JP2014093592A - Image processing device and image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing device which, in a simple configuration as compared with the case without the present configuration, can perform color conversion in each of color regions with optimum accuracy.SOLUTION: A first conversion unit 11 obtains a color signal after conversion corresponding to a color signal imparted by interpolation by using a conversion table in which a color value after conversion is correlated with a color point arranged in a given color region. A second conversion unit 12 obtains a color signal after conversion corresponding to a color signal imparted by interpolation by using a conversion table in which a color value after conversion is correlated with a color point arranged in a partial color region of the color region subject to conversion by the first conversion unit 11. Color conversion by the first conversion unit 11 and the second conversion unit 12 are executed in parallel, and either a color signal after conversion by the first conversion unit 11 or a color signal after conversion by the second conversion unit 12 is selected in a selection unit 13 before being outputted.

Description

  The present invention relates to an image processing apparatus and an image processing program.

  Conventionally, color conversion processing for converting a given color signal into another color signal, such as conversion from a color signal in one color space into a color signal in another color space, has been performed. One method for performing color conversion is to use a conversion table in which colors before conversion and colors after conversion are associated with each other. For example, a color point is arranged in a certain color area of a certain color space, and a conversion table in which the converted color value is associated with the color point is created. Then, it identifies some color points registered in the conversion table from the given color signal, obtains the corresponding color value after conversion and interpolates it, and converts it corresponding to the given color signal A later color signal is obtained.

  In some cases, the color points arranged in the color area divide the range of the values of each color component constituting the color space into several parts and use a color that is a combination of the division points in each color component. In such a case, the accuracy of the color signal after conversion obtained by interpolation increases as the number of divisions increases, but the number of combinations increases and the amount of data in the conversion table increases.

  When color conversion is performed using a certain conversion table, there are variations in accuracy depending on the portion of the color area, and the required accuracy is also different. In this way, it corresponds to the difference in accuracy depending on the part in the color region. For example, in Patent Document 1, the color point value is divided and arranged according to the difference in accuracy without equally dividing the range of color component values. In addition, the accuracy corresponding to each part of the color region is obtained.

  Further, in Patent Document 2, a basic table and a detailed table are provided as conversion tables, and for parts that require higher accuracy than the basic table, address information to the detailed table is associated in place of the converted color values. The color conversion is performed by referring to the detailed table according to the address information. In the case of this configuration, when performing color conversion using the detailed table, the basic table is first referred to and then the detailed table is referred to. In addition, different types of information, that is, the converted color value and the address information to the detailed table, are mixed in the basic table, and processing is performed while determining which information is the information. .

JP 2005-244620 A JP 2011-029853 A

  It is an object of the present invention to provide an image processing apparatus and an image processing program capable of performing color conversion with optimum accuracy in each part of a color area with a simpler configuration than the case without this configuration. It is.

  The invention according to claim 1 of the present application obtains a color signal after conversion corresponding to a color signal given by interpolation using a conversion table in which color values after conversion are associated with color points arranged in a certain color area. A converted color signal corresponding to a color signal given by interpolation using a first conversion means and a conversion table in which the converted color value is associated with a color point arranged in the partial color area of the color area. An image processing apparatus comprising: one or more second conversion means to be obtained; and a selection means for selecting the first conversion means or any one of the second conversion means according to a given color signal. .

  The invention according to claim 2 of the present application is characterized in that the partial color region in the invention according to claim 1 of the present invention is a color region having a lightness equal to or higher than a predetermined lightness in the color region. An image processing apparatus.

  The invention according to claim 3 of the present application is characterized in that the partial color area in the invention according to claim 1 of the present invention is an area of a color of saturation less than or equal to a predetermined saturation in the color area. The image processing apparatus.

  An invention according to claim 4 of the present application is an image processing program for causing a computer to execute the function of the image processing apparatus according to any one of claims 1 to 3.

  According to the first aspect of the present invention, there is an effect that it is possible to perform color conversion with optimum accuracy in each part of the color region with a simple configuration as compared with the case where this configuration is not provided.

  According to the second aspect of the present invention, it is possible to perform color conversion with higher accuracy in a color region having a lightness equal to or higher than a predetermined lightness as compared with a case where the present configuration is not provided.

  According to the third aspect of the present invention, color conversion can be performed with higher accuracy in a color area having a saturation equal to or lower than a predetermined saturation as compared with a case where the present configuration is not provided.

  According to the invention described in claim 4 of the present application, the effect of the invention described in any one of claims 1 to 3 of the present application can be obtained.

It is a block diagram which shows one Embodiment of this invention. It is explanatory drawing of an example of the conversion table used by the 1st conversion part. FIG. 10 is an explanatory diagram illustrating an example of a partial color area in a second conversion unit. It is a block diagram which shows the modification of one Embodiment of this invention. FIG. 16 is an explanatory diagram of an example of a computer program, a storage medium storing the computer program, and a computer when the functions described in the embodiment of the present invention and the modifications thereof are realized by a computer program.

  FIG. 1 is a configuration diagram showing an embodiment of the present invention. In the figure, 11 is a first conversion unit, 12 is a second conversion unit, and 13 is a selection unit. In FIG. 1, a color signal in the LAB color space is given as an example, and it is shown that it is converted into a color signal in the CMYK color space, and the following description will be given along this example. However, the color space of the given color signal and the color space of the color signal after conversion are not limited to this example, and any color space may be used.

  The first conversion unit 11 obtains a color signal after conversion corresponding to the color signal given by interpolation, using a conversion table in which the converted color value is associated with color points arranged in a certain color area. The color area is an area including colors that can be taken by the color signal in the color space of the given color signal.

  The second conversion unit 12 converts the partial color region of the color region that is the target of the color conversion by the first conversion unit 11 and converts the converted color value to the color point arranged in the partial color region. Using the converted conversion table, a color signal after conversion corresponding to the color signal given by interpolation is obtained. The partial color area is, for example, a color area having a lightness equal to or higher than a predetermined lightness among color areas targeted for color conversion by the first conversion unit 11 or a color having a saturation lower than a predetermined saturation. It is good to set it as the area. The number of color points to be arranged in the partial color area is arranged more than the color points arranged in the conversion table used in the first conversion unit 11 at least in the partial color area, and the first conversion unit 11 in the partial color area. Color conversion is performed with higher accuracy.

  In this example, one second conversion unit 12 is illustrated, but two or more second conversion units 12 are provided, and a plurality of partial color regions of the color regions that the first conversion unit 11 is subject to color conversion are provided. The corresponding second conversion units 12 may perform color conversion.

  The selection unit 13 selects the first conversion unit 11 or the second conversion unit 12 (if there are a plurality of second conversion units 12) based on the given color signal. In the example illustrated in FIG. 1, either the color signal converted by the first conversion unit 11 or the color signal converted by the second conversion unit 12 is selected to obtain a color conversion result.

The configuration in the embodiment of the present invention described above will be further described. The first conversion unit 11 performs a color conversion process using a conversion table that has been conventionally performed. The outline of the process will be briefly described. FIG. 2 is an explanatory diagram of an example of a conversion table used in the first conversion unit 11. FIG. 2A shows an example in which color points are arranged in the color area. Since the color space of the given color signal is the LAB color space here, the range of values that each color component can take is as follows: L ^* component is L1 to Lh, a ^* component is al to ah, b ^* The component is bl to bh, and this range is the color area to be converted. Then, the range that each color component can take is divided into several parts, and the color point represented by the combination of division points in each color component is indicated by a black dot in FIG. The color values after color conversion are obtained for the color points indicated by the black dots, and are associated with each other. For example, when each color component range is divided into n, the number of division points including the start point and the end point is (n + 1), and there are (n + 1) ³ combinations of division points for the three color components. In the conversion table, the converted color values are stored at addresses corresponding to the (n + 1) ³ color points. An example of the conversion table is shown in FIG.

  The first conversion unit 11 calculates a color value after conversion corresponding to a given color signal by interpolating the color value after conversion registered in the conversion table using such a conversion table. . When a color signal is given, the converted color value registered in the conversion table is read according to the color signal, and interpolation processing is performed. The interpolation method may be an existing method, and color values after conversion are read from the conversion table according to the interpolation method to be used, and interpolation processing is performed. For example, in the case of triangular pyramid interpolation, a triangular pyramid including the color of a given color signal is specified, and color values corresponding to four color points that are vertices are read from the conversion table, and interpolation processing is performed. If cube interpolation is to be performed, a cube (rectangular solid) containing the color of the given color signal is specified, color values corresponding to the eight color points at the vertices are read from the conversion table, and interpolation processing is performed. . In other interpolation methods, the color value after conversion corresponding to the color point may be read from the conversion table according to the method, and interpolation processing may be performed. The obtained value is output as a color signal after conversion corresponding to the given color signal. In the example shown in FIG. 1, the color signal after the conversion by the first conversion unit 11 is C1M1Y1K1.

The second conversion unit 12 also reads out the converted color value from the conversion table according to the interpolation method, and performs an interpolation process. As the conversion table at that time, a conversion table created by the first conversion unit 11 in the partial color region of the color regions to be subjected to color conversion is used. FIG. 3 is an explanatory diagram of an example of a partial color area in the second conversion unit 12. FIG. 3B shows color areas and color points when creating a conversion table used in the first conversion unit 11 shown in FIG. The conversion table used in the second conversion unit 12 is created in the partial color area of the color area including the color point shown in FIG. An example of the partial color area is shown in FIG. In the partial color region, the L ^* component is Lx1 or more and Lx2 or less (L1 ≦ Lx1, Lx2 ≦ Lh), the a ^* component is ay1 or more and ay2 or less (al ≦ ay1, ay2 ≦ ah), and the b ^* component is bz1 or more and bz2 or less ( bl ≦ bz1, bz2 ≦ bh). In this example, a color region including the lightness (L ^* ) axis and having Lx2 = Lh and having a lightness of Lx1 or more is defined as a partial color region. An example of the partial color area is shown in FIG.

  Color points are arranged in such a partial color space, and converted color values corresponding to the color points are registered in the conversion table. The color point to be arranged is, for example, a color point represented by a combination of division points in each color component by dividing a range that can be taken by each color component in the partial color region. This color point is indicated by a black dot in FIG. At least in the partial color area, the color points are arranged more than the color points arranged in the conversion table used in the first conversion unit 11. In the example shown in FIG. 3A, the color point interval is halved compared to the color point interval shown by the black dots in FIG. Of course, how many color points are arranged is not limited to this example. Color values after color conversion are obtained for color points indicated by black dots in FIG. In the conversion table, each converted color value is stored at an address corresponding to each color point.

  The second conversion unit 12 uses the conversion table created in the partial color region, reads the converted color value from the conversion table according to the interpolation method for the given color signal, performs interpolation processing, and gives A converted color signal corresponding to the received color signal is obtained. In the partial color region, more color points are arranged than in the conversion table used in the first conversion unit 11, and in the partial color region, a color signal subjected to color conversion with higher accuracy than the first conversion unit 11 is obtained. The color signal after being converted by the second converter 12 is C2M2Y2K2 in FIG.

The given color signal may indicate a color outside the partial color area. In such a case, the end point of the range for each color component, specifically, Lx1 or Lx2 for the L ^* component, ay1 or ay2 for the a ^* component, bz1 or bz2 for the b ^* component What is necessary is just to obtain the color signal after conversion. Alternatively, any value such as a fixed color signal after conversion may be used.

  In the example of the partial color region shown in FIG. 3A, the region includes a lightness axis having a lightness of Lx1 or more. In this partial color area, the color at the time of color conversion is corrected compared to other partial color areas, such as correcting the color of the medium at the time of image formation or correcting the difference from the lightness axis for gray. This is the required area. If the color conversion in the partial color region is performed by the second conversion unit 12, the color conversion is performed with higher accuracy than when the first conversion unit 11 performs the color conversion.

Furthermore, in the example of the partial color area shown in FIG. 3A, the a ^* component is in the range of ay1 to ay2 and the b ^* component is in the range of bz1 to bz2, and the saturation is a predetermined saturation or less area. Restricted to In this case, color conversion is performed with higher accuracy than in the case where the first conversion unit 11 performs color conversion in a low-saturation color, and the color discrimination in the low-saturation color is improved. Of course, other regions may be used as partial color regions, or a plurality of partial color regions may be set, and the second conversion unit 12 corresponding to each partial color region may be provided.

The selection unit 13 selects the first conversion unit 11 or the second conversion unit 12 based on the given color signal. In the example illustrated in FIG. 1, the color conversion result CMYK is selected by selecting either C1M1Y1K1 that is the color signal converted by the first conversion unit 11 or C2M2Y2K2 that is the color signal converted by the second conversion unit 12. . Here, the L ^* component is Lx1 or more and Lx2 or less (Ll ≦ Lx1, Lx2 ≦ Lh) and the a ^* component is ay1 or more and ay2 or less (al ≦ ay1, ay2 ≦). ah), b ^* component is in the range of bz1 to bz2 (bl ≦ bz1, bz2 ≦ bh). When the given color signal is (Li, ai, bi), the conversion result of the second conversion unit 12 is obtained when Lx1 ≦ Li ≦ Lx2, ay1 ≦ ai ≦ ay2, and bz1 ≦ bi ≦ bz2. If this condition is not satisfied, the conversion result of the first conversion unit 11 may be selected.

  This condition determines whether or not a given color signal is a color of a partial color area. If the given color signal is a color in the partial color region, the conversion result of the second conversion unit 12 is selected. If the color signal is not in the partial color region, the conversion result of the first conversion unit 11 is selected. Needless to say, the selection condition is determined by the partial color region in which the second conversion unit 12 performs color conversion, and is not limited to the above example. Further, when there are a plurality of second conversion units 12, it is determined whether or not a given color signal is a color of each partial color region, and if it is a color of any partial color region, it corresponds. The conversion result of the first conversion unit 11 may be selected if the conversion result of the second conversion unit 12 is selected and the color of any partial color region is not selected.

  In such a configuration, a method using a conversion table in which the color points are increased for the partial color area, rather than increasing the number of color points when creating the conversion table used in the first conversion unit 11 over the entire color area. However, the amount of data is small, and the color conversion is performed with higher accuracy in the partial color area where accuracy is required than in the other color areas. The color conversion processing by the first conversion unit 11 and the second conversion unit 12 is performed in parallel, and the second conversion unit 12 performs color conversion after accessing the conversion table of the first conversion unit 11 as in the past. Such sequential processing is not performed.

FIG. 4 is a configuration diagram showing a modification of the embodiment of the present invention. In this modification, an example is shown in which the selection unit 13 is provided upstream of the first conversion unit 11 and the second conversion unit 12. The selection unit 13 selects the first conversion unit 11 or the second conversion unit 12 based on the supplied color signal, passes the supplied color signal to the selected conversion unit, and performs color conversion. The partial color region in which the second conversion unit 12 performs color conversion is such that the L ^* component is Lx1 or more and Lx2 or less (L1 ≦ Lx1, Lx2 ≦ Lh), and the a ^* component is ay1 or more and ay2 or less (al ≦ ay1, ay2 ≦ ah) , B ^* component is in the range of bz1 or more and bz2 or less (bl ≦ bz1, bz2 ≦ bh), assuming that a given color signal is (Li, ai, bi), Lx1 ≦ Li ≦ Lx2 and ay1 ≦ The color signal given when the conditions of ai ≦ ay2 and bz1 ≦ bi ≦ bz2 are satisfied is passed to the second conversion unit 12, and the color signal given when the conditions are not satisfied is sent to the first conversion unit 11. Just give it. The first conversion unit 11 or the second conversion unit 12 to which the color signal is passed from the selection unit 13 performs color conversion and outputs the color signal after color conversion.

  In the configuration of this modification, the color conversion process is performed by either the first conversion unit 11 or the second conversion unit 12, and the second conversion is performed after accessing the conversion table of the first conversion unit 11 as in the past. Sequential processing such as color conversion by the unit 12 is not performed.

  FIG. 5 is an explanatory diagram of an example of a computer program, a storage medium storing the computer program, and a computer when the functions described in the embodiment of the present invention and the modifications thereof are realized by a computer program. In the figure, 21 is a program, 22 is a computer, 31 is a magneto-optical disk, 32 is an optical disk, 33 is a magnetic disk, 34 is a memory, 41 is a CPU, 42 is an internal memory, 43 is a reading unit, 44 is a hard disk, 45 is An interface 46 is a communication unit.

  You may implement | achieve the whole or a part of function of each part demonstrated as one Embodiment and its modification of the above-mentioned this invention with the program 21 which a computer runs. In this case, the program 21 and data used by the program may be stored in a storage medium that can be read by a computer. The storage medium refers to the reading unit 43 provided in the hardware resource of the computer, causing a change state of energy such as magnetism, light, electricity, etc. according to the description content of the program, and corresponding signals. In this format, the description content of the program is transmitted to the reading unit 43. For example, there are a magneto-optical disk 31, an optical disk 32 (including a CD and a DVD), a magnetic disk 33, a memory 34 (including an IC card, a memory card, a flash memory, and the like). Of course, these storage media are not limited to portable types.

  The program 21 is stored in these storage media. For example, the storage medium 43 is mounted on the reading unit 43 or the interface 45 of the computer 22 to read the program 21 from the computer, and the internal memory 42 or the hard disk 44 (magnetic disk or the like). (Including a silicon disk etc.) and the program 21 is executed by the CPU 41, and the functions described as the above-described embodiment of the present invention and modifications thereof are realized in whole or in part. Alternatively, the program 21 is transferred to the computer 22 via the communication path, and the computer 22 receives the program 21 by the communication unit 46 and stores it in the internal memory 42 or the hard disk 44, and the program 21 is executed by the CPU 41. Also good.

  Note that the information about the conversion table and the partial color area used in the processing of the first conversion unit 11 and the second conversion unit 12 is also read from the storage medium or received via a communication path and stored in the internal memory 42 or the hard disk 44. In addition, it may be read and used in the color signal conversion process.

  In addition, the computer 22 may be connected to various devices via an interface 45. For example, an image forming unit may be connected and configured to form an image on a medium according to the color signal after color conversion. Or a display means may be connected and the structure which displays an image according to the color signal after color conversion may be sufficient. Furthermore, an image reading device may be connected, and an image read by the image reading device may be a target for color conversion. Of course, it goes without saying that other devices may be connected.

  Note that each component does not have to operate on one computer, and the processing may be executed by another computer depending on the processing stage. In addition, when color conversion processing is performed together with other processing, it may be configured integrally with a program for performing other processing. Furthermore, it may be partially configured by hardware, or all may be configured by hardware.

  DESCRIPTION OF SYMBOLS 11 ... 1st conversion part, 12 ... 2nd conversion part, 13 ... Selection part, 21 ... Program, 22 ... Computer, 31 ... Magneto-optical disk, 32 ... Optical disk, 33 ... Magnetic disk, 34 ... Memory, 41 ... CPU, 42 ... Internal memory, 43 ... Reading unit, 44 ... Hard disk, 45 ... Interface, 46 ... Communication unit.

Claims (4)

  First conversion means for obtaining a color signal after conversion corresponding to a color signal given by interpolation using a conversion table in which color values after conversion are associated with color points arranged in a certain color area; and the color area One or more second conversion means for obtaining a color signal after conversion corresponding to a color signal given by interpolation using a conversion table in which color values after conversion are associated with color points arranged in the partial color area; An image processing apparatus comprising: a selection unit that selects the first conversion unit or any one of the second conversion units according to a given color signal.   The image processing apparatus according to claim 1, wherein the partial color area is a color area having a lightness equal to or higher than a predetermined lightness of the color areas.   The image processing apparatus according to claim 1, wherein the partial color area is an area having a saturation color equal to or lower than a predetermined saturation in the color area.   An image processing program for causing a computer to execute the function of the image processing apparatus according to any one of claims 1 to 3.

Images