JP3393679B2 - Color image processing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention converts image data decomposed into three color components into values in a uniform color coordinate space, and converts image data values in a color adjustment area set in the uniform color coordinate space. The present invention relates to a color image processing device that performs a process of moving a predetermined distance in a desired direction in a uniform color coordinate space.

[0002]

2. Description of the Related Art In a color copying machine or a color photographing machine, a target image read by a scanner or a color image pickup tube is converted into digital image data and subjected to various kinds of image processing, and then output to a printer or a display tube for reproduction. Although the image is reproduced, in order to obtain a reproduced image that is faithful to the original image, the image data that is decomposed into the three primary color components and converted into an electrical signal is subjected to color correction (masking) processing, The complementary color component data was obtained. That is, complementary color component data {C, M,
Y} is given by the conversion formula (4) shown in FIG.
In Equation (4), a _ij is a color correction coefficient, and D _r, D _g, D _b are density signals of the three primary color components R, G, B of the color. The color correction coefficient a _ij is a conversion coefficient that compensates for color reproduction distortion such as ink density characteristics and non-linear characteristics when color inks are mixed. By the way, the color and brightness of an object of interest depending on human visual characteristics may be affected by the color and brightness of a background object, and even the same object may look different. In addition, for example, when a reproduced image is viewed after viewing a document, there is a time lag between them, or an impression is influenced by a memory color empirically cultivated by an individual's preconceptions or expectations. . For example, healthy and bright skin tones are preferred, while bright colors are preferred for plant flowers and leaves. Therefore, when printing the image of the target object or displaying it on the display tube, not only the color and brightness are faithfully reproduced, but also selective emphasis processing is performed so that only the image of a specific color approaches the memorized color. The method of dynamic emphasis has already been proposed.

[0003]

In the above prior art, the R, G, B color signals are L ^* a ^* b which is a uniform color space.
^* Converts to H ⁰ ab _, L ^* _, C ^* polar coordinate system defined in space and has characteristics of step type, trapezoidal type, mountain type, etc.
By using the membership function in the ^* b ^* plane, the color coordinate values in the predetermined region are rotated in the H ⁰ ab direction to obtain C ^* ab
Color adjustment processing is performed so as to expand in the direction. With such a color adjustment process, for example, the colors of the flowers and leaves of the plant can be adjusted to more vivid colors, but the color coordinate values of the skin color image area are adjusted according to the value of the membership function. Although the process of rotating to the yellow side was performed, satisfactory output images were not always obtained for various input images.
Further, since the calculation of the above-mentioned color adjustment processing has to be performed for all the color coordinate values, the calculation circuit becomes complicated and the calculation processing takes a long time. The present invention has been made in order to solve such a problem in the prior art, and can adjust a color corresponding to a color coordinate in an arbitrary color adjustment area to a desired color, and the color adjustment processing time is short and the cost is low. An object is to provide a color image processing device.

[0004]

According to the present invention, in order to solve the above problems, input image data obtained by converting image data decomposed into three color components into values in a uniform color coordinate space by a coordinate space conversion means is uniform. Area determination means for determining whether or not the color adjustment area is within the color adjustment area set in the color coordinate space, and uniform color coordinate values of image data in the color adjustment area are set for the color adjustment area.
Degree of movement distance with respect to fixed movement direction and maximum movement amount
It is calculated using the emphasis function indicating
By doing so, the uniform color coordinates of the image data in the color adjustment area
To the target value of the uniform color coordinates preset in the color adjustment area.
Movement amount calculating means for calculating the distance to be moved in a direction approached,
And this distance calculated by the movement amount calculation means within the color adjustment area.
Includes a subtraction means <br/> for subtracting the value of the uniform color coordinates of the image data, a distance equal color coordinates of the image data of the color correction region-movement-distance calculation means is calculated images uniform color coordinate space
Before moving the uniform color coordinate data in a direction approaching the target value
It is also of the. In addition, the color adjustment area can be divided into multiple sub color adjustment areas.
Subdivided, a moving distance storing unit a movement distance for moving the value of the image data in a direction to approach to a preset target value in the color adjustment area of the color adjustment region and stored for each sub-color adjustment area, the input It is judged against the uniform color coordinates of the image data.
Read the moving distance of the sub color adjustment area from the moving distance storage means.
Add and subtract to take and add to the uniform color coordinates of input image data
Means for calculating the uniform color coordinates of the input image data.
Secondary color adjustment area determined for uniform color coordinates of image data
It may be moved in a direction approaching the target value of the uniform color coordinates by the moving distance corresponding to .

[0005]

In the former method, the coordinate space conversion means converts the image data decomposed into the three color components into the values in the uniform color coordinate space, and the area determination means converts the input image data into the uniform color coordinate space. It is determined whether or not the color adjustment area is within the color adjustment area. Movement amount calculation means is set within the color adjustment area
Degree of movement distance with respect to the specified movement direction and maximum movement amount
Using the emphasis function indicating
By obtains the distance to move the value of the image data of the color correction region in a direction approached, the preset target value in the color adjustment area, this subtraction means, as determined by the movement amount calculating means
To the value of the uniform color coordinates of the image data in the color adjustment area.
Addition and subtraction are performed, and the uniform color coordinates of the image data are moved in the direction in which they approach the target value within the uniform color coordinate space by the distance calculated by the movement amount calculation means. In the latter means, the area determination means determines whether or not the input image data is within the sub color adjustment area obtained by subdividing the color adjustment area into a plurality of areas, and the specific color emphasis processing means is the area determination means. The value of the image data determined to be within the sub color adjustment area is moved in the direction closer to the target value by the movement distance corresponding to the corresponding sub color adjustment area read from the movement distance storage means.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an image processing system of a copying machine according to the first embodiment of the present invention. The image data of the original read by the color scanner 1 is decomposed into three color components of R, G, B and input to the spatial coordinate system conversion unit 2. The three-component data of R, G, and B input to the spatial coordinate system conversion unit 2 is converted into an X, Y, Z system that does not depend on the spectrum of the illumination lamp of the color scanner 1, and then L that is in harmony with human vision. ^It is converted into the ^* a ^* b ^* uniform color space, and further converted from the Cartesian coordinate system to the H ⁰ ab _, L ^* _, C ^* polar coordinate system and output to the color emphasizing unit 3. In the color enhancement unit 3, the color enhancement processing described below is performed and the output H ⁰ ab _, L ^{* is} output ^.
_The C ^* polar coordinate system color data is returned to the original R, G, B color data by the spatial coordinate system conversion unit 4. Then, after the known color correction processing corresponding to the toner density characteristics and the mixing characteristics is performed in the color correction section 5, the complementary color conversion section 6 converts it into Y, M, and C complementary color component data, and outputs it to the printer 7. Then, a reproduced image is formed on the recording paper.

FIG. 8 shows image data obtained by reading a Munsell color chart that gives a color standard, converted into L ^* a ^* b ^* space by a.
FIG. 9 is a diagram showing an equal hue and an iso-saturation curve on the ^* b ^* plane, and FIG. 9 is a conceptual diagram showing an H ⁰ ab _, L ^* _, C ^* polar coordinate system. As shown in FIG. 8, as the hue angle H ⁰ ab increases from 0, the hue changes in the order of red, yellow, green, blue, and purple. The more saturated C ^* , the more vivid the color becomes.
As the lightness L ^* increases, the color becomes lighter. FIG. 3 is an explanatory diagram showing a typical memory color area on the a ^* b ^* plane that is likely to be visually impressive or has a desired color sense. The areas are designed not to overlap each other in order to prevent duplication of processing. In the present embodiment, these memory colors are also subjected to color enhancement processing. However, in the present embodiment, a target value that a majority of people feel is preferable for each memory color, and color coordinates are set. Color enhancement processing is performed so that the value approaches the target value. That is, if the hue value of the input data is I (H), the saturation value is I (C), the hue value of the output data is O (H), and the saturation value is O (C), then the output data O (H). , O (C) are given by the equation (1) shown in FIG. However, in the formula (1), M (H), M
(C) is an emphasis function, and for example, in hue, as shown in FIG. 4, (a) step shape, (b) mountain shape, (c) trapezoidal shape, and other emphasis characteristics. (Hue) and (Chrom
a) represents the maximum shift angle of hue and the maximum shift amount of saturation. (A) The step-like enhancement function is moved by the maximum movement amount in almost the entire region, and (b) the mountain-shaped one is moved by the maximum movement amount in the central part of the region, but it is hardly moved near the region boundary. c) A trapezoidal shape represents an intermediate shape. As described above, the (a) step-like enhancement function has the greatest hue enhancement effect, but there is a risk that discontinuity of hue will occur between adjacent picture patterns and the hue will be unnatural. (B) The mountain-shaped one has a continuous hue between adjacent patterns, so that the image has a natural hue, but the hue emphasis effect is the smallest.

As a specific example, a case will be described in which the target hue value hT is provided in the substantially central portion of the skin color region and (b) mountain-shaped one is selected as the enhancement function. FIG. 5 and FIG. 6 are explanatory diagrams showing a transition state of the color coordinate values in a region having a smaller hue angle than the target hue value hT of the skin color region and an explanatory diagram showing the transition state of the color coordinate values in the entire region, respectively. In a region where the hue angle is smaller than the target hue value hT, the value of M (H) is a positive value, and as shown in FIG. 5, the color coordinate value shifts in the direction in which the hue angle increases, and the target hue value The amount of shift in the vicinity of the center of hT (65) and the minimum hue value hL (38) is the largest. On the other hand, the target hue value hT
In the region between the maximum hue value hH and the maximum hue value hH, the value of M (H) is a negative value, and as shown in FIG. 6, the color coordinate value shifts in the direction of decreasing the hue angle, and the target hue value hT And the maximum hue value hH in the vicinity of the center has the largest amount of shift, and in the vicinity of the boundary the amount of shift is the smallest. The same applies to the memory color areas other than the skin color area. For example, a predetermined target saturation value is set in the flower color area, and the color coordinate value in the area is set to the target saturation value by the color emphasis processing. Move toward the value. As described above, these processes are performed by the color emphasizing unit 3. In reality, however, first, the image data displayed by the color coordinate values input by the region determining unit 31 is within a preset memory color region. It is determined whether or not. For the image data determined to be within the set memory color area, the movement amount calculator 32 calculates the movement amount of the color coordinate value based on the enhancement function. The movement amount calculated by the movement amount calculation unit 32 is added / subtracted to / from the input data by the addition / subtraction unit 34 and output.

As described above, in the first embodiment, for the image data determined to be within the set memory color area, the movement amount calculation unit 32 moves the color coordinate value based on the enhancement function. However, since it takes a considerable time to calculate the movement amount for each color coordinate value, the copying speed cannot be increased. Therefore, a second embodiment of the present invention will be described in which the calculation of the movement amount does not take a long time. In this embodiment, according to the property of the set memory color area,
A large number of sub-divided areas are set in the hue direction or the saturation direction, and the amount of movement with respect to the color coordinate values in the sub-divided areas is assumed to be approximately constant, and the values calculated in advance are associated with each other. is there. That is, the set memory color area is divided into m in the hue direction (h1, h2, ... hm) or n in the saturation direction (c1, c2, ... cn), and the color coordinate value corresponding to each sub-divided area is obtained. Is calculated in advance and stored in the memory, and when it is determined that the image data input by the area determination unit 31 is in the sub-divided area hi, cj in the memory color area, O (H ) = I (H) + Hi (2) O (C) = O (C) + Cj (3) (where Hi and Cj are movement amounts with respect to the color coordinate values corresponding to the sub-divided areas hi and cj) The output data subjected to the color enhancement processing can be obtained only by executing the addition and subtraction represented by. Since the processing time required for addition and subtraction is extremely short, the copying speed can be increased. FIG. 2 is a block diagram showing an image processing system in the vicinity of the color enhancement unit 3 according to this embodiment. The first
The same reference numerals are attached to the portions which are the same as or can be regarded as the same as those of the embodiment. It is determined whether or not the image data input by the area determination unit 31 is within the preset memory color area, and which sub-pixel is added to the image data determined to be within the preset memory color area. It is determined whether it belongs to the divided area. Then, the moving amount Hi, Cj with respect to the color coordinate value corresponding to the sub-divided area hi, cj determined by the reference unit 33 is read, and the read moving amount data Hi, Cj is added to / subtracted from the input data and output. To be done. FIG. 7 shows, as a specific example, sub-divided areas hi and cj of a skin color area and a flower color area. In the present embodiment, the example in which the sub-divided areas are divided into a large number in the hue direction or the saturation direction is shown, but of course, a large number of areas may be divided into both the hue direction and the saturation direction.

[0010]

As described above, according to the first aspect of the invention, the area determining means for determining whether or not the input image data is within the color adjustment area, and the value of the image data within the color adjustment area are provided. and by using the enhancement function and the maximum movement distance, a movement amount calculating means for calculating a distance to move in a direction to approach to a preset target value in the color adjustment region, the movement amount computation hand
This distance obtained by the step is used to equalize the image data in the color adjustment area.
Because it has a subtraction means for subtracting the value of the color coordinates, the movement amount calculating means uniform color coordinates of the image data can be moved in a direction approached, only target distance computed, any color of the color adjustment area The color corresponding to the coordinates can be adjusted to the desired color without excess or deficiency. According to the second aspect of the present invention, the area determination means for determining whether or not the input image data is in the sub color adjustment area obtained by subdividing the color adjustment area into a plurality of areas, and the image data in the color adjustment area. a moving distance storing means for storing the moving distance for moving the value in a direction to approach to a preset target value in the color adjustment region for each sub-color adjustment area, area-size
Judgment for uniform color coordinates of input image data
The movement distance of the selected sub color adjustment area from the movement distance storage means.
Read, add / subtract to the uniform color coordinates of input image data
Because it has a subtracting means, approached, only the target value moving distance corresponding to the sub color adjustment area corresponding area determining means reads the value of the image data determined to be in the sub-color adjustment region from the moving distance storing unit The color adjustment processing time for adjusting to a desired color can be shortened and the apparatus price can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an image processing system of a copying machine according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an image processing system in the vicinity of a color enhancement unit according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a typical memory color area on an a ^* b ^* plane.

FIG. 4 is a characteristic diagram illustrating an enhancement function.

FIG. 5 is an explanatory diagram showing a transition state of color coordinate values in a region where a hue angle is smaller than a target hue value hT.

FIG. 6 is an explanatory diagram showing a transition state of color coordinate values in all areas.

FIG. 7 is an explanatory diagram showing sub-divided areas of a skin color area and a flower color area.

FIG. 8 shows a ^* b image data obtained by reading Munsell color chart.
^* Figure showing iso-hue and iso-saturation curves on a plane

FIG. 9 is a conceptual diagram showing a H ⁰ ab _, L ^* _, C ^* polar coordinate system.

FIG. 10 is a diagram showing a formula for calculating a hue value and a saturation value of output data from a hue value and a saturation value of input data.

FIG. 11 is a diagram showing a conversion formula in color correction processing.

[Explanation of symbols]

1 color scanner 2,4 Spatial coordinate converter 3 color emphasis section 5 color correction section 7 printer 31 area determination unit 32 Movement amount calculation unit 33 Reference 34 Adder / Subtractor

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Claims (2)

(57) [Claims] 1. A coordinate space conversion means for converting image data decomposed into three color components into a value in a uniform color coordinate space, and a value of image data in a color adjustment area set in the uniform color coordinate space. In the color image processing apparatus including a specific color enhancement processing unit that performs a process of moving the image in a desired direction in the uniform color coordinate space by a predetermined distance, the specific color enhancement processing unit determines that the uniform color coordinates of the input image data are Area determining means for determining whether or not the color adjustment area is within the color adjustment area; and a value of the uniform color coordinates of the image data within the color adjustment area for the maximum movement distance set for the color adjustment area .
The emphasis function indicating the degree of moving distance and the maximum moving distance are
The image data in the color adjustment area is calculated by using
The uniform color coordinates of the data are preset in the color adjustment area.
A movement amount calculation means for obtaining a distance to move toward a target value of the uniform color coordinates , and the distance obtained by the movement amount calculation means for the color adjustment region.
Addition and subtraction to the value of the uniform color coordinates of the image data in
And a calculation unit, a distance the average of the uniform color coordinates of the image data of the color adjustment area is the moving amount calculation means has calculated
A color image processing device, characterized in that the color image processing device is moved in a direction approaching a target value of color matching coordinates . 2. A coordinate space conversion means for converting image data decomposed into three color components into a value in a uniform color coordinate space, and a value of image data in a color adjustment area set in the uniform color coordinate space. In the color image processing apparatus including a specific color enhancement processing unit that performs a process of moving the image in a desired direction in the uniform color coordinate space by a predetermined distance, the specific color enhancement processing unit determines that the uniform color coordinates of the input image data are Multiple color adjustment areas
Area determination means for determining whether or not the sub color adjustment area is subdivided, and the value of the uniform color coordinates of the image data in the color adjustment area is set in the color adjustment area. A moving distance storage unit that stores, for each of the sub color adjustment regions, a moving distance to move toward a target value of preset uniform color coordinates , and a uniform color coordinate of the input image data by the region determination unit.
The moving distance of the sub color adjustment area determined for the target
The input image data is read from the moving distance storage means.
And a subtraction means for subtracting the uniform color coordinates, the entering
The uniform color coordinates of the force image data,
The sub color determined with respect to the uniform color coordinates of the input image data
In a direction approaching the target value of only the moving distance the uniform color coordinate corresponding to the adjustment region, color image processing apparatus characterized by moving.