JPH09219797A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the color conversion processing and also to ensure the highly flexible color conversion by performing the color conversion in an area into a designated color based on a designated conversion color code. SOLUTION: The RGB image data received from a scanner part are converted into an XYZ table color system via an XYZ conversion part 201 and furthermore converted into an L*a*b* even color space via an L*a*b* conversion part 202. The L*a*b* data are inputted to a color conversion part 203 and then converted into other L*a*b* data of the corresponding color based on the conversion color code sent from a system control part 105. When the processing code sent from the part 105 is inputted to a selector 205, the output data on one of two conversion processing operations is selected and outputted. In addition, the L*a*b* data outputted from the selector 205 are adversely converted into an XYZ table color system via an L*a*b* adverse conversion part 206 and furthermore converted into the YMCK image data via an XYZ adverse conversion part 207.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image processing for transferring color image information between devices such as CRTs and color printers / color copiers having different color reproduction spaces and between a scanner and a printer in a full color digital copying machine. The present invention relates to an image processing apparatus, and more particularly, to an image processing apparatus capable of adjusting a color space including a designated color to another designated color and performing color conversion according to a user's preference.

[0002]

2. Description of the Related Art In recent years, media handling color images have been developed in various forms. For example, there is known a system in which characters / images are read by a color scanner, edited / processed on a computer display, and the results are printed out by a color printer or the like.

In this case, however, the colors reproduced on the display and the colors printed out are different in the color reproduction method and the color mixture system (RGB, YMC), and the color reproduction range does not match. It is also well known that the colors are different from each other.

Therefore, a color management system using device-independent colors has been studied with the aim of performing simple and accurate color reproduction between different color input / output devices (devices). This system aims to achieve colorimetrically consistent color reproduction among various devices by using an independent color signal for each device.

In such a color management system, by performing mutual color conversion between the device-specific color signal and the standard color signal, it is possible to perform device-independent color conversion within the color reproduction range. .

In general, for device-independent color signals, CIE1931 XYZ signals (XYZ color system) and L ^* a which are three-color color systems defined by CIE (International Commission on Illumination) are used.
A signal matching the human visual characteristics such as the ^* b ^* signal (CIELAB space) is used.

Further, in the conventional digital copying machine, in order to convert the RGB image signal (device signal) read by the scanner into the RGB image data of the printer in the case of performing the color conversion according to the user's preference, 3 For example, L ^* a ^* b ^* signals (device-independent signals) formed by a color space of three-dimensional coordinates are used to perform conversion by three-dimensional to three-dimensional mapping.

Further, as a reference technical document related to the present invention, an arbitrary hue and a hue range are designated so that a general user can perform color adjustment relatively easily, and within the hue range, a hue, a lightness, The one that adjusts saturation is
It is disclosed in "Selective Color Adjustment Method" of Japanese Patent Application Laid-Open No. 3-32162.

[0009]

However, in the conventional color conversion method and color adjustment method as described above, color conversion is performed by mapping the input / output color space in a three-dimensional to three-dimensional manner. Therefore, even when the color conversion is performed according to the user's preference, there are problems that the calculation for the three-dimensional conversion becomes complicated and the flexibility decreases.

The present invention has been made in view of the above, and it is an object of the present invention to realize a relatively simple and flexible color conversion when a color conversion designated by a user is performed. And

[0011]

In order to achieve the above object, in the image processing apparatus according to the first aspect, the color input image information is converted into spatial coordinates of lightness, hue and saturation,
In an image processing device for performing color conversion from a specified color specified from the outside to another specified color using the spatial coordinates, system control means for outputting a conversion color code corresponding to the specified color, and pre-conversion A plane area based on the hue and saturation including a color is adjusted to a range that does not overlap the area including the specified color, and the inside of the area is converted into a specified color based on a conversion color code output by the system control means. And a color conversion means for performing the same.

That is, after the color input image information is converted into the color space of the color system, the two-dimensional coordinates of hue and saturation are used,
The conventional three-dimensional conversion is performed by adjusting the area including the color before conversion to a range that does not overlap the area including the specified color and performing color conversion into the specified color based on the specified conversion color code in the area. A simple color conversion is realized compared to.

Further, in the image processing apparatus according to the second aspect, the color conversion means outputs the color input image information as L
^* a ^* b ^* By using the converted image information, the image information of the planar area including the color input image information is replaced with the image information of the area including the designated color after conversion.

That is, the color input image information is L ^* a ^* b ^* converted via, for example, the XZY color system to obtain a ^* b ^*.
Data using a ^* b ^* coordinate system according to a ^* axis and b ^* axis,
By executing the color conversion by replacing the image information of the area including the input color of the color corresponding to the specified color with the image information of the area including the specified color after conversion, based on the conversion color code provided by the system control means. , Color conversion on a two-dimensional a ^* b ^* plane is realized.

Further, in the image processing apparatus according to the third aspect, the color conversion means outputs the color input image information as L
^{By using the *} a ^* b ^* converted image information, color conversion is performed in the planar area including the color input image information while maintaining color continuity inside and outside the area.

That is, the color input image information is L ^* a ^* b ^* converted through, for example, the XZY color system to obtain a ^* b ^*.
Data using a ^* b ^* coordinate system according to a ^* axis and b ^* axis,
Based on the conversion color code provided by the system control means, the color conversion is executed while maintaining the color continuity between the inside and the outside of the area including the input color, so that the two-dimensional a ^* b
^* Realizes color conversion on a plane.

Further, in the image processing apparatus according to the fourth aspect, the color conversion means is provided with a table in which the two-dimensional data of a ^* b ^* is stored, and when a single color conversion is designated, L ^* the intact without converting the one in which the a ^* b ^* data, and load the a ^* b ^* data corresponding from the table based on the code specified by the system control means outputs.

That is, when the monochromatic conversion is designated, the lightness L ^* is not converted as it is, and the a ^* b ^* data is monochromatic converted using the data loaded from the table designated by the system control means. By doing so, the monochromatic conversion is efficiently output.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the system configuration of a color copying machine to which the image processing apparatus according to this embodiment is applied.

In FIG. 1, 101 is a scanner unit for reading a color image and outputting R, G, B image data according to the input image, and 102 is color conversion specified by the user, color processing such as single color, and A color conversion unit 103 as a color conversion unit for converting Y, M, C, K image data converts the Y, M, C, K image data output from the color conversion unit 102 into printer-dependent image data. It is a gradation processing unit.

A printer unit 104 forms an image of Y, M, C, and K image data processed by the gradation processing unit 103 on recording paper and outputs the image data.
01, a color conversion unit 102, a gradation processing unit 103, and a printer control unit 104, which is a system control unit serving as a system control unit that gives a control signal and a conversion color code.

FIG. 2 is a block diagram showing the detailed arrangement of the color conversion unit 102 in FIG. In FIG. 2, 201
Is an XYZ conversion unit for converting the input R, G, B image data into an XYZ color system, and 202 is an L ^* a for converting XYZ obtained by the XYZ conversion unit 201 into an L ^* a ^* b ^* uniform color space. ^* b ^* conversion unit, 203 is L ^* a ^* b ^* conversion unit 2
02 is a color conversion unit that converts the a ^* b ^* data based on the conversion color code from the system control unit 105.

Further, 204 is a standardized 2 of a ^* b ^*.
A ^* b ^* table in which dimension reference data is stored, 2
Reference numeral 05 is a selector for outputting data by specified color conversion or single color conversion (color processing) described later based on the processing code from the system control unit 105, and 206 is an XYZ color system for the L ^* a ^* b ^* uniform color space. Convert to L ^*
An a ^* b ^* inverse conversion unit 207 is an XYZ inverse conversion unit that converts the XYZ color system into YMCK image data.

Next, the operation of the color copying machine configured as described above will be described. First, referring to FIG. 1, the scanner unit 101 is controlled under the control of the system control unit 105.
The image is read by and the RGB image data is output.

The RGB image data is converted into YMCK image data by the color conversion unit 102 by the color conversion specified by the user. Further, these image data are converted by the gradation processing unit 103 into image data depending on the printer unit 104, and the printer unit 104 outputs the image.

Next, the operation of the color conversion section 102 will be described with reference to FIG. The color conversion unit 102 of the present embodiment selectively executes two conversion processes of designated color conversion (including through process) and color processing such as single color. Hereinafter, description will be made in order.

(1) Specified Color Color Conversion Processing The RGB image data from the scanner section 101 is converted into an XYZ color system by the XYZ conversion section 201 and further L ^*.
The a ^* b ^* conversion unit 202 converts the L ^* a ^* b ^* uniform color space.

Then, this a ^* b ^* data is used for the color conversion unit 2.
03 is input. The a ^* b ^* data is converted into a ^* b ^* data of the corresponding color based on the conversion color code sent from the system control unit 105. There is also a through instruction in the above conversion color code. In the case of through, a ^* b ^*
Output data through.

(2) Color processing such as single color In the color conversion unit 203, color processing such as single color is performed in addition to the above processing. Based on the processing code sent from the system control unit 105, corresponding a ^* b ^* data is output from the a ^* b ^* table 204.

When the processing code sent from the system controller 105 is input to the selector 205, the above-mentioned 2
Output data of either one of the two conversion processes is selected and output. Further, the L ^* a ^* b ^* data output by the selector 205 is the L ^* a ^* b ^* inverse conversion unit 206.
Is converted back to the XYZ color system, and
The Z color system is converted into YMCK image data by the XYZ inverse conversion unit 207 and output.

Next, the color conversion processing by the color conversion unit 102 will be described in more detail. The color conversion method in the present embodiment makes it possible to adjust the color space including the designated color and realize color conversion that matches the user's preference.
Color conversion in the L ^* a ^* b ^* uniform color space will be described as an example.

The RGB image data read by the scanner unit 101 is converted into the XYZ color system by the following conversion formula. It should be noted that this conversion uses the CIE1931 color system (XYZ color system) based on the additive color mixing experiment of the visual field of 2 °.

That is, the conversion formula is given by X = 2.77R + 1.75G + 1.13B Y = 1.00R + 4.59G + 0.06B Z = 0.00R + 0.06G + 5.59B.

Further, X obtained by the above conversion formula
CIE197 using YZ and the following conversion formulas
6L ^* a ^* b ^* Convert to uniform color space.

[0035] That is, conversion formula ~ ^{is, L * = 116 (Y /} Y 0) 1/3 -16 ··· a * = 500 {(X / X 0) 1/3 - (Y / Y 0) 1 ^{/ 3} ··· b * = 200} {(Y / Y 0) 1/3 - (Z / Z 0) 1/3} given by ....

In the a ^* b ^* coordinate system, the distance from the origin is c ^* , the angle between the origin and the vector in the positive direction of the a ^* axis is θ, and a ^* of the specified color before color conversion, Let the values of b ^{* be} a _A ^* and b _A ^* .

The magnitude of the vector (a _A ^* , b _A ^* ) is c _A ^* , and the angle between the a ^* axis and the positive direction is θ _A. In addition, the angle formed by the positive direction of the a ^* axis of the specified color after color conversion is θ _B. Further, it provided respectively theta _th region determines the specified color before color conversion to the positive and negative directions than theta _A.

Further, the image data input from the scanner section 101 are R _in , G _in and B _in . R _in , G _in , B
_in was calculated and converted on the basis of - the above conversion formula L ^* a
Let the values of ^* b ^* be L ^* _in , a ^* _in , and b ^* _in , respectively.

When a ^* _in and b ^* _in fall within the above range, δ calculated by the following formula 1 or formula 2
Output by rotating only a ^* _out , b ^*
Calculate _out .

Further, FIG. 3 shows an example of color conversion (replacement of regions) by L ^* a ^* b ^* of the mathematical formula 1, and L ^{* of} the mathematical formula 2 ^.
FIG. 4 shows an example of color conversion (maintaining continuity of areas) by a ^* b ^* .

[0041]

[Equation 1]

Further, δ in the following equation 2 is obtained by satisfying the following condition in order to maintain continuity at the boundary of the region. That is, when θ _in = θ _A , θ _out = θ _B θ _in = θ _A + θ _th , θ _out = θ _A + θ _th θ _in = θ _A −θ _th , θ _out = θ _A −θ _th .

[0043]

[Equation 2]

Then, L _in , a ^* _out , and b ^* _out are input to the above-mentioned conversion formulas ~, and X _out ,
Calculate Y _out and Z _out . Also, this X _out ,
Y _out and Z _out are input to the above conversion formula, and R _out , G _out , and B _out are calculated by inverse conversion thereof. Further, these R _out , G _out , and B _out are processed in the subsequent processing unit (see FIG. 2).
Then, the image is finally output by the printer unit 104.

In the present embodiment described above, RGB image data is converted into L ^* a ^* b ^* , L ^* is not converted,
Since color conversion is performed on the a ^* b ^* plane, it is possible to perform color conversion in two dimensions, which is easy to process, as compared with conventional three-dimensional mapping.

Therefore, the flexibility for determining the color conversion range is widened as compared with the three-dimensional color conversion, and the calculation for the color conversion can be simplified. Also, 2
Since the mapping is two-dimensional to two-dimensional, it is easy to map the color before conversion and the color after conversion.

Further, by using the standardized L ^* a ^* b ^* , so-called device-independent color conversion that does not depend on the scanner unit 101 (device) is realized.

Further, in the area including the designated color before conversion, the color conversion is performed while maintaining the color continuity inside and outside the area, so that the color continuity at the boundary portion of the designated color can be maintained. Becomes In addition, the lightness L ^* is calculated by the color conversion unit 102.
Since it can be used in another part (single color, etc.), the conversion efficiency is improved.

[0049]

As described above, according to the image processing apparatus (Claim 1) of the present invention, after the color input image information is converted into the color space of the color system, the two-dimensional hue / saturation is obtained. Using coordinates, the area containing the color before conversion is adjusted to a range that does not overlap the area containing the specified color, and the area is converted to the specified color based on the specified conversion color code. It is possible to realize color conversion with a simpler configuration than the dimensional conversion, the conversion process is simplified, and the flexibility is excellent.

Further, according to the image processing apparatus (Claim 2) of the present invention, the color input image information is converted into, for example, XZY.
L ^* a ^* b ^* conversion is performed via the color system, and a ^* b ^* data is converted into a ^* b ^* coordinate system based on the a ^* axis and the b ^* axis based on the conversion color code given by the system control means. , The color conversion is performed by replacing the image information of the area including the input color of the color corresponding to the specified color with the image information of the area including the specified color after conversion, which is simpler than the conventional three-dimensional conversion. With the configuration, the conversion process can be simplified, and the color conversion with excellent flexibility can be realized.

Further, according to the image processing apparatus (Claim 3) of the present invention, the color input image information is converted into, for example, XZY.
L ^* a ^* b ^* conversion is performed via the color system, and a ^* b ^* data is converted into a ^* b ^* coordinate system based on the a ^* axis and the b ^* axis based on the conversion color code given by the system control means. , Since the color conversion is executed while maintaining the continuity of the color inside and outside the area including the input color, the structure is simpler than the conventional three-dimensional conversion and the conversion process is simplified. Moreover, it is possible to realize color conversion with excellent flexibility.

Further, according to the image processing apparatus of the present invention (claim 4), when the monochromatic conversion is designated, the lightness L ^* is not converted as it is and the a ^* b ^* data is controlled by the system control. Since the monochromatic conversion is performed by using the data loaded from the table designated by the means, the monochromatic conversion can be efficiently output.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration of a color copying machine to which an image processing apparatus according to this embodiment is applied.

FIG. 2 is a block diagram showing a detailed configuration of a color conversion unit shown in FIG.

FIG. 3 is an explanatory diagram showing an example of region replacement conversion by L ^* a ^* b ^* according to the present embodiment.

FIG. 4 is an explanatory diagram showing an example of conversion in which the continuity of regions is maintained by L ^* a ^* b ^* according to the present embodiment.

[Explanation of symbols]

101 scanner section 102 color conversion section 201 XYZ conversion section 202 L ^* a ^* b ^* conversion section 203 color conversion section 204 a ^* b ^* table 205 selector

Claims (4)

[Claims] 1. Image processing for converting color input image information into spatial coordinates of lightness, hue, and saturation, and using the spatial coordinates, performing color conversion from a specific designated color externally designated to another designated color. In the device, a system control unit that outputs a conversion color code corresponding to the designated color, and a plane area based on the hue / saturation including the color before conversion are adjusted to a range that does not overlap the area including the designated color, An image processing apparatus comprising: a color conversion unit that converts the inside of the area into a designated color based on the conversion color code output by the system control unit. 2. The color conversion means uses image information obtained by L ^* a ^* b ^* conversion of the color input image information, and specifies the image information of the planar area including the color input image information after the conversion. The image processing apparatus according to claim 1, wherein the image information is replaced with image information of an area including a color. 3. The color conversion means uses image information obtained by L ^* a ^* b ^* conversion of the color input image information, and defines inside and outside of the area in the plane area including the color input image information. The image processing apparatus according to claim 1, wherein the color conversion is performed while maintaining color continuity. 4. The color conversion means comprises a table storing a ^* b ^* two-dimensional data, and when single color conversion is designated, L ^* is left unconverted and a ^*
The b ^* data, the image processing apparatus according to claim 2 or 3 on the basis of the system control means to the specified code to load the a ^* b ^* data corresponding from the table, and outputs.