JPS61248663A - Color picture signal conversion system - Google Patents

Abstract

PURPOSE:To convert a color picture signal into a black and white picture information of well-balanced density by decreasing the color picture signal to accomplish the said convertion. CONSTITUTION:In an electronic file 101, four colors of Y (yellow), M (mazenda), C (cyan), and Bk (black) for purpose of subtractive mixing are stored. The Bk signal 103-1 is supplied to an OR gate 110 without being decreased. Respective picture elements of Y-signal 103-2, of M-signal 103-3, and of C-signal 103-4 are respectively thined in order to provide a density balance i.e. to make proper proportions to the black. The period of decreasing is set by selecting a prime number in order to prevent a bit-missing in the direction of subscanning or moire pattern from occurring due to the repeated decreasing. The decreased signals of Y, M and C (the output from And gates 107, 108, and 109) are synthesized by the OR gate 110 to drive the driver 111 of a laser diode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image signal conversion method for converting color image signals such as color facsimiles and color electronic files into monochrome signals.

"Summary of the Disclosure" This specification and drawings describe, for example, a method for thinning out pixels of each image information separated into multiple colors in a color image signal conversion method that converts a color image signal such as a color facsimile or a color electronic file into a black and white signal. A color image signal conversion method for converting a color image signal into a monochrome image signal is disclosed.

BACKGROUND OF THE INVENTION Currently, facsimiles have been developed for image transmission, and electronic files have been developed for storage, and these are widely used in the market. At the same time, terminal devices connected to these devices have also become widespread. However, most of these terminal devices are intended for black and white binary images. However, in recent years, it has become possible to efficiently transmit color images while maintaining high quality.
Demand for cars with memory has increased, and in response to this demand, color facsimiles and color electronic files have been actively developed. However, as mentioned above, black-and-white facsimile machines, black-and-white electronic files, and their terminals such as printers and various display devices are currently in widespread use, and compatibility between them is desired. Achieving this compatibility requires some form of signal conversion.

Problems to be Solved by the Invention] However, with this type of conventional signal conversion method, it is very difficult to convert color image information into a monochrome signal while maintaining its quality. An object of the present invention is to propose a color image information conversion method for converting color image information into density-balanced black and white image information.

Means for Solving Problem E] To explain with reference to FIG. 1, which is an embodiment when the present invention is applied to a laser beam printer, the color image signal is Y(
yellow), M (magenta), C (cyan) and BK (
Image electronic file 1 divided by color (black)
It is stored in 01. Each color pixel of Y, M, and C read out from the file 101 to the buffer memory 102 is processed by clock generators 104 to 106 and AND gates 107 to 1.
The thinning means constituted by 09 performs thinning according to the brightness of the color.

Function] Since the color image signal is converted into a black and white image signal by thinning, the color image signal can be converted into a black and white image signal while maintaining appropriate quality.

Embodiment As an embodiment of the present invention, a case will be described below in which color image information output from a color electronic file is input to a black and white binary laser beam printer (LBP).

FIG. 1 is a block diagram showing an embodiment of the present invention, and numeral 101 in the figure is a color electronic file. Electronic file lO
In order to perform subtractive color mixing, 1 contains Y (yellow), M (magenta)', 'C (cyan), and BK (black).
The four primary colors are stored so that they can be read simultaneously. The read Y, M, C, and B are stored in the buffer memory 102. □ Writing from the electronic file 101 to the buffer memory 103 and reading from the buffer memory 103 are performed using the clock CLK. The buffer memory 102 may not necessarily be necessary depending on the system configuration. That is, the image data of the electronic file 101 may be used directly. Reference numeral 103-1 is a signal line for BK, and in the embodiment of the present invention, it is directly applied to the OR gate 110 without being thinned out. Y signal 103-2,
Each pixel of the M signal 103-3 and the C signal 103-4 is thinned out so that the density balance, that is, the ratio to black is matched. Then, by selecting a prime number for the thinning period, bit loss in the sub-scanning direction due to repeated thinning,
Preventing moire patterns from occurring. Decimation for this purpose includes clock generators 104, 105, 106 and AND gates 107, 108. and 109 work together. In other words, the gate clock generator 104 for each signal uses a gate clock set in advance so that the ratio matches that of black.
,105,106,Antogame-1107,10
Enter 8,109. Y and M were thinned out by this gate clock.

The respective signals of C (outputs of AND gates 107, 108, and 109) are combined by an OR gate 110 to drive the laser driver lit.

As shown in the timing chart of FIG. 2, the gate clock generators 104, 105 . and 106. That is, among the three subtractive primary colors of color images, Y, M, and C,
In the case of the M (magenta) signal, which has the greatest effect on human visual brightness, the thinning rate is the lowest, and the time the laser diode is driven is Me L K in Figure 2, which results in a dark print. On the other hand, the thinning rate is highest for the Y (yellow) signal, which has little influence on brightness.

Next, the details and operation of the timing clock generation circuit will be explained in detail with reference to FIGS. 2 and 3.

As shown in FIG. 3, the timing clock generation circuit 10
4 to 106 are single counters 2 that count the clock CLK for reading image data from the electronic file 101;
This is realized by a ROM 220 storing gate clocks of 10, Y, M, and C. As shown in the figure, a gate clock data storage memory (ROM) 22
0 has gate clock data storage areas for the Y signal, M signal, and C signal, and the output of the counter 210 is input as a common address for these three data storage areas and is used to advance the counter 210. Each gate clock generator is read out from the ROM 220 in synchronization. The stored gate clock data has one period of thinning N as a prime number, has no periodicity with random thinning intervals, and has a well-balanced density. The read gate clock is YCLK in Figure 2.

MCLK and CCLK.

If the electronic file contains image data that has been teased using a teaser matrix such as 4 x 4.8 x 8,
The image data has periodicity of the teaser matrix size. In addition to this, the period N of the timing clock of this embodiment
If they match, it may cause missing pixels or moiré, but if you choose a number N that is as large as possible, the period will be lengthened by that amount, which will improve the quality of the reproduced image. . This is a vehicle space that can be freely determined by selecting the memory size as needed. According to the embodiments described above, even if the density of each of Y, M, and C is changed and the image is converted into a monochrome image, the quality can be maintained.

Furthermore, when determining the timing clocks for Y, M, and C, it is possible to express appropriate intermediate tones according to the hue when converting the three color combinations of Y+M, M+c, and c+y into a black and white image. Therefore, the difference in hue of the original can be reliably recognized during playback.

In this embodiment, the connection between a color electronic file and an LBP is mentioned, but the connection between a color electronic file or a color facsimile and a black-and-white terminal such as a CRT, an LBP, a thermal transfer printer, or an inkjet printer, and furthermore, a black-and-white facsimile, Connection with black and white electronic files, etc.
It is clear that the present invention can be applied to any combination.

(Effects of the Invention) As explained above, according to the present invention, each pixel signal separated into multiple colors is converted into a monochrome image signal by thinning, so a color image signal is converted into a monochrome image signal while maintaining appropriate quality. can.

Furthermore, as in the embodiment, by making the thinning rate different for each color, it is possible to obtain a black and white image signal having a density level corresponding to the hue of the color. Furthermore, by varying the thinning rate depending on the magnitude of the influence of each color on the visual brightness, it is possible to obtain a black and white image signal having the same density balance as the original brightness change.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation of the embodiment, and FIG. 3 is a block diagram showing details of a gate clock generator. Here, 101...electronic file, 103...backer memory, 103-1...BK (black) signal,
103-2...Y (yellow) signal, 103-3...
・M (magenta) signal, 103-4...C (cyan)
Signal, 104...Y signal gate clock generator, 1-
05...M signal gate clock generator, 106...
C signal gate clock generator, 210 . . . N-ary counter, 220 . . . gate clock data storage memory.

Claims (3)

[Claims] (1) A color image signal conversion method characterized by converting a color image signal into a monochrome image signal by thinning out pixels of each image information separated into a plurality of colors. (2) The color image signal conversion method according to claim 1, wherein the thinning rate is made different for the image information of each color depending on the influence of the color on visual brightness. (3) The color image conversion method according to claim 1, wherein the black and white image signal includes halftones corresponding to hues.