JP3433276B2 - Image signal compression method and apparatus, image signal decompression method and apparatus, image signal compression / decompression method and apparatus, and printer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal used for storing image data in a printer, for example, which is run-length encoded and compressed into encoded data.
The present invention relates to an image signal compression / decompression device that decompresses compressed code data into an original image signal.

[0002]

2. Description of the Related Art In recent years, laser recording type printers have been required to have a function of guaranteeing received data up to paper ejection due to high speed and high reliability. For this reason, a large-capacity memory is required in the printer device, but the cost of the device increases, so it is desirable to store the received data after compressing the received data at the highest compression rate possible.

As a conventional image signal compression method, an MH (Modefied Huffman) based on a Huffman code that can obtain a high compression rate in an image signal transmission device such as a facsimile is used.
n) Coding methods are often used. However, since the MH code has a variable length, it is not easy to decode it. There is a method in which all code patterns and run-length data corresponding to the code patterns are stored in a read-only memory (ROM), and the stored data in the ROM is searched until they match to perform decoding. Further, there are tree search methods and the like as efficient methods, but even if these methods are used, 13 searches are required at the maximum, so that it takes a long time to restore the image signal. Moreover,
At present, it is not possible to expect a high compression rate in the MH coding system when a large amount of data with a short run length appears, such as images and halftone dots.

Further, a compression method for realizing a high compression rate has been disclosed, paying attention to the repeatability of run lengths in which a set of white dots and black dots is set (Japanese Patent Laid-Open No. 55-92077).
Issue). This compression method assigns a common code to a set of a series of white dots and black dots that repeatedly appear as represented by a halftone dot image and a halftone dot image.
We are trying to improve the compression rate. In addition, a compression method has been proposed that focuses on repeatability that does not distinguish between run-length white dots and black dots in a binary image or the like. However, such repeatability is very rare in general documents, and a lot of additional information is required for encoding,
It is not practical in terms of compression rate and processing speed.

[0005]

Therefore, with the conventional MH coding system alone, since the code data to be restored has a variable length, the number of searches increases, and the real-time processing cannot be performed. Even if a compression method that is efficient for repeated code data is used, if the appearance rate of the repeatability is low, the compression rate does not improve for the entire document due to additional information, and the processing time is reduced. There is a problem that it becomes longer.

The present invention has been made in view of the above circumstances, and pays attention to the repeatability of each white dot and each black dot in order to improve the appearance rate of repeated data. In the case of being identical with the immediately preceding white dot row and black dot row, a predetermined repetition code is assigned, and when they are not the same, a code according to a predetermined code table of the MH coding method is assigned, thereby achieving a high compression rate. It is an object of the present invention to provide an image signal compression method and apparatus capable of encoding an image signal, and an image signal compression / decompression method and apparatus.

Another object of the present invention is to convert it into an iterative code that can be instantly decoded when each of the white dot sequence and the black dot sequence has repeatability, and when there is no repeatability, MH.
It is an object of the present invention to provide an image signal decompression method and apparatus, and an image signal compression / decompression method and apparatus, which have a high compression rate and can shorten the decoding processing time as a whole by performing encoding that takes advantage of the encoding method. .

Still another object of the present invention is to provide an image signal compression / decompression device which focuses on the repeatability of each white dot and black dot.
It is an object of the present invention to provide a printer device that can reduce the capacity of a memory for guaranteeing received data by applying it to an image data storage unit.

[0009]

According to the image signal compression method of the present invention, the number of consecutive white dots and the number of consecutive black dots are continuous with respect to an image signal consisting of white dots and black dots obtained by scanning an image. In the image signal compression method for compressing the image signal by encoding the number of times of the white dots and the black dots in accordance with a predetermined rule, the number of times the white dots and the black dots are continuous is the white dot and the black that are continuous before that. It is characterized in that whether or not the number of dots is the same is determined, and if the number of consecutive times is the same, the number of times is encoded into a predetermined code.

[0010] image signal compression apparatus according to the present invention, image
By encoding the number of consecutive white dots and the number of consecutive black dots for an image signal composed of white dots and black dots obtained by scanning according to a predetermined rule,
In an image signal compression device for compressing an image signal, a means for determining whether or not the number of consecutive white dots or black dots is the same as the number of consecutive white dots or black dots before it. When the number of consecutive times is the same, a means for encoding the number of times into a predetermined code is provided.

FIG. 1 is a block diagram showing the principle of an image signal compression apparatus according to the present invention. The image signal compression device includes a run length calculation unit 1, a previous data storage unit 2, a comparison unit 3, a code conversion unit 4, and an iterative code conversion unit 5. Image in a predetermined cycle
An image signal composed of white dots and black dots obtained by scanning at is input to the run length calculation unit 1. The run length calculation unit 1 detects changing points (points changing from white dots to black dots and points changing from black dots to white dots) based on the input image signal, and the change points are continuous. The number of bits (run length) of white dots and black dots is calculated, and the calculated run length is output to the previous data storage unit 2 and the comparison unit 3.

The previous data storage unit 2 temporarily stores the previous run length for each white dot and black dot, and stores it each time the next white dot or black dot run length is input. The previous run length is read to the comparison unit 3. The comparison unit 3 compares the latest run length input from the run length calculation unit 1 with the run length read from the previous data storage unit 2 for each pixel color (for each white dot and black dot). If they do not match, the latest run length is output to the code conversion unit 4, and if they match, a match signal is output to the iterative code conversion unit 5.

The code conversion unit 4 converts the latest run length into a code according to a predetermined code table 6 and outputs the code data. On the other hand, when the coincidence signal is input, the repetition code conversion unit 5 outputs a predetermined repetition code as code data.

In the image signal compression apparatus having the configuration shown in FIG.
For each white dot and black dot, the current run length is sequentially compared with the previous run length in the comparison unit 3, and when they match, the predetermined repeat code is replaced without using the code in the code table 6. If they do not match, the code is converted into a code according to a predetermined code table 6 of the MH coding method, for example. Therefore, when the same dot row is repeated in the white dots or the black dots, it is not necessary to refer to the code table 6, so that the speed can be increased and the compression rate can be improved by converting the code into a simple repetition code.

The image signal restoration method according to the present invention, meet the image signal restoration method for restoring the image signal compression method original image signal compressed code obtained with the present invention
Then , a predetermined code is identified for each white dot and black dot from the compressed code, and when the predetermined code is identified, the number of consecutive white dots and black dots before that is used to determine the original image signal. Characterized by restoration.

An image signal decompression apparatus according to the present invention is an image signal decompression apparatus for decompressing a compressed code obtained by the image signal compression apparatus of the present invention into an original image signal ,
A means for identifying a predetermined code for each white dot and a black dot from the compressed code, and when the predetermined code is identified, the original image signal is obtained by using the number of consecutive white dots and black dots before that. And means for restoring.

FIG. 2 is a block diagram showing the principle of the image signal restoration device of the present invention. The image signal restoration device comprises a code restoration unit 11 and
It has a repetitive code discrimination unit 12, a previous data storage unit 13, and an image signal conversion unit 14. The code data is input to the code restoration unit 11. The code restoration unit 11 converts the code data into a predetermined code table.
15 is retrieved and restored to the run length, and the restored run length is output to the iterative code discrimination unit 12 and the image signal conversion unit 14. When the code data is a repetitive code, the repetitive code is output to the repetitive code discriminating unit 12 as it is and nothing is output to the image signal converting unit 14. The repetition code discrimination unit 12
The appearance of the repetitive code is detected, and the detection signal is output to the previous data storage unit 13. The run length from the code restoration unit 11 is input to the previous data storage unit 13 via the iterative code determination unit 12, and the previous data storage unit 13 calculates the run length calculated one before for each white dot and black dot. Hold temporarily.

The image signal conversion unit 14 selects the run length from the previous data storage unit 13 when the repetition code appears, and selects the run length from the code restoration unit 11 when the repetition code does not appear, The selected run length is converted to the original white dot row and black dot row and output as the original image signal.

When the code data converted by the image signal compression method of the present invention is input, the iterative code discriminating unit 12 successively monitors whether or not it is an iterative code. The same run length that was temporarily stored in the previous data storage unit 13 and was output immediately before is adopted without searching 15. On the other hand, if the repetitive code is not detected, the run length calculated by searching the code table 15 as in the conventional case is adopted. Therefore, when the repetition code is detected, the code table
The run length is instantly required without referring to 15, and the restoration speed can be increased.

The image signal compression / decompression method according to the present invention is
White dots obtained by scanning the image, the image signal composed of black dots, by coding according to the rule a predetermined number of times that number white dots are consecutive and black dots continuously, compressed Then both image signals , An image signal compression / decompression method for decompressing a compressed code into an original image signal in accordance with a predetermined rule, at the time of compression, consecutive white dots,
For each black dot, determine whether the number of consecutive times is the same as the number of consecutive white dots and black dots before it, and if the number of consecutive times is the same, set the number of times to a predetermined code. At the time of encoding and decompression , a predetermined code is identified for each white dot and black dot from the compressed code, and when the predetermined code is identified, the number of consecutive white dots and black dots before that is used to determine the original The image signal of is restored.

An image signal compression / decompression device according to the present invention comprises:
White dots obtained by scanning the image, the image signal composed of black dots, by coding according to the rule a predetermined number of times that number white dots are consecutive and black dots continuously, compressed Then both image signals In an image signal compression / decompression device that restores a compressed code to an original image signal according to a predetermined rule, for each continuous white dot and black dot, the number of times that it is continuous is a continuous white dot before that, A means for determining whether or not the number of black dots is the same as the number of black dots, a means for encoding the number of times in a predetermined code when the number of consecutive times is the same, and a white code and a black dot for each compressed code. It is characterized by comprising means for identifying a predetermined code and means for restoring the original image signal by using the number of consecutive white dots and black dots preceding the predetermined code when the predetermined code is identified.

FIG. 3 is a block diagram showing the principle of the image signal compression / decompression device of the present invention. FIG. 3 (a) shows the configuration of the image signal compression unit, and FIG. 3 (b) shows the image signal decompression unit. Shows the configuration of. Note that the configuration of the image signal compression unit shown in FIG. 3A is the same as that of FIG. 1 and the configuration of the image signal decompression unit shown in FIG. 3B is the same as that of FIG. Is attached and the description thereof is omitted.

In the image signal compression / decompression device of the present invention, when the same dot row is repeated in white dots or black dots, the encoding process and the decompression process can be performed without referring to the code table. It is possible to improve the processing speed and speed up each processing.

The printer device according to the present invention is a printer device having storage means for storing data of an image signal for printing in the form of a compression code, and is connected to the storage means to connect the image signal of the present invention. Equipped with a compression / decompression device,
The compression code obtained by the image signal compression / decompression device is stored in the storage means, and the stored compression code is decompressed into an image signal by the image signal compression / decompression device. .

FIG. 4 is a block diagram showing the principle of the printer device of the present invention. The printer device includes an image signal compression unit 21, a guarantee memory 22, and an image signal decompression unit 23. The image signal compression unit 21 and the image signal decompression unit 23 have the internal configurations shown in FIGS. 1 and 2, respectively. The image signal compression unit 21
An image signal to be temporarily stored in the printer device is converted into code data by the procedure described in the first aspect of the invention, and a guarantee memory is provided.
Output to 22. The guarantee memory 22 stores the code data output from the image signal compression unit 21. The image signal restoration unit 23 converts the code data read from the guarantee memory 22 into the original image signal by the procedure described in the second invention.

Since the printer device of the third aspect of the present invention can perform high-speed and high-compression image signal compression / decompression, it is possible to reduce the capacity of the guarantee memory 22 for temporarily storing image data.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 5 is a block diagram showing the configuration of the printer device of the present invention. The printer device internally has an input port 31 which is an entrance of data from a host device 44, a command analysis unit 32 which analyzes a command in an input data stream, and an operation panel 33 which receives an instruction from the outside.
And a character font memory 34 for storing character fonts,
A drawing expansion processing unit 35 that expands the drawing data by quoting the character font in the character font memory 34, an expansion memory 36 that expands the drawing data, a compression unit 37 that compresses the expanded drawing data, and a compression unit. A guarantee memory 38 for storing the restored encoded data, a restoring unit 39 for restoring the compressed encoded data stored in the guarantee memory 38 to the original drawing data, and a decompression for expanding the restored original drawing data. A memory 40, a video circuit 41, and an engine unit 42 that controls the printing operation.
And a code table memory 43 for storing drawing data and conversion information of code data.

Data from the host device 44 is input port
It is input to the printer device via 31. Command parser
At 32, the command in the data stream is analyzed and the input instruction from the operation panel 33 is analyzed. Drawing development processing unit 35
Thus, the drawing data is expanded in the expansion memory 36 while quoting the character font in the character font memory 34. The expanded data is compressed by the compression unit 37 into code data by referring to the code table in the code table memory 43, and the compressed code data is stored in the guarantee memory 38. Warranty memory 38
The compressed code data stored in (1) is restored to the original drawing data by the decompression unit 39 based on the code table in the code table memory 43, and the original drawing data is expanded in the expansion memory 40. The restored data is sent to the engine section by the video circuit 41.
The image corresponding to the restored data is printed on a sheet of paper.

The details of the compression unit 37 and the decompression unit 39 in the printer device shown in FIG. 5, which are the features of the present invention, will be described below. 6 is a block diagram showing the internal configuration of the compression unit 37 (image signal compression apparatus of the present invention) of FIG. 5, and FIG.
3 is a block diagram showing an internal configuration of a restoration unit 39 (image signal restoration device of the present invention). FIG. In addition, in this example, it is assumed that run-length code conversion using the terminate code and make-up code as shown in FIG. 8 is performed.

In FIG. 6, reference numeral 51 denotes a run-length calculating section for calculating a run-length by detecting a change point of an image signal input from the outside (from the developing memory 36 in the printer apparatus of FIG. 5). Demultiplexer 53, XOR (exclusive OR) circuit
57 and the code conversion unit 58. As the run length calculating method in the run length calculating unit 51, any method such as a method of counting bit by bit or a method of calculating in parallel may be adopted. 52 is a color information register,
The color information register 52 holds color information (whether white dots or black dots) of the n-th run length that is the calculation target in the run length calculation unit 51, and every time the run length calculation unit 51 detects a change point. The color information that should be held in is switched to white / black. The first color information of each line when scanning is white, then
When the change point is detected, the color information is black, white,
Inverted to black, white, .... The color information register 52 outputs the held color information to the demultiplexer 53 and a multiplexer 56 described later.

The demultiplexer 53 has a white run length register for holding the white run length which is one before the target to be calculated by the run length calculation unit 51, that is, the (n-1) th white run length.
54 and a black run length register 55 that holds the (n-1) th black run length are connected to the input side. Both registers 54 and 55 are composed of 16 bits,
Can temporarily store run lengths up to 65534. A multiplexer 56 is connected to the output side of both registers 54 and 55. Then, the color information from the color information register 52 switches the connection between the demultiplexer 53 and the multiplexer 56. Specifically, the run length calculation unit 51
When the white dot row is to be calculated, white information is output from the color information register 52 to the demultiplexer 53 and the multiplexer 56, and the demultiplexer 53 and the multiplexer 56 are switched to the white run length register 54 side. On the other hand, when the black dot row is the calculation target, black information is output, and the demultiplexer 53 and the multiplexer
56 is switched to the black run length register 55 side.
In such an operation process, the run lengths of the white dot rows and the run lengths of the black dot rows from the run length calculating section 51 are alternately held in the registers 54 and 55, respectively, and then the XOR circuit 57. Is output to. The demultiplexer 53, the white run length register 54, the black run length register 55, and the multiplexer 56
The pre-data storage unit 2 of FIG. 1 is configured.

An XOR circuit 57 corresponding to the comparison unit 3 in FIG.
Is the run length calculation unit for each white dot row and black dot row.
The current n-th run length from 51 and the immediately preceding (n-1) -th run length from the multiplexer 56 are compared bit by bit. When all the bits match, a match signal is output to the switches 62 and 63.

The code conversion unit 58 performs code conversion on the run lengths that are not matched by the XOR circuit 57. The code conversion unit 58 searches the code ROM 60 and the code length ROM 61 corresponding to the code table 6 of FIG.
The read code length is output to one input terminal of the switch 63, respectively. Variable length code 16
The code table 60 of FIG. 1 is configured by the code ROM 60 aligned for each bit and the code length ROM 61 storing the code lengths arranged at the same address. Both ROMs 60 and 61
The run length is used as an address signal for reading. In this example using the code table of FIG. 8, when the run length is up to 63, conversion can be performed only by the termination code, but when the run length exceeds 63, it is divided into a plurality of makeup codes. Must be converted to.

On the other hand, the iterative code conversion section 59 outputs a predetermined iterative code, for example, '11' to the other input terminal of the switch 62 and outputs code length = 2 to the other input terminal of the switch 63.

The switch 62 is one of the input terminals when the coincidence signal is not input from the XOR circuit 57, that is, the symbol RO.
The code read from M60 is selected, and when the coincidence signal is input from the XOR circuit 57, the other input terminal, that is, the predetermined repetition code output from the repetition code conversion unit 59 is selected,
Parallel / serial (P / S) converter 65 for selected code
Output to. The switch 63 selects one input terminal, that is, the code length read from the code length ROM 61 when the match signal is not input from the XOR circuit 57, and the other input when the match signal is input from the XOR circuit 57. Terminal,
That is, a predetermined code length output from the iterative code conversion unit 59 is selected, and the selected code length is output to the counter 64.

The variable length code read from the code ROM 60 or the predetermined repeat code ('11') from the repeat code converter 59 is input to the P / S converter 65. Then, these variable length codes or repetitive codes are parallel / serial converted, and then bit data corresponding to the code length is output.
At this time, the counter 64 counts the number of bits output from the P / S converter 65 by the code length read from the code length ROM 61 or the predetermined code length (= 2) from the iterative code conversion unit 59. To do. As described above, the compressed serial code string is output to the outside (in the printer device of FIG.
Output).

Further, in FIG. 7, 71 is a color information register, and the color information register 71 holds color information (whether white dots or black dots) of the run length to be restored and stores one run length. Each time the color information is restored, the color information to be held is inverted in black and white. A signal such as a synchronization signal indicating the beginning of a row is input to set the color information to white, and then the color information is inverted in the order of black, white, black, white, ... Every time the run length is restored. Then, the color information register 71 outputs the held color information to a demultiplexer 76, a multiplexer 79 and a D flip-flop (D-FF) 83 which will be described later.

The read-ahead register 74 and the bit discriminator 72 are arranged in series in this order from the input side of the serial code string, and are arranged from the outside (in the printer device of FIG. 5, a guarantee memory is used).
Bit discriminator for each bit of serial code string (from 38)
72 and the prefetch register 74 are input in this order. Bit discriminator
72, the data value ('0' or '1') stored in the prefetch register 74 is output to the match determination circuit 75 including an AND circuit. Then, the AND of both data values is obtained,
When the output value is 1, the coincidence signal is output to the switch 81. Here, since the repetitive code is "11", when the code length is 2 and both bits "1" are stored in the bit discriminator 72 and the look-ahead register 74, the AND is obtained to determine the match. The repetition code can be detected in the circuit 75. Further, the bit discriminator 72 outputs the discriminated sign bit string to the address control unit 73. The address control unit 73 retrieves the corresponding run length from the code ROM 80 based on the code bit string, and outputs the retrieved run length to one input terminal of the switch 81 and the demultiplexer 76.

The bit discriminator 72 and the address controller 73 constitute the code restoration unit 11 of FIG. 2, and the prefetch register 74 and the coincidence discriminating circuit 75 constitute the repetitive code discriminator 12 of FIG. It is configured. The code ROM 80 corresponds to the code table 15 in FIG.

The demultiplexer 76 has 1
The input side of a white run length register 77 that holds the previous white run length and a black run length register 78 that also holds the previous black run length are connected. Both registers 77 and 78 consist of both registers 5 on the compression side.
It is the same as the configuration of 4, 55. A multiplexer 79 is connected to the output side of both registers 77 and 78. Then, according to the color information from the color information register 71, the demultiplexer 76
And the connection of the multiplexer 79 is switched. Specifically, when the white dot row is the restoration target, white information is output from the color information register 71 to the demultiplexer 76 and the multiplexer 79, and the demultiplexer 76 and the multiplexer 79 are placed on the white run length register 77 side. Can be switched. On the other hand, when the black dot row is to be restored, black information is output and the demultiplexer 76 and the multiplexer are output.
79 is switched to the black run length register 78 side.
In such operation processing, one run length of the white dot row and one run length of the black dot row read from the code ROM 80 are alternately held in both registers 77 and 78, and then the switch 81 It is output to the other input terminal. The demultiplexer 76, the white run length register 77, the black run length register 78, and the multiplexer 79 constitute the previous data storage unit 13 of FIG.

The switch 81 is provided with one input terminal, that is, a symbol R, when a match signal is not input from the match determining circuit 75.
The run length read from the OM 80 is selected, and when the match signal is input from the match determination circuit 75, the other input terminal, that is, the run length output from the multiplexer 79 is selected, and the selected run length is loaded into the counter 82. To do. The counter 82 generates the same number of clocks as the input run length and outputs it to the D-FF 83. D-FF
The 83 outputs white dots or black dots in the same number as the number of clocks from the counter 82 according to the color information from the color information register 71. As described above, the original image signal is output to the outside (to the expansion memory 40 in the printer device of FIG. 5).

Next, the operation will be described. FIG. 9 is a flowchart showing the procedure of compression processing. In FIG. 9, RL indicates run length. First, the run length calculation unit 51 obtains the run length by a predetermined method (step S1). Color information indicating whether the obtained run length is a white dot or a black dot is inverted (step S2). It is determined whether the color information is white or black (step S
3) If it is white, the previous white run length held in the white run length register 54 is output to the XOR circuit 57 via the multiplexer 56 (step S).
4). On the other hand, if it is black, the previous black run length held in the black run length register 55 is output to the XOR circuit 57 via the multiplexer 56 (step S5).

In the XOR circuit 57, the current white (or black) run length obtained is 1 from the multiplexer 56.
It is determined whether or not it is the same as the previous white (or black) run length (step S6). If they are not the same, the color information is determined (step S7). When the color information is white, the white run length register 54 holds the obtained white run length (step S8). On the other hand, when the color information is black, the black run length register 55 obtains the white run length. The black run length thus obtained is held (step S9).

Next, in the code conversion unit 58, the code and the code length are searched by referring to the code ROM 60 and the code length ROM 61 according to the run length, and the code is converted to the P / S converter 65 via the switch 62. Loaded with the code length switch 63
Is output to the counter 64 via (step S10). In this case, depending on the size of the run length, in the example of the code table of FIG. 8, only the termination code (when the run length is 63 or less), one makeup code + the termination code (when the run length is 64 or more and 2560 or less) ), Multiple make-up codes + terminate code (25 run lengths)
The code conversion patterns are roughly classified into three types (when the number exceeds 60).

The retrieved code is subjected to parallel / serial conversion by the P / S converter 65 and then countered bit by bit.
The signals are sequentially output by 64 clocks (step S11).
Each time data is output bit by bit, the value of the counter 64 is decremented by 1 (step S12) and the operation is continued until the value becomes 0 (step S13). Such processing is performed in the order of the makeup code and the termination code when the makeup code is included. When the output of the termination code is finished (step S14), the processing for the run length is finished.

On the other hand, in step S6, if the present white (or black) run length found is the same as the previous white (or black) run length from the multiplexer 56, the XOR circuit 57 The coincidence signal is input to the switches 62 and 63, and the predetermined repetition code ('
11 ') and the code length (= 2) are P / S converters 65,
It is output to the counter 64 (step S15). The repetitive code is parallel / serial converted by the P / S converter 65, and then sequentially output bit by bit by the clock of the counter 64 (step S16). Each time data is output bit by bit, the value of the counter 64 is decremented by 1 (step S17), and is continued until the value becomes 0 (step S18). When it becomes 0, the process for the repeated run length ends. .

In the above example, the calculated run length is held in the register 54 or 55 only when the run length is different from the previous run length. However, the calculated run length is set to the previous run length. Regardless of whether the run length matches or does not match, the register may always be held in the register 54 or 55. In this case, step S4 of FIG.
, The current white run length is held in the white run length register 54, and the previous white run length already held is passed through the multiplexer 56 to the XOR circuit.
57 to the XOR circuit 57 via the multiplexer 56 while holding the current black run length in the black run length register 55 and holding the previous black run length already held in step S5. For example, the subsequent steps S7 to S9 are unnecessary.

As described above, at the time of normal compression processing, the code ROM 60 is referred to based on the input run length to convert it into a terminate code or a make-up code, and the code is loaded into the P / S converter 65. Together with the code length RO
The code length is loaded into the counter 64 by referring to M61, but if the input run length matches the previous run length, the P / S converter 65 is directly loaded with the repetition code '11', At the same time, the code length = 2 is loaded into the counter 64, so if white dots or black dots are repeated, ROM
Can be converted to a shorter code without having to search for.

Next, the operation of the restoration process will be described with reference to the flowchart of FIG. 10 showing the procedure. In FIG. 10, RL indicates run length. First, the color information of the run length to be restored is inverted (step S21). The data of the serial code string is fetched bit by bit in the order of the bit discriminator 72 and the prefetch register 74 (steps S22 and S23). The coincidence determination circuit 75 determines whether or not the values stored in the bit discriminator 72 and the prefetch register 74 are both "1" (step S24). Both '
When it is 1 ', it is an iterative code (' 11 '), and when either is not' 1 ', it is a normal conversion code.

When it is detected that the code is a normal conversion code, the bit discriminator 72, 1 bit at a time, of the data of the serial code string until the code can be recognized (step S25).
It is sequentially loaded into the prefetch register 74 (step S2
6, 27). When the code is recognized (step S25), the corresponding run length is searched from the code ROM 80 according to the recognized code, and the searched run length is output to one input terminal of the switch 81 and the demultiplexer 76 (step S28). .

It is determined whether the color information is white or black (step S29). If the color information is white, the white run length is held in the white run length register 77 (step S29).
30) If black, the black run length is held in the black run length register 78 (step S31).

On the other hand, if it is detected in step S24 that it is a conversion code, the color information is discriminated (step S32), and if it is white, the white run length register 77.
To the other input terminal of the switch 81 (step S33). When it is black, the black run length held in the black run length register 78 is output to the other input terminal of the switch 81. (Step S34).

The switch 81 selects the run length of one input terminal when it is a normal conversion code, and selects the run length of the other input terminal when it is a repetition code.
Then, the color information is determined (step S35). If it is white, "0" is output from the D-FF 83 bit by bit (step S36). Every time 1-bit '0' is output, the value of the counter 82 is decremented by 1 (step S37), and the output of '0' is continued until the value becomes 0 (step S38). On the other hand, if it is black, '
1'is output from the D-FF 83 bit by bit (step S39). Counter every time 1-bit '1' is output
The value of 82 is decremented by 1 (step S40), and the output of "1" is continued until the value becomes 0 (step S41).

As described above, at the time of normal restoration processing, the code ROM 80 is sequentially searched by, for example, the tree search method according to the code input serially, and when the run length is reached, the value is loaded into the counter 82. The dot specified by the color information is output while the counter 82 is decremented, and when the repetition code is detected, the code RO
Since the previously stored run length is output without searching M80, when a repetitive run length is input, the run length can be code-converted in 1 clock and the run length can also be restored in 1 clock at the time of restoration. Can be decrypted.

Next, the effect of the compression / decompression processing of the present invention as described above will be described. FIG. 11 is a diagram showing a run length analysis result for explaining the degree of the effect of the present invention. For a document containing two types of kanji and kana, the run length obtained when scanning in the horizontal direction of the character was obtained, and the results shown in Fig. 11 were obtained. This result shows the number of appearances of each code when 24 lines were scanned over 138 characters composed of a 24 × 24 dot font. According to this result, the repetition rate of white run length is 264 / (5377 in Document (1).
÷ 2) and 1124 / (19824 ÷ 2) for document (2), which is about 10% in both cases, but for black run length, it is 1579 / (53 for document (1).
77/2) and document (2) 4356 / (14344/2), both of which have a probability of about 50%.

This is considered to be because the dot widths of the vertical bars and the horizontal bars are set to be almost constant in the Japanese character font, and the same tendency is observed not only in the Japanese font but also in the alphabet font and the number font. It is expected to be. In addition, the compression processing of the present invention is particularly effective for data having repetitiveness such as shading in a figure and shaded lines, which are relatively difficult to compress. Since such a tendency of repetitiveness is particularly remarkable when the data is expanded based on the font like the printer device, the image signal compression / decompression method according to the present invention is optimally used in the printer device. .

According to the present invention, it is not necessary to refer to the code table in any case of compression processing and decompression processing when the same run length appears subsequently, and at the same time, the length of the repetition code is set to be short. The compression rate is improved as compared with the code based on the code table. In particular, a run length exceeding 2560 pixels in the MH code is conventionally expressed in the form of one or a plurality of make-up codes + terminator code, but in the present invention, it can be converted into one repetitive code. Can be expected to improve significantly.

Next, a specific example of the present invention will be described.
FIG. 12 is a diagram showing an example of code conversion. FIG. 12 (a) shows a case of a general normal line, and FIG. 12 (b) shows a case of all white lines. In each case, a code conversion example using only the conventional MH coding method and the present invention are shown. And an example of code conversion of.

Normal lines shown in FIG. 12A (white run length: 10, black run length: 2, white run length: 8,
In the case of black run length: 4, white run length: 8, black run length: 4, white run length: 12),
2nd and 3rd white run lengths, 2 black run lengths
Repeatability is seen in the third and third. In the case of only the MH coding system, 37 bits are required for compression, but in the present invention, 31 bits can be used for compression. Also, the time required for decoding will be reduced from 37 clocks to 29 clocks.

In the case of the all-white line shown in FIG. 12B (all pixels in three rows are white), repetitiveness is observed over a plurality of lines. The first white line is EO
It requires 47 bits including L (End Of Line), but if all white lines continue, one line including EOL can be compressed with 14 bits from the second line.

In the above example, the iterative code is assigned to '11' using only the black run length table of the MH code table. However, the appearance rate of the iterative code is incorporated into the appearance rate of each run length. If a code table based on the Huffman coding method is created, the effects of the present invention such as high compression and high speed processing can be further expected. Also in the encoding procedure and the decoding procedure, the shift register is used for serial control in the above embodiment, but it is needless to say that parallel control is the best solution. Further, if the processing speed is not expected, it is easy to realize these by software control.

[0063]

As described above, according to the present invention,
Since the compression rate can be further improved compared to the conventional compression method and the processing speed at the time of decoding can be improved, the capacity of the guarantee memory can be reduced without impairing the performance of the printer device, and the memory can be saved. Since the configuration is an extension of the conventional MH encoding method, it can be applied not only to printers but also to other fields such as image compressors, and will contribute to the multimedia society where the amount of information will increase in the future. large.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of an image signal compression apparatus of the present invention.

FIG. 2 is a principle configuration diagram of an image signal restoration device of the present invention.

FIG. 3 is a block diagram showing the principle of an image signal compression / decompression device according to the present invention.

FIG. 4 is a principle configuration diagram of a printer device of the present invention.

FIG. 5 is a block diagram showing a configuration of a printer device of the present invention.

FIG. 6 is a block diagram showing a configuration of a compression unit of the printer device of the present invention.

FIG. 7 is a block diagram showing a configuration of a restoration unit of the printer device of the present invention.

FIG. 8 is a diagram showing an example of a code table used in the present invention.

FIG. 9 is a flowchart showing a procedure of compression processing in the present invention.

FIG. 10 is a flowchart showing a procedure of restoration processing according to the present invention.

FIG. 11 is a diagram showing a run length analysis result for explaining the degree of the effect of the present invention.

FIG. 12 is a diagram showing an example of code conversion in the conventional example and the present invention example.

[Explanation of symbols]

1 Run length calculator 2 Previous data storage 3 comparison section 4 Code converter 5 Iterative code converter 6 Code table 11 Code restoration unit 12 Repeat code discrimination section 13 Previous data storage 14 Image signal converter 15 Code table 21 Image signal compression unit 22 Warranty memory 23 Image signal restoration section

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 1/41-1/419

Claims (7)

(57) [Claims] 1. A white dots obtained by scanning the image, the image signal composed of black dots, by coding according to the rule a predetermined number of times that number white dots are consecutive and black dots are continuous, the image In an image signal compression method for compressing a signal, it is determined whether or not the number of consecutive white dots or black dots is the same as the number of consecutive white dots or black dots preceding that dot A method for compressing an image signal, characterized in that when the number of times is the same, the number of times is encoded into a predetermined code. 2. An image signal decompression method for decompressing a compressed code obtained by using the image signal compression method according to claim 1 into an original image signal, wherein each white dot and black dot is deducted from the compressed code. The image signal restoration method characterized in that the predetermined code is identified, and when the predetermined code is identified, the original image signal is restored by using the number of times the preceding white dot and black dot continue. . 3. A white dots obtained by scanning the image, the image signal composed of black dots, by coding according to the rule a predetermined number of times that number white dots are consecutive and black dots are continuous, the image signal compression Then together, in the image signal compression and decompression method for restoring the compressed <br/> is the code to the original image signal according to the predetermined rule, during compression,
For each consecutive white dot or black dot, determine whether the number of consecutive times is the same as the number of consecutive white dots or black dots before it, and if the number of consecutive times is the same, the number of times. To a predetermined code, and at the time of decompression , the predetermined code is identified for each white dot and black dot from the compressed code, and when the predetermined code is identified, the preceding white dot and black dot are An image signal compression / decompression method, characterized in that an original image signal is decompressed by using a continuous number of times. 4. A white dots obtained by scanning the image, the image signal composed of black dots, by coding according to the rule a predetermined number of times that number white dots are consecutive and black dots are continuous, the image In an image signal compression device for compressing a signal, a means for determining whether or not the number of consecutive white dots and black dots is the same as the number of consecutive white dots and black dots before that, An image signal compression apparatus comprising: means for encoding the number of consecutive times to a predetermined code when the number of consecutive times is the same. 5. The image signal compression device according to claim 4.
An image signal decompression device for decompressing an obtained compressed code into an original image signal, wherein a white dot from the compressed code,
A means for identifying the predetermined code for each black dot and a means for restoring the original image signal by using the number of consecutive white dots and black dots before the predetermined code when the predetermined code is identified An image signal restoration device characterized by the above. 6. A white dots obtained by scanning the image, the image signal composed of black dots, by coding according to the rule a predetermined number of times that number white dots are consecutive and black dots are continuous, the image signal compression then together, in the image signal compression and decompression apparatus for restoring compressed <br/> is the code to the original image signal according to the predetermined rule, white dots continuous in each of the black dots, the number of times that it is continuous means but for encoding consecutive white dots, means for determining whether the same or not the number of black dots, when the number of times of consecutive are the same the number of times predetermined code before it is compressed Means for identifying the predetermined code for each white dot and black dot from the code, and when the predetermined code is identified, the original image signal is obtained by using the number of times the preceding white dot and black dot continue. Means to restore Image signal compression and decompression apparatus, characterized in that it comprises. 7. A printer device having a storage means for storing data of an image signal for printing in the form of a compression code, wherein the image signal according to claim 6 is connected to the storage means. A compression / decompression device is provided, and the compression code obtained by the image signal compression / decompression device is stored in the storage means, and the stored compression code is decompressed into an image signal by the image signal compression / decompression device. A printer device having the above-mentioned configuration.