JPH09149261A - Image coding device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To process binary image data handled by a device such as a facsimile sequentially for each pixel.
The margins located at the left and right ends have the property of appearing at a constant cycle depending on the lateral size of the paper on the transmission side. By omitting such a part from encoding, the data compression rate is improved. SOLUTION: Binary image data from an image data input device 10 is encoded by an encoding unit 13 according to a data line. The encoding control unit 12 uses the binary image data of the encoding line to be encoded and the reference data memory unit 11
By comparing the corresponding pixel with the binary image data of the reference line one line before, which is held in, the pixel position on the coding line where the coding is started in the coding unit 13 and the coding is ended. The pixel position is determined and the encoding unit 1
3 is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image encoding / decoding device, and more particularly to encoding / decoding of binary image data applicable to a communication device such as a facsimile which handles binary image data. The present invention relates to a device for converting the information.

[0002]

2. Description of the Related Art Conventionally, in an image coding apparatus which performs reversible coding on a binary image, it is generally considered that an entropy coding unit including an entropy calculation unit and an entropy coding unit rarely occur. It is composed of exceptional processing means corresponding to data input. Among these means, as the latter example, when the binary image data of the row in which the pixel to be encoded is present and the binary image data of the row immediately above are compared and they are all the same, There is a method in which a flag indicating that is included in a part of the encoded data, and entropy encoding is omitted for that row.

[0003]

Although the above-mentioned conventional method can be applied to binary image data as an object, a device such as a facsimile is used as a binary image data encoding device. can give. Binary image data handled by a facsimile may include a large amount of blank space. Since this margin is not limited to the case where all the data is the same on a line-by-line basis, the conventional method described above is not sufficient. The present invention has been made in view of such a conventional situation, and the image data
In the case of sequential processing for each pixel (unlike the conventional case where all data is the same in row units), the margins located at the left and right ends are:
It has the property of appearing in a substantially constant cycle depending on the lateral size of the paper used on the sending side as the original carrying the image to be sent. The object is to improve the data compression rate by omitting it.

[0004]

According to a first aspect of the present invention, input means for inputting line data of a binary image to be encoded, and binary image data from the input means are encoded according to the data line. An image coding apparatus having a coding means for controlling the coding means and a coding control means for controlling the operation of the coding means is provided with a reference data memory means for holding binary image data of a reference line, and the coding control. The means is 2 of the coding line which is to be coded.
By comparing the value image data with the binary image data of the reference line held in the reference data memory means, the pixel position and the coding on the coding line for starting the coding in the coding means are determined. The position of the pixel to be ended is determined, the encoding means is controlled, and the start and end of the encoding are specified for each pixel on the encoded line by comparison with the binary image data of the reference line. The omission of coding can be applied to various images.

According to a second aspect of the present invention, in the above-mentioned first aspect, the binary image data held in the reference data memory means is data of a line immediately before a coding line to be coded. And can function in practice.

According to a third aspect of the present invention, in the first or second aspect, the binary image of the coded line and the reference line of the binary image are used.
To compare the data of the value images, the values of the corresponding pixels in each line are sequentially compared, and the pixel position where the pixel first becomes a different value and the pixel position where the pixel finally becomes a different value are detected by this comparison. By doing so, the start and end positions of the encoding are determined, and a method of comparing the data to be encoded with the reference data is specifically presented.

According to a fourth aspect of the present invention, in the above-described third aspect, the encoding control means determines the pixel position on the encoding line at which the encoding is started and the pixel position at which the encoding is terminated by the previous code. The pixel position at which the encoding is started and the encoding start pixel position detected at this time are compared, and the pixel position at the front on the line obtained by this comparison is set as the pixel position at which the new encoding is started, and the previous code is set. The pixel position at which the encoding is ended and the encoding end pixel position detected at this time are compared, and the pixel position at a later position obtained by this comparison is set as the pixel position at which a new encoding is ended, and the code is erroneously encoded. This is to avoid omission of conversion.

The invention of claim 5 relates to any one of claims 1 to 4 above.
In any one of the above, the encoding means adds 1-bit data indicating that the encoding start position or the encoding end position has changed to the beginning of the encoded line data obtained after encoding, When the encoding start position or the encoding end position changes, the values of the encoding start position and the encoding end position are encoded into data of a predetermined bit width, and the above 1
Bits are added after the bit to generate the encoded line data that is configured by encoding the binary image data between the encoding start position and the encoding end position, and the configuration of the encoded line data is used for encoding control. The data structure is such that the data of is also included.

According to a sixth aspect of the invention, means for inputting coded line data to be decoded, decoding means for decoding coded line data from the input means according to the data line, and the decoding In an image decoding apparatus having a decoding control means for controlling the means, a reference data memory means for holding binary image data of a reference line is provided, and the decoding control means is provided from the beginning of the encoded line data. After detecting the data indicating that the coding start position or the coding end position has changed,
The data of the pixel position where the encoding is started and the pixel position where the encoding is ended are detected and stored, and the data before the encoding start position and after the encoding end position are stored based on the stored data. Read out from the corresponding pixel data on the line in the reference data memory means, and further control to decode the encoded line data between the encoding start position and the encoding end position into binary image data. In addition, the decoding device is adapted to the structure of the coded line data according to the fifth aspect.

According to a seventh aspect of the present invention, in the above-mentioned sixth aspect, the binary image data held in the reference data memory means is used as data of a line immediately before a coded line to be decoded. And can function in practice.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an image coding apparatus of the present invention, and is a block diagram showing an overall outline. This image encoding device includes an image data input device 10, a reference memory unit 11, and an encoding control unit 1.
2, the encoding unit 13, and the encoded data output device 14. First, the image to be encoded is input to the image data input device 10 by an image reading device (not shown) such as a scanner. Then, after being binarized by the image data input device 10, it is sequentially output as binary image data (a). This 2
The value image data (a) is a FIFO (First-In First-Ou).
It is input to the reference memory unit 11 composed of t). The reference memory unit 11 stores the data for one line of the input image data. The output side of the reference memory device 11 outputs the binary image data of the preceding row as reference data (b).

The binary image data (a) and the reference data (b) are input to the coding control unit 12. The encoding control unit 12 outputs an encoding control signal (c) including a pixel position where encoding starts and a pixel position where encoding ends. More specifically, the binary data (a) of the encoded line, which is the row including the pixel to be encoded, and the binary image data (b) of the reference line are compared. Both data are compared in order on a pixel-by-pixel basis, first the positions where the two pixel data differ are detected, and finally the different positions are detected and output as the encoding control signal (c). The creation of the coding control signal (c) will be described in more detail below (the description relating to FIG. 4). Then, the encoding unit 13 holds the encoding start position that has been used until then, and compares it with the encoding start position in the control signal (c) newly input from the encoding control unit 12. If the detected pixel position is before the encoding start position up to that point, this is set as a new encoding start position. The same is done for the coding end position, and if the detected pixel position is after the previous coding end position, this is set as a new coding end position.

Then, the binary image data between the coding start position and the coding end position is coded. 2 and 3
Indicates the format of encoded data obtained in this way. The first 1 bit of the encoded data shown here is a flag indicating whether or not the pixel position at which encoding starts or ends has changed as compared with the row immediately above. FIG. 2 shows a case where the pixel position at which the coding starts or ends does not change. On the other hand, FIG. 3 shows a case where the pixel position at which the encoding starts or ends changes, and in that case, data indicating the encoding start position and the encoding end position is added following the flag. . The encoded data (d) thus generated is output to the partner terminal by the encoded data output device 14 of FIG.

FIG. 4 is a more detailed block diagram of the encoding unit and the encoding control unit in FIG. FIG.
In the encoding control unit 12 (see FIG. 1), the counter circuit 12a, the comparator 12b, and the range designation register 12c.
It is composed of The binary image data (a) is encoded by the encoding unit 1.
At the same time, the signal is input to the counter circuit 12a and the comparator 12b. The reference data (b) from the reference memory unit 11 is input to the comparator 12b. The counter circuit 12a counts the number of pixels of the input binary image data (a) sequentially input according to the line, and outputs the count value (c). The comparator 12b compares the binary image data (a) with the binary data for each pixel of the reference data (b) and outputs a signal (d) indicating a match / mismatch. The range specifying register 12c inputs the counter value (c) and the coincidence / non-coincidence signal (d), and the counter value when the non-coincidence signal (d) is first input as described above is set to the encoding start position. These are output as the data (c ₁ ), and the counter value at the time when the mismatch signal (d) is finally input as the encoding end position (c ₂ ). The encoding unit 13
Encoding is performed using the position data (c ₁ , c ₂ ) of the start and end of encoding, and the encoded data (g) is output.

FIG. 5 shows an embodiment of the image decoding apparatus of the present invention, and is a block diagram showing an overall outline. In FIG. 5, the encoded data input device 15 outputs the received data from the partner terminal as encoded data (e). Here, the encoded data has the data structure shown in the above-described embodiment of the present invention, and the following decoding device is applied to this data structure. Then, the decoding unit 16 first detects, from the input coded data (e), a flag indicating that the coding start position or the coding end position has changed, from the beginning of the coded data. Then, when the coding start position or the coding end position changes, the coding start position and the coding start position are determined from the coding start and end data (see FIG. 4) in the coding line of the coded data. The value at the end position is separated and output as a control signal (g).
The reference memory unit 18 holds the already decoded binary image data of the previous line. Then, using the reference data (i) from the reference memory unit 18,
For the binary image data before the encoding start position, this reference data (i) is reproduced. Also, the decoding unit 1 decodes the binary image data between the coding start position and the coding end position.
Decrypt at 6. Furthermore, the binary image data after the coding end position is reproduced by reproducing the reference data (i) in the same manner as described above. And the decoded 2 of the whole line
The value image data (f) will be output.

Binary image data (f) and control signal (g) are input to the decoding control section 17. Then, the control signal (h) for controlling the reference memory unit 18 is output. The already-obtained binary image data (f) of the entire one line is input to the reference memory unit 18. Then, the binary image data on one line currently being decoded is output as reference data (i). The image data output device 19 to which the binary image data (f) is input prints the binary image data.

FIG. 6 is a more detailed block diagram of the decoding unit reference memory unit and the decoding control unit in FIG. The decoding control unit 17 (see FIG. 5) includes a counter circuit 17a and a range specifying register 17b. The encoded data (e) is input to the decoding unit 16. The decoding unit 16 outputs the binary image data (f), the coding start position and the coding end position data (g). The decoded binary image data (f) is input to the counter circuit 17a and the reference memory unit 18.

The counter circuit 17a counts the number of pixels of the input binary image data (a) sequentially input according to the line and outputs a count value (k). The range designation register 17b receives the count value (k), the coding start position and the coding end position (g) as input, and the reference memory unit 18
A control signal (h) that specifies the range of the reference binary image data read from, that is, the range of data before the coding start position and the range of data after the coding end position is output. The reference memory unit 18 decodes the binary image data (i) in the range designated by the reference control signal (h) into the decoding unit 16.
Output to

[0019]

According to the present invention, encoding and decoding can be omitted for various binary images by designating the start and end of encoding and decoding in units of pixels on an encoding line. It is possible to adaptively improve the data compression rate and reduce the processing load. For example, when processing an image handled by a device such as a facsimile, the size of the paper used on the transmission side as the original for carrying the image to be transmitted varies, and therefore the paper is placed on the left and right of the margin. However, the present invention can be applied to such a blank portion and the effect can be further improved.

[Brief description of the drawings]

FIG. 1 shows an embodiment of an image coding apparatus of the present invention, and is a block diagram showing an overall outline.

FIG. 2 is a diagram showing a format of encoded data and showing a case where a pixel position at which encoding starts or ends does not change.

FIG. 3 is a diagram showing a format of encoded data and showing a case where a pixel position at which encoding starts or ends changes.

FIG. 4 is a more detailed block diagram of an encoding unit and an encoding control unit in FIG.

FIG. 5 shows an embodiment of an image decoding apparatus of the present invention, and is a block diagram showing an overall outline.

6 is a more detailed block diagram of a decoding unit reference memory unit and a decoding control unit in FIG.

[Explanation of symbols]

10 ... Image data input device, 11, 18 ... Reference memory unit, 12 ... Encoding control unit, 12a, 17a ... Counter circuit, 12b ... Comparator, 12c, 17b ... Range designation register, 13 ... Encoding unit, 14 ... Encoded data output device,
15 ... Encoded data input device, 16 ... Decoding unit, 17 ...
Decoding control unit.

Claims (7)

[Claims] 1. Input means for inputting line data of a binary image to be encoded, encoding means for encoding the binary image data from the input means according to the data line, and the encoding means of the encoding means. An image encoding apparatus having an encoding control unit for controlling an operation includes a reference data memory unit for holding binary image data of a reference line, and the encoding control unit is an encoding line to be encoded. Of the binary image data of the reference line held in the reference data memory means, and the pixel position and code on the coding line for starting the coding in the coding means. An image coding apparatus characterized in that a pixel position at which the coding is finished is determined and the coding means is controlled. 2. The binary image data held in the reference data memory means is used as data of a line immediately before a coding line to be coded. Image encoding device. 3. The data of the binary image of the coded line and the data of the binary image of the reference line are compared with each other by sequentially comparing the values of the corresponding pixels of each line, and by this comparison, the pixels have different values for the first time. The image code according to claim 1 or 2, wherein the start position and the end position of the encoding are determined by detecting a pixel position and a pixel position where the pixel finally has a different value. Device. 4. The encoding control means is now detected that the determination of the pixel position on the encoding line where the encoding starts and the pixel position where the encoding ends is the pixel position for starting the previous encoding. The pixel position on the line obtained by this comparison is compared with the encoding start pixel position, and the pixel position to start a new encoding is set, and the pixel position to end the previous encoding is detected this time. 4. The image coding apparatus according to claim 3, wherein the pixel position after the coding is compared with the pixel position at the rear of the pixel position obtained by this comparison. . 5. The encoding means adds 1-bit data indicating that the encoding start position or the encoding end position has changed to the beginning of the encoded line data obtained after encoding, and the encoding code When the encoding start position or the encoding end position changes, the values of the encoding start position and the encoding end position are encoded into data of a predetermined bit width and added following the 1 bit, and further, the encoding start position. 5. The image coding apparatus according to claim 1, wherein the coded line data formed by coding the binary image data between the coding position and the coding end position is generated. 6. A means for inputting coded line data to be decoded, a decoding means for decoding the coded line data from the input means according to the data line, and a decoding for controlling the decoding means. An image decoding apparatus having an encoding control means includes reference data memory means for holding binary image data of a reference line, and the decoding control means starts the encoding from the head of the encoded line data. After detecting the data indicating that the position or the coding end position has changed, the data of the pixel position where the coding is started and the data of the pixel position where the coding is ended are detected and stored, and based on the stored data, The data before the coding start position and after the coding end position are the corresponding pixel data on the line in the reference data memory means. The image coding apparatus is characterized in that control is performed to read the coded line data between the coding start position and the coding end position into binary image data. 7. An image coding apparatus, wherein the binary image data held in the reference data memory means is used as data of a line immediately before a coded line to be decoded. .