JPS6031388B2 - Color facsimile signal encoding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently encoding color facsimile signals for three colors such as red, black, and white.

As a method for efficiently encoding black-and-white binary facsimile IJ■l, there is a laser-length type redundancy suppression encoding method that focuses on the continuous length of white and black (hereinafter referred to as run length), and also a two-dimensional correlation method. A two-dimensional sequential redundancy reduction coding method that has been actively utilized is well known.

As for the encoding method for originals containing color, a method of separating color television signals into chromaticity components and luminance components and encoding them with high efficiency can be applied.

In addition to manuscripts containing such multicolored or natural colors, in recent years, office documents such as red ruled lines, which can be seen on slips, corrections written in vermilion, and red stamps, etc., have been created using three colors of red, black, and white. There is an increasing demand for technology for encoding manuscripts simply and efficiently. Below, regarding the three colors handled in this invention,
For example, assume that each red, black, and white luminance level is quantized to only one level without intermediate levels. In order to realize such a three-color encoder,
By adding an encoder that suppresses the redundancy of the red run length in addition to the normal black and white binary redundancy suppression encoder,
It is conceivable to configure a color encoder.

However, this method requires a redundancy suppression encoder for red signals, which has the disadvantage of complicating the device configuration. However, when encoding a facsimile signal for documents containing three colors, there is a possibility that it can be encoded using a simpler method than the one described above. (The same applies to the case of

This invention was made in consideration of the above points, and is intended for documents containing three colors such as red, black, and white, and adds some functions to the existing black and white binary facsimile signal redundancy suppression encoder. The purpose of the present invention is to realize an encoder (decoder) that can efficiently and easily encode facsimile signals for documents containing three colors. be.

This invention will be explained below. FIG. 1 shows a Modified Huffman code table as a typical example of redundancy suppression codes for black and white binary signals.

As shown in FIG. 1, since the white run length and the black run length have different statistical properties, two types of run length code tables are usually used. FIG. 2 is a block diagram showing an embodiment of the present invention, and the explanation will be given by taking as an example the case where the first color is white, the second color is black, and the third color is red.

In FIG. 2, 1 is the transmitting side, 0 is the receiving side, and m is the transmission path. In addition, 1 is a transmission side interface circuit, 2 is a run length counter, 3 is a switching circuit for black run length and white run length for transmission, 4 is a code generator for bad run length, and 5 is a code generator for white run length. , 6 is a switching circuit for black run length and white run length for reception, 7 is a decoding circuit for black run length, 8 is a decoding circuit for white run length, 9
is the receiving side interface circuit. In addition, the one-dot chain twill part is an additional circuit for encoding the red signal, 10 is a red, black, and white state identification circuit for the run length that is currently being encoded, and 11 is a circuit that identifies the red, black, and white states for the run length that has already been encoded. A display circuit for displaying red, black, and white states for run length; 12 is a logic circuit for controlling the sliding door circuit 3 in accordance with the run length state of the state identification circuit 10 and display circuit 11;
3 is a red light run length flag sign detection circuit; 14;
is a logic circuit for selecting the black run length decoding circuit 7 or the white run length decoding circuit 8. The operation of this invention will be explained below with reference to FIG.

In the case of black and white binary encoding, according to the rule that white run lengths and black run lengths always appear alternately,
The switching circuit 3 switches alternately, and the code generator 4 for black run length and the code generator 5 for white run length transmit the codes corresponding to FIG. 1 corresponding to the white run length and black run length, respectively. The road plate is sent out. As shown in FIG. 1, since the statistical properties of white run length and black run length are different, it is common to use separate code tables for white run length and black run length. Furthermore, the decoder on the receiving side performs an operation opposite to the encoding described above. By the way, in the case of encoding the run length of a red light, the transmitting side 1 may send out a flag code indicating that it is a red light, and then encode and send the run length.

The flag code needs to be a code that never appears in the white and black run length codes, that is, it needs to be a unique pattern.

On the other hand, it is desirable for the flag code length to be as short as possible for high efficiency encoding.

As an example that satisfies this condition, the RLB(0) code (000110111
) is not actually used, so here we will explain the case where it is used as a flag code to indicate that it is red.

Incidentally, when encoding the run length of a red light, the overall device configuration can be extremely simplified if the existing code generators for black and white run lengths and their decoders are shared.

Therefore, in the present invention, red run-length encoding is performed using two types of run-length code tables for black and white, without using a special run-length code table for red run-lengths. When only the white run length and the black run length are encoded, the above-mentioned rule of switching alternately can be used.

However, when encoding a red run length, the decoder needs to know whether the red run length was encoded with a black run length or with a white run length, so 3 run lengths, the red, black, and white run lengths already encoded before that.
It is necessary to know which of the two states it is in. FIG. 3 shows the history state of run lengths and transmission codes.

The switching circuit 3 in FIG. 2 controls to select the code generators 4 and 5 for black run length or white run length according to the rules shown in FIG. 3. In the decoder on the receiving side 0, In order to know whether code generation was performed for black run length or white run length, it is necessary to use the difference between the black and white run lengths to identify whether the red run length was encoded. It is necessary to add 1 bit of control code.

Here, the case where the white run length code is used is “0”.
, the case where the black run length code is used is set to "1". Of course, the reverse is also possible. Therefore, as shown in Fig. 3, the code bits sent to the transmission path m are a code indicating the run length (in the case of a bad run length or a white run length), and a code indicating the run length in the case of a red run length. A flag code RLB(0) indicating that the red run length is used, a code indicating whether the red run length is used for the black run length or the white run length, and a code indicating the run length are transmitted.

Note that in the above embodiment, the code was encoded by switching alternately between white run length and black run length, but since red can be distinguished from other white and black by flag codes and control codes, black run length is not necessarily switched. Run length code generator 4
, white run length code generator 5)
You may continue to use it.

Alternatively, only one may be used. Also,
In the above embodiment, the three colors white, black, and red were described as the first, second, and third colors, but the present invention is applicable not only to the above three colors but also to encoding of any three colors. Of course it is possible.

Furthermore, the encoding method of the present invention becomes a decoding method if the order is completely reversed. That is, for the first color and the second color, the run lengths of the first color and the second color are respectively decoded,
For the third color, a flag code indicating that it is the third color is decoded, and a control code indicating whether the run length code of the first color or the second color is encoded is detected. All you have to do is decode the run length. As explained above, the color facsimile signal encoding method according to the present invention does not require the use of a special encoder/decoder for color, and only requires some additional circuitry in the redundancy suppression encoder for the first and second colors. It has the advantage of being able to be configured efficiently and simply by simply adding .

[Brief explanation of the drawing]

Figure 1 shows the code table for white and black run lengths of the modified Huffman code used for black and white, and Figure 2
The figure is a block diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing the history state of run lengths and transmission codes. In the figure, 1 is the transmitting side, the receiving side, m is the transmission path, 1 is the transmitting side interface circuit, 2 is the run length counter, 3
, 6 is a conversion circuit, 4 is a code generator for black run length, 5 is a code generator for black run length.
1 is a code generator for white run length, 7 is a decoding circuit for black run length, 8 is a decoding circuit for white run length, 9 is a receiving side interface circuit, 10 is a status identification circuit, 11 is a display circuit, 12 and 14 are logic The circuit 13 is a flag code detection circuit. FIG. 1 Termination>G Code Makeup] The code EOL represents the line equivalence code. Figure 2 Figure 3 Where: RL8 (I, RLW (1) is Mairan. The code corresponding to Hakuon's woman 11. : RLB [0) Hayashi mogo Urushibetsu mememe unique code is here. Use the sign of Mi 0, a friend of the horse world.

Claims (1)

[Claims] 1 A redundancy reduction coding method for a facsimile signal targeting three colors, a first color, a second color, and a third color, comprising means for identifying three types of colors and counting their run lengths; Two types of run length code generators are provided for encoding the run lengths for the first color and the second color. a unique flag code indicating that the signal is a third color and a run length of the third color is encoded based on a run length code generator for each of the third color signals; , a 1-bit control code indicating which run length code of the second color is encoded; and a 1-bit control code indicating which run length code of the second color is encoded; A color facsimile signal encoding method characterized by configuring a transmission code.