JPS6292583A - Data compressing circuit - Google Patents

Abstract

PURPOSE:To increase the data compressing ratio and to fasten the transmitting speed by coding the blank line immediately after the line including the black picture element, with the short code word. CONSTITUTION:When an original is inserted into a reading part 1, the original size is detected, and based upon this, the corresponding code word is selected out of a memory part 32. The reading of the original is executed and by a detecting part 2 the blank line is detected which appears immediately after the line including the black picture element, a coding device 31 codes this by using the selected code word.

Description

[Detailed Description of the Invention] [Summary] A data compression circuit installed in a facsimile machine that transmits and receives signals by compressing both signals using a two-dimensional encoding method, in which a line containing only white pixels appears immediately after a line containing black pixels. (hereinafter referred to as an all-white line) is encoded in horizontal mode to reduce transmission time.

[Industrial application field]

The present invention relates to a data compression circuit provided in a facsimile machine.

A facsimile machine is a device that scans a two-dimensional image, converts it into an electrical signal, and sends and receives the converted image.

In the case of an image composed of black pixels and white pixels, such as a normal document, the electrical signal obtained by scanning is a binary signal with black pixels and white pixels as "■" and "0", respectively. , among which "1" or "0" often occur consecutively.

This series of identical signals is called a run, and its length is called a run length, but if this is replaced with a code, the amount of data to be sent and received can be significantly reduced.

Based on this idea, a facsimile machine compresses both black and white binary signals obtained by scanning by encoding and transmits and receives the signals.

There are two types of encoding methods: one-dimensional compression methods that focus on a single line, and two-dimensional compression methods that focus on multiple lines. Communication procedures were set to be used.

At this time, it is desired to further improve the communication speed between facsimile devices.

[Conventional technology]

Conventional two-dimensional encoding method For example, the standard two-dimensional encoding method by CCITT defines nine types of encoding modes as shown in Table 1 based on the two-dimensional relationship between pixels of original image data, and each code is This method assigns code words such as the notation to each conversion mode.

Table] Encoding mode Code word bus (P) 0001 Horizontal (H) 001+MI +M2 (*) Vertical (V (01') 1 Vertical (VRft)) 011 Vertical (VR (21) 000011 Vertical (Vl?()
31) 0000011 vertical (vL+t))
010 Vertical (VL(2)) 000010 Vertical (νL(3)
)) 0000010 (Note* M, and M2 are
[Problems to be Solved by the Invention] According to the conventional example, as illustrated in FIG. 3.

If the encoded line is an all-white line and the previous line (reference line) is not an all-white line, the encoding mode of the encoded line is vertical mode after many successive pass modes P (0). become.

As shown in the notation, the code word for pass mode P is ``0001'', which is 4 bits, and the code word for vertical mode V(0) is ``1n,'' which is 1 bit. Therefore, for example, if the pass mode continues 20 times, that line The bit length of the codeword is .

4 X20+ 1 = 81, and there is a problem that the bit length of the code word of the immediately following all-white line increases depending on the number of points of change from white pixels to black pixels or from black pixels to white pixels in the reference line. .

Therefore, one object of the present invention is to increase the data compression rate more than the conventional example and shorten the transmission time.

[Means for solving problems]

FIG. 1 is a diagram showing the principle of the present invention.

Reference numeral 1 denotes a #, k @ri unit that reads a black and white image written on paper by scanning it pixel by pixel.

Reference numeral 2 denotes a detection unit that detects an all-white line that appears immediately after a line containing black pixels from the binary signals obtained by the reading unit 1.

3 is a first encoding unit that encodes the all-white line detected by the detection unit 2 in a horizontal mode.

A second encoding unit 4 encodes lines other than the all-white line detected by the detection unit 2 using a standard encoding method.

5, both signals encoded by the first encoding section 3 and both signals encoded by the second encoding section 4,
This is a selection circuit (MPX) that selects and outputs lines in order.

[Effect]

That is, all white lines that appear immediately after lines containing black pixels are encoded in horizontal mode.

Other lines except this one are encoded using the standard encoding method as in the conventional example.

For example, when reading a Δ4 size document with the short side in the main scanning direction at a main scanning line density of 8 pixels/mm.

The run length of the all-white line is 1728. on the other hand.

The horizontal mode code word is expressed as “001 +Ml +M2”, where M+ is the combination of the white run code word “010011011” with a run length of 1728 and the white run code word “001.101.01” with a run length of 0. sum, M
2 is the code word for black run with run length 0 “0OOO11
0111'', it is represented by a total length of 30 bits.

In other words, compared to the 81 bits in the case of a line including the 20 (11i1) bus mode as described above, it can be represented by a much shorter code, and therefore the data compression rate for one page as a whole can be greatly increased. The transmission speed of internal reconnaissance signals can be greatly improved.

〔Example〕

FIG. 2 is a configuration diagram of the embodiment.

The detection unit 2 examines the binary signals obtained by the reading unit 1 and identifies whether the line in question is an all-white line or not. Identification storage unit 22 that stores whether the line immediately before the line is the front white line. and a discriminating section 23 that discriminates from the discriminating result of the discriminating section 21 and the storage contents of the discriminating storage section 22 whether or not the line in question is an all-white line that appears immediately after a line containing black pixels.

Further, the first encoding unit 3 includes an encoder 31. and a code word storage section 32 that stores in advance the entire code word when an all-white line is encoded in the horizontal mode for each run length determined by the size of the document.

That is, when a document is inserted into the reading section 1, the reading section 1
The document size is detected by a detector (not shown) provided in the document, and based on this, a control section (not shown) selects a code word corresponding to the document size from the code word storage section 32 .

When a document is read and the detection unit 2 detects a completely white line that appears immediately after a line containing black pixels,
The encoder 31 encodes this using the code word selected by the control unit.

〔Effect of the invention〕

As explained above, according to the present invention, an all-white line that appears immediately after a line containing black pixels is encoded with a code word shorter than that of the conventional example, thereby increasing the data compression rate and significantly improving the data transmission speed. can do.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention. FIG. 2 is a configuration diagram of the embodiment. FIG. 3 is an explanatory diagram of a conventional example. In the figure. 1 is the reading section, 2 is the detection section. 3 is the first encoding unit, and 4 is the second encoding unit. Principle diagram Figure 1 Figure 3

Claims (1)

[Claims] In a data compression circuit that compresses a pixel-by-pixel binary signal obtained by scanning using a two-dimensional encoding mode and a code word, immediately after a line containing a black pixel, Detection unit (2) that detects lines with only white pixels appearing
and an encoding unit (3) that encodes the detected line in a horizontal mode.