit of the image word GW, and
Wa are compressed image words GWb, GWc,.
The image word GWa to be compressed is set to a predetermined code length (for example, 8 bits) when the image word GWa to be compressed at the time of being unable to be associated is converted to a predetermined code length (for example, 8 bits). Output data 103
This is a circuit that can be output as

Next, the contents considered to be necessary for explaining the image compression apparatus according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a diagram for explaining an example in which an input image word WG used in the first embodiment of the present invention is stored in a storage memory. As shown by a black frame in FIG. 2, the input image data 101 includes a “line L” composed of a plurality of pixels (dots) in the horizontal direction and a “line number ( Row) N ". In addition, these input data 101
Is divided into image words WG using a predetermined number of bits (for example, 32 bits) for each line as one unit, and is encoded (processed) by the encoding means 7 in units of the image word WG.

The number of pixels (dots) in the main scan (one line) of the input image data 101 is not always a multiple of a predetermined number of bits (32 bits). Therefore,
As shown in FIG. 2, the image word GW at the end of the line
In some cases, r may have a portion without image data. In this case, the correction circuit 3 sets “0x00” or “0xFF” for the image word GWr of the last part of the line.
The remaining portion is filled with dummy data DD, so that one line is finally an integral multiple of 32 bits. FIG. 3 is an explanatory diagram showing an encoding algorithm used by the encoding means according to the image compression device of the first embodiment of the present invention. In FIG. 3, an encoding algorithm 2
Numeral 01 is composed of case data 202 of an image word GW and an encoded output 203. This encoding algorithm 201 is provided in the encoding means 7.

FIG. 4 is a diagram for explaining processing of an encoding algorithm in the encoding means according to the image compression apparatus of the first embodiment of the present invention. In FIG.
One line of image data is represented by a current image word WGa,
One previous image word WGb, two previous image words WG
b, three previous image words WGb, four previous image words W
Gb. This one-line image word GW is input to the encoding means 7 one after another. In FIG. 4, the case division word BW1 where case “1” is the same as the immediately preceding image word WGb, and the case division word B where case “2” is the previous image word WGb
Case word BW2, 8 bits before W1, case "3" is case word BW3, 8 bits prior to case word BW2, ..., case "12" is case word B
It is composed of a case division word BW12 eight bits before W11. The encoding means 7 executes processing as shown in FIG. 4 to form encoded data having a predetermined bit length (4 bits). FIG. 5 is a diagram for explaining a code stream output from the encoding unit according to the image compression device of the first embodiment of the present invention. In FIG. 5, the code stream 301 is the number of main scanning pixels (upper 8 bits).
302, number of main scanning pixels (lower 8 bits) 303, number of lines (upper 8 bits) 304, number of lines (lower 8 bits)
305, a code word (8 bits), a code word (8 bits),...

Next, the operation of the image compression apparatus according to the first embodiment of the present invention will be described with reference to FIGS. The memory 5 stores the 32-bit image words GW packed (combined) as described above. The encoding means 7 can store a predetermined amount of past encoded image words GW,
Image words exceeding a predetermined amount can be erased. The encoding means 7 controls the memory 5 under the control of the control means 9.
, The image word GW is taken out, and the encoding process is executed. For example, the encoding unit 7 encodes the image word GWa as shown in FIG. Encoding means 7
Represents the image word GWa to be coded in FIG.
As shown in FIG.
Compare with 12. The encoding means 7 converts the data into a 4-bit code based on the comparison result with reference to the encoding algorithm 201 shown in FIG. The encoding means 7 outputs the image word GWa
Is “000” when all 32 bits are “0”.
"0" and the code "1111" for all 32 bits of "1"
Is output. Further, the encoding means 7 outputs the image word GWa.
Has the same value as the image word GW at the same position on the previous line, the code "1101" is output. In addition, since there is no previous line for the first line of the image word GWa, no encoding is performed in this case. When the encoding unit 7 determines that the image word GWa corresponds to one of the case words BW1 to BW12 shown in FIG. 4, the codes “0001” to “1100” are used in accordance with the algorithm 201. Is output as the code word. As described above, when the encoding unit 7 outputs the code “0001”, the case is “1”, and the case where the input image word GWb is the same as the immediately preceding input image word GWb,
When the encoding means 7 outputs the code “0010”, the case is “2”, and as shown in FIG. 4, the case where the case “1” is shifted by 8 bits in the past is 12 In this case, the code can be output separately. If the image word cannot be classified in any of the above cases, the encoding unit 7 sets the code 1110 as the first code and sets
The bit image word GWa is divided into eight for every four bits from the upper bit, and sequentially output as output data.

The image compression apparatus according to the first embodiment outputs the 4-bit code generated in this way into an 8-bit code word by packing two into one for convenience. Output as data 103. In some cases, the last code word of the line may be an odd part. However, since the encoding means 7 recognizes the number of main scanning pixels, an appropriate dummy data is set in a part which becomes an odd part. Can be included. The code stream 30 of the output data output from the encoding means 7 in this manner
1, as shown in FIG. 5, at the beginning of the code data,
Number of main scanning pixels (upper 8 bits) 302, number of main scanning pixels (lower 8 bits) 303, number of lines (upper 8 bits) 3
04, four headers H each including the number of lines (lower 8 bits) 305, and then a code word (8 bits) 30
6, 307,... Are sequentially output.

As described above, the image compression apparatus according to the first embodiment of the present invention operates, can improve the transfer speed of image data, reduce the amount of storage memory, and can perform image compression using 32 bits as one unit. Since the word GWa is coded in association with the previously input image words GWb, GWc,..., The coding can be performed with a simple algorithm, the hardware can be easily formed, and the processing speed can be improved. Be faster. In addition, the algorithm is easy but the worst case compression ratio is low, or the worst case compression ratio is high but the problem of the conventional device that the algorithm is complicated can be solved. An image compression device having a high compression ratio can be realized.

[Second Embodiment] FIG. 6 is a block diagram showing an image compression apparatus according to a second embodiment of the present invention. The image compression apparatus according to the second embodiment shown in FIG. 6 includes a code word (output data) 103 output from the encoding unit 7 in addition to the first embodiment.
Determining means 11 for determining a specific state of the code word, a counter 13 for counting a specific state under the control of the determining means 11, and determining an output from the determining means 11 or an output from the counter 13. Output means 15 for selecting and outputting under the control of the means 11. That is, the judging means 11 converts the output data (code word) 103 which is serially output and coded using a half (8 bits) of the predetermined number of bits (32 bits) output from the coding means 7 as one unit. It is fetched one after another, it is determined whether or not the same value continues between the currently fetched code word and the previously fetched code word, and the determination result is held. In addition, the counter 13
Can start a count operation in response to a command from the determination means 11 and output the count value. Output means 1
5 outputs the count value of the counter 13 as a code word when the counter 13 operates according to an instruction from the determination means 11, and otherwise outputs the code word input to the determination means 11 as a code word. It is supposed to.

The operation of the image compression apparatus according to the second embodiment will be described. The code word (8 bits) output from the encoding unit 7 according to the first embodiment is input to the determination unit 11. In the determination means 11,
If it is determined that the same value is not continuous by comparing the input code word with the previous code word, the input code word (8 bits) is supplied to the output means 15 as it is. On the other hand, the judging means 11 compares the input code word with the previous code word, and when the same value is repeated twice, gives an operation command from the judging means 11 and
Is operated, and the counter 13 counts how many times the same value continues thereafter. When the counter 13 operates, the count number of the counter 13 is given to the output means 15. However, since the output code word is 8 bits, the maximum count number is set to “0xFF”. If the same value continues more than that, the subsequent count number is put in the next output code word. If the count just ends with "0xFF", put "0x00" in the next output codeword.

As described above, even in the image compression apparatus according to the first embodiment, even if the image data is easily compressible data, the compression ratio is too small in the image compression apparatus according to the second embodiment. To solve the problem that the data is not good, it is possible to further compress the data by using the characteristics of the output data output from the image compression apparatus according to the first embodiment and performing encoding that does not increase the data amount. it can. This makes it possible to increase the compression ratio of the apparatus according to the first embodiment, solve the problem that the compression ratio is not very good even when the image data is easily compressible data, and further increase the compression ratio. .

[Third Embodiment] FIG. 7 is a block diagram showing an image compression apparatus according to a third embodiment of the present invention. The image compression apparatus according to the third embodiment shown in FIG. 7 includes a second determination unit 21 that detects a specific code from a code word output from the output unit 15 according to the second embodiment, A second counter 23 that performs a counting operation in accordance with a command from the second determination means 21 and a second output means 25 that outputs output data from the second determination means or the second counter. More specifically, the second judging means 21 takes in the code words output from the output means 15 according to the second embodiment one after another, and reads the currently taken code word and the previously taken code word. It is possible to determine whether a specific value (for example, “0xFF”) continues between and and hold the determination result. Also,
The second counter 23 can start a count operation in response to an operation command from the second determination means 21 and output the count value. The second output means 25 outputs the count value of the counter as a code word when the counter performs a count operation in response to a command from the second determination means, and otherwise outputs the count value to the second determination means 21. The input code word is output as a code word.

The operation of the image compression apparatus according to the third embodiment will be described. The second embodiment is added to the first embodiment, and the codeword output from the second embodiment is encoded as follows in the third embodiment. That is, the value (8 bits) of the output code word output from the output unit 15 according to the second embodiment is fetched by the second determination unit 21, and the specific value (for example, “ 0xFF ") is determined not to be continuous, the input codeword is output as it is and used as an output codeword. On the other hand, when the second determination unit 21 determines that the specific value (for example, “0xFF”) has continued twice, the second determination unit 21
To cause the second counter 23 to count how many times the specific value continues after the command from the second determination means 21. The second counter 23 outputs the count number as a code word. Second output means 25
When the determination means 11 does not determine the specific value,
The code word input to the judging means 11 is used as an output code word, and when the judging means 11 judges a specific value, the count value of the second counter 23 is output as output data.

As described above, the third embodiment of the present invention operates. As described above, according to the third embodiment, in the image compression apparatus according to the first embodiment, the data compression is performed by using the characteristics of the output data so that the data amount is not increased. I do. This makes it possible to further increase the compression ratio of the image data and solve the problem that the compression ratio is not very good even when the image data is easily compressible data.

[0020]

According to the first aspect of the present invention, one line of input image data is stored in a memory, and a predetermined number of bits of the image data in the memory is defined as one unit of an image word.
The image word to be compressed is coded and output to a predetermined code length in association with the image word compressed in the past, and when it is impossible to associate, the image word to be compressed is output to the predetermined code length and output. Therefore, a high compression ratio can be realized with a simple configuration. According to the second aspect of the present invention, it is determined whether or not the same value continues between the currently fetched code word and the previously fetched code word, and the determination result is held to start the counting operation. The count value can be output, and when it is determined that the same value in the code word has continued for a predetermined number of times or more, the counter is operated to count, and the count value of the counter is output as a code word. Since the current code word input to the means is output as a code word, the compression rate is further increased, and even if the image data is easily compressible data, the compression rate is not so good. Can provide rate. According to the third aspect of the present invention, it is possible to determine whether or not a specific value is continuous between a currently fetched code word and a previously fetched code word, and hold the determination result. The count value is output, and when it is determined that the specific value of the code word has continued for a predetermined number of times or more, the counter is operated to count, and the count value of the counter is output as a code word. Since the code word is output as the code word, it is possible to solve the problem that the compression ratio is not so good even when the image data is easily compressible data, and to further increase the compression ratio.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an image compression device according to a first embodiment of the present invention.

FIG. 2 is a diagram for describing an example in which an input image word WG used in the first embodiment of the present invention is stored in a storage memory.

FIG. 3 is an explanatory diagram illustrating an encoding algorithm used by an encoding unit according to the image compression device of the first embodiment of the present invention.

FIG. 4 is a diagram for describing processing of an encoding algorithm in an encoding unit according to the image compression apparatus of the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a code stream output from an encoding unit according to the image compression apparatus according to the first embodiment of the present invention.

FIG. 6 is a block diagram illustrating an image compression device according to a second embodiment of the present invention.

FIG. 7 is a block diagram illustrating an image compression device according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image compression apparatus 3 Correction circuit 5 Memory 7 Encoding means 9 Control means 11 First determination means 13 First counter 15 First output means 21 Second determination means 23 Second counter 25 Second output means

Claims (3)

[Claims] 1. An image data processing apparatus for encoding and compressing input image data, comprising: a memory capable of storing one line of the input image data; and a predetermined number of bits of the image data in the memory as one unit of an image word. The image word to be compressed is encoded to a predetermined code length in association with the image word compressed in the past and output, and when the image word to be compressed cannot be associated, the image word to be compressed is set to the predetermined code length. An image compression device, comprising: an encoding unit that outputs the image data. 2. A code word of serially output and encoded data is fetched one after another by using a half of the predetermined number of bits output from the encoding means as one unit, and a code word which is currently fetched is preceded. A determining means for determining whether or not the same value continues between the fetched code word and holding the determination result; and a counter capable of starting a count operation and outputting the count value in response to a command from the determining means. Output means for outputting the count value of the counter as a code word when the counter operates according to an instruction from the determination means, and otherwise outputting the code word input to the determination means as a code word; The image compression apparatus according to claim 1, further comprising: 3. A code word output from the output means is fetched one after another, and it is determined whether or not a specific value is continuous between a currently fetched code word and a previously fetched code word. The second that can hold the judgment result
Determination means; a counter capable of starting a count operation in response to a command from the second determination means and outputting the count value; and a count value of the counter when the counter performs a count operation in response to a command from the second determination means. And a second output means for outputting the current code word input to the second determination means as a code word. Image compression device.