JP4557171B2 - Image processing apparatus, image processing method, image processing program, and recording medium - Google Patents

Description

  The present invention relates to a color image processing technique for performing color conversion processing between different color gamuts.

  There are many devices that handle color images, but the range of colors that can be expressed by each device (hereinafter referred to as the color reproduction range) is different. For this reason, even a color that can be expressed by a certain device cannot always be reproduced by another device. As described above, since the color gamut differs depending on each device, color conversion processing, particularly color gamut mapping processing is required in order to match the color reproduction between different devices.

  Each device has a different color space. For example, in a device such as an image forming apparatus such as printing or electrophotography, a color space with four or more inks (color materials) (for example, a CMYK color space), a monitor display, etc. Devices such as cameras and cameras use the RGB color space. The color gamuts often differ between these color spaces, and the color gamut may change if the device type is different between the same RGB color space or the same CMYK color space.

  In order to achieve consistency between such different color gamuts, a device-independent color space is used. As a color space for that purpose, tristimulus values CIEXYZ, CIECAM02 space (such as LCh), LMS space, and the like are also used, but most use a perceptual uniform color space such as CIELAB space. The above-described color gamut mapping process is a process for determining a corresponding color between two devices having different color gamuts in a device-independent color space such as CIELAB space. In particular, when the input device is a monitor and the output device is a printer, the difference in the color gamut is large. For this reason, various ideas have been proposed and many inventions have been made.

For example, as described in Patent Document 1 and Patent Document 2, there is a method in which the reproduced color in the first device color gamut is directly associated with the reproduced color of the second device. The method described in Patent Document 1 is a mapping method for storing brightness, and the first device color gamut outline is L through a conversion unit that matches the brightness of the first device color gamut and the second device color gamut. ^* (Lightness) -C ^* (Saturation) The lightness is kept constant on the high lightness side of the maximum saturation point on the plane to decrease the saturation, and the low lightness side is associated with the minimum color difference. Here, several inventions have been made as methods for matching the lightness of the color gamuts of the two devices, which are disclosed in Patent Document 5, for example. Further, several inventions for reducing the saturation with respect to the same hue have been made, and are described in, for example, Patent Document 6 and Patent Document 7.

  Patent Document 2 describes a method of directly associating a saturated color in the first device color gamut with a saturated color in the second device color gamut. This method is described in Patent Document 8 and Patent Document 9 as well as Patent Document 2.

  As another method, for example, as described in Patent Document 3, the correspondence relationship is once formed with reference to the third and fourth intermediate color gamuts, and then associated with the reproduced color of the second device. There is a way. In the technique described in Patent Document 3, a minimum color reproduction gamut of a plurality of color spaces is formed, and color gamut mapping processing is performed with reference to the minimum color gamut.

  Furthermore, as described in Patent Document 4, for example, there is a method of creating a virtual color gamut from the first device color gamut and the second device color gamut. In Patent Document 4, when one of the two color gamuts is narrower than the other color space, the narrower color space is reproduced as a signal that can be reproduced with a signal exceeding the limit that can be reproduced by the method of forming the color space. Then, the color space is virtually enlarged, the correspondence relationship of the data for associating the measured values in each color space is obtained, the color signal of the first method is converted by the correspondence relationship, and reproduced by the second method. An apparatus is disclosed which is characterized in that the desired color is the desired color.

  In one of several mapping means, when the rendering intent is Colorimetric, for example, clipping is often used in an image that emphasizes photography. Clipping includes a method of mapping to a point where the color difference is minimum, a method of determining lightness and hue and reducing the saturation, and a method of determining a locus of lightness and saturation.

On the other hand, a method has been proposed in which a color space (for example, CIELAB) in which mapping processing is performed is assumed to have no equal hue, and mapping is performed after correction. In many of the above color gamut mapping processes, when a CIELAB color space, for example, is used as a device-independent color space, the device-independent color space is assumed to have a uniform hue. That is, for example, in the CIELAB color space, it is assumed that a plane that includes the L ^* axis and is perpendicular to the a ^* -b ^* plane is an equi-hue plane. Therefore, for example, as described in Patent Document 7, mapping processing in the L ^* axis direction is performed. However, it is known that the CIELAB color space is not actually the same hue, and if the mapping process is performed linearly in the L ^* axis direction (that is, the hue angle is fixed in the CIELAB color space), There is a problem that the hue is converted to a different color. In order to solve such a problem, recently, when performing gamut mapping processing in a device-independent color space such as the CIELAB color space, according to the color locus of the actual equal hue that matches the apparent hue, A mapping process is performed on the color of the first color gamut outside the second color gamut to the outline color of the second color gamut. As a result, the color of the first color gamut outside the second color gamut is converted to the color of the second color gamut without changing the actual hue.

  As described above, assuming that the color space to be mapped is not equal hue, mapping processing is performed so that the hue is actually equal, or described in Patent Document 2, Patent Document 8, Patent Document 9, and the like described above. As described above, when the mapping process is performed so that the saturated colors of the first color gamut and the second color gamut coincide with each other, for example, in a color space in which the mapping process such as the CIELAB color space is performed, the light axis rotates. A moving component in the direction, that is, a component that changes the hue angle is included.

  On the other hand, in the above-described color gamut mapping process, in many cases, the color is not changed in the color gamut. This is a color within the first color gamut and also a color within the second color gamut, so accurate color reproduction is possible, so it tries to faithfully reproduce the color without changing the color as much as possible. Is.

In this way, among the colors in the first color gamut, the colors in the second color gamut are faithfully reproduced, and the colors outside the second color gamut are subjected to the color gamut mapping process including the change of the hue direction as described above. Doing so will cause the following problems. FIG. 6 is an explanatory diagram of problems in the conventional color conversion process. In general, in the second color gamut, when converting to a device-dependent color space, for example, in the CIELAB color space, the color of the plane that includes the L ^* axis and is perpendicular to the a ^* -b ^* plane (that is, the same hue angle). ) Has the same hue. Therefore, the color on the plane is reproduced as a color of equal hue in the device in the second color gamut. In FIG. 6, the line segment OQP is shown as a line segment having the same hue angle on the plane, and the colors between the OQs are reproduced as equal hue colors in the device. However, even if the color is on the same plane, the color outside the second color gamut, for example, the color of the point P, is mapped to a color including a rotation component on the L ^* axis as described above. In FIG. 6, the color of the point P is mapped to the point R. Furthermore, colors between PQs are mapped between RQs. As a result, the color saturation is reversed and the level difference in gradation occurs, resulting in an unnatural color reproduction between the color originally in the second color gamut and the color outside the second color gamut. was there.

  In Patent Document 8 described above, color gamut mapping processing including movement in the hue direction is performed, and color conversion is also performed within the color gamut. As a result, the problem shown in FIG. 6 is considered to be reduced. In Patent Document 8, a function is used for color conversion, but setting of such a function is not easy. Further, if the function is applied uniformly and the hue is greatly moved in the color gamut mapping process, the color in the second color gamut is greatly changed. For this reason, there is a problem that it cannot be applied to an application for reproducing the color in the second color gamut as faithfully as possible.

Japanese Patent Laid-Open No. 11-69189 JP 2004-32140 A JP-A-4-239265 JP-A-2-214266 JP-A-8-223433 Japanese Patent Publication No. 5-88589 Japanese Patent Publication No. 6-36548 JP-A-6-253138 JP 2003-323609 A

  The present invention has been made in view of the above-described circumstances, and color reproduction that preserves gradation as much as possible without easily reducing accuracy while using conventional versatile color gamut mapping means. An object of the present invention is to provide a possible image processing apparatus, an image processing method, an image processing program, and a recording medium.

  The present invention relates to an image processing apparatus and an image processing method for converting color coordinates of a first color gamut into color coordinates of a second color gamut, and the second color of the first color gamut The first color coordinates outside the reproduction range are converted to the second color coordinates of the second color reproduction range by movement including a component that changes the hue angle, and the same first color coordinates are converted at the same hue angle. Then, the third color coordinate in the second color gamut is acquired, and the fourth color coordinate is set between the second color coordinate and the third color coordinate. Then, within the range of the hue angle where the third color coordinate moves to the fourth color coordinate, the color coordinate in the second color reproduction region having the same hue angle as the third color coordinate in the first color reproduction region. The hue angle is changed, and the color coordinate from the third color coordinate to the first color coordinate is converted to the color from the fourth color coordinate to the second color coordinate.

  For example, the color gamut contour point of the first color gamut is set as the first color coordinate, and the first color coordinate is converted so as to have an actual equal hue, and the contour point of the second color gamut is determined. A certain second color coordinate is acquired, and the hue angle of the color coordinate in the second color reproduction area can be changed based on the second color coordinate and the third color coordinate.

  Alternatively, the saturated color in the first color gamut is set as the first color coordinate, and the first color coordinate is set as the second color coordinate that is the saturated color in the second color gamut corresponding to the saturated color. The hue angle of the color coordinate in the second color gamut can be changed based on the second color coordinate and the third color coordinate after conversion.

  The hue angle can be changed, for example, by performing a rotation process in the color coordinate system. At this time, the hue angle may not be changed for some of the colors having the same hue angle as the third color coordinate. Alternatively, the hue angle may not be changed if the distance between the second color coordinate and the third color coordinate is equal to or smaller than a predetermined value.

  Furthermore, the present invention provides an image processing program characterized by causing a computer to execute the function of the image processing apparatus as described above or an image processing method, and stores such an image processing program. The storage medium is provided.

  According to the present invention, mapping outside the second color reproduction gamut can be performed including a component for changing the hue angle by using a versatile color gamut mapping unit that has been conventionally performed. With the color coordinates moved by the mapping process as the optimal color, the amount of change in the second color gamut is kept as close as possible to the moved color coordinates outside the second color gamut. There is an effect that smooth gradation can be maintained.

  FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a first mapping unit, 2 is a second mapping unit, 3 is an outline color setting unit, and 4 is a hue angle changing unit. The present invention shifts from the color coordinates of the first color gamut indicating the color range that can be taken by the color signal on the input side to the color coordinates of the second color gamut showing the color range that can be taken by the color signal on the output side. In the following description, it is assumed that processing is performed in the CIELAB color space. The color space to be processed is not limited to the CIELAB color space, and other color spaces may be used and are not limited. For example, it may be a color space with improved hue and uniformity of hue angle in CIECAM02 space, which is a color appearance model, and CIELAB, which is a perceptual uniform color space, and has both color reproducibility and spatial frequency characteristics. The color space may take into account the visual characteristics.

  The first mapping unit 1 moves the second color gamut of the first color gamut by moving the first color coordinate outside the second color gamut including a component that changes the hue angle. This is converted to the second color coordinate. For example, the color gamut outline point of the first color reproduction gamut can be converted into the outline point of the second color reproduction gamut having an actual equal hue. Alternatively, the saturated color in the first color gamut can be converted to the corresponding saturated color in the second color gamut. The first mapping unit 1 can apply a color gamut mapping unit that is used conventionally and involves changing the hue angle. As a result, the color outside the second color gamut can be converted into the optimum outline point of the second color gamut.

The second mapping unit 2 acquires the third color coordinate in the second color gamut when the first color coordinate used in the first mapping unit 1 is converted with the same hue angle in the CIELAB color space. For example, with respect to the outline point of the first color gamut, the outline point of the second color gamut that has the same hue angle in the CIELAB color space can be obtained as the third color coordinate. Here, the color having the same hue angle as the first color coordinate in the CIELAB color space is a color on a half plane including the first color coordinate with the L ^* axis as a side. As a method for obtaining the third color coordinate, a conventional mapping method without changing the hue angle can be applied, and L ^* is made constant, or only L ^* is changed, or one point on the L ^* axis. It is only necessary to obtain a point of intersection with the outline of the second color gamut by changing linearly toward.

  The outline color setting unit 3 determines the interval between the second color coordinate obtained by the first mapping unit 1 and the third color coordinate obtained by the second mapping unit, and sets the fourth color coordinate therebetween. . For example, an intermediate point between the second color coordinate and the third color coordinate can be set as the fourth color coordinate. If the interval between the second color coordinate and the third color coordinate is equal to or smaller than a predetermined value, the hue angle changing unit 4 can be prevented from changing the hue angle in the second color reproduction range. .

  The hue angle changing unit 4 changes the hue angle for the color coordinates in the second color reproduction area of the first color reproduction area based on the second color coordinates and the third color coordinates. More specifically, the third color coordinate (and the third color coordinate (and the third color coordinate so that the third color coordinate is moved from the second color coordinate and the third color coordinate to the fourth color coordinate set by the outline color setting unit 3). Conversion is performed to change the hue angle for colors in the second color gamut having the same hue angle as the first color coordinate. It should be noted that the hue angle to be changed may not be uniform, and may be performed within the range of the hue angle between the third color coordinate and the fourth color coordinate. For example, the hue angle to be changed may be reduced as the distance from the third color coordinate increases, or the hue angle may not be changed for a color within a certain range. Note that the hue angle can be changed by a rotation process in the CIELAB color space using, for example, affine transformation. In addition, for colors outside the second color gamut, that is, colors having the same hue angle from the third color coordinate to the first color coordinate, the color is converted from the fourth color coordinate to the second color coordinate. . As a result, although the hue of the color outside the second color gamut changes, the gradation can be maintained.

  FIG. 2 is an explanatory diagram of an example of the operation according to the embodiment of the present invention. Here, an example is shown in which the color coordinates of the outline of the first color reproduction area are converted into the color coordinates of the outline of the second color reproduction area that actually has the same hue. In FIG. 2, the broken line indicates the outline of the color gamut, a indicates the outline of the second color reproduction gamut, b indicates the outline of the first color reproduction gamut, and the left side in the drawing is within the color gamut. is there. The first color reproduction area is, for example, an sRGB color reproduction area, and the second color reproduction area is, for example, a printer color reproduction area. Of course, both may be in the color gamut of any device.

  The point P is a color coordinate on the outline of the first color gamut, and this point P will be described below as the first color coordinate. First, the first mapping unit 1 obtains the color coordinates of the outline of the second color gamut that actually has the same hue for the point P as the second color coordinates. The obtained second color coordinate is indicated as a point R.

Further, the second mapping unit 2 obtains the color coordinates of the outline of the second color gamut when the point P is converted with the same hue angle in the CIELAB color space as the third color coordinates. In FIG. 2, a point Q that is the intersection of the line segment OP and the second color reproduction area b is obtained as the third color coordinate. The point O can be one point on the L ^* axis.

  Further, the outline color setting unit 3 determines an interval between the point R obtained by the first mapping unit 1 and the point Q obtained by the second mapping unit 2. If this interval (distance in the color space or difference in hue angle) is smaller than a predetermined value, the subsequent processing may not be performed. In FIG. 2, it is assumed that the distance between the point R and the point Q is large, and an intermediate point S is set as the fourth color coordinate.

  Then, the hue angle changing unit 4 changes the hue angle of the color coordinates on the line segment OQ in the second color gamut to the color coordinates on the line segment OS. Note that the color coordinates on the line segment QP outside the second color reproduction range may be converted so as to be the color coordinates on the line segment SR. In this way, the color coordinates on the line segment OQP are converted into the color coordinates on the line segment OSR.

  FIG. 3 is an explanatory diagram illustrating an example of a locus of color coordinates converted according to the embodiment of the present invention. Each point in FIG. 3 corresponds to each point in FIG. FIG. 3A shows an example of a locus of color coordinates when a conventional color gamut mapping method for changing the hue angle is applied. The color coordinates on the line segment OQP are the color coordinates on the line segment QR, which are the color coordinates on the outline of the second color gamut, by the conventional color gamut mapping method for the line segment QP outside the second color gamut. Converted to coordinates. However, in the second color reproduction range, the color coordinates on the line segment OQ do not move from the viewpoint of faithful reproduction. Therefore, the amount of change in hue from point Q to point R increases.

  FIG. 3B shows an example of the locus of color coordinates when the present invention is applied. In the present invention, the hue angle on the line segment OQ in the second color reproduction range is changed on the line segment OS because the hue angle is changed so that the point Q becomes the point S. Further, the color coordinates on the line segment QP that are outside the second color reproduction range are converted to the color coordinates on the line segment SR. Accordingly, the color coordinates on the line segment OQP are converted to the color coordinates on the line segment OSR. Thereby, the change in hue in the entire section becomes small, smooth gradation reproduction can be performed, and more preferable color reproduction can be realized.

  In FIG. 3B, the hue angle is uniformly changed for the line segment OQ. However, in the example shown in FIG. 3C, for example, the hue angle to be changed is increased as the color gamut outline is approached. Thus, the method of changing the hue angle for the color coordinates on the line segment OQ can be arbitrarily performed within the range of the hue angle where the point Q is changed to the point S.

  2 and 3 show certain color coordinates on the outline of the first color gamut. For example, all the color coordinates on the outline of the first color gamut are set, and some Alternatively, the color coordinates of the outline may be obtained, and the others may be obtained by interpolation. For example, the change of the hue angle may be similarly applied to the in-plane color coordinates having the same hue angle. In this case, the hue angle changing method can be changed not only in the above-described saturation direction but also in the brightness direction.

  FIG. 4 is an explanatory diagram of another example of the operation according to the embodiment of the present invention. Here, an example is shown in which the color coordinates of the saturated color in the first color gamut are converted to the corresponding saturated color in the second color gamut. For example, in the RGB color space, the saturated color is a color in which any one of R (red), G (green), and B (blue) is the maximum or any two are the maximum. , Green, blue, yellow, magenta, and cyan are the most saturated colors. The same applies to the YMCK color space, and any one of Y (yellow), M (magenta), and C (cyan) is the maximum, or any two are the maximum. In FIG. 4, as in FIG. 2, a indicates the outline of the second color gamut, b indicates the outline of the first color gamut, and the left side in the drawing is within the color gamut.

  The point P is the color coordinate of the saturated color having the first color gamut, and this point p will be described below as the first color coordinate. First, the first mapping unit 1 obtains the color coordinates of the saturated color in the second color gamut corresponding to the point p as the second color coordinates. The obtained second color coordinate is indicated as a point r.

  Further, the second mapping unit 2 obtains the color coordinates of the outline of the second color reproduction area when the point p is converted with the same hue angle in the CIELAB color space as the third color coordinates. In FIG. 4, the third color coordinate is obtained as a point q.

  Further, the outline color setting unit 3 determines an interval between the point r obtained by the first mapping unit 1 and the point q obtained by the second mapping unit 2. If this interval (distance in the color space or difference in hue angle) is smaller than a predetermined value, the subsequent processing may not be performed. In FIG. 4, it is assumed that the interval between the points r and q is large, and an intermediate point s is set as the fourth color coordinate.

Then, the hue angle changing unit 4 changes the hue angle of the color coordinates on the line segment Oq in the second color gamut to the color coordinates on the line segment Os. Further, the color coordinates on the line segment qp outside the second color reproduction range may be converted so as to be the color coordinates on the line segment sr. In this way, the color coordinates on the line segment Oqp are converted into the color coordinates on the polygonal line segment Osr. The point O can be one point on the L ^* axis.

  In this way, even when the color gamut mapping process for associating saturated colors is performed, the difference in hue angle between the second color reproduction range and the outside of the color reproduction range is reduced by the present invention, as in the example described with reference to FIG. Therefore, smooth gradation reproduction can be performed and more preferable color reproduction can be realized.

  Note that the color coordinates before and after conversion are associated with each other as described above in the line segment or plane connecting the color coordinates of each saturated color and the point O in the first color gamut. It can be obtained by interpolation from the hue angle obtained from the color or the color difference at the time of mapping.

  FIG. 5 is an explanatory diagram of an example of a computer program and a storage medium storing the computer program when the function of the image processing apparatus or the image processing method of the present invention is realized by the computer program. In the figure, 11 is a program, 12 is a computer, 21 is a magneto-optical disk, 22 is an optical disk, 23 is a magnetic disk, 24 is a memory, 31 is a magneto-optical disk apparatus, 32 is an optical disk apparatus, and 33 is a magnetic disk apparatus.

  Part or all of the functions of the units described in the above embodiments can be realized by a program 11 that can be executed by a computer. In that case, the program 11 and data used by the program (including data of the generated color conversion model) can be stored in a computer-readable storage medium. A storage medium is a signal format that causes a state of change in energy such as magnetism, light, electricity, etc. according to the description of a program to a reader provided in the hardware resources of a computer. Thus, the description content of the program can be transmitted to the reading device. For example, there are a magneto-optical disk 21, an optical disk 22 (including a CD and a DVD), a magnetic disk 23, a memory 24 (including an IC card, a memory card, and the like). Of course, these storage media are not limited to portable types.

  By storing the program 11 in these storage media and mounting these storage media in, for example, the magneto-optical disk device 31, the optical disk device 32, the magnetic disk device 33, or a memory slot (not shown) of the computer 12, the computer 11 The program 11 can be read to execute the function of the image processing apparatus or the image processing method of the present invention. Alternatively, a storage medium may be attached to the computer 12 in advance, and the program 11 may be transferred to the computer 12 via a network, for example, and the program 11 may be stored and executed on the storage medium.

  Of course, some functions may be configured by hardware, or all may be configured by hardware. Alternatively, it can be configured as a program including the configuration of the color conversion apparatus of the present invention together with other configurations. For example, it can be configured as one program together with a control program in a copying machine or an image forming apparatus. Of course, in the case of application to other purposes, integration with a program for that purpose is also possible.

It is a block diagram which shows one Embodiment of this invention. It is explanatory drawing of an example of the operation | movement in one Embodiment of this invention. It is explanatory drawing of an example of the locus | trajectory of the color coordinate converted by one Embodiment of this invention. It is explanatory drawing of another example of the operation | movement in one Embodiment of this invention. FIG. 2 is an explanatory diagram of an example of a computer program and a storage medium storing the computer program when the function of the image processing apparatus or the image processing method of the present invention is realized by the computer program. It is explanatory drawing of the problem of the conventional color conversion process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st mapping part, 2 ... 2nd mapping part, 3 ... Outer color setting part, 4 ... Hue angle change part, 11 ... Program, 12 ... Computer, 21 ... Magneto-optical disk, 22 ... Optical disk, 23 ... Magnetic disk , 24 ... memory, 31 ... magneto-optical disk device, 32 ... optical disk device, 33 ... magnetic disk device.

Claims (14)

  In the image processing apparatus for converting the color coordinates of the first color gamut to the color coordinates of the second color gamut, the first color coordinates outside the second color gamut in the first color gamut. A first mapping means for converting to a second color coordinate of the second color gamut by movement including a component that changes a hue angle; and the first mapping means when the first color coordinate is converted with an equal hue angle. Second mapping means for obtaining a third color coordinate in a second color gamut, setting means for setting a fourth color coordinate between the second color coordinate and the third color coordinate, Colors in the second color gamut having the same hue angle as the third color coordinate in the first color gamut within the range of hue angles in which the third color coordinate moves to the fourth color coordinate. The hue angle is changed with respect to the coordinates, and the first color coordinates are changed from the third color coordinates outside the second color reproduction range. The image processing apparatus characterized by having a changing means for converting the color from the fourth color coordinates to the second color coordinates for the color coordinates in.   2. The first mapping unit converts the color gamut outline point of the first color reproduction gamut into an outline point of the second color reproduction gamut having an actual equal hue. Image processing apparatus.   The image processing apparatus according to claim 1, wherein the first mapping unit converts a saturated color in the first color gamut into a corresponding saturated color in the second color gamut.   The image processing apparatus according to claim 1, wherein the change of the hue angle is a rotation process in a color coordinate system.   5. The image processing apparatus according to claim 1, wherein the hue angle is not changed for a part of the colors having the same hue angle as the third color coordinate. 6.   6. The change according to claim 1, wherein the setting means does not cause the change means to change if an interval between the second color coordinates and the third color coordinates is equal to or less than a predetermined value. The image processing apparatus according to claim 1.   An image processing method for converting color coordinates of a first color gamut into color coordinates of a second color gamut, wherein the second color reproduction of the first color gamut is performed by a first mapping unit. The first color coordinates outside the area are converted to the second color coordinates of the second color reproduction area by movement including a component that changes the hue angle, and the first mapping is performed by the second mapping means. A third color coordinate in the second color gamut when converted by a corner is acquired, and a fourth color coordinate is set between the second color coordinate and the third color coordinate in the setting means. In the changing means, the second color having the same hue angle as the third color coordinate in the first color reproduction area within the range of the hue angle where the third color coordinate moves to the fourth color coordinate. The hue angle is changed for the color coordinates in the color gamut, and the third color coordinates to the first color coordinates are changed. Image processing method characterized by converting the color from the fourth color coordinates to the second color coordinates for the color coordinates.   The first color coordinate is a color gamut outline point of the first color gamut, the second color coordinate is an outline point of the second color gamut, and the first color coordinate The image processing method according to claim 7, wherein the conversion to the second color coordinate is performed so as to obtain an actual equal hue.   The first color coordinate is a saturated color in the first color gamut, and the second color coordinate is a saturated color in the second color gamut corresponding to the saturated color in the first color gamut. The image processing method according to claim 7, wherein conversion is performed from a saturated color in the first color gamut to a corresponding saturated color in the second color gamut.   The image processing method according to claim 7, wherein the change of the hue angle is a rotation process in a color coordinate system.   11. The image processing method according to claim 7, wherein the hue angle is not changed for a part of the colors having the same hue angle as the third color coordinate.   12. The hue angle is not changed when an interval between the second color coordinate and the third color coordinate is equal to or less than a predetermined value. Image processing method.   7. An image processing program for causing a computer to execute image processing for converting color coordinates of a first color reproduction gamut into color coordinates of a second color reproduction gamut, according to any one of claims 1 to 6. An image processing program for causing a computer to execute the function of the image processing apparatus according to claim 13 or the image processing method according to any one of claims 7 to 12.   A computer-readable storage medium storing an image processing program for causing a computer to execute image processing for converting the color coordinates of the first color gamut to the color coordinates of the second color gamut. 13. A computer storing an image processing program for causing a computer to execute the function of the image processing apparatus according to claim 6 or the image processing method according to any one of claims 7 to 12. Is a readable storage medium.

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