JPH05115001A - Color converter - Google Patents

Abstract

PURPOSE:To convert an optional color into an optional color, to attain natural color conversion without causing a color border around the converted color or a loss of the gradation of the converted color and to adjust the range of a hue for color conversion through the operation of a parameter. CONSTITUTION:A color converter is used for color copying machine converting a color in an original into other color, is provided with an achromatic component separate means 32 separating an achromatic color component at an input side, an achromatic component synthesis means 38 adding the achromatic component to an output side, and a color conversion arithmetic operation means 37 implementing the arithmetic operation of color conversion to apply the arithmetic operation of color conversion to a color signal from which the achromatic component is separated.

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 for a copying machine, and when an image signal of a document image scanned and read is output to a printer output device, an arbitrary tint can be selected. The present invention relates to a color conversion device capable of converting the color tones.

[0002]

BACKGROUND OF THE INVENTION A conventional color conversion method for converting one color in an image into another color is a conventional method in which an arbitrary color is directly converted into an arbitrary color.

This causes a color boundary to appear between a color-converted portion and a non-color-converted portion, and even if it can be directly applied to a line drawing such as an animation or sketch drawn with a limited number of colors, Photographs have problems in that color boundaries are conspicuous and gradation is impaired.

As a conventional method, there is a method in which only the hue component is continuously converted. In this case, although the lightness component and the saturation component are preserved, only the hue continuously changes, so that, for example, yellow. When is converted to blue, yellow itself is converted to blue, but if there is inconvenience that the part of the color slightly shifted from yellow does not become bluish but becomes greenish or reddish There is.

This is because it is necessary to pass a completely unrelated hue while the hue changes from yellow to blue. That is, natural conversion cannot be realized only by continuously changing the hue component.

In order to make the color boundaries inconspicuous after conversion, it is necessary to continuously change the amount of color conversion around the portion to be converted. Further, it is necessary to store the component representing the light and shade included in the original image signal in order to prevent the gradation from being deteriorated after the conversion. As a conventional method that satisfies this, the image signal is divided into a primary color (cyan or magenta or yellow), a secondary color (red or green or blue), and a black component, and the converted color is selected from these 7 colors. There are things such as selecting and converting to another color. This is used as a device for color correction rather than color conversion as a direct scanner for printing plate making, but the type of color to be converted and the range of tint to be converted are limited. There is a problem in that even colors change color under the influence of color conversion, and it is functionally insufficient to be used as a color conversion device.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to perform color conversion in which the boundaries of colors are not conspicuous after conversion, the gradation of the converted portion is not impaired, and the tint of the converted color can be freely selected. ,
It is also possible to make the range of tint variable.

[0008]

SUMMARY OF THE INVENTION The present invention achieves the above object. The present invention is a color conversion device for a color copying machine, which converts one color in an original document into another color, and has an achromatic component on the input side. And an achromatic color component separating means, an achromatic color component synthesizing means for adding the achromatic color component to the output side, and a color conversion arithmetic means for performing a color conversion operation, to separate the achromatic color component. The present invention provides a color conversion device characterized by performing a color conversion operation on a tint signal, and as a further preferred embodiment, the color conversion operation means indicates a color to be removed from an original document. And a second converted color signal indicating a color to be added to a portion of the original from which the first converted color has been removed. The hue difference signal indicating the hue difference is obtained from the signal of A color conversion amount control signal indicating the amount of color conversion is calculated from the signal and at least one parameter, and the total amount of components of each pixel of the image signal and the total amount of components of the signal of the first converted color are calculated. The total amount ratio signal is obtained by obtaining the quotient of, and the third converted color signal is obtained by multiplying the signal of the second converted color by the total amount ratio signal, and the image signal is subtracted from the third converted color signal. The present invention provides a color conversion device characterized by multiplying a color conversion amount control signal of a value and adding it to an image signal to output.

[0009]

1 is a block diagram of a color conversion apparatus of the present invention, FIG. 2 is a block diagram showing the flow of image signals of a color copying machine, and FIG. 3 is a part of the structure of the color copying machine. In the perspective view shown in FIG. 3, which is simplified to explain the function of color conversion.

The color conversion function will be described below with reference to the drawings.

Before performing the color conversion process, it is necessary to register in advance which color (first conversion color) is to be converted to which color (second conversion color).

In this embodiment, the first and second conversion colors are input by prescan. The prescan is performed twice to obtain the first conversion color and the second conversion color. A 2-bit scan code SC is generated from the CPU 70 in order to distinguish the type of scan, and the color conversion device 30 and the color correction means 40,
It is supplied to the image recording means 50. SC = 1 means a pre-scan for obtaining the first conversion color, SC = 2 means a pre-scan for obtaining the second conversion color, and SC = 0 means a main scan for making a copy. means.

A small area 92 of about 5 mm square for reading the first and second conversion colors is provided at a predetermined position on the document table 91 of the image reading means 10, and a portion to be the first conversion color of the document is provided here. Place the original so that it comes to the position, and perform the first prescan. The first pre-scan is started by pressing the operation button dedicated to the color conversion function on the operation unit 60.

At this time, the original is scanned and R for each pixel is read.
A GB luminance signal is obtained. This is converted into the density of CMY which is a complementary color by the LUT 20 (ROM or RAM) and is supplied to the conversion color stabilizing means in the color conversion device 30.
Here, when SC = 1 or 2, a small area of 5 mm square 92
The CMY density signals are stored while being appropriately thinned, and their average value is calculated.

As a result, the first converted color signals C ₁ , M ₁ ,
Y ₁ is obtained.

C ₁ , M ₁ and Y ₁ are first supplied to the achromatic color component separating means 32 to separate the achromatic color signal K. This determined the minimum value of among the _{C 1, M 1, Y 1} , which was the K, is output as C _1, M _1, C ₁ is subtracted from the _{Y 1, M 1, Y 1} , K. This can be expressed as follows.

K = min (C ₁ , M ₁ , Y ₁ ) C ₁ ′ = C ₁ −K M ₁ ′ = M ₁ −K Y ₁ ′ = Y ₁ −K where min is a function for obtaining a minimum value. Is shown. The signals C ₁ ′, M ₁ ′ and Y ₁ ′ from which the achromatic color components have been separated are supplied to the chromaticity signal converting means 33. Here, the chromaticity signal xy (tentative name) is obtained by performing calculation according to the following equation.

X = −0.7 · M ₁ ′ + 0.7 · Y ₁ ′ y = C ₁ ′ −0.5 · M ₁ ′ −0.5 · Y ₁ ′ The x axis and the y axis are planes perpendicular to the brightness (density). To make. When the axes of C ₁ ′, M ₁ ′ and Y ₁ ′ are projected on this plane,
The C ₁ ′, M ₁ ′ and Y ₁ ′ axes form an angle of 120 ° with each other, and the C ₁ ′ axis overlaps the y axis.

The xy signal output from the chromaticity signal converting means 33 is supplied to the hue difference signal generating means 34. Here, the scan code SC = 1 is input at the same time.

Here, the hue is calculated from the chromaticity signal xy. The hue is calculated by the following formula.

First, the following calculation is performed from the absolute values | x | and | y | of the chromaticity signal.

H = Tan ⁻¹ (| y | / | x |) At this time, the negative sign of x is sx, the negative sign of y is sy, and H and sx, sy represent the hue.

Here, only when SC = 1, these values are held in the internal registers as the hue signals H1, sx1, sy1 of the first converted color.

CM output from the achromatic component separating means 32
On the other hand, the Y signal is a conversion color generating means for generating a third conversion color.
Also supplied to 36.

Here, only when SC = 1, the total amount ss1 of the components of the first converted color signal is obtained according to the following equation and is stored in the internal register.

Ss1 = C ₁ ′ + M ₁ ′ + Y ₁ ′ With the above, registration of the first conversion color is completed.

Next, the color sample of the second conversion color is positioned in the small area 92 of 5 mm square, and the second prescan is performed. At this time, SC = 2, and like the first prescan, the second prescan is started by pressing the operation button dedicated to the color conversion function on the operation unit 60.

At this time, the original is scanned and R for each pixel is read.
The GB luminance signal is obtained from the image reading means. This is converted into a CMY density which is a complementary color by the LUT 20 and is supplied to the conversion color stabilizing means 31 in the color conversion device 30, and the average value of the CMY density within a 5 mm square is obtained. Further, the achromatic color component separating means 32 is supplied to separate the achromatic color signal. The values of CMY at this time are C ₂ , M ₂ and Y ₂ , which are supplied to the third conversion color generating means 36 and held in the internal register only when SC = 2. This completes the registration of the second conversion color.

Next, the document is set at a predetermined position on the document table 91 of the image reading section and a main scan is performed. The main scan is started by pressing the copy button on the operation unit 60. At this time, SC = 0 is generated from the CPU 70 and sent to the color conversion device 30, the color correction means 40, and the image recording means 50. The RGB luminance signal of the image is obtained for each pixel in the same manner as in the pre-scan, and this is converted into the density of CMY which is a complementary color by the LUT 20 and supplied to the conversion color stabilizing means 31 in the color conversion device 30. However, in this case, the signal passes through as it is and is supplied to the achromatic color component separating means 32 to separate the achromatic color signal K _i . The values of CMY at this time are C _i , M _i , and Y _i .

C _i , M _i and Y _i are supplied to the chromaticity signal converting means 33, converted into chromaticity signals xy and supplied to the hue difference signal generating means 34, and H and sx, sy representing the hue are Ask.
In this case where SC = 0, the hue difference signal dH is further calculated by the following equation. First, only the negative sign is calculated.

S1 = sx .XOR. Sx1 .XOR. S
y .XOR. sy1 s2 = sx .XOR. sx1 Here, .XOR. represents an exclusive OR. Like this
1 and s2 are obtained, and dH is calculated according to the following equation according to the result
Is calculated.

If s1> 0 and s2> 0 dH = | H-Ht | s1> 0 and s2 <0 dH = π− | H-Ht | s1 <0 and s2> 0 dH = H-Ht s1 < If s2 <0 at 0, dH = π− (H−Ht) Here, the argument of the inverse trigonometric function is an absolute value, and it is calculated separately from the negative sign, but when it is realized on hardware, it is calculated. Considering the load, it is necessary to convert Tan ^-1 into a look-up table (ROM or RAM). In that case,
This is because the size of the LUT can be reduced by limiting the range of arguments to absolute values.

The hue difference signal dH is supplied to the conversion control amount generating means 35. Here, the conversion control amount α is calculated according to the following equation using the hue difference signal dH and the parameter.

Α = 1-dH × p1 However, when α <0, α = 0.

The graph shown in FIG. 4 shows the hue H and the conversion control amount α.
And the first conversion color hue H1 to be converted is indicated by a dotted line.

Here, the width of the hue to be converted can be adjusted by changing the value of the parameter p1. The conversion control amount α is supplied to the color conversion calculation means 37.

On the other hand, in the third conversion color generating means 36, the total amount ssi of the components of the image signal is calculated as follows.

Ssi = C _i + M _i + Y _{i The} total quantity ratio signal rss is obtained by the quotient of this and ss1 held in the register.

The total amount of the rss = ssi / ss1 component is the sum of the signal values of the respective color components, which is considered to be the amount of the component representing the tint since the achromatic color components have been separated in advance. Since rss represents the ratio of the tint components, it can be said that the larger the value, the greater the tint amount of the image signal.

Although the saturation of the image signal can be used in place of rss, the calculation of the saturation requires the calculation of the square root, which is not used in this embodiment because the calculation load is large.

Since the value of the second converted color signal is a fixed value within at least one scan, it does not include any image detail information. Therefore, in order to prevent the converted portion from becoming unnatural, the amount of tint is multiplied by the total amount ratio signal rss containing the information to give the detail information of the image. This signal is the third converted color signal.

C ₃ = C ₂ × rss M ₃ = M ₂ × rss Y ₃ = Y ₂ × rss Third converted color signals C ₃ , M ₃ , Y ₃ and image signals C _i , M _i ,
The Y _i and the conversion amount control signal α are supplied to the color conversion calculation means 37. These signals are synchronized for each pixel by passing through a delay circuit (not shown), and calculation is performed according to the following equation.

First, the following calculation is performed.

C _r = C ₁ −C ₁ · α M _r = M ₁ −M ₁ · α Y _r = Y ₁ −Y ₁ · α α is such that the hue difference between the image signal and the first converted color signal is 0. At this time, the maximum (α = 1) is reached, so that C _r , M _r , and Y _r are all 0, resulting in an achromatic color. This removes the first converted color signal component that undergoes conversion. Next, a value obtained by multiplying the third converted color signal by α is added.

C _c = C _r + C ₃ · α M _c = M _r + M ₃ · α Y _c = Y _r + Y ₃ · α By this, the color component registered as the second conversion color is added, and one pixel is added. Minute conversion is complete.

The signals C _c , M _c , Y _c for which the color conversion processing has been completed
Is supplied to the achromatic component synthesizing means 38. Here, the achromatic color signal K _i reduced in the preceding stage of the color conversion processing is synchronized for each pixel by a delay circuit to obtain a signal C _c after the color conversion,
In addition to M _c and Y _c , restore.

C _c = C _c + K ₁ M _c = M _c + K ₁ Y _c = Y _c + K ₁ CMY is supplied to the color correcting means 40, and the image reading means 10
The color correction is performed in consideration of the spectral characteristics of the color sensor and various characteristics of the recording material of the image recording unit 50.
Supplied to 50.

By performing the above-described main scan processing for each image, an image on which color conversion processing has been performed can be obtained from the image recording means 50.

[0049]

As described above, according to the present invention, an arbitrary tint can be converted into an arbitrary tint, and the gradation of the converted part is impaired or the converted part is converted. Natural color conversion can be done without creating borders of surrounding colors.
Further, by operating the parameters, it is possible to adjust the range of hues for which color conversion is performed.

[Brief description of drawings]

FIG. 1 is a block diagram of a color conversion device of the present invention.

FIG. 2 is a block diagram showing the flow of image signals in a color copying machine.

FIG. 3 is a perspective view showing a part of a configuration of a color copying machine.

FIG. 4 is a graph showing the relationship between hue and conversion control amount.

[Explanation of symbols]

 31 conversion color stabilization means 32 achromatic color component separation means 33 chromaticity signal conversion means 34 hue difference signal generation means 35 conversion control amount generation means 36 third converted color generation means 37 color conversion calculation means 38 achromatic color component synthesis means

Claims (2)

[Claims] 1. A color conversion apparatus for a color copying machine, which converts one color in a document into another color, comprising an achromatic color component separating means for separating an achromatic color component on an input side and an output side. It has an achromatic color component synthesizing means for adding the achromatic color component and a color conversion arithmetic means for performing a color conversion operation, and performs an arithmetic operation for color conversion on a tint signal in which the achromatic color component is separated. Characteristic color conversion device. 2. A signal of a first conversion color, which indicates a color to be removed from an original, and a color to be added to a portion of the original from which the first conversion color is removed, in the color conversion calculation means. , A second converted color signal is held, and a hue difference signal indicating a hue difference is obtained from the first converted color signal and the image signal, and the hue difference signal and at least one By calculating the color conversion amount control signal indicating the amount of color conversion by the above parameters, by obtaining the quotient of the total amount of the components of each pixel of the image signal and the total amount of the components of the signal of the first conversion color Obtain a total amount ratio signal, obtain a third converted color signal by multiplying the signal of the second converted color by the total amount ratio signal, color conversion amount control of the value obtained by subtracting the image signal from the third converted color signal A patent contract characterized by multiplying a signal, adding it to an image signal, and outputting The color conversion device range of the first term of the.