JP2010171865A - Apparatus, method and program for processing image and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform detailed adjustment while keeping hue equality when a user performs color conversion. <P>SOLUTION: A color conversion table holding means 101 holds a gradation-preferential color conversion table 102 and a fidelity-preferential color conversion table 103. The color conversion table 102, 103 converts the same input color signal into output color signals having an approximately identical hue. The color conversion table 102 and the color conversion table 103 are designated and weighted by a weighting designating means 104, and a color converting means 106 reads the color conversion tables 102, 103 from the color conversion table holding means 101 and performs color conversion in accordance with a weighting coefficient 105. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, an image processing method, a program, and a recording medium that convert an input color signal into a color signal suitable for an output device, and relates to an image processing apparatus such as a color printer, a color fax, and a color hard copy. It is applied to software for color printers that run on personal computers and workstations.

  Development of a color management 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 actively developed. 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.

  Thus, a technique for mapping a color that cannot be reproduced by an output device to a reproducible color (hereinafter referred to as a gamut mapping technique) has been 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 a color difference defined as a distance in the space corresponds well with a 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 with the smallest color difference calculated by changing the weight of brightness difference, saturation difference, and hue difference among colors that can be reproduced by the output device. (See Patent Document 1). 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, and for colors outside the gamut of the output device, the hue is kept constant and the compression mapping is performed in the gamut of the output device. The technique etc. which perform are known (refer patent document 2, 3).

  By devising a gamut mapping method, it is possible to perform color reproduction by adjusting image quality items that are important, such as color reproduction that emphasizes gradation and color reproduction that emphasizes fidelity. However, in actual CMS, color conversion is performed using data called a color profile including a color conversion table describing the relationship between an input color signal and an output color signal including the result of gamut mapping. Therefore, it is difficult for the user to directly adjust the gamut mapping technology. Therefore, the image quality is usually adjusted by selecting a color profile according to the image. However, the provided color profiles are limited, and for example, there are often about three types of gradation priority / brightness priority / fidelity priority. Therefore, finer adjustments cannot be made.

  As a technique for solving such a problem, for example, the technique described in Patent Document 4 can be used. Patent Document 4 discloses a technique for performing interpolation for each region using a color conversion table that emphasizes fidelity and a color conversion table that emphasizes gradation. However, if this is the case, there is a possibility that a problem occurs in the equi-hue property.

  First, the equi-hue property will be described. In many methods, the color conversion is performed while maintaining the equal hue of the equal hue line. “Maintaining equal hue lines of equal hue lines” means that a set of input color signals having substantially the same hue, that is, a set of substantially identical output color signals corresponds to the equal hue lines. means. For example, the line connecting the primary color R of the sRGB signal and the white point or the black point often performs color conversion while maintaining equal hue (FIG. 15 (a)). However, this does not mean that the input color signal and the output color signal have the same hue. For example, in order to associate the primary color R of the sRGB signal with the secondary color R of the printer, the hue of the sRGB signal primary color R and the line connecting the white point or the black point is maintained while maintaining the same hue. Conversion that shifts may be performed.

  Here, as disclosed in Patent Document 4, it is considered that a new color conversion table is created by interpolating two color conversion tables while changing the weight according to the color region. In this case, if the two color conversion tables are color conversion tables that maintain the same hue, it is desirable that the color conversion tables created by interpolation also maintain the same hue of the equal hue line (FIG. 15B). . However, the two color conversion tables do not always convert the same input color signal into an output color signal having the same hue. Therefore, there is a problem that equal hue cannot be maintained by performing weighted interpolation.

  FIG. 15C plots the output color signal corresponding to the point on the line from the white point to the primary color R of the sRGB signal on the a * b * plane of the L * a * b * space for each color conversion table. Is. The weight conversion interpolated color conversion table is created by performing an interpolation operation such that the closer to R, the stronger the weight of the first profile. For this reason, it is understood that the equi-hue property of the weight conversion interpolated color conversion table is not maintained and the hue is a curved line.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an image processing apparatus and image processing capable of performing detailed adjustment while maintaining the same hue when a user performs color conversion. To provide a method, a program, and a recording medium.

  It is an object of the present invention to be able to make detailed adjustments while maintaining the same hue when the user performs color conversion.

  It is an object of the present invention to be able to adjust the balance between vividness or fidelity and gradation when the user performs color conversion.

  It is an object of the present invention to enable appropriate adjustment for each hue when the user performs color conversion.

  It is an object of the present invention to enable appropriate adjustment separately on the highlight side and the shadow side when the user performs color conversion.

  It is an object of the present invention to be able to adjust the gradation in the hue direction when the user performs color conversion.

  The present invention is an image processing apparatus for converting an input color signal to generate an output color signal, wherein the user designates weighting of the first characteristic and the second characteristic, and the first characteristic. A color conversion table holding means for holding a first color conversion table for performing color conversion with priority on the second color conversion table for performing color conversion with priority on the second characteristic; Color conversion means for performing color conversion using the first and second color conversion tables according to the weighting, and the first and second color conversion tables have a hue for the same input color signal. The most important feature is that it is a color conversion table for conversion to an output color signal having substantially the same value.

  According to the present invention, when the user performs color conversion, detailed adjustment can be performed while maintaining the same hue.

The structure of Example 1 is shown. 1 shows a configuration of a printer to which the present invention is applied. The mapping before and after color conversion by the fidelity priority color conversion table is indicated by two-dimensional arrows of brightness and saturation. The mapping before and after color conversion by the gradation priority color conversion table is indicated by two-dimensional arrows of brightness and saturation. An RGB signal before color conversion is shown. The process sequence of the color conversion process at the time of performing adjustment by a user is shown. 2 shows a user interface of a weight setting unit according to the first embodiment. The mapping before and after color conversion in which the weighting coefficient is color-converted with an intermediate value is shown. The procedure of the color conversion table preparation method based on Example 2 is shown. 12 shows a user interface of a weight setting unit according to the third embodiment. The structure of Example 4 is shown. The example of an interface for hue adjustment is shown. The process sequence of Example 4 is shown. The result of hue adjustment in B hue is shown. It is a figure explaining a prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 shows the configuration of a printer to which the present invention is applied. The printer 200 mainly includes a CPU 201, an NVRAM 202, a program ROM 203, a RAM 204, an engine interface 205, an engine 206, a panel interface 207, a panel device 208, a host interface 209, a disk interface 210, and a disk. The apparatus 211 is comprised.

  The CPU 201 controls the entire controller by a program in the program ROM 204, a user instruction from the panel device 208, or a command from the computer 100 as a host device. The NVRAM 202 is a non-volatile storage device that stores data such as the contents of an instruction from the user from the panel device 208, and the program ROM 203 stores a control program for the controller. The RAM 204 is used as a work memory for the CPU 201, an input buffer for input data, a page buffer for print data, or a memory for download fonts. The engine interface 205 is an interface that communicates commands, statuses, and print data with the engine 206, and the engine 206 performs the actual print operation.

  The panel interface 207 is an interface that communicates commands and status with the panel device 208. The panel device 208 is an input / output device such as a touch panel, displays the status of the printer and the like, and receives instructions from the user. The host interface 209 is an interface that uses RS232C or the like and communicates with the host computer 100. The disk interface 210 is an interface for communicating with the disk device 211. The disk device 211 is a disk device that stores various data such as font data, programs, or print data, and is configured by a hard disk device or the like.

  Here, the operation of the printer 200 in this embodiment will be briefly described. When the user inputs an image output command in the host computer 100, RGB image data is sent to the printer 200. Input RGB image data sent from the host computer 100 through the host interface 209 is divided into three types of objects, characters, graphics, and images, and has a data format that can be interpreted by the printer. Each of these object data has its data format interpreted, and is collectively developed into a one-page RGB bitmap image. The RGB bitmap image is stored in a RAM (page buffer) 204. These processes are performed by the CPU 201.

  Next, the CPU 201 performs image processing including color conversion processing on the RGB bitmap image to form a CMYK bitmap image, which is stored again in the RAM (page buffer) 204. Finally, the CPU 201 performs halftone processing corresponding to the engine 206 and sends it to the engine interface 205.

  A feature of the present invention is color conversion processing, and details of the color conversion processing will be described below. The color conversion process is realized by three means: a color conversion table holding means, a weighting designation means, and a color conversion means.

  FIG. 1 shows the configuration of Embodiment 1 of the present invention. The color conversion table holding unit 101 holds a gradation priority color conversion table 102 and a fidelity priority color conversion table 103. These color conversion tables are tables for converting RGB color signals into CMYK color signals. The color conversion table holding unit 101 is realized by the disk device 211 in FIG.

  The weighting designation unit 104 accepts designation of the weighting coefficient 105 by the user. The weighting coefficient 105 determines the weighting of the tone priority color conversion table 102 and the fidelity priority color conversion table 103. In addition, the weight designation | designated means 104 is implement | achieved by the panel apparatus 208 in FIG. For example, the panel device has a user interface as shown in FIG. When the user slides the triangular mark in FIG. 7, weighting coefficients for fidelity and gradation are set.

  The color conversion unit 106 reads the two color conversion tables 102 and 103 from the color conversion table holding unit 101, and performs color conversion according to the weighting coefficient 105 read from the weighting designation unit 104. Specifically, first, the fidelity priority color conversion unit 107 calls the fidelity priority color conversion table 103 and converts the input color signal R0G0B0 into the output color signal C0M0Y0K0. Similarly, the tone priority color conversion means 108 calls the tone priority color conversion table 102 and converts the input color signal R0G0B0 into the output color signal C1M1Y1K1. Next, the interpolating means 109 calls the weighting coefficient 105, performs the weighted linear interpolation calculation with the color signal C0M0Y0K0 and the color signal C1M1Y1K1 as input, and outputs the output color signal C2M2Y2K2. Note that the color conversion means 106 is realized by the CPU 201, the program ROM 203, and the RAM 204 in FIG.

Next, characteristics of the two color conversion tables held by the color conversion table holding unit 101 will be described. FIG. 3 shows mapping before and after color conversion by the fidelity priority color conversion table 103 with two-dimensional arrows of brightness and saturation. Similarly, FIG. 4 shows mapping before and after color conversion by the tone priority color conversion table 102 with two-dimensional arrows of brightness and saturation. However, the RGB signal before color conversion and the CMYK signal after color conversion are converted into device-independent color signals, for example, L * a * b * signals, and lightness L * and saturation C * = √ (a * ^2). + B * ² ). In addition, as the color signal set, RGB signals before color conversion and CMYK signals corresponding to the RGB signals shown in FIG. 5 are used.

  The fidelity priority color conversion table 103 is converted into a color with the smallest color difference in the gamut that can be reproduced by the output color signal CMYK in order to prioritize fidelity. However, there is a restriction that the same hue as that of the input color signal is maintained, and the color is converted to the minimum color difference color within the equal hue plane. It can be seen from FIG. 3 that the gradation is crushed in the high saturation region as a result of giving priority to the fidelity.

  The tone priority color conversion table 102 is converted into colors having the same brightness in the gamut that can be reproduced by the output color signal CMYK in order to give priority to the tone property in the brightness direction. However, there is a restriction that the same hue as that of the input color signal is maintained, and the color is converted to a constant brightness color in the constant hue plane. It can be seen from FIG. 4 that, as a result of giving priority to the gradation, the color difference is converted into a very large color especially in the low lightness region.

  Thus, it can be seen that the two color conversion tables give priority to different characteristics such as fidelity and gradation, and the fidelity and gradation are in a trade-off relationship. That is, when priority is given to fidelity, the gradation is deteriorated, and when priority is given to gradation, the fidelity is deteriorated.

  However, these two color conversion tables may be color conversion tables for converting the same input color signal into output color signals having substantially the same hue in the L * a * b * space. is important. Thereby, no matter what weighting is performed, the hue characteristics are not distorted with respect to the color signal set on the equal hue line as shown in FIG. 5, for example.

  FIG. 6 shows a processing procedure of color conversion processing when the adjustment by the user is performed. First, the weighting designation unit 104 accepts designation of the weighting coefficient 105 by the user (step 1). Next, the two color conversion tables held by the color conversion table holding unit 101 are read (step 2). Finally, the color conversion means 106 performs color conversion according to the two color conversion tables and the weighting coefficient (step 3).

  For example, when the user performs color conversion with the weighting set to an intermediate value as shown in FIG. 7, the mapping before and after color conversion is as shown in FIG. However, FIG. 8 shows the mapping result under the same conditions as in FIGS. Thus, by adjusting the balance between the two characteristics, fidelity and gradation, the user can output an image with an appropriate balance according to his / her preference and the image to be output.

  In the present embodiment, the characteristics that the two color conversion tables have priority are fidelity and gradation, but two characteristics of vividness and gradation may be used. Also, a color conversion table that prioritizes other characteristics may be used.

  According to the present invention, there is provided an image processing apparatus for converting an input color signal to generate an output color signal, wherein the user designates the weighting of the first characteristic and the second characteristic, and the first Color conversion table holding means for holding a first color conversion table for performing color conversion giving priority to the characteristics of the second color conversion table and a second color conversion table for performing color conversion giving priority to the second characteristic And color conversion means for performing color conversion using the first and second color conversion tables in accordance with the weighting, the first and second color conversion tables for the same input color signal, Since the color conversion table converts the output color signals having substantially the same hue, when the user performs color conversion, detailed adjustment can be performed while maintaining the same hue.

  According to the present invention, since the first characteristic is vividness or fidelity and the second characteristic is gradation, the vividness or fidelity and gradation are changed when the user performs color conversion. And balance can be adjusted.

  FIG. 9 shows a procedure of a color conversion table creation method according to the second embodiment. This embodiment is different from the first embodiment in that a third color conversion table is created instead of performing color conversion using two color conversion tables. The second embodiment can be realized in the form as shown in FIG. 2 as in the first embodiment.

  First, designation of a weighting coefficient by the user is accepted (step 11). Next, the two color conversion tables held are read (step 12). Finally, an interpolation operation is performed according to the two color conversion tables and the weighting coefficient to create a third color conversion table (step 13).

  In other words, in the first embodiment, the color conversion result of the image using the two color conversion tables is interpolated. However, in this embodiment, a new color is obtained by interpolating the output color signals of the two color conversion tables themselves. Create a conversion table. By such a color conversion table creation method, a user can create a color conversion table in advance, and color conversion reflecting user adjustments can be performed using a simple CMS color conversion function. That is, when converting an image, a special configuration as shown in FIG.

  According to the present invention, there is provided an image processing method for creating a color conversion table for converting an input color signal to generate an output color signal, wherein a weighting of a first characteristic and a second characteristic is designated by a user. A weighting designation step, a first color conversion table for performing color conversion with priority on the first characteristic, and a second color conversion table for performing color conversion with priority on the second characteristic; And a color conversion table creating step for creating a third color conversion table using the first and second color conversion tables according to the weighting. The second color conversion table is a color conversion table for converting the same input color signal into an output color signal having substantially the same hue, so that the user can maintain the same hue when performing color conversion. Mom detailed adjustment can be performed.

  According to the present invention, since the first characteristic is vividness or fidelity and the second characteristic is gradation, the vividness or fidelity and gradation are changed when the user performs color conversion. And balance can be adjusted.

  In this embodiment, the user sets a weighting coefficient for each hue, and the user interface of the weight setting means is changed as shown in FIG. About the other part, the structure similar to Example 1 or Example 2 can be used.

  In FIG. 10, it is possible to set weighting coefficients for each of six hues. FIG. 3 shows a mapping of the fidelity priority color conversion table in the blue hue, but here, the gradation is crushed with respect to the input of approximately three points. However, the level of gradation collapse generally differs depending on the hue. This is because the larger the difference between the gamut of the input color signal and the gamut of the output color signal, the more the crushing tends to increase, and the difference in gamut varies depending on the hue. Therefore, by setting a weighting coefficient for each hue, a more appropriate balance adjustment can be performed.

  Further, as a method of finely adjusting, it is effective as a mechanism in which each hue is divided into a shadow side and a highlight side and a weighting coefficient is set for each.

  According to the present invention, since the weight designation means can set the weight for each hue, when the user performs color conversion, an appropriate adjustment can be made for each hue.

  According to the present invention, since the weight designation means can set the weight separately on the highlight side and the shadow side, when the user performs color conversion, appropriate adjustment can be separately made on the highlight side and the shadow side. it can.

  This embodiment has a configuration in which a hue adjusting unit is added to the first embodiment. FIG. 11 shows the configuration of the fourth embodiment. The hue adjusting means 110, which is a feature of this embodiment, will be described. The hue adjustment unit 110 is a unit by which the user adjusts the hue of the input color signal. For example, the hue can be shifted in six hues of red (R), yellow (Y), green (G), cyan (C), blue (B), and magenta (M). An example of an interface for the user to adjust the hue is shown in FIG.

  When the input color signal is an RGB system, the hue can be easily shifted by using the HSL color signal obtained by converting the RGB signal. The HSL color signal is a color signal represented by hue H, saturation S, and lightness L, and can be converted from the RGB signal by a simple conversion formula.

  The processing procedure is shown in FIG. First, R0G0B0 before adjustment is converted to H0S0L0 before adjustment (step 21). Next, the hue H of H0S0L0 before adjustment is adjusted to H1S1L1 after adjustment (step 22). Finally, the adjusted H1S1L1 is converted to the adjusted R1G1B1 (step 23). For example, FIG. 14 shows the result of hue adjustment in the B hue. In FIG. 14, the hue H is adjusted by 3 degrees in the + direction.

  The color conversion means of the first embodiment can perform color conversion with a balance between fidelity and gradation, but the two color conversion tables seem to have substantially the same hue for the same input color signal. It has special characteristics. This guarantees that an unnatural hue change does not occur, but conversely, it cannot be positively adjusted with respect to the hue direction. Therefore, in this embodiment, the hue direction can be adjusted by providing the hue adjustment means independently of the color conversion means. In particular, when the gradation in the hue direction is poor, the color conversion means cannot adjust. In such a case, it is possible to improve the gradation by adjusting the width of the hue in an area with poor gradation by the hue adjustment means.

  According to the present invention, since the hue adjusting means for changing the hue of the input color signal is provided, the gradation in the hue direction can be adjusted when the user performs color conversion.

  The present invention supplies a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and a program in which a computer (CPU or MPU) of the system or apparatus is stored in the storage medium. This is also achieved by reading and executing the code. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments. As a storage medium for supplying the program code, for example, a hard disk, an optical disk, a magneto-optical disk, a nonvolatile memory card, a ROM, or the like can be used. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on an instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included. Further, after the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. This includes the case where the CPU or the like provided in the board or function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing. Further, the program for realizing the functions and the like of the embodiments of the present invention may be provided from a server by communication via a network.

DESCRIPTION OF SYMBOLS 101 Color conversion table holding means 102 Gradation priority color conversion table 103 Fidelity priority color conversion table 104 Weighting designation means 105 Weighting coefficient 106 Color conversion means 107 Fidelity priority color conversion means 108 Gradation priority color conversion means 109 Interpolation means

JP-A-10-84487 Japanese Patent Laid-Open No. 9-168097 Japanese Patent Laid-Open No. 9-18727 JP 2006-31447 A

Claims (11)

  An image processing apparatus for converting an input color signal to generate an output color signal, wherein weight designation means for designating weights of a first characteristic and a second characteristic by a user, and priority is given to the first characteristic Color conversion table holding means for holding a first color conversion table for performing color conversion and a second color conversion table for performing color conversion with priority on the second characteristic, according to the weighting, Color conversion means for performing color conversion using the first and second color conversion tables, wherein the first and second color conversion tables are values having substantially the same hue for the same input color signal. An image processing apparatus characterized by being a color conversion table for converting into output color signals.   The image processing apparatus according to claim 1, wherein the first characteristic is vividness or fidelity, and the second characteristic is gradation.   The image processing apparatus according to claim 1, wherein the weighting designation unit can set the weighting for each hue.   The image processing apparatus according to claim 1, wherein the weighting designation unit can set weighting separately on a highlight side and a shadow side.   The image processing apparatus according to claim 1, further comprising a hue adjustment unit that changes a hue of the input color signal.   An image processing method for converting an input color signal to generate an output color signal, wherein a weighting designation step for designating a weighting of a first characteristic and a second characteristic by a user is given priority to the first characteristic A color conversion table reading step for reading a first color conversion table for performing color conversion and a second color conversion table for performing color conversion giving priority to the second characteristic; A color conversion step for performing color conversion using the first and second color conversion tables, wherein the first and second color conversion tables have substantially the same hue for the same input color signal. An image processing method characterized by being a color conversion table for conversion to an output color signal.   The image processing method according to claim 6, wherein the first characteristic is vividness or fidelity, and the second characteristic is gradation.   An image processing method for creating a color conversion table for converting an input color signal to generate an output color signal, wherein a weighting designation step for designating a weighting of a first characteristic and a second characteristic by a user, Color conversion table reading for reading out a first color conversion table for performing color conversion with priority on the first characteristic and a second color conversion table for performing color conversion with priority on the second characteristic And a color conversion table creation step of creating a third color conversion table using the first and second color conversion tables according to the weighting, wherein the first and second color conversion tables are: An image processing method comprising: a color conversion table for converting the same input color signal into an output color signal having substantially the same hue.   The image processing method according to claim 8, wherein the first characteristic is vividness or fidelity, and the second characteristic is gradation.   The program for making a computer implement | achieve the image processing method of any one of Claim 6 thru | or 9.   A computer-readable recording medium recording a program for causing a computer to implement the image processing method according to claim 6.

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