JP2001326826A - Color matching method and computer readable recording medium for recording color matching program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color matching method by which a desired image can easily be reproduced without being dominated by a color in a moving direction even when a gray axis is moved. SOLUTION: A gray axis (point P) of an input device is moved so as to be coincident with a gray axis (point P') of an output device. In this case, each of data in the gamut of the input device on an equi-lightness plane is moved in the same direction attended with the gray axis movement. The moving amount of each data is smaller as the moved point of data is remoter from the gray axis (point P). Thus, the point P is coincident with the point P' and points with high saturation are not almost moved. A point (q) with high saturation has only to be moved to a closer point q' even after the adjustment of the gray axis. Thus, the color is not much changed even when the gray axis is moved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color matching method and a computer-readable recording medium on which a color matching program is recorded, and more particularly to a CRT.
And a computer-readable recording medium storing a color matching method used to convert digital image data reproducible by a device such as a (cathode ray tube) into image data reproducible by an output device such as a printer. About.

[0002]

2. Description of the Related Art Generally, a range in which color reproduction can be performed by a CRT or a scanner is different from a range in which color reproduction can be performed by a printer. Thus, the color reproduction range between two devices (Gamu
t)), when the image reproduced on one device is reproduced on the other device,
That is, color matching is required. Hereinafter, a color matching method in the related art will be briefly described.

[0006] First, FIG. 6 shows a flow of image data in order to explain a method of color matching between an input device 601 and an output device 607. Here, image data reproduced by an input device 601 such as a CRT or a scanner is RGB data represented by an RGB color space, and image data reproduced by an output device 607 such as a printer is represented by a CMY color space. This is CMYK data.
As shown in the figure, the RGB data is stored in the color conversion processing unit 60.
After various conversion processes in step 3, the data is finally converted into CMYK data.

First, the RGB data in the input device 601 is input to a color conversion processing unit 603, and is converted into data in a color space independent of the device. The device-independent color space is, for example, an L * a * b * space, an XYZ space, or the like. Here, data expressed in the L * a * b * space (L * a
* b * data). For the conversion process, LU
A conversion using T (look-up table) or a masking method is used.

Next, the converted L * a * b * data is
The ut mapping unit 605 converts the data into L * a * b * data that can be reproduced by the output device 607. That is,
Here, in the Gamut mapping unit 605, the input device 60
1 and the output device 607.

The data after color matching is also data in a device-independent color space (L * a * b * data), and is thus converted again into CMYK data. Here, conversion using an LUT (look-up table) or a masking method is used for the conversion process.

As described above, the image data reproduced by the input device 601 is once converted into data in a color space independent of the device, and then subjected to color matching so that the image data can be reproduced by the output device 607.

FIG. 7 shows the Gamut mapping unit 605 of FIG.
3 is a flowchart showing a flow of a color matching process in FIG. Referring to FIG. 7, when independent data (L * a * b * data) is input to the device in step S701 in Gamut mapping section 605, gray axis adjustment is performed in step S703. That is, the entire input Gamut is moved such that the gray axis of the input Gamut (Gamut of the input device) matches the gray axis of the output Gamut (Gamut of the output device). This is because by matching the gray axes of the input device 601 and the output device 607, it is possible to obtain a gray-balanced output image without color cast.

The gray axis is a line segment connecting the white point and the black point in each device. For example, in a CRT, the color when all the RGB lights are a white point, and the color when all the RGB lights are a black point. In this case, in the L * a * b * color space, a line segment connecting both points becomes a gray axis of the CRT. In the printer, the color of the paper used is a white point, and the black color to be output is a black point. In the L * a * b * color space, a line connecting these two points becomes the gray axis of the printer.

Next, in step S704, the input Ga
The hue is adjusted by a mut rotation operation or the like. With the movement of the entire Gamut by the gray axis adjustment processing, an area where the hue changes appears. This is to correct this.

Thereafter, in step S705, the brightness and the saturation are adjusted. That is, the input Gamut
A compression process is performed to match the brightness and saturation of the output Gamut with the brightness and saturation of the output Gamut.

If the brightness range of the input device 601 is significantly different from that of the output device 607, problems such as halation in the output image or crushing of dark areas may occur. Therefore, the adjustment is performed in such a manner that the brightness range is adjusted to the output device 607. Further, the range of the saturation is determined by the input device 601 and the output device 6.
If the output image is greatly different from 07, the output image becomes too bright as a whole, and the output image becomes almost colorless. Therefore, with respect to the saturation, compression adjustment is performed to some extent in accordance with Gamut of the output device 607.

When the brightness and chroma compression processing is completed, finally, in step S707, a pasting process of pasting data outside the gamut of the output device to the gamut surface is performed. This is because input image data outside the output Gamut that cannot be reproduced by the output device 607 at this point can be appropriately reproduced.

When the data pasting process on the output Gamut surface is completed, all the color matching processes have been completed, and the image data after the matching is output in step S709.

The above is the flow of processing in the Gamut mapping unit 605. Next, the gray axis adjustment processing (step S703) of FIG. 7 will be described with reference to FIGS.

FIG. 8 shows an input device in the L * a * b * space.
The gray axis of the device 601 in the gray axis direction of the output device 607
It is a figure showing signs that it is moved. Referring to this figure,
The white point of the force device 601 is P_wi, Black point is P_wiAnd out
The white point of the force device is P_wo, Black point is P_boIt is. others
, P_wiAnd P_wiAnd the gray axis l of the input device 601
_iAnd P_woAnd P_boThe gray axis of the output device 607
l_oDoes not match.

[0017] Therefore, the gray axis l _i, is moved parallel to the data on the gray axis l _i a * b * plane to match the gray axis l _o. That is, each data point on the gray axis l _i is moved to a point on the gray axis l _o with its brightness kept constant. For example, point P ₁ on gray axis l _i is moved to point P ₁ ′ of equal lightness on gray axis l _o , and similarly points P ₂ , P ₃ on l _i are
_They are moved to iso-lightness points P ₂ ′ and P ₃ ′ respectively on l _o .

FIG. 9 is a diagram showing a cross section of the input Gamut in the L * a * b * space before the gray axis movement. Here, a cross section of the input Gamut on an equal lightness plane parallel to the a * b * plane is shown. The area Gin enclosed by the hexagon is the input
Gamut is shown, and a point P therein is a point at which the gray axis of the input Gamut intersects. The point at which the gray axis of the output Gamut intersects the plane of equal lightness is point P ′, which does not coincide with point P.

FIG. 10 is a diagram showing a cross section of the input Gamut in the L * a * b * space after the gray axis movement. Here, the cross section of the input Gamut on the same lightness plane as in FIG. 9 is also shown. A region Gin surrounded by a dotted hexagon indicates an input Gamut before movement in FIG. 9, and a region Gin ′ surrounded by a solid hexagon indicates an input Gamut after movement.

Referring to FIG. 1, the point P is set to the output Gamut by the gray axis adjustment processing.
Is moved so as to coincide with the point P ′ on the iso-luminance plane of the.
That is, all data on the iso-luminance plane is translated in parallel with the vector similar to the vector in which the gray axis moves (the arrow pointing from point P to point P '). Thus, for example, point q on input GamutGin is moved to point q '.

As described above, the gray axis of the input Gamut corresponds to the output G
By moving the entire input Gamut so as to coincide with the gray axis of the amut, it is possible to obtain an output image with a good gray balance without color cast or the like.

Next, referring to FIGS. 11 and 12, FIG.
(Step S707) is described below.

FIG. 11 shows an output G in L * a * b * space.
FIG. 9 is a diagram illustrating a state in which data outside amut is pasted into output Gamut. Here, for simplicity, the output GamutGout is a shape in which two cones having a bottom on a circle parallel to the a * b * plane are combined. The point P is a point outside the output GamutGout, and the point P ′ is a point outside the output GamutGout.
(A point on the surface of Gout). In this figure,
The axes passing through the center of gravity Q of the output GamutGout, which is the center of compression, are given a * and b * for indicating chromaticity.

The point P is compressed at a predetermined compression ratio in the direction of the center of gravity Q, which is the center point of compression, on the equal hue plane H including the point P and the lightness axis L *.

FIG. 12 shows this state on the uniform hue plane H. As shown in the figure, the output GamutGout
The outer point P is compressed in the direction of the center of gravity Q, and the output GamutGo
It is transformed into a point P 'in ut.

[0026]

However, such a conventional color matching method is not sufficient to appropriately and easily reproduce an image of an input device on an output device.

That is, first, when the gray axis adjustment is performed, the entire input Gamut moves with the movement of the gray axis, so that other colors may be converted to slightly different colors. For example, in FIG. 10, the point q in the input Gamut before the movement becomes the point q ′ after the movement due to the gray axis adjustment. In this case, blue in the input device 601 is reproduced as purple in the output device 607. If the input device 601 is a CRT and the output device 607 is a printer, the output image is reproduced as a whole reddish by moving the gray axis.

Thus, the input Gamu by gray axis adjustment
When the movement of t is performed, the reproduced output image is governed by the color in the movement direction, and becomes an image slightly different from the image of the input image.

To correct this, hue adjustment processing is performed. This processing requires a rotation operation of Gamut and the like. For this reason, the processing becomes very complicated and the processing time is long. Moreover, despite such complicated hue adjustment, an image exactly as the image was not easily reproduced. For example, when the entire image is rotated to output blue as blue, green becomes yellow.

Second, since the gray axis of the input Gamut completely matches the gray axis of the output Gamut by the gray axis adjustment processing, the image of the image held by the input device may be damaged. By adjusting the gray axis, a gray-balanced image without color cast can be obtained, but a person has a certain degree of image of the image reproduced by the input device. For this reason, if an image in which the image of the input device is completely damaged is reproduced, it may not be preferable.

The present invention has been conceived in view of the above circumstances, and has as its object the purpose of easily forming a desired image without being influenced by the color in the moving direction even when the gray axis is moved. An object of the present invention is to provide a color matching method that can be reproduced, and a computer-readable recording medium that stores a color matching program.

Another object of the present invention is to provide a color matching method capable of reproducing a desired image by maintaining an image held by the apparatus to some extent even when the gray axis is moved.
Another object of the present invention is to provide a computer-readable recording medium on which a color matching program is recorded.

[0033]

According to one aspect of the present invention, when the color reproduction range of the first device is different from the color reproduction range of the second device, the color reproduction of the first device is performed. A color matching method for converting image data within the range to image data within the color reproduction range of the second device includes:
A moving step of moving each image data within the color reproduction range of the first device so that the gray axis of the first device moves in the direction of the gray axis of the second device in the predetermined color space; The moving step is characterized in that each image data is moved according to a moving amount determined according to a distance in a saturation direction from the gray axis of the first device.

Here, the gray axis of the first device is the first device.
Means a line segment connecting the white point and the black point defined by the device, and the gray axis of the second device is a line segment connecting the white point and the black point defined by the second device. That is.

According to the present invention, when moving all image data within the color reproduction range of the first device so that the gray axis of the first device moves in the gray axis direction of the second device,
Each image data is moved according to a movement amount determined according to a distance in the saturation direction from the gray axis of the first device.

Since each image data is moved in accordance with an appropriate movement amount according to the distance in the saturation direction from the gray axis, the image data having high saturation is largely moved and converted into image data having completely different colors. There is no such thing as. Further, since there is no need to correct the color, it is not necessary to perform complicated and time-consuming hue correction.

Therefore, it is possible to provide a color matching method capable of easily reproducing a desired image without being influenced by the color in the moving direction even when the gray axis is moved.

Preferably, the amount of movement is determined so as to decrease as the distance in the saturation direction from the gray axis of the first device increases.

According to this, each image data is moved so as to decrease as the distance in the saturation direction from the gray axis of the first device increases. Therefore, it is possible to prevent a problem that an image having a different color is reproduced due to a large movement of image data having high saturation.

[0040] Preferably, the moving step includes the first step.
Each image data is moved so that the gray axis of the second device coincides with the gray axis of the second device.

Since all the image data within the color reproduction range of the first device is moved so that the gray axis of the first device coincides with the gray axis of the second device, a gray balance without color cast is obtained. The reproduced image can be reproduced by the second device.

Preferably, the moving step is performed in the first step.
Each image data is moved so that the gray axis of the apparatus moves to a position that does not completely coincide with the gray axis of the second apparatus.

All the images within the color reproduction range of the first device are moved such that the gray axis of the first device moves to a position in the gray axis direction of the second device that does not coincide with the gray axis. Since the data is moved, the image of the first device is not damaged while the gray balance is maintained to some extent.

According to another aspect of the present invention, when the color reproduction range of the first device is different from the color reproduction range of the second device, the image data within the color reproduction range of the first device is converted to the color data of the second device. The color matching method for converting into image data within the reproduction range is such that the gray axis of the first device moves in the direction of the gray axis of the second device in a predetermined color space. A moving step of moving each image data within the color reproduction range, wherein the moving step moves each image data so that the gray axis of the first device does not completely coincide with the gray axis of the second device. Data is moved.

According to the present invention, the color reproduction range of the first device is moved so that the gray axis of the first device moves to a position which is in the gray axis direction of the second device but does not coincide with the gray axis. Is moved. For this reason, a desired image can be obtained without deteriorating the image of the first device, while maintaining a certain gray balance.

Therefore, it is possible to provide a color matching method capable of reproducing a desired image by keeping the image of the first apparatus to some extent even when the gray axis is moved.

Preferably, the moving step comprises the step of moving the first device at a ratio of 0.5 to 0.9 with respect to the amount of movement when the gray axis of the first device coincides with the gray axis of the second device. The gray axis of the device is moved.

According to this, an appropriate image in which the gray balance is in harmony with the image of the first device is reproduced.

Preferably, the moving step is characterized in that the white point of the first device matches the white point of the second device.

According to this, the gray axis of the first device is moved so as not to coincide with the gray axis of the second device.
Only the white point on the gray axis of the first device is matched to the white point on the gray axis of the second device. Therefore, it is possible to maintain the image of the first device to some extent without destroying the image that a person perceives as white.

Preferably, the predetermined color space is a device-independent color space.

More preferably, the device-independent color space includes a Lab color space. According to these, since the moving step is performed in a device-independent color space such as a Lab space, the image data within the color reproduction range of the first device can be appropriately and easily converted to the color reproduction range of the second device. Image data.

According to still another aspect of the present invention, a computer-readable recording medium is provided in a case where the color reproduction range of the first device is different from the color reproduction range of the second device. A color matching program for causing a computer to execute a color matching method for converting image data into image data within the color reproduction range of the second device is recorded. The color matching method moves each image data within the color reproduction range of the first device so that the gray axis of the first device moves in the direction of the gray axis of the second device in a predetermined color space. The method includes a moving step, wherein the moving step moves each image data in accordance with a moving amount determined according to a distance in a saturation direction from the gray axis of the first device.

According to the present invention, when moving all image data within the color reproduction range of the first device so that the gray axis of the first device moves in the gray axis direction of the second device,
Each image data is moved according to a movement amount determined according to a distance in the saturation direction from the gray axis of the first device.

Since each image data is moved according to an appropriate moving amount according to the distance in the saturation direction from the gray axis, the image data having high saturation is largely moved and converted into image data having completely different colors. There is no such thing as. Further, since there is no need to correct the color, it is not necessary to perform complicated and time-consuming hue correction.

Therefore, even if the gray axis is moved, a computer-readable recording medium that records a color matching program capable of easily reproducing a desired image without being influenced by the color in the moving direction is provided. Can be provided.

According to still another aspect of the present invention, a computer-readable recording medium is provided, when the color reproduction range of the first device is different from that of the second device, within the color reproduction range of the first device. A color matching program for causing a computer to execute a color matching method for converting image data into image data within the color reproduction range of the second device is recorded. The color matching method moves each image data within the color reproduction range of the first device so that the gray axis of the first device moves in the direction of the gray axis of the second device in a predetermined color space. The method includes a moving step, wherein the moving step moves each image data such that a gray axis of the first device is not completely coincident with a gray axis of the second device.

According to the present invention, the color reproduction range of the first device is moved so that the gray axis of the first device moves to a position which is in the gray axis direction of the second device but does not coincide with the gray axis. Is moved. For this reason, a desired image can be obtained without deteriorating the image of the first device, while maintaining a certain gray balance.

Accordingly, it is possible to provide a computer-readable recording medium on which a color matching program capable of reproducing a desired image by maintaining an image of the first apparatus to some extent even when the gray axis is moved is provided. Becomes possible.

[0060]

Next, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIG. 1 is a flowchart showing the overall processing flow of a color matching method according to a first embodiment of the present invention. The processing performed here is performed in the Gamut mapping unit 605 shown in FIG.

Referring to this figure, first, in step S101, device-independent data (here, L * a * b *
Is input, the gray axis is adjusted in consideration of the saturation in step S103. This is because the gray scale of the output image to be reproduced is balanced by matching the gray axes of the input device and the output device.

In this step, unlike the conventional gray axis adjustment (step S703 in FIG. 7, etc.), the entire input Gamut is not simply moved in the same manner as the gray axis is moved. Each data in the input Gamut is moved by a movement amount determined according to its saturation (the distance of each data from the gray axis in the saturation direction). Details will be described later.

When the adjustment of the gray axis is completed, the hue adjustment processing as performed conventionally (step S70 in FIG. 7)
The next step (step S105) is performed without performing 4).
Move to.

In step S105, the brightness and the saturation are adjusted. That is, compression processing is performed to match the lightness and saturation of the input Gamut with the lightness and saturation of the output Gamut. By compressing the brightness range according to the output device, problems such as overexposure and crushing of a dark portion occurring in an output image are prevented. In addition, by adjusting the saturation range according to the output device, an output image having a natural color tone is reproduced as a whole.

When the brightness and chroma compression processing is completed, finally, in step S107, a pasting process for pasting data outside the gamut of the output device into the gamut is performed. This is because input image data outside the output Gamut that cannot be reproduced by the output device at this time can be appropriately reproduced.

When the process of pasting the data into the output Gamut is completed, the color matching process is completed, and the image data after the matching is output in step S109.

The above is the general processing flow of the color matching method of the present invention. Next, using FIG. 2, gray axis adjustment processing in consideration of saturation (Step S103 in FIG. 1)
Will be described. Note that L * a * b * before gray axis adjustment
The positional relationship between the gray axis l _i of the input device and the gray axis l _o of the output device in space is the same as that shown in FIG. Also, the point that each data in the input Gamut moves on the equal lightness plane, that is, while maintaining the lightness by the gray axis adjustment processing is the same as the conventional case.

FIG. 2 shows the input Gamut on the isoluminance plane parallel to the a * b * plane in the L * a * b * space after gray axis adjustment.
It is the figure which showed the cross section. Area G enclosed by a dotted hexagon
“in” indicates the input Gamut before the movement, and a region Gin ′ surrounded by a solid hexagon indicates the input Gamut after the movement. The points P and P ′ are points where the gray axis of the input device and the gray axis of the output device intersect on the equal lightness plane.

As shown in the figure, the input GamutGin is moved so that the point P coincides with the point P '. At this time, each data in the input Gamut on the equal lightness plane also moves in the same direction along with the movement of the gray axis, but the movement amount changes according to the distance from the point P.

Specifically, the amount of movement of each data is determined by the input Ga
The distance decreases from the mut gray axis (point P). Assuming that the movement amount of the gray axis on the equal lightness plane is α, the movement amount Δ of each data is determined according to, for example, a relational expression of Δ = α × β / (d + β).

Here, d is the distance of the target pixel data point from the gray axis on the equal lightness plane. In the figure, the distance is from the point P. Β is an arbitrary constant. For β, for example, a number such as 1 to 3 is used.

When each data point in the input Gamut is moved according to such a relationship, the point P coincides with the point P ', but the point with high saturation hardly moves. For example, a point q or the like with a high saturation only moves to a point q ′ in the immediate vicinity even after the gray axis adjustment.

Therefore, the color does not change much, and the phenomenon that blue shifts to purple can be prevented.
Moreover, since the gray axis of the input device coincides with the gray axis of the output device, a gray-balanced image can be obtained.

As described above, according to the color matching method of the present embodiment, it is possible to prevent the phenomenon that blue is shifted to purple when printed out,
It is possible to obtain an image with a good gray balance.

Conventionally, as shown in step S704 of FIG. 7, it was necessary to perform a Gamut rotation operation to adjust the hue. Since a combination of trigonometric functions is used for the rotation operation, much processing time was required.
However, in the present embodiment, since the data is converted according to the saturation simultaneously with the movement of the gray axis, the necessity of the hue adjustment by the rotation operation is eliminated. For this reason, data conversion becomes possible only by four arithmetic operations, and the processing time can be shortened.

Although the case where the moving amount of each data point is determined according to the above-described relational expression has been described above, the present invention is not limited to this. The further away from the gray axis,
Any relationship may be used as long as the amount of movement is small.

Therefore, assuming that the movement amount of the gray axis on the equal lightness plane is α, for example, the movement amount Δ of each data is determined according to the relational expression of Δ = α (1−d / β). Is also good. Here, d is the distance of the target pixel data point from the gray axis on the equal lightness plane, and β is an arbitrary constant. For β, a sufficiently large number such as 150, such as a distance from the gray axis such that the movement distance is 0, is used. [Second Embodiment] Next, a color matching method according to a second embodiment of the present invention will be described. The processing flow of the color matching method in the present embodiment is the same as the processing flow in the first embodiment shown in FIG. However, the content of the gray axis adjustment processing (step S103 in FIG. 1) in consideration of the saturation is different. That is, the color matching method in the present embodiment
When moving the gray axis of the input Gamut, the gray axis of the output Gamut is not completely matched.

Hereinafter, the gray axis adjustment processing according to the present embodiment will be described in detail with reference to FIG. Here, too, the positional relationship between the gray axis l _o of the gray axis l _i and the output device of the input device in a prior gray axis adjustment L * a * b * space, those similar to those shown in FIG. 8 Think. Also, the point that each data in the input Gamut moves on the equal lightness plane, that is, while maintaining the lightness by the gray axis adjustment processing is the same as the conventional case.

FIG. 3 shows the input Ga on the isoluminance plane parallel to the a * b * plane after the gray axis movement in the second embodiment.
It is the figure which showed the mut cross section. Also in this case, the area Gin surrounded by a dotted hexagon indicates the input Gamut before movement, and the area Gin ′ surrounded by a solid hexagon indicates the input Gamut after movement. The points P and P ′ also indicate points where the gray axis of the input device and the gray axis of the output device intersect on the plane of equal lightness.

Unlike the case of FIG. 2, the point P is not moved to the point P ', but is moved to a point P "on a line connecting the points P and P'. The gray axis of
It will not be completely aligned with the gray axis of the output device, but will be moved to a position before it.

For example, if we look at a 9300K CRT, we know that the screen is clearly blue.
Therefore, if each data is moved so that the gray axis of the CRT completely matches the gray axis of the printer as an output device, the blue atmosphere of the CRT is impaired. For this reason, the movement amount of the gray axis is set to a value smaller than the distance to the gray axis of the output device, so that the atmosphere of the CRT is left.

The point that each data in the input Gamut is moved in the moving direction of the gray axis by the moving amount determined according to the distance from the gray axis is the first point shown in FIG.
This is the same as the embodiment. That is, also in the present embodiment, the movement amount of each data is controlled so as to become smaller as the distance from the gray axis (point P) of the input Gamut increases.

Specifically, assuming that the movement amount of the gray axis on the equal lightness plane is α, for example, Δ = α × β / (d + β)
According to the relational expression, the movement amount Δ of each data is determined.

Here, d is the distance of the target pixel data point from the gray axis on the equal lightness plane. In the figure, the distance is from the point P. Β is an arbitrary constant. For β, for example, a number such as 1 to 3 is used.

At this time, the moving amount α of the gray axis is α = α ′
× ε. α ′ is the distance between the gray axis of the input device and the gray axis of the output device on the isoluminance plane. In the figure, it is the distance between point P and point P '. ε is an arbitrary constant less than 1, and may be between 0.3 and 1.
From experimental results, it is desirable that the ratio be 0.5 to 0.9.

In this figure, the moving amount α of the gray axis is
The distance between the point P and the point P "is obtained. By making the amount of movement of the gray axis shorter than the distance between the point P and the point P ', the output image is represented by an input device such as a CRT. It is possible to leave the atmosphere of the image.

As described above, according to the present embodiment, it is possible to maintain the image of the input device to some extent while suppressing the phenomenon that blue shifts to purple, for example.

Note that here, step S103 in FIG.
Although the example applied to the gray axis adjustment processing in consideration of the saturation shown in FIG. 7 has been described, it is also possible to apply the gray axis adjustment processing (step S703 in FIG. 7) in the conventional example.

When applied in step S703 in FIG. 7, the gray axis of the input device is moved to a position closer to the gray axis of the output device as in the case described with reference to FIG. However, each data in the input Gamut moves in parallel with the same movement amount as the movement amount of the gray axis on the equal lightness plane. In this case, since an undesired change in the tint occurs, the hue adjustment processing (step S70 in FIG. 7) is performed thereafter.
4) is performed. <Modification> Finally, a modification of the second embodiment will be described. Also in the color matching method according to the modified example, as shown in FIG. 3, the gray axis of the input GamutGin is not completely coincident with the gray axis of the output device, and is moved to a position before the gray axis. However, only the white point on the gray axis of the input device matches the white point on the gray axis of the output device.
That is, while the gray axis of the input device is moved to a position before the gray axis of the output device, only the white point of the input device is moved so as to match the white point on the gray axis.

If the white points do not match, a color that is supposed to be a white background is output with a color. For example, when a printer is used as an output device, if there is an input image in which characters are written on a white background, a white background portion is colored on an output sheet, which is very unsightly.

Therefore, the second embodiment shown in FIG.
Similarly to the embodiment, the gray axis of the input Gamut itself does not coincide with the gray axis of the output device, but is moved to a position before a predetermined ratio, but only the white point is changed to the white point of the output device. Match. Note that each piece of data in the input Gamut is moved on the iso-luminance plane by a movement amount corresponding to the distance from the gray axis on the iso-luminance plane, as in the case of FIG.

In this way, only the white color can be made to match the white color of the output device while leaving the image of the input device such as a CRT. Therefore, the image received from the whole becomes more appropriate.

Each of the color matching methods in the embodiment described above is realized by a program for causing the above-described series of processing operations to function. Therefore, these color matchings may be performed on a computer.

FIG. 4 is a diagram showing an appearance of a computer for executing the above-described color matching method. A general computer includes a main body 41 and a magnetic tape device 4.
3 and CD-ROM (Compact Disc-Read Only Memor
y) It includes a device 47, a display device 42 such as a CRT, a keyboard 45, a mouse 46, and a modem 49.
A magnetic tape 44 is mounted on the magnetic tape device 43, and C
A CD-ROM 48 is mounted on the D-ROM device 47.

FIG. 5 shows the configuration of this computer in the form of a functional block diagram. Referring to this figure, as is well known,
The computer main body 41 includes a CPU (Central Process).
ingUnit) 50 and ROM (Read Only Memory) 51
, A RAM (Random Access Memory) 52, and a hard disk device 53. These are mutually connected by a bus.

The color matching program of this time may be installed in the hard disk device 53 in advance, or may be recorded on a removable recording medium such as the CD-ROM 48 or the magnetic tape 44. Good.

When the program is recorded on a removable recording medium, the recorded program is read from the recording medium by the magnetic tape device 43, the CD-ROM device 47 or the like and is temporarily stored in the hard disk device 53. After that, as in the case where the hard disk drive 53 is installed in advance, the RA
The program is loaded into M52, and the execution of the program is controlled by the CPU 50.

Examples of the recording medium on which the program is recorded include a tape system such as a magnetic tape and a cassette tape, a magnetic disk (flexible disk, hard disk device, etc.) and an optical disk (CD-ROM / MO / MD / DV).
D), a card system such as an IC card (including a memory card) or an optical card, or a mask RO
A medium that fixedly holds the program, such as a semiconductor memory such as an M, EPROM, EEPROM, or flash ROM, can be considered.

Further, the medium may carry the program in a fluid manner so that the program can be downloaded from the network via the communication modem 49. In addition,
When the program is downloaded from the network as described above, the download program is stored in the main body 41 of the computer in advance, or is installed in the main body 41 in advance from another recording medium.

The content stored in the recording medium is not limited to a program but may be data.

In the embodiment shown this time,
Although a CRT has been described as an example of an input device and a printer has been described as an example of an output device, the present invention is not limited thereto. When performing color matching between devices having different color reproduction ranges, the present invention can be applied to any device.

This time, the color matching processing shown in FIG.
5 has been described. However, the present invention is not limited to such a case.
The mut compression process can be performed at the time of the color conversion process. L * a * b * data expressed in L * a * b * space
For example, when converting to CMYK data represented in the Y space.

The color matching method is not limited to the processing flow shown in the flowchart of FIG. For example, the gray axis adjustment processing (step S10)
The present invention can be applied to the case where 3) and the compression processing of the brightness or the like (step S105) are performed simultaneously, or the case where the processing order is reversed.

The embodiment disclosed this time is an example in all respects, and should not be considered as restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a flow of an overall process of a color matching method according to a first embodiment of the present invention.

FIG. 2 a * in L * a * b * space after gray axis adjustment
FIG. 5 is a diagram showing an input Gamut cross section on an equal lightness plane parallel to a b * plane.

FIG. 3 is a diagram showing an input Gamut cross section on an equal lightness plane parallel to an a * b * plane after a gray axis movement according to a second embodiment. here

FIG. 4 is a diagram illustrating an appearance of a computer for executing a color matching method.

FIG. 5 is a functional block diagram showing the configuration of the computer shown in FIG.

FIG. 6 is a diagram showing a flow of image data in order to explain a method of color matching between an input device 601 and an output device 607.

FIG. 7 is a flowchart showing a flow of color matching processing in the Gamut mapping unit 605 of FIG.

FIG. 8 is a diagram showing a state in which the gray axis of the input device 601 is moved in the gray axis direction of the output device 607 in the L * a * b * space.

FIG. 9 is a diagram illustrating a cross section of an input Gamut in an L * a * b * space before a gray axis movement.

FIG. 10 is a diagram showing a cross section of an input Gamut in an L * a * b * space after a gray axis movement.

FIG. 11 is a diagram showing a state in which data outside the output Gamut is pasted into the output Gamut in the L * a * b * space.

FIG. 12 is a diagram showing a state of being compressed at a predetermined compression ratio on an equal hue plane H.

[Explanation of symbols]

44 magnetic tape, 48 CD-ROM, 601 input device, 605 Gamut mapping unit, 607 output device.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshishi Yamamoto 2-3-13 Azuchicho, Chuo-ku, Osaka-shi Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Kenji Masaki 2-chome Azuchicho, Chuo-ku, Osaka-shi No. 13 Osaka International Building Minolta Co., Ltd. (72) Inventor Fumiko Uchino 2-3-1 Azuchicho, Chuo-ku, Osaka City Osaka International Building Minolta Co., Ltd. (72) Inventor Naoko Hiramatsu Azuchi, Chuo-ku, Osaka City F-term (reference) in Osaka International Building Minolta Co., Ltd. 3-13, 2 chome 2C262 AA24 AB11 BA19 BA20 BC03 BC13 BC19 EA12 EA13 5B057 CA01 CA08 CA12 CB01 CB08 CB12 CE17 CE18 CH01 CH11 DB02 DB06 DB09 DC25 5C066 AA05 EE01 KE04 5 MP08 PP32 PP33 PP36 PP37 PQ12 RR21 SS06 5C079 HB01 HB03 HB08 HB12 LA23 LB02 MA11 NA03 NA27

Claims (11)

[Claims] When the color reproduction range of a first device is different from the color reproduction range of a second device, image data within the color reproduction range of the first device is converted to image data within the color reproduction range of the second device. A color matching method for converting data into data, wherein a gray axis of the first device moves in a direction of a gray axis of the second device in a predetermined color space. A moving step of moving each image data within the color reproduction range, wherein the moving step moves each of the image data according to a moving amount determined according to a distance in a saturation direction from a gray axis of the first device. A color matching method characterized by moving. 2. The color matching method according to claim 1, wherein the moving amount is determined to be smaller as a distance in a saturation direction from a gray axis of the first device is larger. 3. The method according to claim 2, wherein the moving step moves the image data so that a gray axis of the first device coincides with a gray axis of the second device.
The color matching method according to claim 1. 4. The image data is moved so that a gray axis of the first device does not completely coincide with a gray axis of the second device. The color matching method according to claim 1 or 2, wherein 5. When the color reproduction range of the first device is different from the color reproduction range of the second device, the image data within the color reproduction range of the first device is converted to the image data within the color reproduction range of the second device. A color matching method for converting data into data, wherein a gray axis of the first device moves in a direction of a gray axis of the second device in a predetermined color space. A moving step of moving each image data within the color reproduction range, wherein the moving step moves the gray axis of the first device to a position that does not completely coincide with the gray axis of the second device. And moving each of the image data. 6. The moving step is performed at a moving amount of 0.5 to 0.9 with respect to a moving amount when a gray axis of the first device coincides with a gray axis of the second device. Moving the gray axis of the first device;
The color matching method according to claim 4. 7. The color matching method according to claim 4, wherein said moving step matches a white point of said first device with a white point of said second device. . 8. The color matching method according to claim 1, wherein said predetermined color space is a device-independent color space. 9. The color matching method according to claim 8, wherein the device-independent color space includes a Lab color space. 10. When the color reproduction range of the first device and the color reproduction range of the second device are different, the image data within the color reproduction range of the first device is converted to the image data within the color reproduction range of the second device. A computer-readable recording medium on which a color matching program for causing a computer to execute a color matching method for converting data is recorded, wherein the color matching method includes the steps of: A moving step of moving each image data within the color reproduction range of the first device so that a gray axis moves in a direction of the gray axis of the second device; Is moved according to a movement amount determined according to a distance in a saturation direction from the gray axis of the first device. Recording medium. 11. When the color reproduction range of the first device is different from the color reproduction range of the second device, the image data within the color reproduction range of the first device is converted to the image data within the color reproduction range of the second device. A computer-readable recording medium that records a color matching program for causing a computer to execute a color matching method for converting data into data, wherein the color matching method includes the steps of: A moving step of moving each image data within the color reproduction range of the first device so that a gray axis moves in a direction of the gray axis of the second device; The computer according to claim 1, wherein the image data is moved such that a gray axis of the device is not completely coincident with a gray axis of the second device. A readable recording medium.