JPH05119752A - Method and device for adjusting color of color image - Google Patents

Abstract

PURPOSE:To keep the nature of an image before being adjusted in an image after being adjusted as for a method in which an optional color included in a color image is extracted to correct to a specified color. CONSTITUTION:The representative point of the color image is specified at a representative point specifying step S1. Next, a target color being an adjusting target for the color of the representative point is specified at a target color specifying step 2. A correction quantity necessary for changing the color of the represantative point to the target color is calculated at a correction quantity arithmetic step S3, and finally, the correction quantity at the representative point obtained at the step S3 is corrected in accordance with a position where the image data of the respective picture elements of the color image occupies color space, and then a correction quantity correcting step S4 at which the correction quantity of each picture element is decided is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color adjusting method and a color adjusting apparatus for a color image. More specifically, the present invention relates to a color adjustment method for a color image that extracts an arbitrary color included in a color image and corrects it to a predetermined color, and a color adjustment device for the color image used for that purpose.

In recent years, in the field of designing automobiles and clothing, it has become possible to easily adjust the colors that a designer imagines using a color monitor. In order for a designer to determine a color in a design system using a color monitor, a computer is used to process image data. Further, when creating computer graphics, it is necessary to adjust the color when assigning a color to each part of the image on the monitor or changing the color once determined. In such a case, the computer allocates specific colors to each part of the shape of the product created on the monitor, or executes data processing to adjust the color of the screen read from a reading device such as an image scanner. To do.

Therefore, there is a demand for a color adjustment method for a color image that can accurately extract a color and can easily partially correct a color. Here, in particular, a color-corrected color image is adjusted to a target color without losing the original naturalness of the product, and a target is set so as to enhance the interface between the computer and humans at that time.

[0004]

2. Description of the Related Art In conventional color adjustment and correction, there has been a method of simultaneously displaying a color palette on a display and selecting a color desired by an operator from the same screen as an image display. FIG. 7 shows a color palette divided into a plurality of vertical and horizontal sections. Different colors are arranged in the areas 31 and 32 of the color palette 30, respectively. This method has the advantage that the modified color can be visually selected, but the number of colors that can be selected is limited by the partition of the palette. As a result, the stereoscopic effect of the object and the fine color change that the first image had are lost, and the image loses its natural appearance.

Another color adjustment method is to input a color desired by an operator as color data. FIG. 8 shows a color data adjustment screen displayed on the display.
Generally, there are hue, saturation, and lightness as color attributes perceived by humans. Therefore, if the hue (H), the saturation (S), and the lightness (V) of the color data are selected as the three-dimensional orthogonal coordinate values of the color data in the color space, the color image stored in the RGB data can be obtained. The image data is displayed as parameters. Therefore, if an image in which the knobs for adjusting H, S, and V are pseudo-displayed as shown in FIG. 8 is used and these three parameter values are added to or subtracted from the image data before correction, the color of the color image is changed. Can be adjusted.

In the latter color adjustment method, the selection of three parameter values diversifies the color selection, and compared with the former method, the target color is adjusted without losing the original naturalness of the product. Above, it is extremely convenient.

[0007]

However, even in the latter method of adjusting the adjustment amount to the original image data, the adjustment is performed when the same color region is selected as the adjustment target region and the color is corrected. If the lightness and saturation are changed uniformly among the power parameter values, the glossy part of the object before modification, which should be a whitish area in the image, may be colored or shadowed. There is a problem that the part that should be a dark area is colored and the feeling of the object is changed or the contrast is lowered.

There is also a problem that a pseudo contour is generated if there is an area of the same color system in the background of the area to be adjusted.
That is, although the image originally had an unclear outline due to continuous color change at the boundary with the background, an unnatural outline is added as a result of the color correction. In this way, since the adjustment amount is uniformly adjusted in the image data,
There is still a problem that the adjusted image cannot save the same natural feeling as the original image.

The present invention has been made in view of such a point, and the adjustment amount is corrected in accordance with the coordinate value of the image data to be adjusted in the color space, and the adjusted image becomes a natural image of the image before adjustment. It is an object of the present invention to provide a color adjustment method for a color image that saves the color.

Another object of the present invention is to enhance the interface between a computer and a human in adjusting a target color without losing the naturalness of the color-corrected color image. It is to provide an adjusting device.

[0011]

FIG. 1 is a flow chart for explaining the principle of the present invention for achieving the above object.
As shown in FIG. 1, in the color adjusting method of the color image of the present invention, each pixel of the color image is subjected to the representative point specifying step S1, the target color specifying step S2, the correction amount calculating step S3, and the correction amount correcting step S4. The RGB data is adjusted according to the correction amount designated for each.

In the representative point specifying step S1, the representative point of the color image is specified. Next, the target color designation step S2
Then, the target color that is the adjustment target for the color of this representative point is specified. In the correction amount calculation step S3, the correction amount necessary for changing the color of the representative point to the target color is calculated,
Finally, correction amount correction for correcting the correction amount at the representative point obtained in step S3 according to the position of the image data of each pixel of the color image in the color space to determine the correction amount for each pixel. Step S4 is executed.

Further, the color image color adjusting apparatus of the present invention shown in FIG. 6 executes the above-described color image color adjusting method. This color image color adjusting device is an RGB data storage means 11 for storing a color image as RGB data of each pixel, and a representative for inputting a representative color by instructing a representative point in a color adjustment target area from the color image. A point indicating means 13, an image data storage means 16 for holding image data of a color adjustment target area including a representative point indicated by the representative point indicating means 13, and a representative color input by the representative point indicating means 13. Target color input means 17 for inputting the image data of the target color to be the adjustment target of, and correction amount calculating means 19 for calculating the correction amount in the color space of the image data of the representative point and the image data of the target color. A coefficient determining means 20 for determining a coefficient according to the coordinate value of each image data of the image data storage means 16, and a correction amount calculated by the correction amount calculating means 19 by the coefficient. Wherein the correction and color correction calculating means 21 to correct the image data stored in said image data storage means 16, the image data corrected by the color-correction unit 21 RGB data storage section 1
Display means 1 for displaying a color image in which the color of the adjustment target area is corrected from the color image stored in 1.

[0014]

In the method of the present invention, the correction amount is corrected by the coordinate value in the color space of the image data adjusted for the designated target color. As a result, the correction amount for the glossy portion and the shadow portion included in the color image is corrected, the feeling of the image can be saved, and the reduction in contrast can be prevented.

Further, when the target area for color adjustment is extracted and adjusted to change to the designated target color, the correction amount in the target area is weighted by a coefficient according to the coordinate value of each image data. Therefore, it is possible to perform color adjustment so that a pseudo contour does not occur at the boundary with the background color.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method of the present invention will be described below with reference to the drawings. FIG. 2 is a color monitor 1 for displaying a target image.
, A single flower is displayed on the screen 2 as an example of a color image. The target image is read from an original image by an image scanner, for example, and color adjustment is performed on the color monitor 1 by the procedure described below. At the upper left of the screen 2, a palette showing target colors similar to the color palette of FIG. 7 is displayed.

[Extraction of Adjustment Target Area] The operator designates one point of the image displayed on the screen 2 of the color monitor 1 with a mouse or the like to specify the representative point. For example, by pointing one petal with the cursor displayed on the screen 2, the image data of the petal portion is set as the target area for color adjustment. In extracting the target area, first, a representative color is obtained based on the image data of the representative point, a three-dimensional solid in a color space including the representative color is specified, and the image data included therein is common. It is extracted as a region. In this case, the area may be designated in the color space based on the RGB values of the image data, but here, the color data is converted into the color data represented in the color space based on the hue (H), the saturation (S), and the lightness (V). And extract.

[Designation of Target Color] The target color for color adjustment can be designated by pointing one color of the color palette of the screen 2 with a cursor. This target color specification is
Numerical data such as RGB values may be keyed in by an operator, and further, it is possible to specify by a word for specifying a color such as red or blue.

[Color Adjustment] First, the correction amount Δ of the image data required to change the image data of the representative point to the image data of the target color is obtained.

FIG. 3 shows hue (H), saturation (S), and lightness.
It is a figure which shows the color space coordinate by (V). Image here
In order to obtain the correction amount Δ of the data, it is displayed in RGB value.
Convert the target color image data to HSV color data
Then, the correction amount of each coordinate value of hue, saturation, and lightness is determined.
In FIG. 3, the image data D of the pixel corresponding to the representative point₀(H
₀, S₀, V₀) And the target color image data D₁(H₁，
s₁, V₁) Indicates the position occupied in the color space. Obey
And the correction amount Δ is two images in this color space (HSV).
Image data D₀, D₁Corresponds to the difference in each coordinate value of. Also,
Image data of the petals, which is the adjustment target area shown in FIG.
Is the image data D in the color space of FIG.₀Predetermined distance including
The image data D exists in a closed area separated by a distance.₀To
Shown here as image data {hx, sx, vx}
There is.

FIG. 4 shows a correction curve for correction based on the saturation value in the image data. The horizontal axis represents the saturation S and the vertical axis represents the correction coefficient value f ₁ (S) determined according to the saturation. ) Represents.
Further, the correction coefficient value f ₂ (V) can be determined from the brightness V by similarly setting the correction curve of the brightness value.

Next, each extracted image data {hx, s
x, vx} is corrected based on the correction amount Δ, the coefficients f ₁ (sx) and f ₂ (vx) determined by the coordinate values sx and vx of the saturation S and the lightness V are obtained, and the correction amount Δ Correct the corresponding component of. The coefficient for determining the correction amount can be determined by setting the correction curves shown in FIG. That is, each image data {hx, sx, vx} of the extracted adjustment target area is a new image centered on the image data D ₁ (h ₁ , s ₁ , v ₁ ) of the target color according to the following conversion formula. It is converted into data {hy, sy, vy}.

Hy = hx + (h ₁ −h ₀ ) sy = sx + f ₁ (sx) · (s ₁ −s ₀ ) vy = vx + f ₂ (vx) · (v ₁ −v ₀ ) Thus, the correction coefficient value is Both the saturation and the lightness are determined based on a correction curve that is the maximum at the median of the coordinate values of the color space. Here, the correction amount Δ is expressed by The shape is corrected linearly. However, the correction coefficient values g ₁ (sx) and g ₂ (vx) can be determined based on the Gaussian distribution curve shown in FIG. Further, although the shape of the function of the correction curve is the same for both the saturation and the lightness, it may be a straight line for the saturation and a curve (or the opposite) for the lightness.

Further, the correction amount at the representative point is
(S₁-S₀), For brightness (v₁-V₀)
For example, the representative point can be adjusted to the target color by the above conversion formula.
Therefore, according to the correction curve shown in FIG. 4 or FIG.
Saturation value s at the representative point when determining the shape of the number₀And Ming
Degree value v₀Correction coefficient value f at₁(S₀), F
₂(V ₀) Is set to 1 respectively,
-Saturation value sx and lightness value in the color space of each pixel of the image
The correction amount Δ is corrected according to the coordinate value of vx, and
Then, the color adjustment for each pixel is performed.

By performing such color adjustment, even if the color of the color image is corrected according to the target color, the relationship between the whitish area and the blackish area in the image is preserved, and the glossy part and the shadow part of the object are preserved. The contrast with and does not decrease, and the feeling of the object does not change. Also, like the conversion above, the saturation,
The black-and-white relationship of a color image can be preserved by correcting only the lightness without correcting the lightness correction amount.

Further, a specific image area is extracted from the color image as an adjustment target area and only the RGB data of the target area is adjusted according to the correction amount designated for each pixel. No pseudo contour is generated at the boundary with the background area.

FIG. 6 is a block diagram showing an example of the arrangement of the color adjusting apparatus of the present invention. The image input device 10 changes from the original image to R
Input image data such as a GB signal is captured in pixel units, and an image scanner or the like is used, for example. RG
The B data storage unit 11 stores the input color image as RGB data of each pixel. This image data is sent to the display memory 12 of the monitor 1 as it is, and the color image is displayed on the screen 2 of the monitor 1.

The representative point designating means 13 is, for example, a mouse connected to the color monitor 1 shown in FIG. 2, and can designate a representative point in the color adjustment target area from the color image displayed on the screen 2. As a result, the color data of the representative color is stored in the representative color data holding memory 14 from the representative point designating means 13. Further, the color adjustment area extraction circuit 15 extracts the area of the pixel including the representative point designated by the representative point designating means 13. In this extraction, it is possible to use the hue data of the representative points. The image data storage means 16 holds the image data of the color adjustment target area including the representative point designated by the representative point designating means 13 via the color adjustment area extraction circuit 15.

On the other hand, the target color input means 17 is displayed on the screen 2 of FIG.
The specific color of the color palette shown in is designated, or the target color is input as numerical data. By the target color input means 17, the target color data holding memory 1
Image data of a target color, which is an adjustment target of the representative color, is input to 8. The correction amount calculation means 19 includes image data D ₀ (h ₀ , s ₀ , v ₀ ) of a representative point and a target color image data D ₁ from the representative color data holding memory 14 and the target color data holding memory 18, respectively. (H ₁ , s ₁ , v ₁ ) is received and the correction amount Δ (Δh, Δs, Δv) in the color space is calculated.

The coefficient determining means 20 determines the coefficient according to the coordinate value of each image data from the image data storage means 16. This coefficient is determined on the basis of the correction curve shown in FIG. 4 or FIG. 5, and is used for correction processing of the correction amount Δ (Δh, Δs, Δv) obtained by the correction amount calculating means 19, for example, saturation and lightness. It That is, the color correction calculation means 21 has the coefficient value f ₁ (s
x), f ₂ (vx), each image data (hx, sx, vx) of the extracted adjustment target area, and the correction amount calculation means 19
The correction amount Δ calculated in step 3 is input, and the image data held in the image data storage means 16 is corrected in pixel units. The image data {hy, sy, vy} corrected by the color correction calculation means 21 is sent to the display memory 12 via the inverse conversion circuit 22. In this way, the color image whose color is corrected in the adjustment target area can be displayed on the color monitor 1 from the color image stored in the RGB data storage means 11.

In the above description, the case where the color adjustment area is extracted by designating the representative point has been described, but the target area can be extracted by specifying the target pixel by specifying the hue.

[0032]

As described above, according to the present invention, when the target color of the color image to be adjusted is designated and the color adjustment is performed,
The color adjustment is performed with the correction amount corrected based on the coefficient corresponding to the coordinate value of each image data. Therefore, the weighting of the colors in the color adjustment target area can be easily performed, and the relationship between the white glossy portion and the black shadow portion of the image can be saved. Further, since a pseudo contour does not occur at the boundary between the adjustment area and the background area, it is possible to adjust the target color without losing the original naturalness of the color image.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating the principle of a color adjustment method of the present invention.

FIG. 2 is a diagram showing an example of a target image displayed on a color monitor.

FIG. 3 is a diagram showing image data in color space coordinates.

FIG. 4 is a diagram showing a correction curve for correction based on a saturation value.

FIG. 5 is a diagram showing another correction curve for determining a correction coefficient value.

FIG. 6 is a block diagram showing a configuration of a color adjusting apparatus of the present invention.

FIG. 7 is a diagram showing a color palette divided into a plurality of sections.

FIG. 8 is a diagram showing a color data adjustment screen displayed on a display.

[Explanation of symbols]

 1 Color Monitor 10 Image Input Device 11 RGB Data Storage Means 12 Display Memory 13 Representative Point Indication Means 14 Representative Color Data Holding Memory 15 Color Adjustment Area Extraction Circuit 16 Image Data Storage Means 17 Target Color Input Means 18 Target Color Data Holding Memory 19 Correction amount calculation means 20 Coefficient determination means 21 Color correction calculation means 22 Inverse conversion circuit

Claims (5)

[Claims] 1. In a color image color adjusting method for adjusting RGB data according to a correction amount designated for each pixel of a color image, a representative point specifying step (S1) for specifying a representative point of the color image, A target color designating step (S2) for designating a target color to be an adjustment target for the color of the representative point, and a correction amount computing step (S3) for computing a correction amount necessary for changing the color of the representative point to the target color. ) And a correction amount correction step (S4) of correcting the correction amount at the representative point according to the position of the image data of each pixel in the color space to obtain the correction amount for each pixel. A color adjusting method for a color image, comprising: 2. In the correction amount correction step (S4),
The correction amount at the representative point is corrected with reference to the coordinate value of each pixel in a color space having the hue, saturation, and lightness of the color image as parameters. Color adjustment method for color images. 3. A specific image region including the representative point is extracted from the color image as a target region for color adjustment, and at least the coordinate value of each pixel of the extracted target region in the color space is extracted. 3. The color adjusting method for a color image according to claim 2, wherein the correction amount at the representative point is corrected according to the saturation or the lightness to obtain the correction amount for each pixel of the target area. 4. A correction amount for each pixel of the color image,
4. The color adjusting method for a color image according to claim 2, wherein the correction is performed based on a correction curve that has a maximum at a median value of each coordinate value of the color space. 5. A color image color adjusting device for adjusting RGB data according to a correction amount designated for each pixel of a color image, wherein RGB data storage means (11) stores the color image as RGB data of each pixel. A representative point designating means (13) for designating a representative color in the color adjustment target area from the color image and inputting a representative color; and a color including the representative point designated by the representative point designating means (13). Image data storage means (16) for holding the image data of the adjustment target area, and target color input means for inputting the image data of the target color that is the adjustment target of the representative color input by the representative point designating means (13). (17), and a correction amount calculation means (19) for calculating a correction amount in the color space between the image data of the representative point and the image data of the target color.
A coefficient determining means (20) for determining a coefficient according to the coordinate value of each image data of the image data storage means (16); and a correction amount calculated by the correction amount calculating means (19) by the coefficient. Image data storage means (16) corrected
Color correction calculation means (21) for correcting the image data held in the image data, and adjustment from the color image stored in the RGB data storage means (11) by the image data corrected by the color correction calculation means (21) A color adjusting device for a color image, comprising: a display unit (1) for displaying a color image in which the color of the target area is corrected.