JPH0330329B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an encoding circuit, and particularly to an encoding circuit that encodes an image signal using a two-dimensional encoding method used for facsimile, electronic files, etc. .

(Prior art) Conventionally, for the purpose of speeding up facsimile communication or efficiently storing data in electronic files,
Image signals obtained by photoelectrically converting document information are compressed by encoding and then transmitted or stored. In such image data encoding methods, for example, CCITT
As specified in Recommendation T.6 for group 4, facsimile equipment encoding, two-dimensional encoding systems are often used. In this two-dimensional encoding method, the coded pixel on the coding line (coding line) is either the reference pixel on the reference line (reference line) that is the line immediately before the coding line (coding line) This is a method of encoding based on the location of the object. This method is based on the CCITT Group 4 T.6 based on the relationship between the change point positions on the reference line and the encoded line.
According to the recommended encoding procedure, it is determined and encoded into path mode, vertical mode, and horizontal mode. The encoding procedure first detects whether it is in pass mode or not, and then if it is not in pass mode, the distance between the starting point of the encoding line or the next changed pixel of the reference changed pixel and the first changed pixel of the reference line is 3 or less. If the distance is greater than 3, it is encoded as a vertical mode, and if the distance is greater than 3, it is encoded as a horizontal mode. FIG. 2 shows an example of the horizontal mode. In the same figure, the starting pixel of the encoded line is the line address “1”.
This can be determined as horizontal mode because the distance between the next changing point pixel a ₁ located before the encoding line and changing point pixel _{b 1 of} the reference line of the same color is greater than 3. .

FIG. 3 is a block diagram showing the configuration of a conventional encoding circuit using a two-dimensional encoding method. In the figure, 1 is an input terminal for inputting an image signal that has been binarized and sampled for each pixel, 2 is a buffer memory that stores the image signal for each line, and 3 is a buffer memory 2 that outputs the image signal of the reference line. A reference line output line, 4 is an encoding line output line of the buffer memory 2 that outputs the image signal of the encoded line, and 5 is a change point for detecting a change point pixel of the image signal read out from the buffer memory 2 via the output lines 3 and 4. A point detection circuit 6 selects pass mode, horizontal mode, vertical mode, etc. based on the output signal of the change point detection circuit 5 and black and white run length count values of a white run length counting circuit and a black run length counting circuit, which will be described later. A control circuit that determines the encoding mode and controls the entire encoding circuit; 7 is an encoding mode setting circuit that sets each of the above modes based on the encoding mode determination of the control circuit 6; 8 is a control circuit from the control circuit 6; a white run length counting circuit that counts and holds the white run length of
9 is a black run length counting circuit that counts and holds the black run length from the control circuit 6; 10 is a black run length counting circuit that counts and holds the black run length from the control circuit 6; A code generation circuit 11 generates a code, and 11 is an output terminal that outputs an encoded signal from the code generation circuit 10.

Next, the operation will be explained using FIGS. 2 and 3. First, an image signal is sent from an input terminal 1 to a buffer memory 2, and the image signal is accumulated line by line in the buffer memory 2. The image signal of the reference line and the image signal of the encoded line are simultaneously read out from the buffer memory 2 via the reference line output line 3 and the encoded line output line 4, and the change point detection circuit 5 detects the color (i.e., Detects the location of a change point pixel that changes (black or white). In the case of FIG. 2, the change point detection circuit sequentially reads the reference line and the encoded line from the buffer memory while detecting the change point pixel from the land address "1".

Next, the pass mode, vertical mode, and horizontal mode are set based on the determination of the control circuit 6 based on the output signal of the change point detection circuit 5. The horizontal mode encoding method indicates horizontal mode. By following the code “001” and the length encoded from the starting point or reference pixel of the encoding line to the next change point pixel, and from that change point pixel to the next change point pixel, expressed. In this case, not only the length is encoded, but the code also differs depending on the color. In the case of Figure 2, the starting pixel is before the line address "1" on the encoding line, and the change point pixel _a1 is detected by the change point detection circuit at the line address "4", and the detection result is It is sent to the white run length counting circuit 8 via the control circuit 6. The white run length circuit 8 counts the length of white color (white run length) from the starting pixel to the change point pixel _a1 . Next, after detecting the change point pixel a ₁ , the next change point pixel a ₂ is detected at the run length "6" by the change point detection circuit 5, and the detection result is sent to the black run length via the control circuit 6. Sent to the counting circuit. The black run length counting circuit 9 counts the length of black color (black run length) from the change point pixel _a1 to the change point pixel _a2 . On the other hand, regarding the encoding mode settings, when the first change point pixel a ₁ is detected, there is no change point pixel on the reference line to the left of change point pixel a ₁ , so the horizontal mode other than the pass mode is set to the vertical mode. The control circuit 6 determines which one is the case. Next, when the line address is "8", the change point pixel b ₁ of the reference line is detected by the change point detection circuit 5, and the control circuit 6 detects that the distance between the change point pixel a ₁ and the change point pixel b ₁ is 3. Because of the above, it is determined that the mode is horizontal. When the control circuit 6 determines that the mode is the horizontal mode, the encoding mode setting circuit 7 outputs a signal indicating the horizontal mode, the white run length counting circuit 8 and the black run length counting circuit 9.
The length of white color is “3” and the length of black color is “2”.
This signal is sent to the code generation circuit 10. Encoding generation circuit 0 performs encoding according to CCITT Group 4 T.6 recommendation. In the case of Figure 2, the horizontal mode is "001" and the length of white is "3", so next is "1000", and then the length of black is "2", so "11" continues, so , is encoded as “001100011”. The code created by the code creation circuit 10 is outputted from the output terminal 11 as a coded signal.

(Problems to be Solved by the Invention) However, in the configuration of the encoding circuit, in order to count and hold the white run length and the black run length, respectively, in horizontal mode encoding, the white run length counting circuit 8 and the black run length are Two run-length counting circuits, the run-length counting circuit 9, are required, and there is a problem in that the circuit size becomes large and complicated.

The present invention aims to solve the above problems and provide a simplified encoding circuit.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides an encoding circuit that encodes an image signal using a two-dimensional encoding method, in which an image signal is sequentially sampled and binarized. a change point detection means for sequentially reading out an encoded row and a reference row which is the immediately preceding row of the encoded row from the encoded signal and detecting a pixel whose value changes; a determining means for selecting and determining one of three encoding modes: mode, vertical mode, and horizontal mode, and counting and outputting the first run length from the determining means, and counting and outputting the next run length. a single run-length counting means for holding a run-length count, a run-length holding means for holding a run-length count output from the run-length counting means, and a code for encoding based on an encoding mode instructed by the determining means. and generating means, and when the determining means determines that the mode is pass mode or vertical mode, the encoding code is sequentially output from the determining means via the code generating means, and when the mode is determined as horizontal mode, the encoded code is generated. After outputting an encoded code indicating the horizontal mode from the means, the information of the run length holding means and the information of the run length counting means are sent to the code creation means via the run length holding means, and a run length code is generated. It is characterized by sequential encoding.

(Operation) According to the present invention, since the encoding circuit is configured as described above, the technical means operates as follows.
The detection means works to sequentially read the encoded row and the reference row to detect changed pixels, and the determination means determines the encoding mode such as pass mode, vertical mode, horizontal mode, etc. based on the detection result of the detection means. work like that. The counting means counts and outputs the first run length (for example, white run length) input from the discrimination means, and counts and holds the next input run length (for example, black run length). The holding means serves to hold the run length (eg white run length) from the counting means. The encoding means encodes based on the encoding mode given by the determining means, and in the case of horizontal mode, first encodes the run length (i.e., white run length) input from the holding means, and then encodes the run length input from the holding means, and then encodes the run length input from the holding means. It serves to encode run lengths (ie black run lengths) inputted from the storage unit through the holding means. Therefore, by providing a simple holding means after one counting means, run lengths can be counted and held, thereby solving the problems of the prior art.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of an encoding circuit according to the present invention. In this figure, the same reference numerals as in FIG. 3 indicate the same components.
12 determines the encoding mode such as pass mode, horizontal mode, vertical mode, etc. based on the output signal of the change point detection circuit 5 and the counted values of black and white run lengths of a run length circuit 13 and a latch circuit 14, which will be described later. 13 is a run length counting circuit that counts the white and black run lengths from the control circuit 12; 14 holds the white and black run lengths input from the run length counting circuit 13; A latch circuit 15 is a code creation circuit that creates a code based on the output signals of the encoding mode setting circuit 7 and the latch circuit 14.

Next, the operation shown in FIG. 1 will be explained. Control circuit 12
When it is determined that the mode is the pass mode or vertical mode, the mode of the encoding mode setting circuit 7 is set, and encoded codes are sequentially output from the control circuit 12 via the code generating circuit 15. In the horizontal mode, it is necessary to count and maintain the white run length and black run length as described above. Therefore, control circuit 1
The white run length inputted from 2 is counted by a run length counting circuit 13, and after counting is completed, the white run length is inputted to a latch circuit 14. The latch circuit 14 holds the white run length. Next, the black run length output from the control circuit 12 is counted and held by a run length counting circuit 13. When the control circuit 12 determines the horizontal mode, the encoding mode setting circuit 7 outputs a signal indicating the horizontal mode to the code generating circuit 15. Further, the white run length held in the latch circuit 14 is sent to the code creation circuit 15, and further,
The black run length held in the run length counting circuit 13 is sent to the code generation circuit 15 via the latch circuit 14. The code generation circuit 15 sequentially encodes these inputs and outputs them from the output terminal 11.

As described above, according to this embodiment, by providing the simple latch circuit 14 after the run-length counting circuit 13, only one run-length counting circuit is required compared to the conventional two. This makes it possible to simplify the circuit and reduce its scale.
It is also economical.

(Effects of the Invention) As explained above, according to the present invention, an economical encoding circuit can be provided with a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an encoding circuit according to the present invention, FIG. 2 is a diagram showing an example of a horizontal mode, and FIG. 3 is a block diagram showing a conventional encoding circuit. 1...Input terminal, 2...Buffer memory, 3...
... Reference line output line, 4 ... Encoding line output line, 5 ... Change point detection circuit, 7 ... Encoding mode setting circuit, 11 ... Output terminal, 12 ... Control circuit, 13 ... Run length counting Circuit, 14... Latch circuit, 15... Code creation circuit.

Claims (1)

[Scope of Claims] 1. In an encoding circuit that encodes an image signal using a two-dimensional encoding method, the image signal is sequentially sampled and binarized, and the encoded row and the immediately preceding row of the encoded row are A changing point detecting means for sequentially reading out a certain reference row and detecting a changed pixel whose value changes; a single run length counting means that counts and outputs the first run length from the determination means, and counts and holds the next run length; a run-length holding means for holding a count output of the run length from the counting means; and a code creation means for coding based on the encoding mode instructed by the judging means, and the judging means is a pass mode, a vertical When it is determined that the mode is the horizontal mode, the determination means sequentially outputs encoded codes via the code generation means, and when it is determined that the mode is the horizontal mode, the code generation means outputs an encoded code indicating the horizontal mode, and then the An encoding circuit characterized in that information of a run-length holding means and information of the run-length counting means are sent to the code creation means via the run-length holding means, and a run-length code is sequentially encoded.