JPS6065669A - Picture coding system - Google Patents

Abstract

PURPOSE:To improve a coding compressing rate by applying plural number of times of coding processing and transmitting code information with a short code length to a reception side in a picture coding system used for a facsimile device or the like. CONSTITUTION:The maximum repetitive number of times is set so as to apply plural number of times of coding processings in the coding processing as to each main scanning line. When the 1st coding processing is finished, the outputs of counters 40, 60 are compared, and the result of comparison C is informed to a coding section 30. When the code length after the coding is longer than the length of the original picture information, the coding processing is finished, the storage content of a memory 20 having a short code length is transferred to an output buffer 80- and is transmitted to the reception side. When the code length after the coding is shorter than the length of the original picture information, the 1st coding information stored in a memory 50 is inputted again to the coding section 30 and the 2nd coding processing is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image encoding method used in facsimile machines and the like, and particularly to an image encoding method that realizes encoding with a high compression ratio.

[Prior art]

Traditionally, the encoding methods used in facsimile machines include one-dimensional encoding methods such as the Modified Huffman method (hereinafter referred to as the MH method) and two-dimensional encoding methods such as the Modified Read method. With the encoding method, depending on the content of the read image, the code length may be longer than the original image axis length (video information),
Alternatively, encoded information with a high compression ratio may not be obtained.

[Purpose of the invention]

This invention was made in view of the above circumstances, and aims to shorten the transmission time by increasing the encoding compression rate as much as possible.
The purpose of this invention is to provide an image encoding method that contributes to reducing communication costs.

[Structure of the invention]

Therefore, in the present invention, when encoding each main scanning line, the encoding process is repeated a plurality of times. In other words, when encoding each main scanning line, if the code length after encoding is longer than the code length before encoding, the encoding process for that main scanning line is finished and the shorter code length is used. In addition, if the code length after the encoding process is shorter than the code length before the encoding process, the same encoding process is performed further, and the maximum number of repetitions of this operation is set. Alternatively, the encoding process for each main scanning line is repeated at least once or more times by repeating the encoding process until the code length after encoding becomes longer than the code length before encoding.

Embodiments] The image encoding method according to the present invention will be described in detail below with reference to embodiments shown in the accompanying drawings.

The figure shows one embodiment of the invention.

In the figure, a reading device 10 includes, for example, an image sensor and a sensor driver that drives and controls the image sensor, and reads an image of a transmitted document. The image information V read by the reading device 10 is input to the memory 20 as a black and white binary signal.

The memory 20 is a line memory capable of storing image information for at least one main scanning line, and as a first operation, the stored image information is input to the encoding section 30. The total length of the image information at this time (for example, 1728 bits for an A4 size document) is counted by a counter 40.

The encoding unit 30 encodes the image information using a one-dimensional band compression method such as a modified Huffman method,
The encoded output is input to memory 50. The code length of the encoded output at this time is counted by a counter 60.

The memory 50 is a line memory like the memory 20,
The encoded information input as the first operation is stored.

At the end of this first encoding process, the comparator 70
compares the output of the counter 40 and the output of the counter 60, and notifies the encoding unit 30 of the comparison result C. Then, if the output of the counter 60 is larger than the output of the counter 40, that is, if the code length after encoding is longer than the length of the original image information, the encoding process for the main scanning line is finished, After the stored contents of the memory 20 with a short code length are transferred to the output buffer 80 and a scanning line synchronization signal (for example, EOL) is added thereto, the information of the scanning line is transmitted to the receiving side via the transmission section 90. transmitted to. However, in this case, if the output of the counter 60 is smaller than the output of the counter 40, that is, if the code length after encoding is shorter than the length of the original image information, the code length is stored in the memory 50 in order to further shorten the code length. The first encoded information is input again to the encoder 30 to perform the second encoding process. Regarding this second encoding process, taking the Modified Huffman method as an example, the first encoding information stored in the memory 50 is a combination of a makeup code and a terminating code. simply[
Although this is different from video information that indicates white or black with a signal of ``0'' or ``1,'' this encoded information is regarded as the video information and encoding processing is performed using the modified Huffman method similar to the previous time. Note that at this time, the counter 60 holds the code length of the first encoded information. When the second encoding process is completed in the encoding unit 30, this encoded information is input to the memory 20 and stored, while the counter 40 counts the code length at this time. Then, the comparison section 70 again compares the output of the counter 60 and the output of the counter 40, and notifies the comparison result C to the encoding section 30. As a result, if the output of the counter 40 is larger than the output of the counter 60, that is, if the code length of the first encoded information is longer than the code length of the second encoded information, the code of the main scanning line The encoding process is now completed, and the stored contents of the memory 50 having a short code length are transferred to the output buffer 80, and after a scanning line synchronization signal is added thereto as described above, it is transmitted to the receiving side via the transmission section 90. However, if the output of the counter 40 is smaller than the output of the counter 60, that is, the code length of the second encoded information is the same as that of the first encoded information.
If the code length is shorter than the code length of the encoded information of the first time, the second encoded information stored in the memory 20 is inputted into the encoding unit 30 again to make the code length of the third encoded information shorter. Perform conversion processing.

Thereafter, the above-described encoding process is repeated multiple times in the same manner.

By the way, regarding the number of repetitions of the above encoding process, assuming that the number of pixels in the main scanning line is 1,728 bits, the maximum number of pixels is 1,727 if each bit is reduced in one encoding.
It is possible to consider multiple encoding processes.

In this way, when encoding processing for one main scanning line, the encoding processing is ended when the code length after encoding becomes longer than the code length before encoding, without setting the maximum number of repetitions. However, in this embodiment, an appropriate maximum number of repetitions n is set in advance. That is, (n
-1) Regarding the encoding process up to the nth time, the encoding process ends when the code length after encoding becomes longer than the code length before encoding, but the encoding process extends to the nth time. In this case, the shorter code length in the n-th encoding is used as the final encoded information, and then the encoding process ends at the n-th encoding.

Further, when performing such encoding processing, since the maximum number of repetitions n for one main scanning line is determined, the actual number of repetitions can be identified by a finite bit length. For example, if the maximum number of repetitions is 4, the actual number of repetitions can be identified using at least 2 bits. If information indicating the actual number of repetitions is added to the encoded information for each main scanning line and transmitted to the receiving side, the receiving side can recognize in advance the number of repetitions required for decoding processing. This eliminates the need for a control configuration for, for example, checking the bit length of the final decoded information.

In this way, in this embodiment, when encoding processing for each main scanning line, the maximum number of repetitions is set and the encoding processing is performed multiple times, and the encoding information with the shorter code length is always sent to the receiving side. Since the information is transmitted, the encoding compression rate can be reliably improved.

Note that the band compression method used in the present invention is a modified
One-dimensional band compression methods such as the Huffman method are particularly effective.

〔Effect of the invention〕

As explained above, according to the image encoding method according to the present invention, it is possible to reliably improve the encoding compression rate with a simple control configuration, thereby shortening the transmission time and reducing communication costs. It has the excellent effect of

[Brief explanation of the drawing]

The figure is a block diagram showing an example of a configuration for implementing the image encoding method according to the present invention. 10.Reading device, 20.50-Memory, 3o.Encoding section, 40.60...Counter, 7o..Comparison section, 80.
Output buffer, 90...transmission section.

Claims (2)

[Claims] (1) In an image encoding method in which the image information of a read document is encoded for each main scanning line using a predetermined band compression method, the code length after the encoding process is determined for each main scanning line. If the code length is longer than the code length before the encoding process, the encoding process for the main scanning line is finished, the shorter code length is used as the final encoded information, and the code length after the encoding process is the same as before the encoding process. If the code length is shorter than the code length, the encoding process is further performed using the band compression method, thereby repeating the above encoding process at least once or more times for each main scanning line. An image encoding method that uses (2) The image encoding method according to claim 1, wherein a maximum number of repetitions of the encoding process for each main scanning line is set in advance.