JPS6113261A - Color image processor - Google Patents

Abstract

PURPOSE:To reproduce an ideal black color by judging whether the noted picture element in a color image signal is intermediate color or black, making the black density data at the heighest level when said element is black and lowering the level when the picture elements before and behind said element are judged to be black. CONSTITUTION:The image signals Y, M, C are inputted to a register 2 and a black judging part 1. The data is then fed via the registers 2, 3, a data selector 11 and 1-bit registers 4-6 to an encoder 7 and a data selector 12 in synchronization with a shift clock 21. The signal is inputted as the select signal to the selector 12 when the output of the register 5 is discriminated to be black. The black signal of a high-level signal generating circuit 9 is then outputted from the selector 12. The encoder 7 outputs the signal as the black signal when the noted picture element is not judged to be black in the circuit 1. The selector 11 adopts the Y', M' and C' from the low-level signal as well when the noted picture element and the picture elements before and behind the same are outputted as black from the registers 4-6. The color reproduction of the black is thus mase sure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a color image processing apparatus, and more particularly to an image processing apparatus that takes into consideration the image characteristics of a digital color copying machine or the like.

[Prior Art] Conventional color printers output images using black and yellow (
It was expressed in three color signals: Y), magenta (M), and cyan (C). When these conventional image processing signals are output to a printer such as a copying machine, three colors of developer are placed on one spot in the printer. In many cases, the color was not completely black.

[Objective] An object of the present invention is to provide a color image processing device that eliminates these conventional drawbacks and enables ideal black color reproduction.

[Embodiment, Example] Fig. 1 is a block diagram showing an embodiment of the present invention. shift register,
7 is an encoder, 8 is a low level signal generation circuit, 8 is a high level signal generation circuit, 10 is a black data generation circuit synthesized by UCR or the like, and 11 and 12 are data selectors regarding the three primary color signals and the black signal.

As shown in FIG. 1, the pixel signals of interest, Y, M, and C, are input to a register 2 and further input to a non-judgment circuit 1, where they are determined whether they are black or an intermediate color as will be described later. is determined and input to the register 4 as a 1-bit signal. This black determination signal is shifted by a shift clock from shift clock generation circuit 21 in synchronization with the Y, M and C signals. In other words, the black determination signal and the Y, M, and C signals by the first shift clock are as follows.
It is outputted from shift registers 2 and 4, and outputted from shift registers 3 and 5 by the second shift clock. If the output of the register 5 is determined to be black at this point, this signal is input to the data selector 12 as a select signal, and the high level black signal output from the high level signal generator 8 is sent to the data selector 12. Output from.

The output signal from the black data generation circuit 1° synthesized by UCR etc. is data delayed by two shift clocks in advance, and when the pixel of interest is not determined to be black by the non-judgment circuit 1, this output signal is output by the encoder 7. It is selected as black data and output from the data selector 12. Similarly, at the time when signals are output from shift registers 3 and 5, the black determination output of a certain pixel of interest and its surroundings are output from shift registers 4, 5, and 8, so that a select signal is output from encoder 7.

When the outputs from the shift registers 5, 4, and 6 are all determined to be black, the data selector 11 selects and outputs the low level signal from the low level signal generating circuit 8 as Y, M, and C density data; If not, Y
, M and C signals are output from the data selector 11 as they are.

High level signal generation circuit 8 and low level signal generation circuit 8
generates a highest level signal and a lowest level signal when a pixel of interest is determined to be a binary image by image area separation or the like. Therefore, more ideal color reproduction can be performed.

The non-judgment circuit 1 can have the configuration shown in FIG. 2, for example.

Each of the Y, M and C signals is compared with predetermined thresholds Pi, P2 and P3 in comparators 13.14 and 15, and only when Y>PI, M>P2 and C>P3, each comparator 13.14 and 15 The output signal from the encoder 16 is input to the encoder 16, from which a black determination output signal is output.

The operation of the present invention will be described with reference to FIG. 4, which shows an example of the selection of the black signal and the selection of Y, M, and C signals in the black portion of the image. The surrounding N pixels (1 pixel in FIG. 4) of the area determined as black by the no-determination signal from the no-determination circuit 1 are determined by the encoder 7 based on the signals from the registers 4.5 and 8. ,M
and C data are output as they are from the data selector 11, and black is also output at a high level from the data selector 12, so that the printer output image becomes black, which is a composite of four colors (three primary colors and black). Furthermore, the inside of the area determined as black is a high level black output from the data selector 12 based on the select signal from the register 5, and a low level output of <Y, M and C based on the select signal from the encoder 7. is output to the printer. Therefore, more realistic black is reproduced on the print, and an image with good toner adhesion can be obtained.

According to the present invention, since the interstices between the intermediate color and black areas are composed of black and three primary color developers, the periphery of the black area is emphasized, and moreover, even if a registration error occurs in the printer, the intermediate color If the misregistration of (three colors) and black is within N pixels, white will not appear between the intermediate color and black. This is shown in a printed sectional view in FIG. 5 (the output level of the low level signal generating circuit 8 is the lowest, and the output level of the high level signal generating circuit 8 is the highest). 4), it is possible to prevent white or low-level MMC signals from significantly deteriorating the image even if a registration error occurs at the point where the intermediate color changes to black.

Note that in the present invention, when one pixel before and after a certain pixel of interest and the pixel of interest are determined to be black, Y, M, and C density are set to low levels, but N pixels before and after a certain pixel of interest (N: It can be easily inferred that it is effective when the width of 1.1 pixels is small by using a natural number) as the criterion for judgment.

Furthermore, the present invention can be processed by a microcomputer, etc., and a simple flowchart in that case is shown in FIG. 3.As shown in FIG. Read the data and select Y of it in S2.

Determine whether the pixel signal is black from M and C,
If it is determined that the pixel is black, proceed to step 532; otherwise, proceed to step S4. In step 33, the black data is made a high level signal and proceed to step S5. In step S5, it is determined whether all N pixels before and after the pixel of interest are black. If the judgment is Yes, proceed to S8, and if No, proceed to S7. In S8, the three primary color signals (Y, M, C) are set to low levels.
In S7, the three primary color signals are left as they are and the process goes to S8.In S4, the black signal is left as is and the process goes to S8.In S8, the Y, M, C and black signals are output or as appropriate. write to memory.

Furthermore, it goes without saying that the present invention can be applied not only to the main scanning direction of an image but also to the sub-scanning direction.

[Effects] As described above, according to the present invention, black can be ideally reproduced, and toner can be reliably fixed on the print.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing an embodiment of an image processing apparatus according to the present invention. FIG. 2 is a block diagram showing an example of a black determination circuit, FIG. 3 is a flowchart showing an example of image processing according to the present invention, FIG. 4 is a diagram showing an example of signal output according to the present invention, and FIG. It is a figure which shows an example of a printed cross section. 1... Black judgment circuit, 2.3, 4, 5.6... Register, 7... Encoder, 11.12... Data selector. Figure 2 Figure 3 Cause 5

Claims (1)

[Claims] Discrimination means for determining whether a pixel of interest is a neutral color or black from a color image signal, and when the determination means determines that the pixel of interest is black, black density data is set to a high level or maximum means for converting the color image signal of the pixel of interest to a low level or the lowest level when the pixel of interest is determined to be black and N pixels (N: natural number) before and after it are determined to be black. A color image processing device comprising: