JPS62176371A - Transmission system for dither halftone - Google Patents

Abstract

PURPOSE:To easily compress data by encoding a two-dimensional code by counting black picture elements out of dither picture information, converting the counted value into a Gray code, compressing the data and two-dimensionally encoding the data. CONSTITUTION:A dither picture signal is inputted through an AND circuit 13a and a counter 14 counts the number of the black picture elements in one line under the control of a control part 15, for instance, every four picture elements and outputs to a memory 16. The memory 16 successively loads the counted value every stored four picture elements to the counter 14 during the counting of the next line and the counter 14 adds the number of the black picture elements in the our picture elements in the next line and outputs the added value to the memory 16. When the operation of the four lines is carried out, the added value latched in a latch circuit 17 is inputted to a Gray code converter 18, is converted into the data of the Gray code of 4 bits (reflected binary code), and the data is encoded to the two-dimensional code by an encoder 12 to go to a compression data signal and transmitted.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention J The present invention relates to dithered halftone transmission for facsimile machines.

[Technical Blue Application of the Invention] Conventionally, this type of device has been configured with a dither image signal transmitting/receiving section 10.20 shown in FIGS. 5 and 6. In other words, the image information of the halftone original read by the reading section (not shown) is it 1 #I, "O" as shown in FIG.
The dither pattern is converted into a serial dither pattern, and the data signal is two-dimensionally encoded by the Cog 12 via the analog switch 11 as a serial dither image signal to become a compressed data signal, which is transmitted from the transmitter.

This data signal is received by the receiving section of the transmission partner, decoded from the two-dimensional code by the decoder 22 via the analog switch 21, returned to the original dither image signal, and sent to the printer section where it is recorded on recording paper, etc. was.

[Problems in the Background Art] However, in the above device, two-dimensional encoding and decoding are effective means when the reference line has little change from the previous line, but With such a dither pattern, there are drastic changes from line to line, making it difficult to apply two-dimensional encoding, and the data cannot be compressed well by encoding, resulting in a data signal transmission time that is longer than if it were transmitted without encoding. The problem was that it was long.

[Purpose of Defense] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a dither halftone transmission method suitable for two-dimensional encoding.

(Summary of the invention 1) In this Komei, the black pixels of the dither image information are counted, the counted value is converted into a gray code, the data is compressed, and then the data is two-dimensionally encoded. has achieved its objectives.

[Embodiment of Explanation] An embodiment of the invention will be explained in detail based on the drawings of FIGS. 1 to 4.

1 and 2 show a dither image signal transmitting and receiving section of the present invention, and parts having the same functions as those in FIGS. 5 and 6 are given the same reference numerals for convenience of explanation.

1 and 2, the difference from the conventional example is that the dithered image signal transmission section 10 is provided with a dithered image signal compression section 13, and the dithered image signal reception section 20 is provided with a dithered image signal decomposition section 23. .

In halftone originals, the gradation often changes gradually as the document progresses in the sub-scanning direction. When such a document is converted to a medium tone, it becomes, for example, as shown in FIG. 3(a), and in this state, there is little correlation between the reference line and the previous line.

The dither pattern as shown in Figure 3(a) is 0'', II I
When the dithered image signal converted to II is serially input to the counter 14 via the AND circuit 13a according to the image signal clock, the counter 14 calculates the number of black pixels of one line, that is, 111 + 1, for example, 4 pixels under the control of the control unit 15. It counts each time and outputs it to the memory 16. The memory 16 is capable of storing each count value for one line counted every four pixels as 4-bit data, and when counting the next line, the count value for every four pixels stored in the memory is stored. counter 14
Load them sequentially. The counter 14 adds the number of black pixels among the four pixels of the next line to the count value from the memory 16 and outputs this added value to the memory 16.

When the above operation is performed for 4 lines, the number of black pixels in the 4×4 pixels becomes clear as shown in FIG. 3(b), and a correlation in gradation occurs between adjacent cells. Therefore, when the number of sub-scanning steps reaches 4, the control unit 15 controls the latch circuit 17 to latch each added value. Next, this latched addition value is input to the Gray code converter 18, where it is converted into 4-bit Gray code (alternating binary code) data based on the correspondence table shown in FIG.

As a result, the amount of information of the data is 1 compared to the initial information ff1 (see FIG. 3(a)), as shown in FIG. 3(C).
It can be reduced to /4.

By the way, the reason why we used the Gray code in this defense is because
For example, in binary, when changing from 7 to 8, 0111 → 1
000 and a 3-bit change is performed, but if the number of blacks in a 4 x 4 pixel is represented by the gray code, for a change of one gradation like the above, 4 bits are changed as shown in Figure 4. This is because it can be handled by changing only one bit of the pitch 1, and even if a mistake is made, the difference will be at most a difference in level tone.

The Gray code data is then two-dimensionally encoded by the Cog 12 to become a compressed data signal and transmitted from the transmitter.

This data signal is received by the receiving unit of the transmission partner, decoded from the two-dimensional code by the decoder 22, and returned to a 4-bit Gray code data signal, and the dither image signal decoding unit 23 decodes the data signal.
Output to. In the dither image signal decoding section 23, the Gray code data signal is first converted into 4-bit binary data by the Gray code converter 24, and then this binary data is converted into a dither data signal in which a fixed dither pattern is stored. Input to pattern generator 25. The dither pattern generator 25 selects one dither pattern for input data under the control of the control section 26, and outputs the selected dither pattern to the printer line by line.

Therefore, even if the dither pattern changes drastically from line to line, compression by two-dimensional encoding can be performed satisfactorily, and the distance between data signal transmission sections can be shortened.

[Effects of the Invention] As explained above, in the present invention, the black pixels of the dither image information are counted, the counted value is converted into a gray code, the data is compressed, and then the data is two-dimensionally encoded. As a result, data can be easily compressed by encoding and decoding two-dimensional codes.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the dither picture signal transmitting section of this Komei, Fig. 2 is a block diagram showing an embodiment of the dither picture signal receiving part, and Fig. 3 (a) is a dither halftone diagram. (b) is a diagram showing the number of black pixels in 4 x 4 pixels, (C) is a diagram showing the above (b) in gray code, and Figure 4 is the correspondence between hexadecimal numbers and gray code. The table and FIG. 5 are block diagrams of the conventional dither image signal transmitter, and FIG.
The figures are the same (configuration diagram of a conventional dithered image signal receiving section), and FIG. 7 is an example of dithered halftone printing, where one square represents one pixel. 12...Korg, 13...Dither picture signal pressure line part, 1
4...Counter, 15.26...Control ηO section, 16.
...Memory, 17...Rudge circuit, 18.24...
Gray code converter, 22...decoder, 23...
Dither picture number 1 receiving section, 25... dither pattern generator. □Main running Yu r5 same figure 3 16 sun 1 Hime f Ray code o ooo. Figure 5

Claims (1)

[Claims] In a dither halftone transmission method that converts image information into dithered image information and transmits the converted image information, a black pixel of the dithered image information is converted into n of the dithered image information.
xn pixels, and the counted value is m bits (m is m≧
A dither halftone transmission method characterized in that data is two-dimensionally encoded after being converted and compressed into a Gray code with a minimum integer value that satisfies the relationship: 2×log_2n.