JPH08307701A - Runlength encoding and decoding method - Google Patents

Abstract

PURPOSE: To generate a code in which the gap of the code is easy to discriminate and decoding is performed easily and in a short time. CONSTITUTION: '1' is added on the runlength of black and white picture element data which comprises picture data (step S5). After that, data of (runlength + one) is converted to a Fibonacci code with property in which no two or more '1's exist successively (step S6). Moreover, '1' is added on the high-order position of '1' at the most significant digit in a converted code (step S7). Therefore, two '1's always appear successively on the high-order digit of each encoded data, which makes the gap of the code easy to discriminate setting '11' as a break-point symbol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a run-length encoding method and a decoding method, which are applied to, for example, a facsimile apparatus, and encode and decode the run-length of black-and-white pixel data forming image data. .

[0002]

2. Description of the Related Art Generally, for example, in a facsimile machine, when storing received image data and the like in an image memory, the image data is stored in a modified Huffman system (MH
Method), modified read method (MR method), or MMR method, and the like data is stored in a compressed state as much as possible.

[0003]

However, in the conventional MH system, MR system and MMR system, it is difficult to determine the break of the code when decoding the coded data read from the image memory. There is a problem that the processing is troublesome and takes time. That is, for example, MH
In the method, the run length (consecutive number) of the black and white pixel data forming the image data is represented by a predetermined code, but the coded data does not include a code indicating a break at the code break. One line is continuously stored in the image memory. Therefore, in order to detect a break in the code, it is necessary to sequentially determine which run length the code represents while sequentially checking the code bit by bit, and the processing takes time. It was a thing.

On the other hand, in addition to the above-described encoding method, there is also a method in which each run length in image data is represented by a code having a fixed bit length of 2 bytes and stored in an image memory. According to this method, since each run length is always represented by a code having a fixed bit length, it is possible to easily discriminate the break of the code and to easily perform the decoding process in a short time. However, in this method, no matter how short the run length is, since a data amount of a fixed bit length is always required to represent each run length, the data compression rate is low and the image memory size is low. There was a problem that the capacity was wasted.

The present invention has been made by paying attention to the problems existing in such conventional techniques. Its main purpose is run-length coding that makes it easy to identify code breaks, facilitates decoding in a short time, maximizes the data compression rate, and suppresses memory consumption. It provides a method.

Another object of the present invention is to provide a run-length decoding method suitable for decoding the code generated by the run-length coding method.

[0007]

In order to achieve the above object, in the invention of a run length encoding method according to claim 1, the run length of black and white pixel data constituting image data is converted into a Fibonacci code. Then, 1 is added to the uppermost digit of the most significant digit 1 in the converted code.

According to a second aspect of the present invention, in the run length encoding method according to the first aspect, a value obtained by adding 1 to the run length is converted into a Fibonacci code. In the invention of the run-length decoding method according to claim 3, two consecutive 1's in the code are detected, the code is separated, and each separated code is subjected to image data in accordance with weighting of each digit based on the Fibonacci transform. Is converted into the run length of the black and white pixel data constituting the above.

[0009]

[Operation] In the run length encoding method according to the first aspect, when encoding the run length of the black and white pixel data forming the image data, first, the run length is converted to a Fibonacci code. In this Fibonacci code, two or more "1" s do not exist consecutively. Next, 1 is added to the higher order of the most significant digit 1 in the converted code.

In the data thus encoded, two "1" s always appear in the upper digit of each code. Therefore, when the coded data is continuously stored in the memory or the like, the break of the code can be easily discriminated using "11" as a delimiter, and the decoding can be performed easily and in a short time. Further, if the run length is short, the Fibonacci code is also short, so that the data compression rate does not become so low and the consumption of the memory capacity can be suppressed as much as possible.

In the run length encoding method according to the second aspect, a value obtained by adding 1 to the run length is converted into a Fibonacci code. That is, since the run length of 0 is 0 even in the Fibonacci code, the most significant digit in the code is not 1. Therefore, this Fibonacci code of 0 cannot be represented by a code having a delimiter of “11”. However, if the value obtained by adding 1 to the run length is converted into a Fibonacci code, a code with a delimiter of "11" is generated for all run lengths including the code corresponding to the run length of 0. You can

In the run-length decoding method according to the third aspect of the present invention, for example, when reading and decoding a code continuously stored in a memory or the like, first, a delimiter symbol "11" is detected from the code and the code is detected. Delimit. Next, each separated code is converted into a run length of black and white pixel data that constitutes image data according to weighting of each digit based on Fibonacci conversion.

According to this run length decoding method, the code generated by the run length encoding method can be easily and quickly decoded.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a facsimile machine will be described in detail below with reference to FIGS. FIG. 1 shows the circuit configuration of the facsimile apparatus of this embodiment. A CPU (Central Processing Unit) 11 constitutes an encoding and decoding means, and a ROM (Read Only Memory) 12 and a RAM (Random Access Memory) are included in the CPU 11.
13 is connected. The ROM 12 stores programs for controlling the operation of the entire device. RAM1
3 temporarily stores various information. The NCU (Network Control Unit) 14 controls the connection between the facsimile device and the telephone line. The modem 15 performs modulation and demodulation of transmitted / received data.

The reading unit 16 optically reads an image on a document set on a document table (not shown). Image memory 17
Stores the received image data and the image data read by the reading unit 16 in a state of being encoded by the encoding method described later under the control of the CPU 11. The print buffer 18 is
The image data read from the image memory 17 and decoded by the decoding method described below under the control of the CPU 11 is stored for each line (line data). The recording unit 19 prints on recording paper based on the line data stored in the print buffer 18. The operation unit 20 includes various operation keys such as a dial key for inputting a telephone number and the like, and a start key for starting a facsimile operation.

Next, the run length encoding operation at the time of receiving image data executed by the CPU 11 will be described with reference to the flowchart of FIG. Now, when image data encoded by the MH system, MR system or MMR system is transmitted from the transmission side and the image data is received, it is added to the end of the received image data for one page of the original. It is determined whether or not the RTC signal (control return signal) is detected (steps S1 and S2). R
When the TC signal is not detected, it is determined whether or not the EOL signal (line end signal) added to the end of each line data is detected (step S3). Incidentally, R
The TC signal consists of 6 consecutive EOL signals,
It is added to the end of the last line of the received image data for one page of the document. Here, when the EOL signal is not detected, the received data encoded by any one of the above encoding methods is converted into the run length of the black and white pixel data forming the image data (step S4). .

Next, "1" is added to the run length (step S5). For example, a run length of "0" is expressed as "1" by adding "1", and a run length of "1" is expressed as "2" by adding "1". This is to enable encoding with delimiters as will be described later for all run lengths including the run length of "0".

Thereafter, the run length + 1 data is converted into the Fibonacci code (step S6). The Fibonacci transformation is a transformation of an integer based on the Fibonacci sequence. The Fibonacci sequence is
It is a sequence of numbers with the sum of the bases of the lower two digits as the base of the next digit.
Therefore, in the Fibonacci sequence, the bases are 1, 2, 3, 5, 8, 13, ... From the lower digits, so when a decimal number is converted to Fibonacci according to the base,
A Fibonacci code as illustrated in FIG. 4 is obtained. For example, when "7" in decimal number is converted to Fibonacci, "1" is set corresponding to the base digit of "2" and the base digit of "5" in the Fibonacci sequence. That is, the sum of the bases corresponding to the digit for which "1" is set "2+
The Fibonacci code is obtained by setting any one of 1 and 0 corresponding to each base digit in the Fibonacci sequence so that 5 "becomes the value" 7 "in the decimal number. In the Fibonacci code obtained as described above, two or more "1" s do not exist consecutively.

Further, "1" is added to the higher order of the most significant digit "1" in the Fibonacci transformed code (step S7). As a result, as illustrated in FIG. 6, each run length is represented by a conversion code having an upper digit with a delimiter of “11”. Then, the encoded data is stored in the image memory 17 (step S
8). In this case, as shown in FIG. 5, each coded data is sequentially transferred to and stored in the image memory 17 with the lower bit as the head for convenience of decoding to be described later. Then, returning to step S2, the operations of steps S2 to S8 are repeatedly performed, and the received encoded data is sequentially converted into a conversion code using the Fibonacci code, and the image memory 1
Stored in 7.

Each line data in the encoded data transmitted from the transmission side is always a code that represents the run length of a white pixel, regardless of whether the head is actually a white pixel or a black pixel. It has begun. That is, on the transmitting side, when the head of the line data actually starts with the run length of the black pixel, the code representing the white run of "0" is added before the black run. Therefore, in the image memory 17, the code representing the white run is always stored first, and the code representing the white run and the code representing the black run are alternately stored.

When the EOL signal is detected in the determination in step S3, it is determined that the reception and encoding processing of the data for one line is completed, and the EOL code is stored in the image memory 17. (Step S
9). Then, in order to shift to the reception and encoding process of the next line data, the process returns to the step S2 and the operations of steps S2 to S9 are performed. On the other hand, the step S2
If the RTC signal is detected in the above judgment, it is judged that the reception and encoding processing of the data for one page of the original document is completed, the RTC code is stored in the image memory 17, and the data of the next page is stored. It is determined whether or not there is (steps S10 to S11). If there is data for the next page, the process returns to step S2 and proceeds to step S2 in order to shift to the process of receiving and encoding the data for the next page.
The operations from S11 to S11 are performed, and if there is no next page, the process ends.

Next, the decoding operation to the run length at the time of printing the image data, which is executed by the CPU 11, will be described with reference to the flowchart of FIG. By the way, at the time of this printing, two consecutive "1" s from the code data in which one line is stored in the image memory 17 are
That is, the delimiter symbol "11" is detected and, as shown by the triangle mark in FIG. 5, it is delimited for each code data corresponding to one run length (step S12). Then, the separated code data is read from the image memory 17 (step S13). After that, the read code is RT
It is determined whether or not it is the C code, and when it is not the RTC code, it is determined whether or not the read code is the EOL code (steps S14 to S15).

If it is not the EOL code, the read code data is converted (decoded) from the Fibonacci code to white or black run length according to the weighting of each digit based on the Fibonacci conversion (step S16). That is, for example, as shown in FIG. 5, the most significant digit "1" in the code data delimited by the triangle marks is added at the time of the encoding process, and is therefore excluded.
010 "is the Fibonacci code corresponding to the run length. And, in this Fibonacci code," 1 "is set in correspondence with the base digit of" 2 "and the base digit of" 8 "in the Fibonacci sequence. Therefore, the same code is converted into a run length of "10" which is the sum of the weightings "2" and "8".

The division of the code data and the weighting conversion of each digit are performed from the head side of the line data in the image memory 17. In this case, as shown in FIG. 5, since the code data is stored in the image memory 17 starting from the lower bit, the division of the code data and the weighting conversion of each digit are searched from the lower digit side. And can be done easily.

Then, "1" is subtracted from the run length (step S17). That is, the step S
The run length converted in 16 is the actual run length at the time of reception plus one (run length + 1). Therefore, “1” is subtracted from the data of this run length + 1 to restore the actual run length. Then, the run-length data is developed into white or black image data for forming an image, and the image data is transferred to the print buffer 18 and stored (steps S18 to S19). Then, the process returns to step S12 and steps S12 to S12.
The operation of 19 is repeated.

In the image memory 17, a code representing a white run is always stored first, and a code representing a white run and a code representing a black run are alternately stored. Therefore, when converting the Fibonacci code to the run length, it can be easily determined whether the run length represents white or black.

On the other hand, if it is determined in step S15 that the read code is the EOL code, one line of image data is read from the print buffer 18 and printed on the recording paper by the recording unit 19. (Step S20). Then, in order to shift to the processing of the next line, the process returns to step S12, and step S1
The operations of 2 to S20 are performed. In addition, the step S1
When the read code is the RTC code in the determination of 4, it is determined whether or not there is data for the next page (step S21). If there is data for the next page, the process returns to step S12 and steps S12 to S12.
21 is performed, and if there is no next page, the process ends.

As described above, in the run length encoding method of this embodiment, first, the run length of the black and white pixel data forming the image data is such that two or more "1" s do not exist consecutively. Is converted into a Fibonacci code having Then, "1" is added to the higher order of the most significant digit "1" in the converted code. Therefore, as illustrated in FIG.
In the encoded data, two "1" s always appear in the upper digit of each code. Therefore, when this coded data is continuously stored in the image memory 17, the break of the code can be easily discriminated using "11" as a delimiter, and decoding can be performed easily and in a short time. .

Further, if the run length is short, the Fibonacci code is also short, so that the data compression rate is higher than that in the method of expressing the run length by the code of the fixed bit length described in the above-mentioned prior art. Therefore, the data compression rate does not become so low, and the consumption of the memory capacity can be suppressed as much as possible.

Further, in the run length encoding method of this embodiment, the value obtained by adding "1" to the run length is converted into the Fibonacci code. That is, since the run length of "0" is "0" even in the Fibonacci code, the most significant digit in the code is not "1". Therefore, the Fibonacci code "0" is
It cannot be represented by a code with a delimiter of “11”. However, if the value obtained by adding "1" to the run length is converted into the Fibonacci code, as shown in FIG.
It is possible to generate a code having a delimiter of "11" for any run length including a code corresponding to a run length of "0". Therefore, even if the code representing the white run of "0" is added to the head of the line data in the received data, the code for the white run of "0" can be reliably generated, and black and white will be used in the subsequent processing. The problem of misjudging does not occur.

Further, in the run length decoding method of this embodiment, the code "11" is detected by detecting the delimiter "11" in the code data in which one line is continuously stored in the image memory 17. . Then, each delimited code is converted into a black and white run length and decoded according to weighting of each digit based on the Fibonacci transform. Therefore, the code generated by the run-length encoding method can be easily and quickly decoded, and when the data in the image memory 17 is read and printing is performed, the printing operation is performed smoothly and quickly. be able to.

[0032]

Another Embodiment Next, another embodiment of the present invention will be described with reference to FIG.
~ It demonstrates based on FIG. First, the run-length encoding method shown in the flowchart of FIG.
The operation of S4c is different from the run length encoding method shown in the flowchart of FIG. 2 described above. That is, in this embodiment, after the received data is converted into the run length in step S4, it is determined whether or not the run length is smaller than "64" (step S4).
4a).

In this determination, the run length is "6".
When it is smaller than 4 "," 1 "is added to the run length as in the above embodiment (step S5). On the other hand, when the run length is" 64 "or more, as shown in FIG. Then, the run length is divided into a make-up value that is a multiple of "64" and a remaining terminating value (step S4b), and "1" is added to the terminating value (step S4c). In this embodiment, as in the case of the MH coding method, run lengths up to 63 pixels are represented by a terminating code,
It is intended to represent a run length of 64 pixels or more by a makeup code and a terminating code that follows it. Therefore, in step S5, "1" is added to the terminating value.

After that, from step S4c to step S6
And the run-length Fibonacci transformation is performed. In this case, the makeup value divided into two and the terminating value + 1 are converted into Fibonacci codes separately. As shown in FIG. 9, for the terminating value + 1, the integer indicating the value of run length + 1 is converted into the Fibonacci code as it is. On the other hand, for the make-up value, the Fibonacci transformation is performed corresponding to the value obtained by adding 1 to each of the integers 64, 65, ... 89, 90 that are continuous with the run length of “63”. For example, the makeup value of "64" is
The integer value of 65 (= 64 + 1) is represented by a code obtained by Fibonacci transform, and the makeup value of "128" is
The integer value of 66 (= 65 + 1) is represented by a code obtained by Fibonacci conversion, and the makeup value of “1728” is represented by a code obtained by performing Fibonacci conversion of an integer value of 91 (= 90 + 1).

Then, similarly to the above-described embodiment, in the next step S7, "1" is added to the higher order of the most significant digit "1" in each code, as illustrated in FIG.
A conversion code having a delimiter of "11" is generated.

Next, the run-length decoding method shown in the flowchart of FIG. 8 is different from the run-length decoding method shown in the flowchart of FIG. 3 in the operations of steps S16a to S16b. That is, in this embodiment, after the read code data is converted from the Fibonacci code to the run length in step S16, it is determined whether or not the run length is larger than "64" (step S16a). .

In this judgment, the run length is "6".
If it is 4 "or less," 1 "is subtracted from the run length (step S17) to return to the actual run length, as in the above embodiment. The run length here is the terminating value. On the other hand, when the run length is larger than “64”, it is determined that it is not the run length but the integer value corresponding to the makeup value, and the corresponding makeup value is based on the integer value. (Step S16b) In other words, here, in the actual run length, a multiple of “64” is obtained.After that, the processing shifts to step S18, as in the above-described embodiment. Run length is expanded to image data.

In this embodiment, when the code data is converted into the makeup value, the next code data is determined to be the terminating value following the makeup value, and the makeup value and the terminating value are determined. With value, processing is performed as one run length in which black and white are the same.

As described above, in this other embodiment, as in the case of the MH coding method, the run length up to 63 pixels is represented by the terminating code, and the run length of 64 pixels or more is the makeup code. And a terminating code following it. Therefore, the data compression rate can be further increased and the consumption of the memory capacity can be further suppressed, as compared with the encoding method of the above embodiment in which the run length is simply converted as it is into the Fibonacci code.

The present invention can be modified and embodied as follows. (1) The encoded data is stored in the image memory 17 with the upper bits as the head without the lower bits as the head.
Be configured to transfer sequentially to.

(2) In the above embodiment, the case where the received data is coded and stored in the image memory 17 has been described. However, the case where the image data read by the reading unit 16 is coded and stored in the image memory 17 is described. Also, perform the same encoding process.

(3) In another embodiment, the separation between the terminating value and the makeup value in the run length is changed to other than 63 pixels. (4) Two or more "1" s are added to the higher order of the most significant digit "1" in the Fibonacci transformed code. Also in this case, similarly to the above-described embodiment, it is possible to easily discriminate the break of the code by using "1" which appears three or more consecutively as a delimiter.

(5) In each of the above embodiments, "1" and "0" are inverted to form a code. In this case, the code has a delimiter of "00". Therefore,
At the time of decoding, this "00" can be detected to easily discriminate the code break.

The technical idea which can be understood from the above-mentioned embodiment will be described below. (1) Convert run lengths up to 63 pixels into a Fibonacci code as a terminating value, and divide the run length of 64 pixels or more into a makeup value that is a multiple of 64 and a surplus terminating value. The run-length encoding method according to claim 1, wherein each of the terminating values is converted into a Fibonacci code.

According to this method, the data compression rate can be further increased, and the consumption of the memory capacity can be further suppressed. (2) A conversion means for converting the run length of the black-and-white pixel data forming the image data into a Fibonacci code and an addition means for adding 1 to the uppermost digit of the most significant digit 1 in the converted code are provided. Run length encoder.

In this case, the conversion means and the addition means are CPUs.
It is composed of 11. (3) The run-length coding method according to claim 1, wherein the code is generated by inverting 1 and 0 in the code.

In this case, the break of the code can be determined by using "00" as a delimiter.

[0048]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it has the following effects. According to the first aspect of the present invention, it is possible to easily determine the break of the code, the decoding can be performed easily and in a short time, the data compression rate can be maximized, and the consumption of the memory capacity can be suppressed. You can

According to the second aspect of the present invention, it is possible to generate a code having a delimiter of "11" for all run lengths including a code corresponding to a run length of 0.

According to the third aspect of the invention, it is optimum for decoding the code generated by the run-length coding method, and the decoding of the code can be performed easily and in a short time.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an embodiment embodying the present invention.

FIG. 2 is a flowchart showing a run length encoding operation.

FIG. 3 is a flowchart showing a decoding operation corresponding to the encoding operation.

FIG. 4 is a diagram for explaining conversion of a Fibonacci code.

FIG. 5 is an explanatory diagram showing code data stored in an image memory.

FIG. 6 is a diagram showing an example of run-length conversion codes in this embodiment.

FIG. 7 is a flowchart showing another example of run length encoding operation.

FIG. 8 is a flowchart showing a decoding operation corresponding to the encoding operation.

FIG. 9 is a diagram exemplifying run-length conversion codes in this another example.

[Explanation of symbols]

11 ... CPU constituting encoding means and decoding means, 17
... image memory, 19 ... recording section.

Claims (3)

[Claims] 1. A run length encoding method in which the run length of black and white pixel data forming image data is converted into a Fibonacci code, and 1 is added to the uppermost digit of the most significant digit 1 in the converted code. 2. The run length encoding method according to claim 1, wherein a value obtained by adding 1 to the run length is converted into a Fibonacci code. 3. A run of black and white pixel data that constitutes image data according to weighting of each digit based on the Fibonacci transform, by detecting two consecutive 1s in the code and dividing the code. Run-length decoding method for converting to length.