JP2000050058A - Resolution conversion method, apparatus and recording medium - Google Patents

Abstract

(57) [Summary] [Problem] To perform high-speed resolution conversion processing while maintaining image quality as a whole by selecting a resolution conversion method for each color component. SOLUTION: Original image CMY stored in a memory 2
Since the color with the lowest visibility among K is Y, when the point of the original image corresponding to the point converted into the coordinates of the output system is at a non-grid point, the Y color is interpolated by the nearest neighbor method 5. , And other color components are interpolated by the linear interpolation method 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resolution conversion method and apparatus for converting the resolution of image information into image information for an output device such as a printer, and a recording medium on which a resolution conversion processing program is recorded.
This technology is applied to device drivers such as display drivers and printer drivers.

[0002]

2. Description of the Related Art With the spread of computers, complicated documents including vector fonts, natural images, graphics, and the like can be easily created. The resolution of the printer has been improved so that such a document can be printed with high quality. However, since the improvement of the resolution causes an increase in the amount of data to be printed, it is necessary to improve the printing speed.

When the above-mentioned document is output using a printer having a predetermined resolution and gradation expression capability, resolution conversion and halftone processing are generally performed in a printer driver. In order to increase the speed, it is necessary to speed up these processes.

Incidentally, as typical methods of the halftone processing, a dither method and an error diffusion method are well known.
These methods have the following characteristics in terms of processing speed and image quality. That is, processing speed: dither method (fast)> error diffusion method (slow) image quality: dither method (bad) <error diffusion method (good).

[0005] The printer usually prints a color image by forming dots of ink of four colors of cyan (C), magenta (M), yellow (Y) and black (K) on paper. The halftone processing is performed for each ink color (for each ink plane). Conventionally, the same method has been applied to this halftone process for each ink color.

Although the processing speed and the image quality have a trade-off relationship as described above, a method for solving this problem is, for example, a color image gradation number conversion method described in Japanese Patent Application Laid-Open No. 8-307720. In this method, when a color image is printed, at least one image containing a yellow component is printed.
Halftone processing is performed on the color components by the dither method, and halftone processing is performed on the remaining color components by the error diffusion method. That is, since the yellow component has almost no effect on the visual image quality, if a high-speed halftone processing method is applied to the yellow component, the processing speed can be improved without lowering the image quality as a whole.

[0007]

As described above, as described above,
Recently, a document including an image such as a natural image is often created. For example, a document image 61 shown in FIG.
(This image is taken in, for example, from a scanner (not shown) or the like).
pi) and size S1 (for example, horizontal 100 dots × vertical 2)
00dot), but since the image 62 pasted on the document in the application can be arbitrarily enlarged or reduced by the user, the original size S1
In many cases, the size is different from the size S2.

When such a document is output by a printer or the like having a resolution R2, (resolution, size) = (R
1, S1) image on paper (resolution, size) =
Since it is necessary to reproduce the (R2, S2) image 63, resolution conversion (geometric conversion) is usually performed in the printer driver.

Conventionally, three methods of resolution conversion, namely, a nearest neighbor method, a linear interpolation method, and a cubic interpolation method are well known (for example, "Introduction to Computer Image Processing" (supervised by Hideyuki Tamura, Soken Shuppan) ) Pp113-117). These three methods are considered in terms of processing speed and image quality. Processing speed: nearest neighbor method (fast)> linear interpolation method> cubic interpolation method (slow) Image quality: nearest neighbor method (bad) <linear interpolation method <cubic interpolation Because of the characteristic of good (good), the processing speed and the image quality are in conflict. The conventional resolution conversion does not satisfy both the processing speed and the image quality because a common process is applied to each color component as in the above-described halftone process.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to select a resolution conversion method for each color component, thereby maintaining the image quality as a whole and at a high speed. An object of the present invention is to provide a resolution conversion method, device, and recording medium for performing processing.

[0011]

According to a first aspect of the present invention, there is provided a resolution conversion method for converting the resolution of color image data comprising a plurality of color components. It is characterized in that a first resolution conversion method is used for at least one color component among components, and a second resolution conversion method is used for other color components.

[0012] According to a second aspect of the present invention, the one color component is a color component having the lowest visibility among the plurality of color components.

According to a third aspect of the present invention, when the color image data has yellow, cyan, magenta, and black color components, the one color component is a yellow color component.

According to a fourth aspect of the present invention, the first resolution conversion method is used for the color component with the lowest value among the component values for each color component, and the other color components are used for the other color components. It is characterized in that a second resolution conversion method is used.

According to a fifth aspect of the present invention, there is provided a resolution conversion method for converting color image data of a first color system having a first resolution into color image data of a second color system having a second resolution. Wherein a first resolution conversion method is used for a blue component of the first color system, and a second resolution conversion method is used for another color component of the first color system. It is characterized by:

According to a sixth aspect of the present invention, the first resolution conversion method is a nearest neighbor method, and the second resolution conversion method is a linear interpolation method.

According to a seventh aspect of the present invention, there is provided a resolution conversion method for converting the resolution of color image data comprising a plurality of color components, wherein when the color image data has green, red, and blue color components, Is characterized by using the third resolution conversion method for the color component and using the second resolution conversion method for the other color components.

According to an eighth aspect of the present invention, there is provided a resolution conversion method for converting the resolution of color image data comprising a plurality of color components, wherein a component value for each of the color components is obtained, and the component value having the highest value is obtained. The third resolution conversion method is used for color components, and the second resolution conversion method is used for other color components.

According to a ninth aspect of the present invention, the second resolution conversion method is a linear interpolation method, and the third resolution conversion method is a cubic interpolation method.

According to a tenth aspect of the present invention, there is provided a resolution conversion device for converting color image data of a first coordinate system comprising a plurality of color components into color image data of a second coordinate system, When the position in the first coordinate system corresponding to the pixel position in the second coordinate system is a non-grid point,
Means for calculating a color component value at the pixel position using a first interpolation method for at least one color component of the plurality of color components, and a method for calculating a pixel value using a second interpolation method for other color components. Means for calculating a color component value at the position.

According to an eleventh aspect of the present invention, in the resolution conversion apparatus for converting color image data of a first coordinate system composed of a plurality of color components into color image data of a second coordinate system, Of the color components that make up the data,
Means for calculating a color component having the smallest value or the largest value; and a step of calculating the color component when the position in the first coordinate system corresponding to the pixel position in the second coordinate system after the conversion is a non-grid point. Among the color components, the color component at the pixel position is calculated using the first interpolation method for the color component having the calculated minimum value and using the third interpolation method for the color component having the maximum value. Means, and means for calculating a color component value at the pixel position using a second interpolation method for other color components.

According to a twelfth aspect of the present invention, a function of converting color image data of a first coordinate system composed of a plurality of color components into color image data of a second coordinate system, When a position in the first coordinate system corresponding to a pixel position in the coordinate system is a non-grid point, the pixel position of the pixel position is determined using a first interpolation method for at least one of the plurality of color components. A computer-readable recording medium storing a program for causing a computer to realize a function of calculating a color component value and a function of calculating a color component value of the pixel position using another interpolation method for another color component. It is characterized by being.

According to a thirteenth aspect of the present invention, a function of converting color image data of a first coordinate system composed of a plurality of color components into color image data of a second coordinate system, and constitutes the color image data. A function of calculating a color component having the smallest value or the largest value among the respective color components; and a position in the first coordinate system corresponding to a pixel position in the second coordinate system after the conversion is a non-grid point. A function of calculating a color component value at the pixel position using a first interpolation method for a color component having the calculated minimum value among the plurality of color components; and a color component having the maximum value. Calculating a color component value at the pixel position using a third interpolation method for
It is a computer-readable recording medium in which a program for causing a computer to realize a function of calculating a color component value of the pixel position using the second interpolation method for another color component is recorded.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the drawings. Before describing the present invention, the three types of resolution conversion methods described above will be described.

As shown in FIG. 13, an original image is usually given as a set of rectangular pixels, and each pixel has an (R, G, B) value or (C, M, Y, K) value as color information. have. Here, R, G, B, C, M, Y, and K are red,
Green, blue, cyan, magenta, yellow, and black. When the resolution conversion is performed, the coordinates of one point A of the original image in the document, the number of pixels XE in the horizontal direction and the number of pixels YE in the vertical direction of the original image, and the post-conversion corresponding to the point A are usually used. , The number of pixels XE ′ in the horizontal direction and the number of pixels YE ′ in the vertical direction are given.

When the original image is in a document in an application and the converted image is output to a CRT monitor, the above information is provided from the operating system to the display driver, and the coordinates of the point A ′ are set in the CRT. XE ′ and YE ′ correspond to the number of dots on the CRT. When the converted image is output to the printer, the above information is given from the operating system to the printer driver, the coordinates of the point A ′ correspond to the coordinates on the print medium (paper), and X
E 'and YE' correspond to the number of dots on the printer.

As shown in FIG. 13, the coordinate system of the original image is X
Assuming that Y and the coordinate system of the converted image are X'Y 'and that the two coordinate systems are in a linear conversion relationship (when outputting to a CRT or a printer, the conversion is almost linear), the relationship between the two is as follows. It looks like this: x = ax '+ by' + cy y = dx '+ ey' + f (Equation 1)

Therefore, the relationship between the two coordinates can be obtained by calculating a to f using the coordinate values of the corresponding six points. As shown in FIG. 13, it is easy to obtain the coordinates of the corresponding six points based on information given from the operating system or the like. For example, the six points A, B, C, D, E,
F and six corresponding points A ′, B ′, C ′, D ′,
The coordinates of E ', F' are used. When calculating a to f, these six points do not necessarily need to be grid points (integer coordinate points).

From equation (1), for all points of the converted image, corresponding points on the original image are obtained, and the color information of the points on the original image is used as the color information of the points of the converted image. Then, the resolution conversion ends. However, like the point Z ′ shown in FIG. 14, not all the corresponding points Z on the original image become grid points, and therefore, the desired color information is interpolated using the color information of surrounding grid points. .

As the interpolation method, the nearest neighbor method employs the color information of the nearest grid point as it is. That is, in the example of FIG. 14, the color information of the point G closest to the point Z is adopted. To obtain the nearest point, the coordinates of the point Z may be rounded off. If the color information of the point G is represented by f (G), f (Z) = f (G) (Equation 2). The color information of each grid point takes a value from 0 to 255 when each color component is represented by, for example, 8 bits.

In the linear interpolation method, color information is interpolated by the following equation using four points G to J around a point Z. f (Z) = f (J) (1−α) (1−β) + f (I) α
(1-β) + f (G) (1-β) β + f (H) αβ

(Equation 1) here

(Equation 2) Is the x coordinate of point I, and so on. On the other hand, in the cubic interpolation method, color information is interpolated by the following equation (4) using 16 points T to N around the point Z.

(Equation 3)

Here, since C (t) is an approximate expression of the function sinπx / πx that constitutes the sampling theorem, the present interpolation method can theoretically obtain the most accurate interpolation result. However, the calculation speed is the slowest.

The color information of the original image is (R, G,
B), the above equations (2), (3), and (4) are used for each of the R, G, and B components, and are given by (C, M, Y, K). Are satisfied, the equations (2), (3),
(4) is used.

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the above-described interpolation method, and other interpolation methods may be appropriately combined and used. (Embodiment 1) FIG. 1 shows the configuration of Embodiment 1 of the present invention.
In the figure, 1 is a processing system, 2 is a memory storing an original image, 3 is a resolution conversion unit comprising coordinate calculation and interpolation processing, 4 is a coordinate calculation unit for converting the coordinate system of the original image into the coordinate system of the output image, Reference numeral 5 denotes an interpolation unit for performing interpolation processing by the nearest neighbor method, 6 denotes an interpolation unit for performing interpolation processing by a linear interpolation method, and 7 denotes an image output device such as a printer or a CRT.

FIG. 2 is a processing flowchart of the first embodiment of the present invention. In the present embodiment, the original image is given by each of the C, M, Y, and K planes in the memory 2. The coordinate calculation unit 4 obtains a non-grid point (Z) on the original image corresponding to the point (Z ′) on the output image (step 101). Next, the nearest point of the non-grid point (Z) is determined (step 102), and four points around the non-grid point (Z) are determined (step 103).

In C, M, Y, and K, the color with the lowest visibility (visibility) is yellow (Y). The Y value of point (Z) is converted to the Y value of point (Z ′)
Value (step 104). Other C, M, and K values are obtained by the linear interpolation unit 6 using four points (steps 105, 106, and 107). The above processing is performed for all pixels of the original image (step 1).
08) The resolution-converted image is output to an image output device 7 such as a printer.

As described above, since the processing speed of the nearest neighbor method is higher than that of the linear interpolation method, it is possible to obtain a processing speed higher than that of performing linear interpolation on the entire C, M, Y, and K. Also, Y
Has lower visibility than C, M, and K, and as a whole, an image quality comparable to that obtained by linearly interpolating the entire C, M, Y, and K can be obtained.

(Embodiment 2) FIG. 3 shows the configuration of Embodiment 2. This embodiment is an embodiment in which an original image is provided in RGB and an output image is output by a printer.
FIG. 4 is a processing flowchart of the second embodiment.

When an original image given in RGB is output by a printer, resolution conversion is performed on RGB in a printer driver, and RGB values are converted into CMY by firmware (color conversion unit 28) of the printer. May be output. In this case, the color with the lowest visibility in the image output by the printer is Y. Since RGB and CMY have a relationship of C = 255-RM = 255-G Y = 255-B, Y of the printer output after color conversion is changed to B in the printer driver (resolution conversion unit 23). Equivalent to.

Therefore, in this embodiment, the B value of the point (Z) obtained by the nearest neighbor method 25 is set as the B value of the converted point (Z ') (step 204). Other R and G values are obtained by the linear interpolation method 26 (step 205,
206). The processing in steps 201 to 203 is the same as in the first embodiment.

The above-described resolution conversion is performed in the printer driver. Since the printer driver affects the performance of the entire printing system by the computer, by implementing the above-described resolution conversion in the printer driver, the processing of the entire printing system can be sped up while suppressing the effect on the image quality. it can.

(Embodiment 3) FIG. 5 shows the configuration of Embodiment 3. FIG. 6 is a processing flowchart of the third embodiment. In this embodiment, the original image is given by R, G, B. The sampling unit 33 samples n points in the original image in the memory 31 and
Multiplies the values of R, G, and B for these n points. Then, the minimum value detection unit 35 detects a component W (W is one of R, G, and B) with the smallest integrated value (Step 301).

As in the first embodiment, the coordinate calculator 36 calculates the non-grid point Z (step 302), and calculates the nearest point (step 303) and four surrounding points of Z (step 30).
4).

The detected component W is regarded as a component having the least effect on the entire image, and the W is interpolated by the nearest neighbor method 37 (step 305), and the other color components are subjected to the linear interpolation method 38. It is determined (step 306).

For example, for an original image containing no R component, the difference in resolution conversion method for the R component does not affect the converted image. Therefore, by appropriately setting the number of sampling points n, it is possible to appropriately cope with the color components of the original image and suppress the influence on the image quality.
High-speed processing can be realized.

Each of the above embodiments aims at increasing the processing speed while suppressing the effect on the image quality. Each of the following embodiments is an embodiment for improving the image quality while suppressing the influence on the processing speed. (Embodiment 4) FIG. 7 shows the configuration of Embodiment 4. FIG. 8 is a processing flowchart of the fourth embodiment. In this embodiment, the original image is given by R, G, B, and the converted image is output to the CRT monitor 47. A non-grid point (Z) is determined (step 401), 16 points around Z are determined (step 402), and four points around Z are determined (step 403).

Of the colors R, G and B, the color with the highest visibility is G
Therefore, in this embodiment, the G value of the point (Z) obtained by the cubic interpolation method 45 using the 16 surrounding points is converted to the converted point (Z ′).
(Step 404). Other R and B values are obtained by the linear interpolation method 46 (steps 405 and 406).

In this embodiment, since a high-precision interpolation method is used for the G component, the image quality is better than when all the components are obtained by the linear interpolation method, and the linear interpolation method is used for the R and B components. Since it is used, a high processing speed can be obtained. Therefore, by implementing the above resolution conversion in the display driver, while suppressing the influence on the processing speed of the entire computer system,
Image quality can be improved.

(Embodiment 5) FIG. 9 shows the configuration of Embodiment 5. In this embodiment, the minimum value detection unit of the third embodiment is replaced with a maximum value detection unit 55, and the nearest neighbor method is replaced with a cubic interpolation method 57. FIG. 10 is a processing flowchart of the fifth embodiment.

In the present embodiment, contrary to the third embodiment, the original image is sampled, and the component W having the largest integrated value is calculated.
The component having the greatest effect on the entire image is considered, and W is interpolated by the high-quality cubic interpolation method 57 (step 5).
06), and for other color components, the linear interpolation method 58
(Step 505). For example, for an image in which the R component is dominant, the difference in the resolution conversion method of the R component has the greatest effect on the converted image.
Therefore, by appropriately setting the number of sampling points n, it is possible to appropriately correspond to the color components of the original image and to obtain a higher-quality image while appropriately suppressing the influence on the speed.

(Embodiment 6) The present invention is not limited to the above embodiment, but can be realized by software. When the present invention is realized by software,
As shown in FIG. 11, a computer system including a CPU, a memory, a display device, a hard disk, a keyboard, a CD-ROM drive, and a scanner is prepared.
-A computer-readable recording medium such as a ROM stores a program for realizing the resolution conversion function of the present invention. When executing the resolution conversion process of the present invention, the processing function of the present invention is realized by reading out the program recorded on the above-mentioned recording medium and incorporating it into a part of the OS as a printer driver or a display driver. You.

Further, since the device driver is software, it is easy to upgrade the version by adopting a new resolution conversion method or the like, and an interface for selecting the priority of speed and image quality according to the needs of the user. Can be easily constructed.

[0053]

As described above, as described above, claims 1 and 1
According to the inventions described in 0 and 12, the resolution conversion method applied to at least one color component is different from the resolution conversion method applied to other color components, so that the processing speed can be reduced while suppressing the influence on the image quality. At the same time, it is possible to improve the image quality while suppressing the influence on the processing speed.

According to the second aspect of the present invention, the resolution conversion method applied to the color component having the lowest visibility among the color components is faster than the resolution conversion method applied to the other color components. In addition, the processing speed can be increased while suppressing the influence on the image quality when the observer actually looks.

According to the third aspect of the present invention, the resolution conversion method applied to the yellow (Y) color component of the color image data is faster than the resolution conversion method applied to the other color components. When output is performed by an output device (for example, a printer) using at least Y, the processing speed can be increased while suppressing the influence on the image quality when viewed by an observer.

According to the fourth, eleventh, and thirteenth aspects, the resolution conversion method applied to the color component having the lowest value in the entire color image is faster than the resolution conversion method applied to the other color components. Therefore, the processing speed can be increased while suppressing the influence on the image quality according to the color components of the original image.

According to the fifth aspect of the present invention, since the resolution conversion method applied to the blue color component is faster than the resolution conversion method applied to the other color components, the resolution conversion is performed using the RGB values. After the conversion, if the image is converted into CMYK and then output by a device (for example, a printer), the processing speed can be increased while suppressing the influence on the image quality when viewed by the observer.

According to the present invention, since the nearest neighbor method is used as the first resolution conversion method, high-speed processing can be realized with a simple algorithm.

According to the seventh aspect of the present invention, the resolution conversion method applied to the green color component is higher in quality than the resolution conversion method applied to the other color components. When output is performed by a device (for example, a CRT monitor), the image quality when viewed by an observer can be increased while suppressing the effect on the processing speed.

According to the eighth, eleventh, and thirteenth aspects of the present invention, the resolution conversion method applied to the color component having the highest value as the whole image has higher quality than the resolution conversion method applied to the other color components. So, according to the color components of the original image,
The image quality can be improved while suppressing the influence on the processing speed.

According to the ninth aspect of the present invention, since the third-order interpolation method is used as the third resolution conversion method, the highest image quality can be theoretically obtained.

[Brief description of the drawings]

FIG. 1 shows a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a processing flowchart according to the first embodiment of the present invention.

FIG. 3 shows a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is a processing flowchart according to a second embodiment of the present invention.

FIG. 5 shows a configuration of a third embodiment of the present invention.

FIG. 6 is a processing flowchart according to a third embodiment of the present invention.

FIG. 7 shows a configuration of a fourth embodiment of the present invention.

FIG. 8 is a processing flowchart according to a fourth embodiment of the present invention.

FIG. 9 shows a configuration of a fifth embodiment of the present invention.

FIG. 10 is a processing flowchart according to a fifth embodiment of the present invention.

FIG. 11 shows a configuration of a sixth embodiment of the present invention.

FIG. 12 is a diagram illustrating an example of resolution conversion of a document image.

FIG. 13 is a diagram illustrating conversion of a coordinate system of a document image.

FIG. 14 is a diagram for explaining various interpolation methods.

[Explanation of symbols]

 Reference Signs List 1 processing system 2 memory 3 resolution conversion unit 4 coordinate calculation unit 5 nearest neighbor interpolation unit 6 linear interpolation unit 7 image output device

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B057 CA01 CB01 CD06 CE18 DA17 DB06 5C076 BB04 BB40 5C077 LL18 MP08 NN08 NN11 PP20 PP28 PP32 PP33 PP43 PQ08 PQ12 RR19 SS06 TT02 5C079 HB01 HB02 HB12 LA31 LA37 PA05

Claims (13)

[Claims] 1. A resolution conversion method for converting the resolution of color image data comprising a plurality of color components, wherein a first resolution conversion method is used for at least one of the plurality of color components. And a second resolution conversion method for other color components. 2. The resolution conversion method according to claim 1, wherein the one color component is a color component having the lowest visibility among the plurality of color components. 3. The resolution conversion method according to claim 1, wherein when the color image data has yellow, cyan, magenta, and black color components, the one color component is a yellow color component. Method. 4. A method for determining a component value for each color component, using a first resolution conversion method for a color component having the lowest value, and a second resolution conversion method for another color component. 2. The resolution conversion method according to claim 1, wherein: 5. A resolution conversion method for converting color image data of a first color system having a first resolution into color image data of a second color system having a second resolution. The first resolution conversion method is used for the blue component of the first color system, and the second resolution method is used for the other color components of the first color system.
A resolution conversion method characterized by using the resolution conversion method described above. 6. The resolution conversion method according to claim 1, wherein the first resolution conversion method is a nearest neighbor method, and the second resolution conversion method is a linear interpolation method. 7. A resolution conversion method for converting the resolution of color image data composed of a plurality of color components, wherein the color image data has green, red and blue color components, A resolution conversion method characterized by using a third resolution conversion method and using a second resolution conversion method for other color components. 8. A resolution conversion method for converting the resolution of color image data composed of a plurality of color components, wherein a component value for each color component is obtained, and a color component having the highest value among the color components is determined. A resolution conversion method using the third resolution conversion method and the second resolution conversion method for other color components. 9. The resolution conversion method according to claim 7, wherein the second resolution conversion method is a linear interpolation method, and the third resolution conversion method is a cubic interpolation method. 10. A resolution conversion device for converting color image data of a first coordinate system composed of a plurality of color components into color image data of a second coordinate system, wherein
When the position in the first coordinate system corresponding to the pixel position in the coordinate system is a non-grid point, of the plurality of color components,
Means for calculating a color component value at the pixel position using a first interpolation method for at least one color component, and calculating a color component value for the pixel position using a second interpolation method for another color component And a resolution conversion device. 11. A resolution conversion device for converting color image data of a first coordinate system composed of a plurality of color components into color image data of a second coordinate system, wherein each color component constituting the color image data is converted. Means for calculating a color component having the smallest value or the largest value, and a case where a position in the first coordinate system corresponding to a pixel position in the second coordinate system after the conversion is a non-grid point. The color component value at the pixel position using the first interpolation method for the color component having the calculated minimum value and the third interpolation method for the color component having the maximum value among the plurality of color components. Means for calculating
Means for calculating a color component value at the pixel position using a second interpolation method for another color component. 12. A function of converting color image data of a first coordinate system composed of a plurality of color components into color image data of a second coordinate system, and a function of converting the color image data into a pixel position of the second coordinate system after the conversion. When the corresponding position in the first coordinate system is a non-grid point, a color component value of the pixel position is calculated using a first interpolation method for at least one of the plurality of color components. A computer-readable storage medium storing a program for causing a computer to realize a function and a function of calculating a color component value of the pixel position using a second interpolation method for another color component. 13. A function of converting color image data of a first coordinate system consisting of a plurality of color components into color image data of a second coordinate system, and A function of calculating a color component having a small value or a maximum value; and a step of calculating the plurality of color components when a position in the first coordinate system corresponding to a pixel position in the second coordinate system after the conversion is a non-grid point. Of the color components, a function of calculating a color component value at the pixel position using the first interpolation method for the color component having the calculated minimum value, and a third interpolation method for the color component having the maximum value. A function of calculating a color component value at the pixel position by using
A computer-readable recording medium storing a program for causing a computer to realize a function of calculating a color component value at the pixel position by using the interpolation method.