JPH04186967A - Color image processor - Google Patents

Abstract

PURPOSE:To reduce and suppress the deterioration of an image caused in accordance with the decrease of the sub-color information amount by providing a thinning-out means for executing thinning-out to image signals of each separate color component selected by a selecting means, and a converting means for converting an image signal of a principal color inputted by an input means and a result thinned out by the thinning-out means to density signals, respectively. CONSTITUTION:In selectors 101a-101c, in accordance with color separation signals of three colors of R (red), G (green), and B (blue) passing through an A/D converting circuit which is not shown in the figure, R, G, and B are selected as principal color signals at the time of generating a C (cyan) image, and at the time of generating M (magenta) and at the time of generating K (black), and at the time of generating Y (yellow), respectively by a selector 101, and at each time, other two signals (for instance, G and B at the time of generating C) are selected as sub-color signals. In this case, by taking the time of generating an image as an example, it is assumed that G, and R and G are selected as a principal color, and sub-colors, respectively. R and G being sub-colors enter into a sub-color image thinning-out circuit 102, an image signal of a picture element of high density is selected from each continuous two picture elements, and converted to one output signal placed as a time series.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a color image processing device, and particularly to a color image processing circuit number having means for reducing the resolution of information at positions other than the main color when forming an image of each color. related.

[Prior Art] Conventionally, in this type of apparatus, when generating an M (magenta) output image during image processing, a G (green)
, R (red) for C (cyan), B (blue) for Y (yellow), (hereinafter referred to as the main color) only at 40'
Process with O line and the remaining two colors (e.g. R, B when generating M) (
An apparatus and method have been proposed that reduce the number of image processing circuits by reducing the data of subcolors (hereinafter referred to as subcolors) to 200 lines and passing the two subcolors through one processing circuit in time series.

In this method, the resolution of the sub-color color separation signal generated in 400 lines is reduced to 200 lines by using the color separation signal of every other pixel as it is, or by taking the average of the signals of two adjacent pixels. Examples include methods of converting pixels into pixels.

[Problems to be Solved by the Invention] However, in the conventional example described above, the 200-line image signal generated by thinning out the sub-color image signals always has this constant value, regardless of the input image. Generated in steps. For this reason, when the tonal power S of an image changes rapidly, a change in color tone or a deterioration in resolution may occur at the border due to the effect of a decrease in the amount of information of the subcolor.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and its purpose is to provide a color image processing device that can prevent image deterioration while reducing the amount of information of secondary colors. It is in.

[Means for Solving the Problems] In order to solve the above-mentioned problems and achieve the purpose, the color image processing measure according to the present invention provides a color image processing device that processes pixels corresponding to a pixel of interest and pixels surrounding the pixel, respectively. an input means for inputting an image signal by dividing it into a primary color or a subcolor by color component; and a level of an image signal corresponding to the subcolor among the image signals input by the input means, for each color component; a comparison means for comparing; a selection means for selecting one image signal from the image signals input by the input means for each color component based on the comparison result of the comparison means; The present invention is characterized by comprising a thinning means for thinning out image signals, and a converting means for converting the main color image signal input by the input means and the result of thinning by the thinning means into density signals, respectively.

[Operation] According to this configuration, the input means inputs the image signals corresponding to the pixel of interest and the surrounding pixels of the pixel, respectively, according to color components, as primary colors or subcolors, and the comparison means inputs the image signals corresponding to the pixel of interest and the surrounding pixels of the pixel, respectively, and the comparison means inputs the image signals corresponding to the pixel of interest and the surrounding pixels of the pixel. Among the input image signals, the levels of the image signals corresponding to the sub-colors are compared for each color component, and the selection means selects one of the image signals input by the input means for each color component based on the comparison result of the comparison means. The thinning means thins out the image signals for each color component selected by the selection means, and the converting means thins out the raw color image signal inputted by the input means and the result thinned out by the thinning means. Convert to concentration signal.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, a full-color copying machine having means for reducing the image resolution of color separation signals other than those corresponding to recorded colors will be taken as an example.

(First Embodiment) <Circuit Configuration> FIG. 1 is a block diagram schematically showing the configuration of a first embodiment of a color image processing apparatus according to the present invention.

In the same figure, 101 a, 10 l b, 10
1 c is a selector that selects an image signal corresponding to the primary color or secondary color from the color separation signals of the three primary colors; 102 is a secondary color image that reduces the image resolution of the secondary color and converts the two colors into one time-series signal; Thinning circuit, 103 and 107 are shading circuits, 104 and 108 are light amount-density conversion (-1og)
The circuit 105 is a decomposition circuit that decomposes the image signals of the two sub-colors arranged in time series into two signals, and the numeral 106 is a UCR circuit that performs UCR/masking. In addition, the selector 10
1a selects a main color, selectors 101b and 101c select subcolors, and each selector's selection signal Sl
, S2. S3 is input from outside.

<Operation> In the selectors 1018 to 101c, A/
R (red), G (green), and B that have passed through the D conversion circuit
(Blue) Selector 101 according to three color separation signals
When generating a C (cyan) image, R, M (magenta)
G, Y (yellow) when generated and K (black) when generated
During generation, B is selected as the primary color signal, and at each time, the other two signals (for example, G and B during C generation) are selected as secondary color signals. Here, for example, when generating an image, it is assumed that G is selected as the main color and R and B are selected as the sub-colors. The sub-colors R and G enter the sub-color image thinning circuit 102, where the image signal of the pixel with the highest density is selected from each of the two consecutive pixels, and is output into one output signal arranged in time series. converted.

FIG. 2 is a diagram illustrating the flow of signal conversion in the selectors 101a to 101c and the sub-color image thinning circuit 102.

First, the secondary color R201. 8 in B2O2, the signal sizes of two adjacent pixels such as R1 and R2, R3 and R4, Bl and B2, and B3 and B4 are compared, and the one with the smaller signal (lower light amount, that is, higher density) is compared. Only the two signals (one of the two) are used and output alternately, and a time-series signal (time-series signal) 204 is generated.

The time series signal 204 and main color signal 2 created in this way
02 is each shading circuit 103, 107, -
The sub-color signals pass through the 1og circuits 104 and 108, are restored into two-color signals 205 and 206 by the decomposition circuit 105, and are input to the LICR circuit 106.

FIG. 3 is a circuit diagram showing the configuration of the sub-color image thinning circuit 102. In the figure, 301 to 304 are image signals 20
A flip-flop that delays 1,203 by one clock (
(hereinafter referred to as rF/FJ), 305 and 306 are digital comparators, and 307 and 308 are selectors for selecting one of the two signals. 309 is a selector for outputting two sub-colors in time series.

The sub-color image signal 201 passes through two F/Fs 301 and 302. The output R2 of 301 and the output R1 of 302 are image signals of two consecutive pixels. The magnitudes of these two signals are compared by a digital comparator 3.5, and based on the output thereof, R1 is selected and outputted by a selector 307 when R1<R2, and R2 is selected and outputted when R2<R1. Similarly, for the sub-color image signal 203, the smaller signal (higher density signal) of B1 and B2 is output.

These two output signals are input to selector 309.

The selector receives a signal 31 whose frequency is the video clock divided by 2.
0 alternately selects R and B for each pixel, and the signal 204
Output.

The reason why a signal with a high concentration is selected in this way will be explained below.

FIG. 4 is a diagram for comparing and explaining the thinning and thinning methods of the conventional example and this embodiment.

In the same figure, examples of signals generated by UCR processing are shown in (a) a case where one pixel out of two pixels is simply taken out and thinned out, and (b) a case where the thinning is carried out using the method of the present invention.

Reference numeral 401 shows an input image as an example, in which a gray image changes to black and white. 402 (indicated by a dotted line in the figure) is a signal obtained by converting the main color signal into light amount and density, 403 is a signal obtained by thinning out the sub color signal using the conventional method and then converting the light amount into density, and 404 is a signal obtained by converting the light amount and density using the method according to the present invention. Thinning out, light amount -
Each signal shows a concentration-converted signal.

When these signals are input to the UCR circuit 106, the main color and
In areas where the densities of the sub colors overlap, each color signal is subtracted and a K (black) signal is generated instead.

Looking at the conventional example (a), in the part where the input signal changes from white to black, the density of the main color becomes greater than the density of the sub-color for every other pixel, and the main color component that protrudes from the K signal (in the figure , indicated by diagonal lines) appears as a tint. On the other hand, in the part where the input signal changes from black to white, the density of the sub-color becomes greater than the density of the main color for every other pixel, but since the sub-color contributes little to the density signal, no significant tint appears. .

In order to prevent the main color from protruding, as shown in (b) of this embodiment, if the one with the larger density signal (the one with the smaller light amount signal) is always taken out of the two pixels and thinned out, the result will be as shown in Fig. 4. ,K
Since the signal is generated in accordance with the main color signal, blurring and image deterioration due to color tint can be suppressed in areas such as the left edge of characters where there is a sudden transition from white to black.

As described above, according to the first embodiment, in a color image processing apparatus having means for reducing the image resolution of color separation signals other than those corresponding to recorded colors, a plurality of By comparing the densities of the image signals and selecting one image signal based on the comparison result, image deterioration due to a decrease in the amount of sub-color information can be suppressed to a minimum.

(Second Embodiment) In the first embodiment described above, the light intensity of the pixel of interest and one pixel before or after it is compared, and the smaller pixel (that is, the one with higher density) is removed and thinned out. However, the present invention is not limited to this. Instead of comparing the signals of each pixel as they are, equivalent signals calculated from each pixel may be compared.

FIG. 5 is a diagram illustrating the outline of the second embodiment. In the example in Figure 5, instead of each pixel point, the density signal (light amount signal) is equivalently obtained by interpolation for two points that are divided into three between pixels, and the magnitude is compared. is used as a thinning signal.

FIG. 6 is a diagram showing a signal after light amount-density conversion when the input image shown in FIG. 4 is thinned out using the thinning method shown in FIG.

Compared to the conventional thinning method shown in FIG. 4(a), the hatched areas where UCH does not work are dispersed, and the amount of protrusion of the main color in each area is kept small.

Furthermore, compared to the first embodiment, at the right end where black changes to white, the level of the sub-color signal appearing in the part where there is no black signal is lower. In this way, signals in areas with no density originally suffer from deterioration of resolution at the edges of characters, etc.
Therefore, the second embodiment is effective in a character mode where it is desired to make the edges clear.

In FIG. 6, the density value is determined by interpolation at two points inside the three equal parts, but by changing the position of these points, it is possible to generate an image with emphasis on color and resolution.

FIG. 7 is a circuit diagram showing a part of the sub-color thinning calculation circuit in the second embodiment. There are two secondary colors, but only one color is shown here.Those that are the same as those in FIG. 3 are represented by the same symbols, and their explanation will be omitted.

Through F/Fs 301 and 302, a sub-color image signal A for one pixel and an image signal B for one pixel after it are taken out.

These two signals A and B are sent to multipliers 701 and 703, respectively.
702 and 704, and the multiplication is combined with the coefficients a H1a z , b 11 b 2 set by the CPU. As shown in the figure, each signal passes through adders 705 and 706 to generate a signal as expressed by the following equation (1). In other words, it is expressed as (1).

After that, instead of A and H in Figure 3, A' and B'
are compared, and a sub-color thinned-out image signal is generated according to the result.

Even in this case, the same effects as in the first embodiment can be obtained.

[Effects of the Invention] As described above, according to the present invention, image deterioration due to a decrease in the amount of sub-color information can be suppressed to a minimum.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing the configuration of a first embodiment of a color image processing apparatus according to the present invention, and FIG.
1a to 1olc and the flow of signal conversion in the sub-color image thinning circuit 102, FIG. 3 is a circuit diagram showing the configuration of the sub-color image thinning circuit 102, and FIG. 4 shows thinning in the conventional example and this embodiment. A diagram for comparing and explaining thinning methods, FIG. 5 is a diagram for explaining the outline of the second embodiment, and FIG. 6 is a diagram for explaining the outline of the second embodiment.
A diagram showing a signal after light intensity-density conversion when the input image shown in FIG. 4 is thinned out using the thinning method shown in the figure. FIG. In the figure, 101a, 101b, 101cm selector, 10
2... Sub-color image thinning circuit, 103, 107... Shading circuit, 104, 108...-1og circuit, 105... Decomposition circuit, 106... UCR circuit, 3
01~304,311...F/F, 305°306.
...Digital comparator, 307.308.309
... Selector, 701 to 704 ... Multiplier, 705
, 706... is an adder.

Claims (3)

[Claims] (1) In a color image processing device, an input means for inputting image signals respectively corresponding to a pixel of interest and surrounding pixels of the pixel, divided into primary colors or subcolors according to color components; Comparing means for comparing the level of the image signal corresponding to the sub-color among the image signals, for each color component; and based on the comparison result of the comparing means, from the image signal input by the input means for each color component. a selection means for selecting one image signal; a thinning means for thinning out the image signal for each color component selected by the selection means; and a main color image signal input by the input means and thinning by the thinning means. 1. A color image processing apparatus, comprising: conversion means for converting the respective results into density signals. (2) The color image processing apparatus according to claim 1, wherein a result of thinning by said thinning means is made into a time series signal. (3) The color image processing apparatus according to claim 2, wherein the conversion means includes a decomposition means for decomposing the time-series signal into color components.