JP2009071715A - Color gamut generating method, color gamut generating device, program, and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve color gamut reproduction precision of a polygon assembly approximating the color gamut of a device in a device-independent color space, and to reduce the calculation load of generation of the polygon assembly. <P>SOLUTION: Device color signals on respective color gamut boundary surfaces of the device are indexed and stored in a storage means 1001, and device-independent color signals corresponding to those device signals are indexed and stored in a storage means 1003. A polygon generating means 1004 polygon-divides the respective color gamut boundary surfaces of the device, wherein lines connecting a white point, and a primary color and a secondary color of the device and lines connecting a black point, and the primary color and secondary color are all selected as polygon division lines. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for approximating a color gamut of an image input / output device with a polygon aggregate in a device-independent color space.

  Development of a color matching system (CMS) that performs color matching processing of image data when color image data on a computer is output to a color output device such as a color printer has been active.

  The basis of CMS is to convert image data represented by RGB signals into color signals for output devices that match colorimetrically. However, since the color reproduction range of electrophotography and inkjet printers is extremely narrow compared to the color reproduction range of the display, it is impossible to faithfully reproduce the colors on the display.

  Therefore, conventionally, a technique (gamut compression technique) for mapping a color that cannot be reproduced by an output device to a reproducible color is known, and many methods have been proposed. Most of them convert input data into device-independent color signals, for example, L * a * b * signals that are signals in CIELab space, and determine a mapping destination in CIELab space. In the uniform color space, colors can be expressed by three components such as brightness, saturation, and hue, and the color difference defined as the distance in the space corresponds well with the color difference perceived by humans. Therefore, it is possible to perform mapping with less discomfort when viewed by humans. For example, for colors that cannot be reproduced by the output device, a technology is known that reproduces colors that minimize the calculated color difference by changing the weights of brightness difference, saturation difference, and hue difference among colors that can be reproduced by the output device. Yes. In addition, a projection target point is set on the achromatic color axis or on the saturation axis of the same hue as the input color signal. Technology to do is known.

  In such a gamut compression technique, it is necessary to obtain a reproducible color gamut of the output device in a device-independent color space. One effective method for defining the color gamut of the output device is to define it as a polyhedron in a three-dimensional space. Examples thereof include methods disclosed in Patent Documents 1 and 2.

  In these methods, first, in the device color space, a set of vertices existing on the boundary surface of the color gamut that the device can reproduce is set. For example, among the grid points obtained by dividing the device color space (RGB color space) into a grid pattern as shown in FIG. 2, a grid point existing on the color gamut boundary surface is set. The quadrangle formed by the vertex groups arranged in a lattice pattern is divided into two triangles by diagonal lines. By converting the vertex coordinates of the triangle created in this way into coordinates on the device-independent color space, the device color gamut is expressed as a set of polygons (here, triangles) in the device-independent color space. be able to. This is shown in FIG.

  Here, when the square is divided into two triangles by diagonal lines, two types of diagonal lines can be drawn, so there are two types of division methods. As to which of the two types of division methods is selected as the polygon division line, in Patent Document 1, the quadrature vertex coordinates and the quadrature barycentric coordinates are converted into a device-independent color space, and the device-independent color space is selected. The diagonal line with the smaller error in the barycentric coordinates at is selected as the polygon dividing line. In Patent Document 2, the diagonal line with the larger volume in the device-independent color space is selected as the polygon division line.

JP 2003-8912 A Japanese Patent No. 3684158

  However, in Patent Document 1, it is necessary to perform an operation for obtaining the center-of-gravity coordinates, and Patent Document 2 must perform an operation for obtaining a volume, and it is necessary to perform such an operation with a large calculation load for each quadrangle. There is a problem that it takes a long calculation time.

  In addition, there is a possibility that the primary color line and the secondary color line may not be appropriately expressed, and there is a problem with the color gamut reproduction accuracy in this respect. For example, referring to FIG. 14B, since the line connecting the white point W and the blue point B of the device is not a polygon division line, it becomes a concave shape at this portion. Originally, this part should have a convex shape with the line connecting the point W and the point B as a ridge, and if this part is concave, the color gamut reproduction accuracy will deteriorate. In Patent Documents 1 and 2, there is a possibility that inappropriate polygon division that causes such deterioration of the reproduction accuracy of the color gamut may be performed.

  Therefore, the present invention improves the reproduction accuracy of the color gamut by appropriately expressing the primary color line and the secondary color line of the device when expressing the device color gamut as a polygon aggregate in the device-independent color space. An object of the present invention is to provide a color gamut creation method and a color gamut creation apparatus that can perform the calculation with a large calculation load as described in Patent Documents 1 and 2.

  By the way, the color gamut of a general input / output color device may be represented by a dodecahedron as a rough approximation in a device-independent color space. In this case, a line connecting the white point of the device with the primary color and the secondary color, a line connecting the black point of the device with the primary color and the secondary color, and a line connecting the adjacent primary color and the secondary color are dodecahedron. It becomes the side of. This is a natural shape considering that the target device is reproduced with device color signals of three primary colors such as RGB or CMY. If the target device is a printer represented by a CMY signal, for example, a line connecting the white point W and the cyan point C corresponds to a color reproduced with a single color of a cyan color material. Such primary color lines and secondary color lines help intuitive understanding when the color gamut is displayed in three dimensions. Therefore, it is desirable that a primary color line and a secondary color line exist also in the polygon model. Further, by performing polygon division along the primary color line and the secondary color line, it can be expected that the color gamut reproduction accuracy will be improved.

  The present invention is based on the above consideration and has the following characteristics.

That is, the invention according to claim 1 divides each device gamut boundary surface in the device color space into polygons, and creates a polygon gamut in a device-independent color space corresponding to the aggregate of the divided polygons. A creation method,
When dividing each color gamut boundary surface of the device into polygons, all lines connecting the white point of the device and the primary color of the device and lines connecting the white point of the device and the secondary color of the device are divided into polygons. It is characterized by selecting as a line.

The invention according to claim 2 is the color gamut creating method according to claim 1,
When dividing each device gamut boundary surface into polygons, all lines connecting the black point of the device and the primary color of the device and lines connecting the black point of the device and the secondary color of the device are divided into polygons. It is characterized by selecting as a line.

According to a third aspect of the present invention, there is provided a device color signal storage means for storing a plurality of device color signals and their indexes on each color gamut boundary surface of the device in the device color space,
Device-independent color signal storage means for storing a device-independent color signal corresponding to the device color signal stored in the device color signal storage means and its index;
Based on the device color signal on each color gamut boundary surface of the device stored in the device color signal storage means and the index thereof, each color gamut boundary surface is divided into polygons, corresponding to the vertexes of each divided polygon. A set of index data which is a set of indexes is created, and the set of index data and a set of index-independent device-independent color signals stored in the device-independent color signal storage means, or the index data A polygon that outputs the data representing the polygon aggregate in the device-independent color space by replacing the set index with the device-independent color signal stored in the device-independent color signal storage means means,
Have
The polygon creation means, when dividing the polygons of the color gamut boundary surface of the device, a line connecting the white point of the device and the primary color of the device and the white point of the device and the secondary color of the device A color gamut creation device that selects all connecting lines as polygon division lines.

The invention according to claim 4 is the color gamut creating device according to claim 3,
The polygon creation means, when dividing the polygon of each color gamut boundary surface of the device, the line connecting the black point of the device and the primary color of the device and the black point of the device and the secondary color of the device All connecting lines are selected as polygon dividing lines.

The invention according to claim 5 is the color gamut creating device according to claim 3 or 4,
The device color signal stored in the device color signal storage means is a device color signal arranged in a grid pattern on each color gamut boundary surface of the device with a uniform grid width.

The invention described in claim 6 is the color gamut creating device according to claim 3 or 4,
The device color signal stored in the device color signal storage means is a device color signal arranged in a grid pattern on each color gamut boundary surface of the device with a narrower grid width in a darker area of the device color space. It is characterized by.

The invention according to claim 7 is the color gamut creating device according to any one of claims 3 to 6,
Color conversion means for converting a device color signal stored in the device color signal storage means into a device-independent color signal;
The device-independent color signal converted by the color conversion unit is stored in the device-independent color signal storage unit.

  The invention according to an eighth aspect is a program that causes a computer to function as each means of the color gamut creating means according to any one of the first to seventh aspects.

  The invention described in claim 9 is a computer-readable storage medium in which a program for causing a computer to function as each means of the color gamut creating means described in any one of claims 1 to 7 is recorded.

  In the present invention, a polygon aggregate that approximates the device gamut boundary surface is created in the device-independent color space, but when the polygon is divided on the device gamut boundary surface, the white point and primary color of the device are determined. All connecting lines and lines connecting the white point of the device and the secondary color are selected as polygon dividing lines (claims 1 and 3). Furthermore, a line connecting the black point of the device and the primary color and a line connecting the black point of the device and the secondary color are all selected as polygon division lines (claims 2 and 4). Therefore, such primary color lines and secondary color lines always serve as ridges of the polygon aggregate, and there is no possibility that the portions of the lines are recessed as in Patent Documents 1 and 2. Therefore, it is possible to create a polygon aggregate with good device color gamut reproduction accuracy. Then, it is not necessary to perform a calculation with a large calculation load for obtaining the center of gravity and volume as in Patent Documents 1 and 2 for determining whether or not to select at least those lines as polygon division lines. The device color signal stored in the device color signal storage means is a device color signal arranged in a grid pattern on the color gamut boundary surface of the device with a uniform grid width. The reproduction accuracy of the color gamut can be made uniform from dark to dark. The device color signal stored in the device color signal storage means is a device color signal arranged in a grid pattern on the color gamut boundary surface of the device by narrowing the grid width in the darker region (claim 6). ), The reproduction accuracy of the color gamut in the dark region where the shape of the color gamut is likely to be complicated can be improved, and the like can be achieved.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram for explaining an embodiment of a color gamut creating apparatus according to the present invention. In FIG. 1, 1001 is a device color signal storage means, 1003 is a device-independent color signal storage means, 1004 is a polygon creation means, and 1002 is a color conversion means. However, the color conversion unit 1002 is not an essential element.

  The device color signal storage unit 1001 stores a plurality of color signals existing on each color gamut boundary surface of the device in the device color space. Assuming that the device color space is a device RGB space and each device RGB signal takes an integer value of 0 to 255, a point K (0,0,0), a point R (255,0,0), 8 points of point G (0,255,0), point B (0,0,255), point C (0,255,255), point M (255,0,255), point Y (255,255,0), point W (255,255,255) A cube is the color gamut of the device on the device color space. Therefore, RGB signals on the outermost shell surface of the cube, that is, the color gamut boundary surface of the device are extracted and stored in the device color signal storage unit 1001. For example, as shown in FIG. 2, the device RGB space is divided into grids, and among the grid points, RGB signals of grid points on the color gamut boundary surface are stored in the device color signal storage unit 1001.

  In this example, the device RGB space is divided into two in the RGB signal directions for easy understanding. However, it is usually preferable to divide the device RGB space into 8 divisions, 16 divisions, or 32 divisions in each signal direction. As the number of divisions increases, the approximation accuracy of the color gamut that is finally created improves. However, if the number of divisions is increased too much, the amount of data to be handled increases and the processing time increases.

  The device-independent color signal storage unit 1003 stores a device-independent color signal corresponding to the device color signal stored in the device color signal storage unit 1001. As the device-independent color signal, for example, a CIELab color signal (L * a * b * signal), a CIECAM97s JCH or QMH signal, a CIECAM02 JCH or QMH signal, or the like can be used.

  Here, it is assumed that the L * a * b * signal is used as the device-independent color signal. For example, the target device is an sRGB monitor. In this case, since the device RGB signal is an sRGB signal, the color conversion unit 1002 converts the device RGB signal stored in the device color signal storage unit 1001 into an XYZ signal according to the definition of the sRGB signal, and then L * a It can be converted into a * b * signal, and this L * a * b * signal can be stored in the device-independent color signal storage means 1003. If the target device is a printer, the device RGB signal patch is actually output in advance by the printer, colorimetrically obtained to obtain an L * a * b * signal, and conversion is performed by referring to the result. be able to. Note that such conversion may be performed externally and the result may be stored in the device-independent color signal storage unit 1003. In this case, it is not necessary to provide the color conversion unit 1002.

  The polygon creation means 1004 is a means for creating a polygon aggregate having a plurality of device-independent color signals stored in the device-independent color signal storage means 1003 as vertices. There are features. This will be described in detail later. The polygon aggregate data output from the polygon creating means 1004 may be a set of three device-independent color signals constituting the vertices of each polygon (triangle), or a set of three indexes indicating the vertices of the triangles. A set of index data consisting of and a set of indexed device-independent signals may be used.

  Such a processing system can be realized by a program on a computer having a general configuration including a CPU, a memory, and the like. Such a program, that is, a program that causes a computer to function as each means of FIG. 1 is also included in the present invention. Various computer-readable storage media such as a semiconductor storage element, a magnetic disk, an optical disk, and a magneto-optical disk in which such a program is recorded are also included in the present invention.

  Hereinafter, some examples will be described.

  In this embodiment, an RGB signal is assumed as a device color signal, and a printer using CMY color materials is assumed as a target device. Because of the use of CMY color materials, C (cyan), M (magenta), and Y (yellow) in the device RGB color space are called primary colors, and R (red), G (green), and B (blue) are secondary. Called color.

  In the present embodiment, as shown in FIG. 2, the device RGB color space is divided into a grid and is on the six outermost shell surfaces (device color gamut boundary surfaces in the device RGB color space) of the device RGB color space. Grid points are extracted, and RGB color signals corresponding to the grid points are stored in the device color signal storage unit 1001 (see FIG. 3). Further, as shown in FIG. 3, indexes of 0 to 53 are assigned to the respective RGB color signals stored in the device color signal storage unit 1001. Here, in order to simplify the description, the device RGB color space is divided into two in the RGB signal directions. However, as described above, the number of divisions may be increased.

  The color conversion unit 1002 converts each device RGB signal shown in FIG. 3 into a device-independent color signal. The converted device-independent color signal is stored in the device-independent color signal storage unit 1003, and these device-independent color signals are assigned indexes 0 to 53 as in the device RGB signal. Here, the device-independent white signal is described as an L * a * b * signal, but the present invention is not limited to this as described above. The L * a * b * signals are not obtained by the conversion of the color conversion unit 1002, but may be input from the outside and stored in the device-independent color signal storage unit 1003 as described above. Street.

  Next, processing by the polygon creating unit 1004 will be described. FIG. 4 is a flowchart for explanation.

  Next, the polygon creation unit 1004 will be described. The device RGB signals stored in the device color signal storage unit 1001 are located on the outermost shell surface (device color gamut boundary surface) of the device RGB space, and are arranged in a grid pattern with a uniform grid width. The polygon creating means 1004 generates polygon index data representing the vertices of the polygon (triangle) by forming two polygons (triangles) by dividing such a grid with diagonal lines.

  Specifically, first, one of the six outermost shell surfaces of the device RGB color space is selected, and the device RGB signal and the index on the outermost shell surface are extracted as processing targets (step 1). . When the selected outermost shell surface is a WCGY surface, for example, device RGB signals and indexes as shown in FIG. 5 are extracted. Corresponding to these device RGB signals, an L * a * b * signal and its index as shown in FIG. 7 are stored in the device-independent color signal storage means 1003.

  Next, one grid on the selected outermost shell surface is selected, an index set corresponding to the vertex of the grid is extracted (step S2), and the extracted grid is divided into two triangles (polygons) diagonally. Then, polygon index data, which is a set of indices of the vertices of each triangle, is created (step S3). Until the last lattice of the outermost shell surface is processed (until the determination result of step S4 becomes Yes), the processes of steps S2 and S3 are repeated.

  FIG. 8A shows a lattice on the WCGY plane and an index of its vertex. 0 to 3 enclosed in parentheses indicate lattice numbers. Therefore, when the WCGY surface is selected as a processing target, in step S2, index data corresponding to the lattice vertices as shown in FIG. 6 are sequentially extracted in ascending order of lattice numbers.

  In step S3, the grid is divided into two triangles (polygons) by diagonal lines. At this time, one of the two types of diagonal lines is selected as a polygon division line. The feature of the present invention is that when one of the two types of diagonal lines is a part of a line connecting the white point W of the device and the primary color or secondary color, the diagonal line is always selected as a polygon dividing line. is there. However, here, the line connecting point W and point C, the line connecting point W and point M, and the line connecting point W and point Y are grid division lines (polygon division lines) from the beginning. Therefore, what is actually subject to the selection process is the line that connects point W and point R, the line that connects point W and point G, and the line that connects point W and point B are polygon division lines . In step S3, a line connecting the black point K of the device and the primary color or secondary color, that is, a line connecting point K and point C, a line connecting point K and point M, and point K and point Y , A line connecting point K and point R, a line connecting point K and point G, and a line connecting point K and point B are selected as polygon division lines. This point is also a feature of the present invention. Although it is desirable to select a line connecting the point K and the primary color or the secondary color as a polygon division line, an aspect without such a restriction is possible, and such an aspect is also included in the present invention.

  Thus, in the case of the WCGY plane, each lattice is divided into polygons as shown in FIG. For grid (1) and grid (2), either of the two diagonal lines may be selected as the polygon division line. In FIG. 8B, polygon division of all grids on the same outermost surface is performed. The polygon division lines of the grid (1) and the grid (2) are selected so that the lines are aligned.

  In the case of the WCGY plane, since polygon division as shown in FIG. 8B is performed, polygon index data as shown in FIG. 9 is generated in step S3. The three indexes in each row in FIG. 9 are index data corresponding to the three vertices of one polygon (triangle). Here, since one outermost shell surface (color gamut boundary surface) is divided into four grids, nine sets of index data corresponding to three vertices of nine polygons are generated as polygon index data. become.

  When the process for one outermost shell surface of the device RGB color space is completed, the process returns to step S1 and the same processing is repeated for the next outermost shell surface. When the process for the last of the six outermost shell surfaces is completed, the series of processes is completed. Polygon index data for the six outermost shell surfaces of the device RGB color space was generated.

  As described above, the polygon creating unit 1004 performs polygon division on each outermost shell surface (each color gamut boundary surface) of the device RGB color space to generate polygon index data. The device RGB signal and L * a The * b * signal is associated with an index. Therefore, the above polygon division processing is equivalent to performing polygon division in a device-independent color space (here, CIELab color space).

  Although not shown in FIG. 4, the polygon creating unit 1004 generates a set of generated polygon index data and an indexed device-independent color signal stored in the device-independent color signal storage unit 1003. The data is output as polygon aggregate data, or is output as polygon aggregate data in which the index of the polygon index data is replaced with a device-independent color signal (L * a * b * signal here) corresponding thereto. This polygon aggregate data represents a polygon aggregate that approximates the device gamut boundary surface in the device-independent color space, in other words, a polygon aggregate that covers the device gamut.

  FIG. 10 shows the result of polygon division. FIG. 10A shows how polygons are divided in the device RGB color space, and FIG. 10B shows how polygons are divided in the CIELab color space. As shown in FIG. 10B, the line connecting the point W and the point B is selected as a polygon dividing line, and the line is a ridge, so that the portion is recessed as shown in FIG. 14B. Since the shape does not become a shape, the color gamut reproduction accuracy of the polygon aggregate is good.

  In this embodiment, the device RGB color space is divided so that the region closer to the black point K, that is, the darker region, the grid width is narrowed to increase the number of lattice points around the point K, and the device color gamut. A device RGB color signal corresponding to each grid point on the boundary surface is stored in the device color signal storage unit 1001. An example of such a device RGB color space division is shown in FIG. The rest is the same as in the first embodiment.

  In a printer, for example, an image is formed by placing a color material on a medium such as white paper and darkening it. As the image becomes darker, more color material is used. Depending on the characteristics of the color material, a device-independent color signal is used. And the non-linearity between the color material signal tends to be strong. This means that non-linearity also becomes strong with respect to the color gamut shape in a dark region. When the target device is such a printer, the color gamut reproduction accuracy can be improved by dividing the device RGB color space non-uniformly so that the number of grid points in the dark area increases as in this embodiment. There is.

  In the first and second embodiments described above, the device color signal is handled as a three-dimensional signal, but it is also necessary to handle a four-dimensional device color signal. For example, many printers use CMYK four color materials. Some printers receive RGB signals and convert the RGB signals into CMYK four-color color material signals by internal processing, while others receive CMYK signals directly. When handling the latter printer, it is necessary to approximate the color gamut of the four-dimensional device CMYK signal in a device-independent color space.

  In this embodiment, the device color gamut in the device CMYK color space is approximated by a polygon in the device-independent color space.

The device color signal storage unit 1001 stores a plurality of device CMYK signals existing on each color gamut boundary surface of the device. The device CMYK signal present on the color gamut boundary is
Face with Y = 0 and K = 0 (1)
Face with M = 0 and K = 0 (2)
Face with C = 0 and K = 0 (3)
Surface where Y is 0 and M is the maximum value (4)
Surface where Y is the maximum and M is 0 (5)
Surface with M = 0 and Y maximum (6)
Surface where M is the maximum and C is 0 (7)
Surface where C is 0 and Y is the maximum value (8)
Surface where C is maximum and Y is 0 (9)
Surface where Y is the maximum and K is the maximum (10)
Surface with M at maximum value and K at maximum value (11)
Surface with C at maximum and K at maximum (12)
(See, for example, Japanese Patent No. 2952489). From this, the color gamut of the device represented by the device CMYK signal is roughly similar to the polyhedron of FIG. 12 in the CIELab space.

  Therefore, in this embodiment, grid points are prepared by dividing the signal axes having degrees of freedom in the planes (1) to (12) into a grid pattern. For example, in the case of the surface (1), the Y and K axes are fixed at Y = K = 0, so that the C axis and the M axis are divided into a lattice shape. Then, the device CMYK signal corresponding to each grid point is assigned an index and stored in the device color signal storage unit 1001. In addition, device-independent color signals (for example, L * a * b * signals) corresponding to the device CMYK signals are assigned indexes and stored in the device-independent color signal storage unit 1003. Such a device-independent color signal may be obtained by conversion by the color conversion unit 1002 or may be input from the outside.

The processing procedure of the polygon creating means 1004 can be shown as shown in FIG. Steps S11 to S15 in FIG. 13 are basically the same as steps S1 to S5 in FIG. The difference is that in step S11, one outermost surface is selected from the 12 outermost surfaces (color gamut boundary surfaces) of the device CMYK color space. The processing in step S13 is the same, and each lattice on the selected outermost shell surface is divided into polygons (triangles) by diagonal lines. At this time, lines connecting the white point of the device with the primary color and the secondary color Are selected as polygon dividing lines, and all lines connecting the black point of the device with the primary color and secondary color are selected as polygon dividing lines. However, the white point is a point having CMYK coordinates (0,0,0,0), and the black point is a point having CMYK coordinates (255,255,255,255). For example, a line connecting a black point and a cyan point (255, 0, 0, 0) is a line passing through a point (255, 0, 0, 255) where C = K = 255.
Although the color gamut creation device according to the present invention has been described so far, it is obvious that the description is also an explanation of an embodiment of the color gamut creation method according to the present invention. The procedure of the color gamut creation method can be easily executed by a program on a computer having a general configuration including a CPU, a memory, and the like. A program for this purpose and various computer-readable storage media on which the program is recorded are also included in the present invention.

It is a block diagram for demonstrating embodiment of this invention. It is a figure which shows the example of the lattice division of a device RGB color space. 6 is a flowchart for explaining processing of a polygon creating unit according to the first embodiment. It is a figure which shows the example of the memory content of a device color signal memory | storage means. It is a figure which shows the example of the device RGB signal and index on one outermost shell surface of a device RGB color space. It is a figure which shows the example of the index corresponding to the vertex of four lattices in one outermost shell surface of device RGB color space. It is a figure which shows the example of the L * a * b * signal corresponding to the device RGB signal shown in FIG. 5, and an index. It is a figure which shows the example on the grid on the WCGY surface of device RGB color space, and its polygon division | segmentation. It is a figure which shows the polygon index data produced | generated with respect to a WCGY surface. It is a figure which shows the example of polygon division | segmentation. FIG. 10 is a diagram illustrating an example of non-uniform division of a device RGB color space in the second embodiment. It is a figure for demonstrating the shape on L * a * b * space of the color gamut of the device represented by the device CMYK signal. 12 is a flowchart for explaining processing of a polygon creating unit in the third embodiment. It is a figure which shows the example of a polygon division | segmentation by a prior art.

Explanation of symbols

1001 Device color signal storage means 1002 Color conversion means 1003 Device independent color signal storage means 1004 Polygon creation means

Claims (9)

A color gamut creating method for creating a polygon aggregate in a device-independent color space corresponding to a group of divided polygons by dividing each device gamut boundary surface in the device color space into polygons,
When dividing each color gamut boundary surface of the device into polygons, all lines connecting the white point of the device and the primary color of the device and lines connecting the white point of the device and the secondary color of the device are divided into polygons. A method of creating a color gamut characterized by selecting as a line.   When dividing each device gamut boundary surface into polygons, all lines connecting the black point of the device and the primary color of the device and lines connecting the black point of the device and the secondary color of the device are divided into polygons. The color gamut creation method according to claim 1, wherein the color gamut creation method is selected as a line. A device color signal storage means for storing a plurality of device color signals and their indexes on each color gamut boundary surface of the device in the device color space;
Device-independent color signal storage means for storing a device-independent color signal corresponding to the device color signal stored in the device color signal storage means and its index;
Based on the device color signal on each color gamut boundary surface of the device stored in the device color signal storage means and the index thereof, each color gamut boundary surface is divided into polygons, corresponding to the vertexes of each divided polygon. A set of index data which is a set of indexes is created, and the set of index data and a set of index-independent device-independent color signals stored in the device-independent color signal storage means, or the index data A polygon that outputs the data representing the polygon aggregate in the device-independent color space by replacing the set index with the device-independent color signal stored in the device-independent color signal storage means means,
Have
The polygon creation means, when dividing the polygons of the color gamut boundary surface of the device, a line connecting the white point of the device and the primary color of the device and the white point of the device and the secondary color of the device A color gamut creating apparatus that selects all connecting lines as polygon dividing lines.   The polygon creation means, when dividing the polygon of each color gamut boundary surface of the device, the line connecting the black point of the device and the primary color of the device and the black point of the device and the secondary color of the device 4. The color gamut creation device according to claim 3, wherein all connecting lines are selected as polygon division lines.   5. The device color signal stored in the device color signal storage means is a device color signal arranged in a grid pattern on each color gamut boundary surface of the device with a uniform grid width. The color gamut creation device described in 1.   The device color signal stored in the device color signal storage means is a device color signal arranged in a grid pattern on each color gamut boundary surface of the device with a narrower grid width in a darker area of the device color space. The color gamut creation device according to claim 3, wherein: Color conversion means for converting a device color signal stored in the device color signal storage means into a device-independent color signal;
7. The color gamut creation device according to claim 3, wherein the device-independent color signal converted by the color conversion unit is stored in the device-independent color signal storage unit.   A program that causes a computer to function as each unit of the color gamut creating unit according to claim 1.   A computer-readable storage medium in which a program for causing a computer to function as each unit of the color gamut creating unit according to any one of claims 1 to 7 is recorded.

Images