JPH06105155A - Luminance signal binarization device - Google Patents

Abstract

(57) [Summary] [Object] To provide a binarization device of a luminance signal capable of rapidly binarizing line data with a smaller memory capacity. [Structure] The dither table storage unit 18 stores threshold values in a matrix of 4 rows and 4 columns. The dither table address counter 16 designates a column of the dither table storage unit 18 according to the value, and the threshold value of the designated column is stored in each register 0 to 3 of the dither register 19. Then, when the reading device 10 starts reading an image and inputs the read data to the comparator 11, the comparator 11 registers 0 to 3 sequentially indicated by the value of the dither register counter 15.
The read data is binarized by comparing the read data with the threshold value stored in. When the reading device 10 finishes reading the 1-line data, the dither table address counter 16 is updated, and the four threshold values in the next column are stored in the dither register 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a luminance signal binarizing device which binarizes an input luminance signal and outputs it.

[0002]

2. Description of the Related Art Conventionally, as a device for binarizing a luminance signal forming two-dimensional image data, a device using a systematic dither method is generally known. In the binarization apparatus using this systematic dither method, a two-dimensional dither pattern having threshold values set in a matrix is stored.
Then, the brightness data of the image area corresponding to the dither pattern is read, the brightness data of the read image area is compared with the corresponding threshold value of the dither pattern, and the brightness data is binarized according to the comparison result. Is.

[0003]

However, in such a conventional binarization apparatus using the systematic dither method, the threshold value set by the two-dimensional dither pattern and the image area corresponding to the threshold value are set. Since binarization is performed according to the comparison result with the luminance data of, in order to perform binarization,
The existence of two-dimensional luminance data is indispensable. Therefore, not only a memory for storing a two-dimensional dither pattern but also a memory for storing corresponding two-dimensional luminance data is required, and a large memory capacity is required for the entire device. Further, since the binarization is performed for each image area, the processing time required for binarizing the line data for one scan over a plurality of image areas becomes long, and the line data can be rapidly binarized. It wasn't something.

The present invention has been made in view of such conventional problems, and has a smaller memory capacity.
It is an object of the present invention to provide a luminance signal binarizing device capable of rapidly binarizing line data.

[0005]

In order to solve the above problems, according to the present invention, a brightness signal input means for sequentially inputting a brightness signal of a scanning line and a brightness signal sequentially input by the brightness signal input means. Line detecting means for detecting the scanning line of the two-dimensional dither pattern, a dither pattern storing means for storing the threshold of the two-dimensional dither pattern, and a threshold of the two-dimensional dither pattern corresponding to the scanning line detected by the line detecting means. Based on the threshold designating means designated in the pattern storing means and the threshold of the two-dimensional dither pattern designated by the threshold designating means, the binarizing means for sequentially binarizing the luminance signal input from the luminance signal inputting means. And have.

Alternatively, threshold value storage means for reading out and storing the threshold value of the two-dimensional dither pattern corresponding to the scanning line detected by the line detection means from the dither pattern storage means, and the two values stored in the threshold value storage means.
And a binarization unit for sequentially binarizing the luminance signal input by the luminance signal input unit based on the threshold value of the dimensional dither pattern.

[0007]

In the above structure, when the brightness signals of the scanning lines are sequentially input from the brightness signal inputting means, the line detecting means detects the scanning lines of the sequentially input brightness signals. Then, the threshold value designating means designates the threshold value of the two-dimensional dither pattern corresponding to the scanning line detected by the line detecting means in the dither pattern storing means, and the binarizing means designates the 2 value specified by the threshold value designating means. The luminance signal is sequentially binarized based on the threshold value of the dimensional dither pattern. Therefore, the luminance signal of the scanning line input from the luminance signal input means is sequentially binarized based on the threshold value of the two-dimensional dither pattern corresponding to the scanning line, and the binarization of the luminance signal of the scanning line is completed. Then, when the luminance signal of the next scanning line is input from the luminance signal input means, the luminance signal is binarized based on the threshold value of the two-dimensional dither pattern corresponding to this scanning line. In this way, the luminance signal of each scanning line is sequentially binarized on the basis of the threshold value of the two-dimensional dither pattern corresponding to each scanning line, whereby the luminance signal of the scanning lines constituting one screen is binarized. Is completed.

Incidentally, even in the structure provided with the threshold value storage means for reading out the threshold value of the two-dimensional dither pattern corresponding to the scanning line detected by the line detection means from the dither pattern storage means, the same operation is performed. The luminance signal of each scanning line is sequentially binarized by the threshold value of the two-dimensional dither pattern stored in the threshold value storage means.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. That is, FIG. 1 is a block diagram showing the overall configuration of the present embodiment. The reading device 10 has a lens (not shown), a CCD in which elements are vertically arranged, and the like, and the CCD moves horizontally. By doing so, the image for one screen is read. That is, the reading apparatus 10 in this embodiment uses the scanning line in the vertical direction of the image, reads the luminance of the scanning line by the elements arranged in the vertical direction, inputs the read data to the comparator 11, and scans one scanning line. After inputting the read data of (1), it is moved in the horizontal direction by one line step, and the brightness is read in the next vertical scanning line. Further, the reading operation and the horizontal movement timing of the reading device 10 are controlled by the reading execution determination unit 12.

The 1-line clock generator 13 outputs to the 1-line INT control section 14 a clock pulse (1-line clock) having a constant period, which is slightly longer than the time required for the reading device 10 to finish reading one scanning line. To do.
The 1-line INT control unit 14 resets the dither register counter 15 in response to the input of the clock pulse, and operates the reading execution determination unit 12 to start reading of one scanning line of the reading device 10. . When the reading of one scanning line of the reading device 10 is completed, the reading execution determination unit 12 detects this and outputs a signal to the dither table address counter 16 and the dither register writing control unit 17.

On the other hand, the dither table storage section 18 has a storage area consisting of a matrix of 4 rows and 4 columns from addresses 00 to 33, and the threshold value of the dither pattern is stored as data in each storage area. The dither table address counter 16 specifies a column in the dither table storage unit 18 of 4 rows and 4 columns according to the value, and updates the value of the specified column in response to the output signal from the reading execution determination unit 12. . The dither register write control unit 17 reads out four data (threshold values) stored at each address of the column designated by the dither table address counter 16 and registers each register 0 of the dither register 19.
Store in ~ 3.

On the other hand, a basic clock is input from the basic clock generator 20 to the read execution determination unit 12, the dither register counter 15 and the dither register write control unit 17. The basic clock is a clock that determines the timing of binarizing the read data (luminance signal) of the image input from the reading device 10. Then, the reading execution determination unit 12
Instructs the reading device 10 to read one pixel in synchronization with the output timing of the basic clock. Therefore, the reading data of one pixel is input from the reading device 10 to the comparator 11 at the same timing. .

The dither register counter 15 updates the value in response to the basic clock and repeatedly designates the registers 0 to 3 provided in the dither register 19 by the value. Then, the comparator 11 compares the threshold value stored in the registers 0 to 3 designated by the dither register counter 15 with the read data for one pixel input from the reading device 10 at the timing, Binarized data is output according to the comparison result.

Next, the operation of this embodiment having the above configuration will be described with reference to the flow chart shown in FIG. 2 and the timing chart shown in FIG. That is, when a 1-line clock is output from the 1-line clock generator 13, the 1-line INT control unit 14 resets the dither register counter 15 in response to this (S
1). As a result, the value of the dither register counter 15 becomes "0", and the threshold value previously stored in the register 0 of the dither register 19 is designated at the timing of the basic clock as shown in FIG.

Further, the 1-line INT control unit 14 synchronizes with the output of the 1-line clock, and the reading execution judging unit 1
2 to send the signal to the reading execution determining unit 12
Instruct 0 to start reading the image. Then, the comparator 11 synchronizes with the basic clock, and the threshold value stored in the registers 0 to 3 corresponding to the value of the dither register counter 15 and the read data (luminance signal) for one pixel input from the reading device 10. ) Are compared with each other, the read data is converted into a black digital image signal if the read data is equal to or more than the threshold value, and is converted to a white digital image signal if the read data is less than the threshold value.
2).

Further, the reading execution judgment unit 12 is provided in the reading device 1.
From the control situation for 0, it is judged whether or not the reading device 10 has finished reading the one line data which is the luminance signal for one scanning line (S3), and if it is not finished, the dither register counter The value 15 is updated at the timing of the next basic clock (S4). Therefore, in the same manner as described above, the comparator 11 stores the threshold values of the registers 0 to 3 designated by the updated value of the dither register counter 15 and the read data for one pixel input at the same basic clock timing. It compares and outputs the binarized data. That is, the loop of S2 to S4 is repeated until the reading of the 1-line data is completed, so that the dither register counter value (the value of the dither register counter 15) becomes 0 by the timing of the basic clock as shown in FIG. → 1 → 2 → 3 → 0 ... The luminance signal is sequentially binarized by the dither values stored in the registers 0 to 3 of the dither register 19 designated by the dither register counter value. Is output.

When the binarization of the 1-line data is completed by the completion of the reading of the 1-line data, the read-execution judging section 12 outputs a signal to the dither table address counter 16 and then writes the dither register. The signal is output to the control unit 17. As a result, the dither table address counter 16 is updated (S5), and the value of the dither table address counter 16 indicates the next column in the dither table storage unit 18 after the column that has been displayed so far. Then, the dither table write control unit 17 reads out the four data in the column indicated by the dither table address counter 16 from the dither table storage unit 18,
The read four pieces of data are written in the registers 0 to 3 of the dither register 19 to update the dither register 19 (S6). Therefore, at the time when the flow shown in FIG. 2 becomes END, each of the registers 0 to 3 of the dither register 19 stores four threshold values to be used for binarizing the next 1-line data. There is.

Therefore, when the next 1-line clock is output from the 1-line clock generator 20 and the operation according to the flowchart of FIG. Binarization of 1-line data is executed using the four threshold values stored in the column. That is, when binarizing, one column of the threshold values of 4 rows and 4 columns stored in the dither table storage unit 18 is sequentially stored in the dither register 19 for each line data, and this 1 column is configured. The one-line data is binarized using the threshold value. Then, by using the sequentially binarized 1-line data, for example, by driving a thermal head, the image forming one screen is thermally transferred line by line to the thermal paper.

[0019]

As described above, the present invention designates or stores the threshold value of the two-dimensional dither pattern corresponding to the scan line among the threshold values of the two-dimensional dither pattern stored in the dither pattern storage means, Based on the designated or stored threshold value of the two-dimensional dither pattern, the input luminance signal of the scanning line is sequentially binarized. Therefore, it is possible to generate a two-dimensional luminance signal without generating the two-dimensional luminance data and storing it in the memory as in the conventional case.
It can be binarized and can be binarized with a small memory capacity. In addition, since the luminance signal is sequentially binarized for each scanning line without performing binarization for each image area, line data for one scan over a plurality of image areas can be binarized quickly. You can Further, since the luminance signal is binarized by using the threshold value having a different dither pattern for each scanning line, the gradation characteristic of the entire image can be precisely controlled.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flow chart showing the operation of the embodiment.

FIG. 3 is a timing chart showing the operation of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Reading device 11 Comparator 12 Reading execution determination unit 13 1 line clock generation unit 14 1 line INT control unit 15 Dither register counter 16 Dither table address counter 17 Dither register write control unit 18 Dither table storage unit 19 Dither register

Claims (2)

[Claims] 1. A luminance signal input means for sequentially inputting luminance signals of scanning lines, a line detecting means for detecting scanning lines of luminance signals sequentially inputted by the luminance signal input means, and a threshold for a two-dimensional dither pattern. A stored dither pattern storing means, a threshold designating means for designating a threshold of a two-dimensional dither pattern corresponding to the scanning line detected by the line detecting means in the dither pattern storing means, and a threshold designating means. And a binarizing means for sequentially binarizing the luminance signal input from the luminance signal inputting means on the basis of the threshold value of the two-dimensional dither pattern. 2. A brightness signal input means for sequentially inputting a brightness signal, a line detection means for detecting a scanning line of the brightness signal input by the brightness signal input means, and a threshold value of a two-dimensional dither pattern. Dither pattern storage means, threshold storage means for reading the threshold of the two-dimensional dither pattern corresponding to the scanning line detected by the line detection means from the dither pattern storage means, and storing the threshold, and the threshold storage means stored in the threshold storage means. A binarizing unit for binarizing the luminance signal sequentially input from the luminance signal inputting unit on the basis of a threshold value of a two-dimensional dither pattern.