JP2806310B2 - Encoding device and facsimile device having the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an encoding apparatus for encoding the run length of black and white pixel data constituting image data, and a facsimile apparatus having the encoding apparatus.

[0002]

2. Description of the Related Art Generally, for example, in a facsimile apparatus, when received image data and the like are stored in an image memory, the image data is stored in a modified Huffman system (MH).
System), modified read system (MR system), or modified MR system (MMR system), and the data is encoded and stored in a compressed state.

[0003]

However, in the conventional MH system, MR system and MMR system, when decoding the encoded data read from the image memory, it is difficult to distinguish between the code breaks. There is a problem that the processing is time-consuming and troublesome. That is, for example, MH
In the method, the run length (the number of continuations) of the black and white pixel data constituting the image data is represented by a predetermined code, but the coded data is not inserted with a code indicating a delimiter at a code break. , One line is continuously stored in the image memory. For this reason, in order to detect a break in a code, it is necessary to sequentially determine which run length the code represents, while sequentially checking the code one bit at a time, and this processing takes time. Was something.

On the other hand, besides the above-mentioned encoding method, there is a method of expressing each run length in image data by a code having a fixed bit length of, for example, 8 bits and storing the same in an image memory. According to this method, since each run length is always represented by a code having a fixed bit length, a break in the code can be easily determined, and the decoding process can be easily performed in a short time. However, in this method, since a data amount of a fixed bit length is always required to represent each run length, there is a problem that the data compression rate is low and the capacity of the image memory is wasted.

SUMMARY OF THE INVENTION An object of the present invention is to make it easy to determine a break in a code, to perform decoding easily and in a short time, to increase a data compression rate as much as possible, and to suppress consumption of memory capacity. An object of the present invention is to provide an encoding device and a facsimile device including the same.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a run length of black and white pixel data constituting image data is converted into a code having a fixed bit length. A conversion unit for converting a predetermined run length having a high frequency of occurrence into a code different from a high-order bit of other run lengths having a low frequency of occurrence.
And a code having a bit length shorter than the other run lengths .

According to a second aspect of the present invention, in the encoding apparatus according to the first aspect, the converting means includes a step of converting the size of the image data.
In this case, a predetermined run length having a high appearance frequency is converted into a 4-bit code, and the other run lengths are converted into an 8-bit code.

According to a third aspect of the present invention, in the encoding apparatus according to the first or second aspect, first decoding means for decoding the received encoded data into a black and white run length,
Said conversion means for converting the decoded data into code of a fixed bit length, the encoded data and error of the fixed bit length
An image memory for storing the encoded data of a fixed bit length indicating the line, as well as decoding the run length of black and white reads the encoded data in the image memory, e
And second decoding means for judging the error line .

Therefore, according to the first aspect of the present invention, the run length of black and white pixel data constituting image data is converted into a code having a fixed bit length. Therefore, when the encoded data is decoded to run-length, the boundaries of each code can be easily determined, and each code can be easily and quickly decoded in fixed bit units.

[0010] The predetermined run length having a high appearance frequency is set to a higher order bit than other run lengths having a low appearance frequency.
Code that is different from the
Is converted into a code having a bit length shorter than the code length.
Therefore, the encoded data can be compressed as much as possible,
It is also possible to suppress consumption of memory capacity.

According to the second aspect of the present invention, the image data
Depending on the size, a predetermined run length with a high appearance frequency
The code is converted into a code of bits, and the other run lengths are converted into codes of 8 bits. When decoding the encoded data in a run length, for example, each code is read in units of 4 bits, and it is determined whether or not the code is a 4-bit code. Here, if the code is not a 4-bit code, four more bits may be read and decoded in units of eight bits. For this reason, the boundary of each code can be easily determined, and decoding can be performed easily and in a short time.

A predetermined run length having a high appearance frequency is converted into a 4-bit code. Therefore, the data compression ratio can be increased and the consumption of memory capacity can be suppressed as compared with a case where all run lengths are converted into codes having a fixed bit length of 8 bits and stored in the image memory. .

Normally, in a facsimile apparatus, when image data is received, the image data is decoded into a run length to check whether or not each line data has an error. Here, in the invention described in claim 3, the first
The error check of the received data is performed based on the decoded data by the decoding means, and at the same time, the decoded data is converted into a fixed bit length code and stored in the image memory. In other words, since data decoded for error checking is converted into a code having a fixed bit length and stored in the memory, no processing is wasted. When data in the image memory is read for printing and decoded by the second decoding means, the decoding can be easily performed in a short time, and the printing operation can be performed quickly and smoothly.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 shows a circuit configuration of the facsimile apparatus of this embodiment. A CPU (Central Processing Unit) 11 constitutes a conversion unit, a first decoding unit, and a second decoding unit, and a ROM (Read Only Memory) 12 and a RAM (Random Access Memory) 13 are connected to the CPU 11. . ROM1
Reference numeral 2 stores a program and the like for controlling the operation of the entire apparatus. The RAM 13 temporarily stores various information. NCU (Network Control Unit) 1
Reference numeral 4 controls the connection between the facsimile machine and the telephone line. The modem 15 performs modulation and demodulation of transmission / reception data.

The reading section 16 optically reads an image on a document set on a document table (not shown). Image memory 1
Reference numeral 7 stores received image data and image data read by the reading unit 16 in a state converted into an intermediate code described later under the control of the CPU 11. The print buffer 18
The image data read from the image memory 17 and decoded under the control of the CPU 11 is stored for each line (line data). The recording unit 19 stores the print buffer 1
The printing is performed on the recording paper based on the line data stored in 8. 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.

In the ROM 12, for example, FIGS.
As shown in FIG. 7, an MH code and an intermediate code are stored as table data corresponding to each of the black and white run lengths constituting the image data. FIG. 4 shows table data corresponding to image data of A4 size, and FIG. 5 shows table data corresponding to image data of B4 size or more.
The required table data is selected according to the size of the image data. Note that information on the size of the communication data is transmitted from the transmitting side to the receiving side by a facsimile control signal (protocol) exchanged between the transmitting side apparatus and the receiving side apparatus prior to the communication of the image data. . The intermediate code is one in which the run length is represented by two types of codes having a fixed bit length of 4 bits or 8 bits. In the MH code, a run length with a higher appearance frequency is represented by a code with a shorter bit length. As is clear from FIGS. 4 and 5, a run length with a higher appearance frequency is also 4 bits in the intermediate code. , And the other run lengths are represented by the longer code of 8 bits. In this embodiment, “1” to “1” are set for A4 size image data.
The run length of "0" is represented by a 4-bit intermediate code.
For image data larger than the size, the run length of "1" to "9" is represented by a 4-bit intermediate code. Also, in the intermediate code, as in the case of the MH code, the run length up to 63 pixels is represented by a terminating code, and the run length of 64 pixels or more is represented by a makeup code and the following terminating code. I have. Further, the ROM 12 stores an 8-bit intermediate code corresponding to an EOL code (line end code) added to the end of each line data of the communication image data, and indicates that the line data is an error line. The stored 8-bit intermediate code (referred to as ERL code) is stored.

Next, the processing operation performed by the CPU 11 when receiving image data will be described with reference to the flowchart of FIG. By the way, MH method from the transmitting side,
When image data encoded by the MR method or the MMR method is transmitted and the image data is received, the RT added to the end of the received image data for one page of the document is received.
It is determined whether the C signal (control return signal) has been detected (steps S1 and S2). If no RTC signal is detected, the EO added to the end of each line data
It is determined whether or not the L signal (line end signal) has been detected (step S3). The RTC signal is composed of six consecutive EOL signals, and is added to the end of the last line of the received image data for one page of the document. here,
If the EOL signal is not detected, the encoded received data is decoded into a run length of black and white pixel data constituting the image data (step S4).

Next, it is determined whether or not the run length is smaller than "64" (step S5). In this determination, if the run length is “64” or more, the run length is a makeup value that is a multiple of “64”;
It is divided into the remaining terminating value (step S6). Then, according to the table data of FIG. 4 or FIG.
It is converted into a bit intermediate code (8-bit code) (step S7). For example, a make-up value of “64” is represented by an intermediate code “01000001” obtained by binarizing an integer value of “65” obtained by adding “64” to a quotient “1” obtained by dividing the value by “64”. , “128” is represented by an intermediate code “01000010” obtained by binarizing an integer value of “66” obtained by adding “64” to a quotient “2” obtained by dividing the value by “64”. . That is,
The makeup value is obtained by dividing the value obtained by dividing the value by “64” by “6”.
The result of addition to 4 "is converted into a binary code.
The value to be added is not limited to “64”.

On the other hand, if it is determined in step S5 that the run length is smaller than "64",
The run length is determined to be a terminating value. Next, it is determined whether or not the terminating value belongs to an exception area (step S8). Here, the exceptional area is a range of run length converted into a 4-bit intermediate code. That is, when the received data is A4 size, the exceptional area has a run length range of "1" to "10" as shown in FIG.
When the received data is equal to or larger than the B4 size, the run length ranges from "1" to "9" as shown in FIG.
After step S7, the process proceeds to step S8.
It is determined whether the terminating value divided in step S6 also belongs to the exception area.

If the terminating value corresponds to the exceptional area, the terminating value is converted to a 4-bit intermediate code as a terminating code according to the table data of FIG. 4 or 5 (step S9). For example, as shown in FIG.
In the case of the size, the terminating value of “1” is an integer value of “6” obtained by adding “5” to the value, and 2
It is represented by an intermediate code “0110” converted into a base number. As shown in FIG. 5, when the received data is B4 size or more, the terminating value of “1” is an intermediate code obtained by binarizing an integer value of “7” obtained by adding “6” to the value. 0111 ". That is, when the received data is A4 size, the terminating value of “1” to “10” is converted into an intermediate code in which the result of adding “5” to the value is converted into a binary number. If the received data is B4 size or larger, the terminating value of “1” to “9” is converted into an intermediate code in which the result of adding “6” to the value is converted into a binary number.

Here, the encoding of the terminating value of the exceptional area based on the result obtained by adding a predetermined numerical value of "5" or "6" to the value is performed when decoding an intermediate code described later by four bits. Top 4 of codes and 8-bit codes
This is to ensure that the bits can be distinguished. As apparent from FIGS. 4 and 5, the 4-bit code in the intermediate code and the upper 4 bits of the 8-bit code are different codes.

On the other hand, if the terminating value does not correspond to the exceptional area in step S8, the terminating value is converted to an 8-bit intermediate code (8) as the terminating code in accordance with the table data shown in FIGS. (Step S10). In this case, the terminating value is directly converted into a binary code.

Then, the encoded data is stored in the image memory 17 (step S11). Thereafter, returning to step S2, the operations of steps S2 to S11 are repeatedly performed, and the received encoded data is sequentially converted into an intermediate code after being decoded and stored in the image memory 17.

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

If the EOL signal is detected in step S3, it is determined that the reception and encoding of one line of data have been completed, and it is determined whether the line is an error line. (Step S
12). The determination as to whether or not this is an error line is made, for example, by determining the total of one line of the run length decoded in step S4, in other words, the total number of pixel data of one line.
Specified amount (1728 for A4, 20 for B4
48), and so on. If it is determined that the line is not an error line, the EOL code is converted into an intermediate code and stored in the image memory 17 according to the table data of FIG. 4 or 5 (step S13).
As shown in FIGS. 4 and 5, the EOL code is converted into an 8-bit intermediate code “01000000” obtained by converting an integer “64” into a binary number. On the other hand, if it is determined that the line is an error line, the address in the memory 17 is returned to the head of the error line in order to invalidate the error line stored in the image memory 17 (step S).
14). Then, an ERL code as an intermediate code indicating that the reception line is an error line is stored in the image memory 17 (step S15).

Thereafter, returning to step S2, the operations of steps S2 to S15 are performed in order to shift to the reception and encoding processing of the next line data. On the other hand, if the RTC signal is detected in the determination in step S2, it is determined that the reception and encoding of the data of one page of the document have been completed, and the RTC code is stored in the image memory 17.
(Step S16). That is, six intermediate codes representing the EOL code are stored consecutively. Thereafter, it is determined whether there is data for the next page (step S).
17). If there is data for the next page, the process returns to step S2 to perform the process of receiving and encoding the data for the next page, and the operations of steps S2 to S17 are performed. The process ends.

Next, the processing operation at the time of printing image data executed by the CPU 11 will be described with reference to the flowchart of FIG. By the way, during this printing process,
First, code data in which one line of data stored in the image memory 17 is successively read out in units of 4 bits (step S18). Then, it is determined whether or not the read code is a 4-bit code (4-bit intermediate code) (step S19). At this time, since the 4-bit code and the upper 4 bits of the 8-bit code are different codes,
It is possible to easily and reliably determine whether the read code is a 4-bit code. If the read code is a 4-bit code, the 4-bit code is decoded into run length according to FIG. 4 or FIG. 5 according to the size of the stored data (step S20). For example, as shown in FIG. 4, when the storage data is A4 size,
The intermediate code of “0111” is converted into a run length of “2” which is obtained by subtracting “5” from a value “7” obtained by converting the intermediate code into a decimal number. Also, as shown in FIG.
In the case of four or more sizes, the intermediate code of “0111” is converted to a run length of “1” obtained by subtracting “6” from a value “7” obtained by converting the intermediate code into a decimal number.

On the other hand, if it is determined in step S19 that the read code is not a 4-bit code, it is determined that the code is an 8-bit code, and a continuous 4-bit code is read (step S19). Step S2
1). Then, it is first determined whether or not the 8-bit code is an RTC code (step S22). If not, it is determined whether or not the read code is an ERL code (step S23). ). Where ER
If it is not the L code, it is determined whether the read code is an EOL code (step S24). If the code is not the EOL code, the read 8-bit code data is decoded to run length according to FIG. 4 or 5 (step S25).

Next, it is determined whether or not the run length is smaller than "64" (step S26). here,
If the run length is less than "64", it is determined that the run length is a terminating value. In the image memory 17, a code representing a white run and a code representing a black run are always stored alternately with the code representing a white run first, and when the decoded run length is a terminating value, Each time, the run length is changed between black and white (step S27). Step S19
In steps S20 to S20, the run length decoded from the 4-bit code is similarly processed as the terminating value. Then, the run-length data is developed into white or black image data for forming an image, and the image data is transferred to and stored in the print buffer 18 (steps S28 to S29).

On the other hand, if the run length is "64" or more in step S26, it is determined that the run length is a makeup value. In other words, here, a multiple of “64” has been obtained during the actual run length. Thereafter, the process proceeds to step S28, and the run length is developed into image data in the same manner as described above. When the code data is converted to a makeup value, the next code data is determined to be a terminating value following the makeup value, and the makeup value and the terminating value are the same in black and white. Processing is performed as run length. Thereafter, returning to step S18, the operations of steps S18 to S29 are repeatedly performed.

If it is determined in step S24 that the read code is an EOL code, one line of image data is read from the print buffer 18 and printed by the recording unit 19 on recording paper. (Step S30). Thereafter, the process returns to the step S18 to shift to the processing of the next line.

If it is determined in step S23 that the read code is an ERL code, a predetermined error process is performed. For example, line data immediately before the error line portion is repeatedly printed.
(Step S31). Thereafter, the process returns to the step S18 to shift to the processing of the next line.

If it is determined in step S22 that the read code is an RTC code, it is determined whether there is data for the next page (step S22).
32). If there is data for the next page, the process returns to step S18, and the operations of steps S18 to S32 are performed. If there is no next page, the process ends.

As described above, when the facsimile apparatus of this embodiment receives encoded image data, it first decodes the received image data into a black and white run length. Next, the run length is converted into an intermediate code having a fixed bit length of 4 bits or 8 bits, and
To memorize. At this time, a short 4-bit code is assigned to a predetermined run length having a high appearance frequency. Then, the intermediate code in the image memory 17 is read, decoded to a run length, and recorded. At this time, since each intermediate code has a fixed bit length of 4 bits or 8 bits, the boundary of each intermediate code can be easily determined. In addition, each intermediate code can be decoded in units of 4 bits or 8 bits. Therefore, decoding can be performed easily and in a short time, and a printing operation can be performed smoothly and quickly.

Moreover, the intermediate code is a code based on the run length. Since the 4-bit code of the intermediate code and the upper 4 bits of the 8-bit code do not overlap, it is possible to determine whether the read code is the 4-bit code or the upper 4 bits of the 8-bit code. Easy. Therefore, even if the intermediate code is composed of a plurality of fixed bit lengths, the boundary of each intermediate code can be clearly determined, and decoding can be performed more easily and in a shorter time.

Further, a short 4-bit code is assigned to a predetermined run length having a high appearance frequency. Therefore, the run length can be directly converted into an 8-bit binary code and the data can be compressed as compared with the case where the code is stored in the image memory 17, and the consumption of the memory capacity of the image memory 17 can be suppressed. Can also.

In addition, since the intermediate code is divided into the terminating code and the makeup code, the data can be further compressed, and the consumption of the memory capacity of the image memory 17 can be further suppressed.

In the present embodiment, the received encoded data is decoded, and an error check of each line data is performed based on the decoding result. Then, the data decoded at this time is converted into an intermediate code and stored in the memory 17. In other words, the data decoded for error checking is converted into an intermediate code and stored in the memory 17. For this reason, even if the received encoded data is decoded and re-encoded, the processing is not wasted. Moreover, memory 1
7 is intermediate code data,
As described above, the process of decoding and printing the data can be performed easily and in a short time, and the load on the CPU 11 required for the process can be reduced.

That is, some recent facsimile apparatuses perform a plurality of processes at the same time, such as receiving image data during printing of data stored in the memory 17. However, in such an apparatus, when standard encoded data such as an MH code is stored in the memory 17 as in the prior art, the standard encoding is performed to print the data in the memory 17 and check the received data for errors. It is necessary to simultaneously perform two decoding processes on the decoded data, and the load on the CPU 11 required for the two decoding processes increases.

However, in the present embodiment, the load on the CPU 11 required for one of the decryption processes is reduced. Therefore, when the printing of the data in the memory 17 and the reception of the image data are performed in parallel, The burden can be reduced. As a result, an inexpensive CPU 11 can be used.

The present invention can be embodied with the following modifications. (1) In the above embodiment, the case where the received data is encoded and stored in the image memory 17 has been described. However, the same applies to the case where the image data read by the reading unit 16 is encoded and stored in the image memory 17. Performing an encoding process.

(2) In the above embodiment, the division between the terminating value and the makeup value in the run length is changed to a value other than 63 pixels. Next, technical ideas that can be grasped from the above embodiment will be described below.

(1) In claim 1 or 2, the conversion means converts a run length of up to 63 pixels into a code as a terminating value, and a run length of 64 pixels or more has a makeup value of a multiple of 64 and a residual terminator. An encoding device that separates the makeup value and the terminating value into codes, respectively, by dividing the makeup value and the terminating value into codes.

In this way, the data can be further compressed, and the consumption of the memory capacity can be further suppressed. (2) The encoding apparatus according to claim 2, wherein the 4-bit code and the upper 4 bits of the 8-bit code are different codes.

In this manner, the 4-bit code constituting the code and the upper 4 bits of the 8-bit code do not overlap, and when decoding the code, whether the code is a 4-bit code or the upper 4 bits of the 8-bit code. It is easy to determine whether the bit is a bit. Therefore, even if a code is composed of a plurality of fixed bit lengths, the boundaries between the codes can be clearly determined, and the decoding can be performed more easily and in a shorter time.

(3) The run length of the black and white pixel data constituting the image data is converted into a code having a fixed bit length, and the code is converted from a predetermined run length having a high appearance frequency to another run length having a low appearance frequency. An encoding method for converting to a shorter bit length code.

(4) In the above item (3), the predetermined run length having a high appearance frequency is converted into a 4-bit code.
An encoding method for converting other run lengths into 8-bit codes.

According to these encoding methods, the boundaries of each code can be easily determined, the decoding can be performed easily and in a short time, and the data can be compressed as much as possible. The consumption of capacity can be suppressed.

(5) In the above item (3) or (4), a run length of up to 63 pixels is converted into a code as a terminating value, and a run length of 64 pixels or more is converted to a makeup value of a multiple of 64 and a remainder. And an encoding method for converting the makeup value and the terminating value into codes respectively.

According to this encoding method, data can be further compressed, and the consumption of memory capacity can be further reduced. (6) An encoding method according to the above item (4), wherein the upper 4 bits of the 4-bit code and the upper 4 bits of the 8-bit code are different codes.

According to this encoding method, similarly to the above-mentioned item (2), even if a code is composed of a plurality of fixed bit lengths, the boundary of each code can be clearly determined, and its decoding can be performed. Can be performed more easily and in a shorter time.

[0052]

Since the present invention is configured as described above, it has the following excellent effects. According to the first and second aspects of the present invention, the boundaries between codes can be easily determined, and decoding can be performed easily and in a short time. Further, the data compression ratio can be increased as much as possible, and the consumption of memory capacity can be suppressed.

According to the third aspect of the present invention, even if the received encoded data is decoded and re-encoded, no waste is caused in the processing, and the data is read out when the data in the image memory is printed. The data can be easily decoded in a short time, and the printing operation can be performed quickly and smoothly.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a facsimile apparatus according to an embodiment.

FIG. 2 is a flowchart showing a processing operation at the time of reception.

FIG. 3 is a flowchart showing a processing operation at the time of recording.

FIG. 4 is an explanatory diagram showing table data used for A4 size data.

FIG. 5 is an explanatory diagram showing table data used for data of B4 size or more.

[Explanation of symbols]

11 ... CPU constituting the conversion means, first decoding means and second decoding means, 17 ... Image memory.

Claims (3)

(57) [Claims] A conversion means for converting a run length of black and white pixel data constituting image data into a code having a fixed bit length, wherein the conversion means converts a predetermined run length having a high appearance frequency into a code having a low appearance frequency. Top run lengths other than
Code that is different from the
Encoding apparatus and converting a short bit length code than Nrengusu. 2. The image processing device according to claim 1, wherein
2. The encoding apparatus according to claim 1, wherein a predetermined run length having a high appearance frequency is converted into a 4-bit code, and the other run lengths are converted into an 8-bit code. 3. A first decoding means for decoding received encoded data into a black and white run length, said converting means for converting the decoded data into a code having a fixed bit length, and encoding the fixed bit length. Data and error lines
An image memory that stores coded data of a fixed bit length indicating that the coded data is read out, the coded data in the image memory is read out, decoded into a black and white run length, and an error line is determined.
Facsimile apparatus having a coding apparatus according to claim 1 or 2 and a second decoding means for.