JPH09200539A - Method for detecting pixel change point for image data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute coding and decoding processing quickly with a simple processing configuration by using exclusive OR between image data and data obtained by shifting the image data by one bit right for change point detection data. SOLUTION: Image data d1 being a bit image and mask data d2 obtained by shifting the image data d1 by one bit right are XORed to generate change point detection data d3. Then the change point detection data d3 are referenced to detect a bit location in which an arithmetic operation result is true '1' as a change point between a pixel and a black pixel of the image data d1. Since one line is started from a white level image without fail, in the case of conversion to run length data d4, number of bits from a bit detected as a change point till a bit just before a succeeding change point is sequentially counted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a pixel change point of image data used in a facsimile apparatus, such as encoding at the time of transmitting image data or decoding at the time of reception.

[0002]

2. Description of the Related Art A facsimile apparatus encodes image data read from an original at the time of transmission to compress and transmit the image data, while at the time of reception, reproduces the original image data by decoding the compressed encoded image data. Then, it is designed to print out. Here the encoding method is
There are MH coding (one-dimensional coding system), MR coding (two-dimensional coding system), etc., and by performing data compression by these, efficient data transmission with reduced line usage time is realized. There is.

FIGS. 4A to 4C show an example of the encoding process, and show the case where the image data is MH encoded. Bit image data (binarized data) for each pixel of image data for each line (scanning line)
(Black pixel is “1”, white pixel is “0”), the continuous number of the same bit of this data is counted and converted into run length data of white run or black run, and this is determined in advance. It is converted into an MH code composed of the generated terminating code and makeup code.

In this process, when the bit image image data is converted into run length data, the number of consecutive same pixels is counted. Specifically, only the change points of white pixels and black pixels are detected. , We are trying to improve the efficiency of this process. An example of a method of detecting a pixel change point is shown in FIG.
It is shown in (c). In this figure, to detect black pixels,
Mask data (for detecting black pixels, “1111
1111 ”,“ 00000000 ”for white pixel detection) is used to perform a logical operation by exclusive OR (XOR), and the change point detection data obtained from this is referenced bit by bit, and“ 0 ”(false ) Is the color corresponding to the mask data,
"1" (true) is determined to be the color (white pixel in the figure) opposite to the color corresponding to the mask data, and the start point of the bit data of each color is set as the pixel change point.

The detection of such a pixel change point is particularly effective when special image processing is performed on the image data to be transmitted, and in the case of MR encoding, one line before is used as the reference line. Since the encoding is performed by comparing the pixel position with this line, it is also processed at the time of decoding.

[0006]

However, in the above-mentioned conventional pixel change point detection method for image data, the bit image data is referred to bit by bit, and the position at which the bit becomes different from the continuous reference bit is changed. Since it is a point, it takes a lot of time to process and it is complicated. The present invention has been proposed in view of the above circumstances, and an object of the present invention is to provide a pixel change point detection method for image data, which enables quick encoding and decoding processing with a simple processing configuration.

[0007]

SUMMARY OF THE INVENTION The present invention as set forth in claim 1 proposed to achieve the above object, comprises image data which is a bit image and data obtained by right-shifting the image data by 1 bit. An exclusive OR is generated as change point detection data, and the position of the bit for which the calculation result is true is detected as the change point between the white pixel and the black pixel of the image data in the change point detection data. As a result, it is not necessary to count the number of consecutive same bits, and the generated change point detection data can be used as it is as pixel change point data. Further, in the case of a facsimile, the image data for each line is assumed to always start from a white pixel, so the first pixel change point is the black pixel start point.

According to a second aspect of the present invention, the CPU performs arithmetic processing for generating the change point detection data and detecting the pixel change point of the image data according to the first aspect. As a result, the processing can be performed at a higher speed than in the case where the same bit counting is performed by the conventional software processing. According to the present invention of claim 3, the CPU of claim 2 refers to the change point detection data, and sequentially counts the number of bits from the bit detected as the change point to the bit immediately before the next change point. To convert the image data into run length data.
As a result, the encoding process of the image data by software becomes faster than the conventional one.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1A to 1D schematically show a pixel change point detection method of image data according to the present invention, in which image data obtained by reading and scanning an original is coded in a facsimile apparatus. It shows an example of conversion.

The image data d1 which is a bit image is
The mask data d2 obtained by right-shifting the image data d1 by 1 bit is logically operated by an exclusive OR (XOR) to generate change point detection data d3. Then, with reference to the change point detection data d3, the position of the bit for which the operation result is true “1” is detected as the change point of the white pixel and the black pixel of the image data d1.

In this figure, the image data for one line is shown from the beginning, and since one line always starts from a white pixel, the run length data d4 is (d).
The data will be as shown in. That is, when converting to run length data d4, the number of bits from the bit detected as the change point to the bit immediately before the next change point may be sequentially counted, except for the white pixels of the first few bits.

Next, FIG. 2 is a block diagram showing the internal construction of the facsimile apparatus for carrying out the method of the present invention. here,
A facsimile machine using thermal paper will be described.
In the figure, 1 is a CPU that controls the signals by connecting the following parts with an address bus AB and a data bus DB, and 2 is an NCU 2a that performs network control of outgoing and incoming calls to a telephone line L.
And a modem 2b for executing a facsimile communication procedure and transmitting and receiving image data and the like,
Reference numeral 3 denotes an image sensor 3a for reading a document image.
The image reading unit 4 including an image processing circuit 3b for performing shading correction of image data, a transmission motor 3c for feeding and discharging a transmission original, and a motor driver 3d apply heat. The thermal head 4a for printing on thermal paper, the image DRAM (4b) for temporarily storing the image data to be printed out, the image data for the image DRAM (4b), and the thermal head 4a instructing the printout. A print output unit 5 including a gate array 4c having a logic circuit, a receiving motor 4d for sending a thermal paper for printing a received image, and a motor driver 4e, and 5 is an operation including a liquid crystal display 5a and an operation panel 5b. Part, 6 is R
It is a storage unit including an OM 6a and a RAM 6b.

The CPU 1 performs arithmetic processing for generating change point detection data and detecting pixel change points of image data, which is the method of the present invention. FIG. 3 is a flowchart (steps 100 to 114) of an example of arithmetic processing performed by the CPU 1.
Is shown with. Here, the operation of taking out the image data d1 for one line from the internal buffer memory of the image processing circuit 3b and converting it to the run length data d4 is shown.

The CPU 1 has the image data d1 for each byte.
And the mask data d2 are sequentially calculated, and one line (A
In the case of 4 sizes, after the change point detection data d3 of maximum 1728 pixels (bits) is generated (step 100-
105), refer to this data one byte at a time, and if the reference data are all "0", increment the run length by 8; otherwise, reference one bit at a time,
If the referenced bit is "1", it is a pixel change point,
Count up the length of white run and black run one by one,
The run length data d4 for the line is created (steps 106 to 114). It should be noted that if the initial position is shifted to the right by one, if the change point is counted, the count value becomes the run length as it is, so that higher-speed processing becomes possible.

[0015]

As can be understood from the above description, according to the pixel change point detection method for image data according to claim 1 of the present invention, mask data for detecting a white pixel or a black pixel is previously stored. It is not necessary to prepare it, and the change point of the pixel can be easily detected by generating the mask data based on the image data which is a bit image and performing the logical operation by this. Further, since it is not necessary to detect the pixel change point by counting the number of consecutive same bits, the processing is simplified, and the encoding / decoding processing speed is increased.

According to the pixel change point detecting method of the image data described in claim 2, the CP incorporated in the facsimile device
Since the change point detection data is generated by software by U and the pixel change point of the image data is detected, the processing can be performed at high speed and easily. According to the pixel change point detecting method of the image data described in claim 3, since the image data can be converted into the run length data by the simple processing by the CPU, the encoding processing speed by the software can be increased. .

[Brief description of drawings]

1A to 1D are schematic diagrams illustrating a method for detecting a pixel change point of image data according to the present invention.

FIG. 2 is a block diagram showing an example of the internal configuration of a facsimile apparatus that carries out the method of the present invention.

FIG. 3 is a flowchart illustrating an example of the method of the present invention.

4A to 4C are schematic diagrams for explaining the encoding process.

5A to 5C are schematic diagrams illustrating a conventional pixel change point detection method for image data.

[Explanation of symbols]

d1 ... Image data (bit image) d2 ... Mask data (image data is shifted right by 1 bit) d3 ... Change point detection data d4 ... Run length data 1 ... CPU 2 ... Line control unit 3 ... Image reading unit 4 ... Print output unit 5 ... Operation unit 6 ... Storage unit

Claims (3)

[Claims] 1. An exclusive OR of image data that is a bit image and data obtained by right-shifting the image data by 1 bit is generated as change point detection data, and among the change point detection data, A method for detecting a pixel change point in image data, wherein the position of a bit for which the calculation result is true is detected as a change point between a white pixel and a black pixel in the image data. 2. The method for detecting pixel change points of image data according to claim 1, wherein the generation of the change point detection data and the detection of pixel change points of the image data are processed by a CPU. . 3. The CPU refers to the change point detection data and sequentially counts the number of bits from the bit detected as the change point to the bit immediately before the next change point to run the image data. The method for detecting pixel change points of image data according to claim 2, wherein the method is performed by converting to length data.