JP2011130087A - Image processing apparatus and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep features of color correction which individual mixed color conversion tables have, when mixing a plurality of color conversion tables to generate a new color conversion table. <P>SOLUTION: When a new color conversion table is generated, weighted averages of lattice point information are obtained with respect to respective corresponding lattice points of two tables. In this case, weighting in weighted averages is adjusted by retention coefficients, namely, relative degrees of importance of two tables (color correction) for the lattice points. Thus, a color conversion table wherein features of two color conversion tables are kept as much as possible is generated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image processing method, and more particularly to a technique for generating a new color conversion table by mixing the contents of a plurality of color conversion tables.

  Conventionally, color correction is performed for the purpose of adjusting the gradation and color of an image recorded by a recording apparatus such as a printer. In this color correction, as a process of a printer driver or the like, the user selects one correction mode from a plurality of color correction modes, and corrects the image data in the selected color correction mode. Examples of this color correction mode include color correction modes known as “perceptual”, “saturation”, “colorimetric”, and the like. “Perceptual” is a color correction mainly used in a photographic image, and emphasizes gradation. “Saturation” is often used for graphics, documents, posters, and the like, and enables color reproduction with relatively high saturation. “Colorimetric” is intended to reproduce numerically faithful to the color of the input color space, and is often used for high-precision proofs such as printing presses.

  However, when recording an image in which a plurality of types are combined with respect to the purpose of color correction, such as a poster including a photograph, for example, any one of them may be advantageous. In the above example, the normal user selects either “perceptual” or “saturation”. However, since the former is mainly intended for use in photographic images and the latter is intended for color reproduction with high saturation, color correction may be biased to either one.

  To deal with such a problem, Patent Document 1 describes that contents of a plurality of color correction modes are mixed to generate a new color correction mode and used for color correction. Specifically, the table data is mixed from a plurality of color correction tables at a mixing ratio set by the user. Thereby, for example, when a poster including a photographic image is recorded, it is possible to record an image that has been subjected to more appropriate color correction that is not biased to one color correction.

Japanese Patent No. 3163987

  However, the method of generating a new color correction by mixing a plurality of color corrections described in Patent Document 1 performs a uniform correction over the entire color gamut related to the color correction. There is a problem that the purpose or feature itself is reduced.

  FIG. 1 shows the above-described “perceptual”, “saturation”, and a color reproduction range obtained by mixing these colors. That is, the color reproduction ranges 201 and 202 are color reproduction ranges obtained by color correction of “perceptual” and “saturation”, respectively. The color reproduction range 203 is a color reproduction range by color correction obtained by mixing the above two color corrections by the method described in Patent Document 1. As shown in this figure, in the color reproduction range 203 by the mixed color correction, for example, the color reproduction of the high saturation color originally possessed by the color reproduction range 202 by “saturation” is lost.

  It is an object of the present invention to provide an image processing apparatus and an image processing method capable of mixing a plurality of color corrections so as not to reduce the characteristics of the individual color corrections to be mixed as much as possible.

  Therefore, according to the present invention, an image processing device that generates one color conversion table based on a plurality of color conversion tables, and each grid point has post-conversion color information and importance corresponding to the post-conversion color information. For each of the determined plurality of color conversion tables, an acquisition means for acquiring a contribution ratio to the color conversion table to be generated, and for each corresponding grid point of the plurality of color conversion tables, the corresponding plurality By using the converted color information of each of the grid points at the ratio acquired for each of the plurality of color conversion tables, the converted color information of the color conversion table to be generated is generated and the corresponding in the generation Generating means for adjusting the generated post-conversion color information in accordance with the degree of importance of each of the plurality of grid points according to the relative degree between the plurality of grid points; And wherein the door.

  According to the above configuration, the degree of importance representing the characteristics of the plurality of color conversion tables is reflected, so that it is possible to generate a color conversion table that minimizes the characteristics of the respective color conversion tables.

It is a figure which shows the color reproduction range by the color correction which mixed multiple types of color correction. 1 is a block diagram illustrating a configuration of an image processing apparatus according to an embodiment of the present invention. It is a flowchart which shows the process which mixes the content of the several color conversion table which concerns on embodiment of this invention, and produces | generates a new color conversion table. It is a figure which shows the user interface for selecting the color correction table regarding the process shown in FIG. It is a figure which shows the example of a general color conversion table. It is a figure which shows the color conversion table which concerns on embodiment of this invention. (A) And (b) is a figure explaining the process which determines importance information based on embodiment of this invention. (A) And (b) is a figure which respectively shows the color conversion table of two color correction based on embodiment of this invention. (A) is a figure explaining the weighted average of the RGB value after each conversion of the color conversion element k in two color conversion tables, (b) is the importance information for every lattice point with respect to the result of the weighted average It is a figure explaining the process which adjusts with the holding coefficient based on this.

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

  FIG. 2 is a block diagram showing a configuration of the image processing apparatus according to the embodiment of the present invention. A host computer 301 constituting the image processing apparatus includes a CPU 302 that executes various calculations and processing described later with reference to FIG. 3 and a main memory 304 that stores various control programs and temporarily stores data. The host computer 301 further includes a hard disk 306 that stores various applications such as a printer driver and data, and an input / output port 305 that inputs and outputs various data. The CPU 302, main memory 304, hard disk 306, and input / output port 305 are signal-connected by the bus 302. The host computer 301 is connected to a keyboard 308 and a mouse 309 for inputting information from the user, and a display 307 for displaying various information on the screen. Further, the host computer 301 is connected to a printer 310 for recording and outputting image data.

  The processing for image recording in the above configuration is performed as follows. First, an image application stored in the hard disk 306 is activated by the CPU 302 based on an OS program that has received a user instruction. Subsequently, the image data stored in the hard disk 306 is transferred to the main memory 304 in accordance with processing in the image application according to a user instruction. The image data held in the main memory 304 is D / A converted by an instruction from the CPU 302 and displayed on the display 307. Here, when the user instructs the printer 310 to record an image held in the main memory 304, the image application transfers the image data to the printer driver. The printer driver performs color conversion using the color correction table by mixing described below, and finally generates CMYK image data and transmits it to the printer 310. As a result of the series of processes described above, a CMYK image is recorded by the printer 310.

  The printer driver performs table mixing processing according to the present embodiment, which will be described later with reference to FIGS. 3 and 4, and also performs processing for generating a new color correction table.

  FIG. 3 is a flowchart showing processing for generating a new color conversion table by mixing the contents of a plurality of color conversion tables according to the present embodiment. FIG. 4 is a diagram showing a user interface related to the processing shown in FIG.

  In this embodiment, a new color conversion table is created by adjusting the grid point information of a plurality of color conversion tables based on the weighted average and the importance for each grid point with respect to this average. Here, the above-described color corrections such as “perceptual” and “saturation” are basically realized by corresponding color conversion tables. The color conversion or color correction is generally performed as a process for converting the color reproduction range of an input device such as a display into the color reproduction range of an output device such as a printer. The color range after color correction becomes a difference in the shape and size of the color reproduction range as shown in FIG.

  The present embodiment relates to a form in which a new color conversion table is generated based on a color conversion table corresponding to each of two types of color correction. In FIG. 3, first, in step 401, color conversion tables for two types of color correction are selected.

  Specifically, one type of color correction (“color correction A”, “color correction B”) is selected from a plurality of types of color corrections displayed in the color correction table selection fields 502 and 503 on the user interface 501 shown in FIG. ") Is selected by the user. Thereby, the color conversion table corresponding to each color correction is selected. In the following description, it is assumed that “perceptual” is selected as “color correction A” and “saturation” is selected as “color correction B”. A color conversion table corresponding to each color correction is held in the hard disk 306 in advance.

  Next, in step 402, the ratio of each of the two selected color conversion tables that contributes to the color conversion table to be generated is determined. This ratio can be determined according to the position where the user has moved the slider bar 504 in the user interface 501 shown in FIG. By this operation, the user can mix the two color conversion tables at a ratio suitable for the user's preference. For example, when outputting a poster including a photo, if the image is recorded and output so that the photo portion occupies most of the poster, the ratio of “perceptual” is increased, and the mixing that leaves the “perceptual” characteristics as much as possible is used. Can be done. Conversely, when outputting a poster with a small photographic area, it is possible to increase the ratio of “saturation” and perform a weighted average that retains the characteristics of “saturation” as much as possible.

  Next, in step 403, a process of generating a new color conversion table by mixing the two selected color conversion tables is performed. Specifically, as will be described later with reference to FIGS. 9A and 9B, for each grid point corresponding to the two color correction tables, a weighted average of the converted signal values that are the grid point data is taken. . Then, the weighted average is adjusted in accordance with the importance of each grid point to generate new table grid point data.

  FIG. 5 is a diagram illustrating an example of a general color conversion table. As shown in the figure, a lookup table is not prepared for all RGB values (255 × 255 × 255), but a predetermined interval for each RGB signal (in the example shown in FIG. 5, 0, 32). , 64,..., 255), input RGB values 603 and converted RGB values 604 are described (hereinafter referred to as color conversion elements). Then, in actual color conversion, the converted RGB value for the input RGB value that is not at the grid point is obtained by, for example, tetrahedral interpolation using eight color conversion elements surrounding the input RGB value.

  FIG. 6 is a diagram showing a color conversion table according to the present embodiment, and is a table corresponding to “Perceptul” (for photo mode) which is one of the tables held in the hard disk. In the color conversion table of this embodiment, importance level information 705 is determined for each lattice point corresponding to a set of input RGB values 703 and converted RGB values 704 that are conversion elements.

  The importance level information is determined according to the use of each color correction, and is a numerical value for each grid point indicating how important the input RGB value 703 is for each use. For example, since the color conversion table corresponding to “perceptual” is for photographic use, RGB values that are frequently used in photographic images such as skin color, sky, and forest are important. In addition, since the color conversion table corresponding to “saturation” is a color conversion mode for posters and graphics, RGB values in which relatively vivid colors are easily used, such as color palette colors for document creation software, are important. . In the example shown in the figure, “1” is the lowest importance level and “10” is the highest importance level.

  In the present embodiment, the importance level information (importance level) is determined according to the frequency of use by acquiring RGB values from a plurality of image contents corresponding to respective uses. The image content for each use is a photographic image if the image content is for a photographic use, and an image of a poster or documents if the image content is for a poster use. FIGS. 7A and 7B are diagrams for explaining processing for determining importance information. As shown in FIG. 7A, the image content 801 is acquired by scanning. Then, as shown in FIG. 7B, the acquired RGB values are accumulated as the accumulated values of the corresponding element numbers. Thereby, a histogram 802 is created, and the created histogram is normalized with a predetermined numerical value to obtain importance information. In the example shown in FIG. 7B, normalization is performed at 10.

  Next, details of the color conversion table generation processing by the weighted average in step 403 shown in FIG. 3 will be described.

  FIGS. 8A and 8B are diagrams respectively showing color conversion tables for color correction A related to “perceptual” and color correction B related to “saturation” selected in step 401.

  First, a holding coefficient is calculated based on importance information for each grid point held in two color correction tables. That is, for each color correction color conversion table, the importance information 905 of the grid point of the element number k is m (k), and the importance information 911 of the color correction B is n (k). When the color correction A holding coefficient 906 is M (k) and the color correction B holding coefficient 912 is N (k), each holding coefficient is calculated by the following equation.

Then, calculation is performed so that the sum of the retention coefficients of the corresponding grid points in the two color conversion tables is 1.

Next, a weighted average of the converted RGB values for each corresponding grid point in the color conversion tables of the color correction A and the color correction B is performed. FIG. 9A is a diagram for explaining a weighted average of converted RGB values for each of the color conversion elements k in the two color conversion tables. As shown in the figure, the RGB value 1001 after conversion by color correction A is T _k (R, G, B), and the RGB value 1002 after conversion by color correction B is S _k (R, G, B). The ratio determined in step 401 (FIG. 3) is x: y for the color correction A and the color correction B. At this time, P _k (R, G, B), which is the result 1003 of the weighted average according to this ratio, can be obtained by the following equation (3).

  In this embodiment, the weighted average result is further adjusted by a holding coefficient based on importance information for each grid point, and the final converted RGB value (converted color information) of the color conversion table to be generated Ask for.

FIG. 9B is a diagram for explaining this process. As shown in the figure, it is calculated as the vector R1105 that is created on a line segment P _k T _k, the vector Q1104 to be created on the line segment P _k S _k. Then, as shown in the following equations (4) and (5), the calculated vectors are multiplied by the holding coefficients obtained by the above equations (1) and (2).

Then, as shown in the equation (6), by adding these two vector sums U1106 (R + Q) to P _k (R, G, B) 1103, the post-conversion color information F (R , G, B) 1107, that is, the converted RGB values in the color conversion table to be generated are acquired.

  As described above, when a new color conversion table is generated, simply taking a weighted average of the converted color information for each corresponding grid point in the two tables (Equation (3)), Features (importance of color information of grid points) are not considered. Therefore, in the present embodiment, as shown in the equations (4) to (6), the contribution ratio in the weighted average depends on the retention coefficient, that is, the relative importance of the two tables (color correction) with respect to the grid point. (Weighting; x: y) is adjusted. Thereby, it is possible to generate a color conversion table in which the features of the two color conversion tables are minimized.

(Other embodiments)
The embodiment described above relates to an example in which a new table is generated based on two color conversion tables, but it goes without saying that the application of the present invention is not limited to this form. The fact that the present invention can also be applied to a case where a new color conversion table is generated based on three or more color conversion tables is apparent from the fact that the equations (1) to (6) show a linear relationship. .

  Further, the form of adjustment of the contribution ratio (weighting) in the weighted average by the holding coefficient is not limited to the above example. Any form may be used as long as the importance of the color information of the grid points in the plurality of tables is adjusted according to the relative degree between the grid points of the plurality of tables.

(Still another embodiment)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media. Then, the computer or the like is executed by reading the program into the computer (or CPU or MPU) of the system or apparatus.

301 Computer 302 CPU
303 Main memory 306 Hard disk

Claims (4)

An image processing apparatus that generates one color conversion table based on a plurality of color conversion tables,
Acquiring the ratio of contribution to the color conversion table to be generated in each of the plurality of color conversion tables in which the color information after conversion and the importance corresponding to the color information after conversion are determined for each grid point Means,
For each grid point corresponding to the plurality of color conversion tables, the color to be generated is obtained by using the converted color information of each of the plurality of corresponding grid points at the ratio acquired for each of the plurality of color conversion tables. Generated post-conversion color information of the conversion table, and the generated post-conversion color information according to the relative degree between each of the plurality of corresponding lattice points in the generation, A generating means to adjust;
An image processing apparatus comprising:   The said production | generation means produces | generates the color information after the conversion of the said color conversion table which should be produced | generated by the weighted average which weighted the ratio acquired about each of these color conversion tables. Image processing device. An image processing method for generating one color conversion table based on a plurality of color conversion tables,
Determining post-conversion color information and importance corresponding to the post-conversion color information for each grid point of the plurality of color conversion tables;
An acquisition step of acquiring a ratio of each of the plurality of color conversion tables that contributes to the color conversion table to be generated;
For each grid point corresponding to the plurality of color conversion tables, the color to be generated is obtained by using the converted color information of each of the plurality of corresponding grid points at the ratio acquired for each of the plurality of color conversion tables. Generated post-conversion color information of the conversion table, and the generated post-conversion color information according to the relative degree between each of the plurality of corresponding lattice points in the generation, Generation process to be adjusted;
An image processing method characterized by comprising:   A program that causes a computer to function as the image processing apparatus according to claim 1 by being read by the computer.

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