JP3060640B2 - Color converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color conversion device used for a color hard copy, a color image processing device and the like.

[0002]

2. Description of the Related Art With the recent development of digital image processing apparatuses and digital image processing techniques, there have been increasing opportunities for adjusting and processing the color of color images in various image systems.

One of the color image processing methods is a single color mode. In some digital color copying machines, not only color copying but also single-color copying can be obtained. For example, Japanese Patent Application Laid-Open No. 2-87778 discloses that color digital data of three color components read by a reading device is decomposed into brightness and chromaticity data, and only the chromaticity data is converted into an arbitrary single color while maintaining the brightness data. States that a single color copy can be obtained.

A conventional monochromatic mode color converter will be described below. FIG. 3 shows a conventional single-mode color conversion device. In FIG. 3, reference numeral 301 denotes a color image;
2 is an input device, 303 is a color system conversion unit, 304 is a monochrome mode output unit, 305 is a color correction unit, 306 is a recording medium,
Reference numeral 307 denotes RG of one pixel color read by the input device 302.
The B signal 308 is an L ^* a ^* b ^* signal .

[0005] The operation of the monochromatic mode color conversion device configured as described above will be described below. First,
The color image 301 is read by the input device 302, and an RGB three-color signal 307 is obtained. The color system conversion unit 303 converts the RGB signal 307 into lightness data and chromaticity data by using a conversion formula of a uniform color space LAB recommended by the CIE (International Commission on Illumination) shown below, and converts the L ^* a ^* b ^* signal.
No. 308 is generated.

[0006]

(Equation 1)

The monochrome mode output means 304 outputs a lightness signal L ^*.
Is converted, and the chromaticity signal a ^* b ^* is converted into an arbitrary single color. The output signal of the monochrome mode output unit 304 is converted into a signal suitable for the recording medium 306 by the color correction unit 305 (for example, when the recording medium 306 is a hard copy device, the output signal of the monochrome mode output unit is output by the color correction unit 305). Is converted into a YMC signal).

[0008]

However, the above-mentioned conventional configuration has a problem that only a single color can be output.

An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a color conversion apparatus which can generate not only a single color but also a two-color image of an arbitrary single color and an achromatic color. I do.

[0010] A color conversion apparatus which enables color conversion more suitable for human color sense by applying weighting processing by a membership function to threshold processing for selecting an arbitrary monochromatic or achromatic color output. The purpose is to provide.

[0011]

SUMMARY OF THE INVENTION In order to achieve this object, the present invention provides an input device for inputting a color image, and a hue of one pixel read from the input device from a color signal output from the input device. A hue calculation unit for calculating, a saturation calculation unit for calculating the saturation of one pixel read from the input device from a color signal output from the input device, and the input device based on a color signal output from the input device A brightness calculator for calculating the brightness of one pixel read from
Color <br/> phase converter for converting the output of the hue calculation unit in any single color hue, saturation output of any single color of the chroma calculating unit
A saturation conversion unit for converting the brightness to an arbitrary value;
A lightness conversion unit for converting the brightness into a single color lightness, and three outputs of the hue calculation unit, the saturation calculation unit, and the lightness calculation unit.
A color determination unit that performs input and determines the color of an input pixel;
If the conversion unit and the saturation converting portion 3 outputs of the brightness conversion portion
Input, and convert each converted signal to a signal corresponding to the output device.
A color output signal generation unit that converts the output of the lightness calculation unit into a gray signal corresponding to an output device, and a color output signal generation unit that converts the output of the color determination unit into a color signal. The color signal output of the generation unit and the gray signal output of the gray output signal generation unit are one pixel.
And a selector for switching every time.

[0012]

According to the present invention, not only a single-color image but also a two-color image of an arbitrary single color and an achromatic color can be generated with the same configuration.

Further, by calculating weights of hue data, saturation data, and lightness data by an arbitrary membership function in color judgment, color conversion more suitable for human color sense can be performed.

[0014]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a color conversion apparatus according to an embodiment of the present invention. In FIG. 1, 101 is a color image, 102 is an input device, 103 is a hue calculation unit, 104 is a saturation calculation unit, 105 is a brightness calculation unit, 106 is a hue conversion unit, 107 is a saturation conversion unit, and 108 is brightness conversion. Department, 109
Is a color output signal generation unit, 110 is a gray output signal generation unit, 111 is a color determination unit, 112 is a selector, 113
Is a hue signal, 114 is a saturation signal, 115 is a lightness signal, 1
16 is a monochrome signal, 117 is an achromatic signal, and 118 is a color determination signal.

The operation of the color conversion apparatus configured as described above will be described with reference to FIGS. 1, 2 and 4.
For the sake of explanation, consider the case of a two-color image of yellow and gray in which only red is output in yellow (single color) and the other areas are output in gray (achromatic color) as shown in FIG. In FIG. 4, 401 is a multicolor original image, 402 is a red area,
403 is a green area, 404 is a blue area, 405 is an achromatic area in the original image, 406 is a two-color image obtained by processing the original image 401, 407 is a yellow area, and 408 is an achromatic area in the processed image.

First, the original image 401 is read by the input device 102 as the color image 101 in FIG. 1, and the RGB signals of one pixel color read by the input device 102 are output by the hue calculation unit 103, the saturation calculation unit 104, and the brightness calculation. Part 105
To calculate the hue, saturation, and brightness. Hue calculator 103, saturation calculator 104, lightness calculator 105
The calculation of hue, saturation, and brightness in
This is realized by using a conversion formula of the uniform color space LAB recommended by the (International Commission on Illumination), a ^{Hol *} C ^* polar coordinate system.

[0018]

(Equation 2)

[0019] H ^o hue signal 113, L ^* is the lightness signal 11
4. C ^* corresponds to the saturation signal 115. The calculated hue signal 113 is sent to the hue converter 106, the saturation signal 114 is sent to the saturation converter 104, and the brightness signal 115 is sent to the brightness converter 10.
8 and color-converted into an arbitrary single color. When yellow is output as a single color, the hue of all image data is converted to yellow by the hue conversion unit 106. That is, the H ^o of (number 2) is set to yellow. Also, by converting L ^* and C ^* here, color emphasis can be performed. The image data converted to yellow is output to the signal generator 10 for color output.
9 and converted to a single color signal 116 suitable for the output device. When the output device is a hard copy device, the hue data, saturation data, and brightness data are converted into a YMC signal (or a YMCK signal) by the color output signal generation unit 109.
Is converted to When the output device is a color CRT, the color output signal generation unit 109 is used as a color CRT gamma correction circuit. The brightness signal 115 is also input to the gray output signal generation unit 110, and the gray output signal generation unit 11
A value of 0 generates an achromatic signal 117 suitable for the output device. Further, a hue signal 113, a saturation signal 114, and a brightness signal 115
Is also input to the color determination unit 111. The color determination unit 111 determines an area to be output as a single color. Since the red area is output as yellow, the color determination unit 111 determines whether one pixel read by the input device 102 is red. The color determination method in the color determination unit 111 will be described later with reference to FIG.
This will be described with reference to FIG. The color determination unit 111 inputs the color determination result to the selector 112 as a binary color determination signal 118, and outputs a single-color signal 116 when one pixel read by the input device 102 is in the red region, and outputs a single-color signal 116 when the pixel is not in the red region. An achromatic signal 117 is output. By the above operation, the red area is output in yellow and the areas other than red are output in achromatic color, and a two-color image of yellow and gray is obtained.

Next, a method of color determination will be described with reference to FIGS. 1, 2 and 5. In FIG. 2, reference numeral 201 denotes a hue calculation unit;
2 is a saturation calculation unit, 203 is a brightness calculation unit, 204 is a hue weight generation unit, 205 is a saturation weight generation unit, 206 is a brightness weight generation unit, 207 is a hue binarization unit, and 208 is saturation binarization. Unit, 209 is a brightness binarization unit, 210 is a selector, 211
Is a hue signal, 212 is a saturation signal, 213 is a lightness signal, 2
14 is a hue determination signal, 215 is a saturation determination signal, 216 is a brightness determination signal, 217 is a color determination signal, 218 is a hue weight signal, 219 is a saturation weight signal, and 220 is a brightness weight signal. The hue signal 211 calculated by the hue calculation unit 201 is input to the hue weight generation unit 204, and the weight of the hue signal 211 is calculated by a membership function having a peak only in the hue range to be output as a single color. The weight of the hue signal means the hue signal 21 when the red area is output in a single color.
1 is a numerical value indicating how red-like it is. The weight is used as a hue weight signal 218 as a hue binarization unit 207.
, And is binarized by setting an appropriate threshold value in the hue binarization unit 207 to generate a hue determination signal 214 indicating whether or not the color falls within a single color hue range. In the case of the red area determination, the hue determination signal 214 has binary information indicating whether the hue of the color of one pixel read by the input device is red or not. Any color-size by changing the shape and thresholds hue membership functions
Constant is possible. Operations of the hue weight generation unit 204 and the hue binarization unit 207 will be described in detail with reference to FIG.

In FIG. 5, reference numeral 501 denotes a hue membership function, 502 denotes a hue range that seems to be red, 503 denotes a red hue to be extracted, 504 denotes a binarization threshold, 505 denotes a weight of an input pixel, and 506 denotes a hue of an input image. , 507 are non-red hues. The hue H1 to the hue H2 correspond to a red-like region as a human visual response. By the hue membership function 501 having a peak only in the hue range 502 like red, the redness of one pixel read by the input device, that is, the weight 505 of the input pixel is obtained.
Next, when a binarization threshold 504 is set for the weight, a red hue 503 and a non-red hue 507 are determined. In the case of the hue 506 of the input image, since the weight 505 is larger than the binarization threshold 504, it is determined to be “red”. The color conversion region can be freely determined by arbitrarily setting the shape of the hue membership function 501 and the binarization threshold 504.

The same applies to saturation and lightness. The weight of the saturation signal 212 is calculated by the saturation membership function, and the saturation determination signal 215 is obtained by threshold processing of the saturation binarization unit 208. . Further, the weight of the brightness signal 213 is calculated by the brightness membership function, and the brightness binarizing unit 20 is used.
9, the brightness determination signal 216 is obtained. Finally, a logical AND of the hue determination signal 214, the saturation determination signal 215, and the lightness determination signal 216 is obtained to obtain a color determination signal 217. The color determination signal 217 is input to the selector 210,
, And an achromatic signal 117.

As described above, according to the present embodiment, by providing the weight determining section based on the membership function and the binarizing section in the color determining section 111, the shape of the membership function and the threshold value can be changed to provide an arbitrary value. It is possible to output a color region as an arbitrary single color and an arbitrary color region as an achromatic color. In addition, by introducing a membership function to threshold processing, it is possible to express the ambiguity of human color perception,
It is possible to perform color conversion more suited to human color sense.
Further, it is needless to say that a conventional monochrome image can be obtained by setting the membership function and the threshold value at which the value range becomes 1 with respect to the entire domain in the color determination unit 111 to 1.

[0024]

As described above, the present invention provides a hue calculator , a chroma calculator, a brightness calculator, a color output signal generator for outputting a single color, and a gray output generator for outputting an achromatic color. By providing a color determination unit for determining the color of one pixel read by the input device and a selector area for switching the output between a single color signal and an achromatic signal based on the color determination signal, it is possible to use a single-color image and an arbitrary single-color image with the same configuration. An excellent color conversion device capable of outputting a two-color image composed of colors can be realized. In addition, by introducing a membership function to the binarization processing in color determination, it becomes possible to process the ambiguity of human color sensation, and a color conversion device more suited to human color sensation can be realized.

The present invention provides an unprecedented intelligent image processing apparatus in an image system in which colorization is progressing, and its effect is very large.

[Brief description of the drawings]

FIG. 1 is a block diagram of a color conversion apparatus according to an embodiment of the present invention.

FIG. 2 is a block connection diagram of a color determination unit which is a main part of the color conversion apparatus according to the embodiment.

FIG. 3 is a block diagram of a conventional monochrome mode color conversion device.

FIG. 4 is a conceptual diagram of a color image and two-color conversion of a color conversion device according to an embodiment of the present invention.

FIG. 5 is a diagram showing in detail a method of determining a red hue in the embodiment.

[Explanation of symbols]

 Reference Signs List 101 color image 102 input image 103 hue operation unit 104 saturation operation unit 105 lightness operation unit 106 hue conversion unit 107 saturation conversion unit 108 lightness conversion unit 109 color output signal generation unit 110 gray output signal generation unit 111 color determination unit 112 selector 113 hue signal 114 chroma signal 115 lightness signal 116 single color signal 117 achromatic signal 118 color determination signal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-87778 (JP, A) JP-A-63-141448 (JP, A) JP-A-2-1133663 (JP, A) JP-A-3- 171975 (JP, A) JP-A-63-280577 (JP, A) JP-A-62-154868 (JP, A) JP-A-3-91088 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1/40-1/409 H04N 1/46 H04N 1/60

Claims (3)

(57) [Claims] An input device for inputting a color image;
From the color signal output from the input device,
A hue calculation unit for calculating the hue of one pixel read
From the color signal output from the input device
A saturation calculator for calculating the saturation of one pixel read from
From the color signal output from the input device, the input device
Brightness calculation unit that calculates the brightness of one pixel read from the unit
When,The output of the hue calculation unit is converted into an arbitrary single color hue.
ToA hue conversion unit,The output of the saturation calculator is
Convert to saturationA saturation conversion unit,The output of the brightness calculation unit is
Convert to any single color brightnessA brightness conversion unit, and the hue rendering
Calculation unit, the saturation calculation unit, and the brightness calculation unit3 outputs
To determine the color of the input pixelA color determination unit,
HueConversion unitAnd the saturationConversion unitAnd the brightness converter3 outputs
And input each converted signal according to the output device.
Color signalSignal generator for color output
Output of the brightness calculation unit to the output deviceGray according toChange to a signal
An output signal generator for gray output, and an output of the color determination unit.
The color output signal generation unitColor signal output
And the gray output signal generation unitGray signal outputAnd
A selector that switches every pixelA color conversion device provided with. 2. The method according to claim 1, wherein the output of the signal generator for color output and the output of the generator for gray output are switched using the output of the color determination unit, so that the output of a single color and an achromatic color can be arbitrarily switched. The color conversion device according to claim 1. 3. A color judging section calculates weights of a hue signal, a saturation signal, and a brightness signal by an arbitrary membership function, and binarizes the weights by an arbitrary threshold value.
2. The color conversion device according to claim 1, wherein the color of one pixel read by the input device can be determined.