JPS62165475A - Method for emphasizing edge of color image - Google Patents

Abstract

PURPOSE:To remove the color shift of an outline part and to improve the picture quality of an image by emphasizing the edge of an image by a synthesized signal between a black signal and the edge information of a color information. CONSTITUTION:Respective color TV signals Er, Eg, Eb are converted into digital signals R, G, B by an A/D converter 5 in a video printer and then respective color signals consisting of yellow, Y, Magenta M and cyanide C and a black signal BK are formed by correcting colors by a color correcting and UCR blackboard forming part 6. A lightness signal L is formed by a lightness signal forming part 7 based on the signals R, G, B and processed by an edge emphasizing component forming part 3 to form an edge emphasizing component signal E. The signal E is added to a signal BK by a signal synthesizer 4 and the synthesized signal BK' and the signals Y, M, C outputted from the forming part 6 are dither-converted by an intermediate processing part 1 and the converted signal is recorded in an image recording part 2. Thus, the outline part can be prevented from color shift.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to an image processing method, and particularly to a method for performing edge enhancement of a reproduced image when reproducing a color image based on image information obtained by reading an image of a color original using a scanner. This invention relates to an edge enhancement method for color images.

Generally speaking, edge enhancement is used as pre-processing for dither conversion when a color image is reproduced based on the image information obtained by reading the image of a color original using a scanner, and when a grayscale image is to be expressed in pseudo-halftones. This prevents the outline from moving or disappearing, thereby improving the quality of the reproduced image.

Conventionally, in the case of color images, edge enhancement processing was performed independently for each of the three primary colors, but the color balance was disrupted in the image contours, resulting in color tone shifts, resulting in an unnatural reproduced image. The image quality deteriorates.

The present invention has been made in consideration of the above points, and it is an object of the present invention to provide a method for enhancing the edges of a color image, which allows the contours of the color image to be naturally emphasized without causing color shift. be.

To achieve the object of the present invention, the outline of a color image is emphasized using black color based on the edge information of the color image signal.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the color image edge enhancement method according to the present invention,
As shown in Figure 1, the three primary colors of a color image are R and G.
, yellow (Y), each color corrected based on the B signal,
Dither conversion is performed in the halftone processing section 1 according to the magenta (M), cyan (C,) color image signals and the black (BK) signal generated by the OCR black plate, and the processed image information is sent to the image recording section. 2 to record a color image, the edge emphasis component signal %E from the edge emphasis component generation section 3 and the black (BK) signal are sent to the signal synthesizer 4.
An image signal for black ink is created by combining the two.

However, by adopting such a means, the amount of black ink is appropriately increased or decreased in the outline portion of one image according to the edge information, and it becomes possible to record a natural color image without color shift.

FIG. 2 shows a specific configuration example of a video printer in which edge information is generated based on the brightness signal of a color image.

Here, by converting color image signals Er, Eg, and Eb of the three primary colors into digital signals, R, G, and B
A/D converter 5 that obtains the signal and the obtained R, G, B
Based on the color correction and UCR black plate main generator 6 which generates each Y, M, and C signal color-corrected according to the signal and the BK multiplied signal generated by the UCR black plate, and the R, G, and B signals, the following formula is used. A brightness signal generation section 7 generates a brightness signal by executing the calculation according to (1), and an edge emphasis component signal E is generated by executing the calculation according to the following formula (2) based on the brightness signal. The edge emphasis component generation unit 3 adds the edge emphasis component signal E and the BK multiplied signal (BK multiplied signal positive signal).

A signal synthesis section 4 performs dither conversion according to the synthesized BK' signal and Y, M, and C signals, and a halftone processing section 1 performs dither conversion based on the processed image information. image recording section 2 for recording color images;
It is composed of.

L=0.3OR+0.59G+0.11B...(1)
E=k (-L+2L-L)...
- (2) k; Edge enhancement/harmonic coefficient FIG. 3 shows a specific example of the configuration of the edge enhancement component generation section 3. In the figure, 31 and 32 indicate the shift register, and 3
3 indicates an adder/subtractor, and 34 indicates a table converter, which outputs a manual brightness signal and sends it to each shift register 31.
．． 32, the signals obtained by shifting each L are -L+2L in the adder/subtractor 33 according to L.
-L, and depending on the result, table converter 3
4, E=k (-L+2L-L) is obtained.

In the configuration shown in Figure 2, the outline of the image is expressed by increasing or decreasing black ink based on the brightness signal, so it is possible to record a color image with excellent resolution and no color shift. It becomes like this.

Also, since the brightness signal has the largest contribution from the C signal, the fourth
As shown in the figure, by replacing the brightness signal with the C signal, the circuit configuration can be simplified.

■ As described above, in the method for edge enhancement of color images according to the present invention, color images are colored in yellow and magenta.

When reproducing data based on the cyan three-color signal and the black signal generated by the black plate, the edges of the reproduced image are emphasized using a composite signal of the black signal and the edge information of the color image. It has the excellent advantage of being able to reproduce high-quality color images without color shift.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a basic configuration for implementing the color image edge enhancement method according to the present invention, FIG. 2 is a block diagram showing an example of a system configuration for specifically implementing the present invention, and FIG. 4 is a block diagram showing a specific example of the configuration of the edge emphasis component generation section, and FIG. 4 is a block diagram showing another example of the system configuration for concretely implementing the present invention.

Claims (1)

[Claims] 1. When a color image is reproduced based on three-color signals of yellow, magenta, and cyan and a black signal generated by a black plate, the reproduced image is reproduced by a composite signal of the black signal and edge information of the color image. A color image edge enhancement method that performs edge enhancement. 2. The method for edge enhancement of a color image according to item 1 above, characterized in that edge information is generated based on a brightness signal of the color image. 3. The method for edge enhancement of a color image according to item 2 above, characterized in that the brightness signal is replaced with information on the G component of the color image.