JPS6141466B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of Application of the Invention The present invention relates to improvements in facsimile encoding systems mainly based on run lengths.

(2) Prior Art Various types of facsimile run-length encoding systems have been proposed, but they can be classified into open types and closed types. The former is a code system, such as the well-known wire code or B code, that can express any long run according to certain rules. The latter is a code system that can express up to a predetermined length but cannot define anything beyond that, such as a modified Huffman code. The latter method had a problem in that it could not be applied when there were more pixels in the scanning line.

(3) Purpose of the invention The purpose of the present invention is to enable this to be applied within the same coding system for any length of time.

(4) General description of the invention FIG. 1 shows the configuration of a conventional, well-known general run-length encoding facsimile. The image signal obtained from the image sensor 1 is, in other words,
A counting circuit 2 counts the run length of the binary level signal corresponding to the black and white level. Then, the code converter 3 converts it into a predetermined code (a code that has an upper limit on the run length that can be expressed).
At this time, in the case of the modified Huffman code described above, this is done by searching the ROM (read-only storage device) 4. This result is sent to the transmitter 5 and transmitted. At this time, if the length is longer than a predetermined length, encoding becomes impossible due to the encoding system as described above. To solve this problem, when the continuation (run) of a certain predetermined state such as black or white is longer than the code that can be represented, the run is divided and encoded, and the two divided and encoded If the other states (i.e. when the above given state is black, the other states are white) between the signs run 0
A code is inserted to indicate that it exists.

For example, if we try to express the run length of the white state as 1800 using a conventional modified Huffman code (MH code), the maximum value of the run length that can be expressed using conventional MH is 1728 + 63, so The above 1800 cannot be represented by one code.

Therefore, according to the present invention, this white 1800 (white)
It is expressed as 1728 + (black) 0 + (white) 72. This is white M
(1728)+white T(0)+black T(0)+white M(64)+white T(8). Here, M is a make up code and T is a terminating code word. Expressing this with a sign is encoded as

(5) Examples Hereinafter, the present invention will be explained in detail with reference to examples.

In the embodiment of the present invention, the code conversion circuit 3 and
The above problem is solved by inserting a circuit for continuation division between the ROMs 4.

In other words, the counting results are not immediately retrieved from the ROM as in the conventional method, but instead are stored in the subtraction circuit 6.
, the default maximum number N (here, the international standard
1728). This result is added to the judgment circuit 7, and if it is negative, it is "1", and if it is positive, it is "0".
is converted to the output. This is the subtraction circuit
Matches the MSB (most significant digit). However, the subtraction result is 0
is included in the negative.

If it is negative, that is, if it is equal to or smaller than 1728, it can be encoded using the predetermined encoding system, so it passes through gate 8 and searches for ROM 4 as it is.

On the other hand, if it is positive, then we do this division. Therefore, first, only the value "1728" is sent to the ROM 4 via the gate 9. Next, the run length result of "0" is sent to the ROM via the gate 11 by the signal delayed by the delay element 10.
Finally, the result of the subtraction circuit is passed through the delay element 12.
Send to ROM. Here, the run length result of 0 corresponds to the opposite color, that is, if the run to be encoded is white, it corresponds to black, and if white and black are different codes as in modified Huffman codes, It is necessary to add this information and look it up from another table.

The results of searching the ROM as described above are sequentially sent to the code conversion circuit 3 and transmitted.

In the receiving section, there is no particular change due to the above, and the data can be decoded as is.

Now, the following various modifications can be considered to the above configuration.

(1) For facsimile devices in which the maximum run length value is twice or more the predetermined maximum number N, the above operation may be repeated two or more times.

(2) In the embodiment of the present invention, the code conversion unit 3 and the ROM
4, the counting section 2 may be configured in advance as in the embodiment of the present invention.

(3) In the international standard modified Huffman code, for example, in the case of white, 1728 is expressed in 17 bits, but 1666 is expressed in 10 bits. Therefore, in some cases, runs longer than 1728
Instead of expressing it as 1666 and its remainder, it might be possible to express it as 1666 and its remainder. However, an increase in circuits cannot be avoided.

(4) It is applicable not only to facsimile but also to any method that encodes the duration of a state.

(5) The present invention can also be applied to an open code system in principle, although it is not necessarily significant. This may be useful, for example, if the number of bits in the decoder register in the receiving section is limited.

In the present invention, the normal maximum value N in the international standard
= 1728, but even in this international standard, it is possible to express up to 1728 + 63 = 1791.

Therefore, it is also possible to consider N=1792.

(6) Summary As explained above, the present invention is extremely effective in that a closed code system can be used to encode the run length of a device that has the possibility of a longer lamp. This is particularly effective in practical applications, such as when handling large documents such as not only A4 size but also B4 size, or when the resolution has increased.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional run-length encoding facsimile apparatus. Figure 2 shows
3 shows a circuit configuration for dividing a run and inserting opposite colors in an embodiment of the present invention. 1... Image sensor, 2... Counting circuit, 3...
...Code converter, 4...ROM, 5...Transmitter, 6
...Subtraction circuit, 7...Judgment circuit, 8, 9, 11,
13...gate, 10...delay element.

Claims (1)

[Claims] 1 In a method of encoding the run length of a binary level signal with a code that has an upper limit on the run length that can be expressed, one run length of one level is divided and the signal of the other level is inserted at the dividing point. An extended encoding method characterized by encoding by inserting a code with a run length of zero.