JP4720930B2 - Image processing apparatus and program - Google Patents

Description

  The present invention relates to a technique for selecting or creating a color chart according to desired processing items or processing accuracy when performing image processing.

  In image quality evaluation of an image output by an image forming apparatus or an image display apparatus, a color chart composed of color charts of a plurality of colors is usually used. A rough procedure for image quality evaluation will be described using a printer example. First, color chart data serving as a reference for evaluation is input to a printer, and an image of a color chart is formed on the paper surface based on the color chart data. Next, the color of the image formed on the paper surface is measured using a measuring device to obtain a colorimetric value. Then, the reference value based on the color chart data is compared with the colorimetric value, and evaluations such as density, gradation, color difference, and color reproducibility are performed. Further, color reproducibility can be improved by creating a color conversion profile from the reference value and the colorimetric value obtained in this way and performing color conversion using the profile. An image display device such as a display can also perform image quality evaluation or color conversion profile creation in the same procedure.

  By the way, it is not always necessary to use the same color chart, and it is necessary to select or create an appropriate one according to the purpose and the required accuracy. Accordingly, various techniques for selecting or creating an appropriate color chart have been proposed. For example, the technique described in Patent Document 1 is a technique for creating a color chart that is optimal for image quality evaluation of a printer in accordance with the output characteristics of the printer. The procedure is briefly described. First, an image is printed by a printer using reference data (for example, color values of division points obtained by equally dividing the RGB color space), and the color of the printed image is measured by a measuring instrument. taking measurement. This measured value is plotted in a three-dimensional color space to obtain a color reproduction solid. This color reproduction solid represents the range of colors that can be output by this printer. Next, the color of the existing color chart is measured with the same measuring device and plotted in a three-dimensional space. Then, the color reproduction solid is divided into a plurality of spaces so that the number of measurement values included therein is equal. Then, an average value of the measurement values of each area obtained by the division is obtained, and the measurement value closest to the average value is set as the representative color of the area. In this way, a representative color suitable for printer image quality evaluation can be determined within the range of colors that can be actually output by the printer.

  In the technique described in Patent Document 2, the color of the image to be evaluated and the color of the color chart are measured. Then, for each pixel of the image to be evaluated, a color whose color difference is within a predetermined range is extracted from the color chart. Then, the measurement values of the extracted color are plotted in the color space, the color space is divided equally, and the measurement value closest to the center of each divided area is set as the representative color. In this way, it is possible to determine a representative color suitable for image quality evaluation of the printer within the range of colors actually used in the image to be evaluated.

However, with the technique described in the above-mentioned patent document, it is necessary to measure the colors of a large number of color charts, and much labor and time are required for measurement work and processing of measurement values.
On the other hand, ISO / JIS-SCID (Standard Color Image Data) provides a color chart composed of basic data and extended data, and the user can select and use a color chart according to the purpose. However, since the appropriate number of color charts and evaluation accuracy differ depending on the type of image output device, the selection work is very complicated, and considerable knowledge and experience are required to select a color chart according to the purpose. The

JP-A-5-336552 Japanese Patent Laid-Open No. 11-234534

  The present invention has been made under the above-described background, and an object of the present invention is to provide a technique capable of selecting a color chart to be used for image quality evaluation or a color conversion profile in accordance with a desired processing item and processing accuracy.

In order to solve the above-described problems, the present invention provides each of a plurality of color chart data groups each consisting of a plurality of color chart data of CMYK, color chart data for verifying color conversion by a profile, Image processing that can be performed using a color chart data group , and gradation evaluation for obtaining an evaluation value representing gradation of an image output using color chart data of the color chart data group , and Performing at least one of color reproducibility evaluation to obtain an evaluation value representing the color reproducibility of an image output using the color chart data of the color chart data group and the color chart data for performing the verification, each processing item in the image processing comprising the created color conversion profile to profile a color conversion to the image output device, a storage means for storing in association with processing accuracy levels achieved by the color patch data group, An input means for designating the processing item and the processing accuracy level, and a color chart data group corresponding to the processing item and the processing accuracy level designated by the input means are read from the storage means, and the color chart data group is used. Image processing means for performing image processing corresponding to the processing item, and when the designated processing item is the profile creation, the color chart data group corresponding to the designated processing accuracy level, and the color The image processing means for creating the profile using the measured values of the image output based on the vote data group, the color chart data for performing the verification, and the color created by the profile created by the image processing means Based on the measured value of the image output using the color chart data for performing the verification after the conversion, an evaluation value indicating the processing accuracy of the profile is obtained. Therefore, it is determined whether or not the obtained evaluation value satisfies a predetermined criterion. If the criterion is not satisfied, the processing accuracy higher by one in the color chart data group used at the time of creating the profile is determined. There is provided an image processing apparatus characterized by comprising a re-creating means for adding a color chart data group corresponding to a level and creating a profile again .
In the image processing apparatus having the structure above SL, the re-creation means divides the color space into a plurality of regions, each region, obtains an evaluation value representing the processing accuracy of the profile created by the image processing unit When it is determined whether or not the evaluation value satisfies a predetermined criterion, and there is a region that does not satisfy the criterion, it corresponds to the region and is not the same as that used when creating the profile. the color chart data, wherein the benzalkonium create again profile in addition to the color chart data used in creating the profile.
In the image processing apparatus having the above-described configuration, the re-creation unit satisfies the determination criterion when all of the color chart data groups stored in the storage unit are used for creating the profile. A color chart data group corresponding to a non-existing area is created to create the profile.

According to another aspect of the present invention, there is provided a computer, each of a plurality of color chart data groups each including a plurality of color chart data of CMYK, color chart data for verifying color conversion by a profile, and the color chart data group Image processing that can be performed by using the color chart data group, and the color chart data group, and the color chart data group for obtaining an evaluation value representing the gradation of the image output using the color chart data of the color chart data group An image output apparatus for performing at least one of color reproducibility evaluation for obtaining an evaluation value representing color reproducibility of an image output using the color chart data and color chart data for performing the verification each processing item in the image processing comprising the created color conversion profile to profile a color conversion, and storage means for storing in association with processing accuracy levels achieved by the color patch data group, the processing An input unit for specifying an item and the processing accuracy level, and a color chart data group corresponding to the processing item and processing accuracy level specified by the input unit are read from the storage unit, and the processing is performed using the color chart data group. Image processing means for performing image processing corresponding to an item, and when the designated processing item is the profile creation, the color chart data group corresponding to the designated processing accuracy level and the color chart data Color conversion is performed by the image processing means for creating the profile, the color chart data for performing the verification, and the profile created by the image processing means, using the measured values of the images output based on the group. Based on the measured value of the image output using the color chart data for performing the verification, an evaluation value representing the processing accuracy of the profile is obtained, It is determined whether or not the evaluated value satisfies a predetermined criterion. If the criterion is not satisfied, the processing accuracy level is increased by one to the color chart data group used at the time of creating the profile. A program for adding a corresponding color chart data group and causing it to function as a re-creation unit for creating a profile again is provided.

  According to the present invention, it is possible to select a color chart to be used for image quality evaluation or a color conversion profile according to a desired processing item and processing accuracy.

4 is a diagram illustrating an output example of a color chart 20. FIG. It is a figure which shows a response | compatibility with a process item, process accuracy, and a color chart data group. It is a figure which shows the example of the input screen for designating a process item and a process precision. It is a figure which shows the flow of density / gradation evaluation. It is a figure which shows the example of the result of density / gradation property evaluation. It is a figure which shows the flow of color reproducibility evaluation. It is a figure which shows the example of the result of color reproducibility evaluation. It is a figure which shows the flow of color conversion profile creation. It is a figure which shows the flow of color conversion profile creation in 2nd Embodiment. It is a figure which shows the example of the area | region division of L * a * b * color space. It is a figure which shows the procedure of the conversion from RGB data to CMYK data. 1 is a diagram illustrating a configuration of an image processing apparatus 10.

Embodiments of the present invention will be described below with reference to the drawings.
<First Embodiment>
FIG. 12 is a diagram showing a configuration of the image processing apparatus 10 according to the first embodiment of the present invention. A CPU (Central Processing Unit) 101 reads a basic program such as an OS (Operating System) stored in a ROM (Read Only Memory) 102 or a storage unit 104 and develops these programs in a RAM (Random Access Memory) 103. As a result, each part of the image processing apparatus 10 is controlled. The storage unit 104 is, for example, a hard disk drive, and stores a program describing an image processing procedure to be described later. A communication I / F (interface) 105 mediates data transmission / reception between the image processing apparatus 10 and an external device. The instruction input unit 106 includes a keyboard, a mouse, and the like, and can input an instruction to the image processing apparatus 10. The display unit 107 includes, for example, a CRT (Cathode Ray Tube) or a liquid crystal panel, and displays an input screen for inputting instructions to the image processing apparatus 10.

  An image input device 50 and an image output device 60 are connected to the image processing device 10 via a communication I / F 105. The image input device 50 is, for example, a scanner that optically reads a document and generates document image data representing a document image. The image output device 60 is, for example, a printer that forms a toner image on the surface of a recording sheet based on image data by an electrophotographic method.

  FIG. 1 is a diagram illustrating an output example of the color chart 20 according to the present embodiment. The color chart 20 includes a plurality of color chart groups, and each color chart group includes a plurality of color charts. However, the color chart group does not include common color charts. That is, the color charts constituting the color chart 20 are color charts each representing a unique color, and there are no overlapping color charts. FIG. 1 illustrates an output example of the color chart 20 by the image output device 60, and color chart data representing the contents of the color chart 20 is stored in the storage unit 104 of the image processing device 10. In the following description, data representing a color chart is referred to as “color chart data”, and a group of color chart data of a plurality of color charts constituting the color chart group is referred to as “color chart data group”. The color chart data is data representing the RGB values of the color chart.

  Each color chart data group is stored in the storage unit 104 in association with a processing item that can be processed by the color chart data group. Each color chart data group is stored in the storage unit 104 in association with the processing accuracy level achieved by the color chart data group. Here, processing items and processing accuracy levels will be described.

  In order to ensure sufficient processing accuracy in image processing such as image evaluation and color conversion profile creation, it is possible to use a color chart having color charts of as many colors as possible. Further, such a color chart can theoretically correspond to any processing item. However, it is not practical to use such a color chart in terms of image processing speed, data amount, and the like. In practice, a limited number of color charts may be sufficient depending on the processing items, and the maximum processing accuracy is not always required. That is, it is desirable to use a color chart according to the processing items and required processing accuracy.

  Therefore, the present invention proposes a technique in which a plurality of color chart data groups are created in advance according to processing items and processing accuracy, and the color chart data groups are selected and used according to desired processing items or processing accuracy. Is. FIG. 2 is a diagram showing the correspondence between processing items, processing accuracy, and color chart data groups. First, processing items are classified into three categories: “density / gradation evaluation”, “color reproducibility evaluation”, and “color conversion profile creation”. Furthermore, for color reproducibility evaluation and color conversion profile creation, the processing accuracy is divided into three levels of level 1, level 2, and level 3. Level 1 has the lowest processing accuracy, and level 3 has the highest processing accuracy. Specifically, this processing accuracy is quantified by obtaining a color difference from the colorimetric value of the color chart output from the image output device 60 and the reference value, and the magnitude of the color difference. This quantification will be described later.

  In the present embodiment, the color chart 20 includes a color chart group 1, a color chart group 2, a color chart group 3, and a color chart group 4, and processes one or more of these color chart groups. Used according to items and processing accuracy. Specifically, when performing “density / gradation evaluation”, color chart group 1 is used. When performing level 1 color reproducibility evaluation or color conversion profile creation, color chart group 1 and color chart group 2 are used. When performing level 2 color reproducibility evaluation or color conversion profile creation, color chart groups 1 to 3 are used. When performing level 3 color reproducibility evaluation or color conversion profile creation, color chart groups 1 to 4 are used.

  In the density / gradation evaluation, it is not necessary to use color charts of all colors, and it is possible to perform evaluation by using color chart groups in which the density is changed stepwise for several representative hues. is there. Therefore, the color chart group 1 is composed of, for example, color charts in which the density is changed stepwise for three colors of red, green, and blue.

  In color reproducibility evaluation or creation of a color conversion profile, it is necessary to use color charts of colors used in actual image output. Therefore, the color chart group 2 is composed of color charts that supplement colors that are not included in the color chart group 1. By using the color chart group 1 and the color chart group 2 in combination, a color reproducibility evaluation or a color conversion profile is used. It can be created. However, since the number of color charts is minimized, the processing accuracy in color reproducibility evaluation or color conversion profile creation is minimized. Instead, the processing time required for color reproducibility evaluation or color conversion profile creation at level 1 is the shortest among levels 1 to 3. That is, the processing at level 1 is suitable when only a minimum processing accuracy is required and / or when processing is desired in a short time.

  The color chart group 3 includes color charts that supplement colors that are not included in the color chart groups 1 and 2. By using the color chart groups 1 to 3 in combination, it becomes possible to evaluate color reproducibility or create a color conversion profile at level 2 with higher accuracy than level 1. Furthermore, the color chart group 4 includes color charts that supplement colors that are not included in the color chart groups 1 to 3. By using the color chart groups 1 to 4 in combination, it becomes possible to evaluate color reproducibility or create a color conversion profile at level 3 with higher accuracy than level 2.

In the present embodiment, the processing accuracy of color reproducibility evaluation and color conversion profile creation is divided into three stages of level 1 to level 3, but this is an example, and more stages may be provided.
A part of the color chart group 2 is a color conversion profile verification area for verifying the accuracy of the color conversion profile. This color conversion profile verification area will be described later.

  FIG. 3 is a diagram illustrating an example of an input screen for designating processing items and processing accuracy. (A) is a density / gradation evaluation, (b) is a color reproducibility evaluation, and (c) is a screen for designating color conversion profile creation. A user can designate a process item by checking a check box provided at the left end of a desired process item using the instruction input unit 106. When color reproducibility evaluation and color conversion profile creation are specified, processing accuracy from level 1 to level 3 can be specified. Color reproducibility evaluation and color conversion profile in order of level 1, level 2, and level 3 The accuracy of creation increases. The user can specify the processing accuracy indicated by the pull-down menu using the instruction input unit 106.

  FIG. 4 is a diagram showing a flow of density / gradation evaluation. Here, the image processing apparatus 10 is already turned on, the CPU 101 is executing a program, and the input screen shown in FIG. 3 is displayed on the display unit 107. First, in step S <b> 401, the user inputs an instruction for specifying “density / gradation evaluation” using the instruction input unit 106. In step S <b> 402, the CPU 101 receives the input instruction and transmits a color chart data group representing the color chart group 1 to the image output apparatus 60. In step S403, the image output device 60 receives the color chart data group transmitted from the image processing apparatus 10, and the image output apparatus 60 displays an image representing the color chart group 1 on the recording paper surface based on the color chart data group. Form. In step S404, the user measures the color of the color chart group 1 formed on the surface of the recording paper using a measuring instrument, and the optical density or CIE (Commission Internationale de l'Eclairage) L * a * b * color space. The color values in are obtained, and these values are input to the image processing apparatus 10. In step S405, an image quality evaluation value is calculated based on the measurement result. Note that the measurement of the color chart group may use a dedicated measuring device, or may calculate a measurement value from an RGB signal obtained by reading an image using the image input device 50.

  FIG. 5 is a diagram illustrating an example of the result of density / gradation evaluation. (A) shows the relationship of optical density to input data, that is, color chart data. (B) shows the relationship of L * to the color chart data. These show the output characteristics for the input data of the image output device 60. These are only examples, and evaluation may be performed using other evaluation indexes.

  FIG. 6 is a diagram showing a flow of color reproducibility evaluation. First, in step S <b> 601, the user inputs an instruction for specifying “color reproducibility evaluation” using the instruction input unit 106. In step S602, an instruction for designating a processing accuracy level is input. In step S <b> 603, the CPU 101 receives the input instruction, and transmits a color chart data group corresponding to the specified processing accuracy to the image output device 60. For example, when level 1 is designated, color chart data groups corresponding to color chart groups 1 and 2 are transmitted. In step S604, the image output device 60 receives the color chart data group transmitted from the image processing apparatus 10, and the image output apparatus 60 displays images representing the color chart groups 1 and 2 based on the color chart data group on the recording paper. Form on the surface. In step S605, the user measures the color chart groups 1 and 2 formed on the surface of the recording paper by using a measuring instrument, obtains the measured value in the L * a * b * color space, and uses the measured value as the image processing apparatus. Enter 10.

  In step S606, the CPU 101 acquires a reference value in the L * a * b * color space based on the color chart data groups 1 and 2. This reference value is a measurement value of the color chart output by the output device that is a reference for color reproduction. This measurement value is stored in the storage unit 104 of the image processing apparatus 10 in advance, and the measurement value is read out. get. In step S607, the CPU 101 calculates an image quality evaluation value from the measurement result of the color chart groups 1 and 2 output from the image output apparatus 60 and the reference value. Note that the measurement of the color chart group may use a dedicated measuring device, or may calculate a measurement value from an RGB signal obtained by reading an image using the image input device 50.

そして、以下の式により、Ｌ＊ａ＊ｂ＊信号を算出することによって変換プロファイルを作成することができる。

なお、これは変換プロファイルの一例であり、他の方法で作成してもよい。 The procedure for calculating the measurement value from the data obtained by the image input device 50 is shown below. First, a conversion profile for converting an RGB signal into a signal in the L * a * b * color space is created, and the RGB signal obtained by the image input device 50 is converted to L * a * b * using this conversion profile. Convert to signal and use as measured value. To create a conversion profile, first, based on the RGB signal obtained by reading a known sample with the image input device 50 and the XYZ signal measured using a dedicated measuring instrument, the following method is used by the least square method: Determine the conversion factor.

A conversion profile can be created by calculating the L * a * b * signal according to the following equation.

This is an example of a conversion profile and may be created by other methods.

なお、これは画質評価値の一例であり、色域、色差の頻度分布以外の評価指標を用いてもよい。また、他の色差式を用いてもよい。 FIG. 7 is a diagram showing an example of the result of color reproducibility evaluation, and corresponds to the image quality evaluation value shown in S607 of FIG. (A) is a color gamut, (b) is an example of the frequency distribution of the color difference with respect to a reference value. If the reference values calculated in S606 are L1 *, a1 *, b1 *, and the color chart measurement values measured in S605 are L2 *, a2 *, b2 *, the color difference is expressed by the following equation. .

This is an example of the image quality evaluation value, and an evaluation index other than the color gamut and color difference frequency distribution may be used. Also, other color difference formulas may be used.

  FIG. 8 is a diagram showing a flow of creating a color conversion profile. First, in step S <b> 801, the user inputs an instruction for specifying “color conversion profile creation” using the instruction input unit 106. In step S802, an instruction for designating a processing accuracy level is input. In step S803, the CPU 101 receives the input instruction and calculates a determination value corresponding to the designated processing accuracy. The determination value is a value serving as a reference for determining the image quality evaluation value, and is represented by an average color difference of the color chart. For example, level 1: ΔE = 8, level 2: ΔE = 5, level 3: ΔE = 2. In step S <b> 804, the CPU 101 transmits a color chart data group corresponding to the designated processing accuracy to the image output device 60. For example, when level 2 is designated, color chart data groups corresponding to color chart groups 1 to 3 are transmitted. In step S805, the image output device 60 receives the color chart data group transmitted from the image processing apparatus 10, and the image output apparatus 60 displays images representing the color chart groups 1 and 2 based on the color chart data group on the recording paper. Form on the surface. In step S806, the user measures the color chart groups 1 and 2 formed on the surface of the recording paper by using a measuring instrument, obtains the measured value in the L * a * b * color space, and uses the measured value as the image processing apparatus. Enter 10.

  Next, in step S807, the CPU 101 creates a color conversion profile based on the color chart data and measurement values of the portion excluding the color conversion profile verification area. In step S808, color conversion is performed on the color conversion profile verification region using the created color conversion profile. Then, the image quality evaluation value is calculated from the L * a * b * color chart data of the color conversion profile verification area subjected to the color conversion and the measurement values of the color chart of the color conversion profile verification area.

In step S809, it is determined whether the calculated image quality evaluation value is lower than the determination value. If the image quality evaluation value is lower than the determination value, the creation of the color conversion profile is terminated. If the image quality evaluation value is not lower than the determination value, it is determined whether or not all color chart groups have been used (step S810). When all the color chart groups are used, the creation of the color conversion profile is finished. When all the color chart groups are not used, the color chart groups are added (step S811), and after step S805. To create a color conversion profile. For example, when level 2 is designated in S802, color chart groups 1 to 3 are used first. If the average color difference of the color chart is ΔE = 7 in S809, it is not less than the determination value ΔE = 5. Further, since it is determined in S810 that all color chart groups are not used, the color chart groups are changed to color chart groups 1 to 4 in Step S811, and a color conversion profile is created again. The color conversion profile is created using a known method such as a least square method or a neural network method.
In addition, although the example which uses the average color difference of a color chart as an image quality evaluation value was shown, you may use the function value which combined not only this but the minimum value of the measured value, the maximum value, the standard deviation value, or those.

  As described above, according to the present invention, a color chart used for image quality evaluation or color conversion profile creation can be selected according to desired processing items and processing accuracy. Further, when the processing accuracy does not satisfy the determination criterion, the color chart data group corresponding to the next higher processing accuracy level is added and the image processing is performed again. Therefore, the image processing can be performed with the desired processing accuracy. it can.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. The second embodiment is characterized in that the L * a * b * color space is divided into a plurality of areas, and the color conversion profile is verified for each area.
FIG. 9 is a diagram showing a flow of creating a color conversion profile in the second embodiment. First, in step S <b> 901, the user inputs an instruction for specifying “color conversion profile creation” using the instruction input unit 106. In step S902, an instruction for designating a processing accuracy level is input. In step S903, the CPU 101 receives the input instruction and calculates a determination value corresponding to the designated processing accuracy. The determination value is a value serving as a reference for determining the image quality evaluation value, and is represented by an average color difference of the color chart. For example, level 1: ΔE = 8, level 2: ΔE = 5, level 3: ΔE = 2.

  In step S <b> 904, the CPU 101 transmits a color chart data group corresponding to the designated processing accuracy to the image output device 60. For example, when level 2 is designated, color chart data groups corresponding to color chart groups 1 to 3 are transmitted. In step S905, the image output device 60 receives the color chart data group transmitted from the image processing apparatus 10, and the image output apparatus 60 prints images representing the color chart groups 1 to 3 based on the color chart data group. Form on the surface. In step S906, the user measures the color chart groups 1 to 3 formed on the surface of the recording paper by using a measuring instrument, obtains the measured value in the L * a * b * color space, and uses the measured value as the image processing apparatus. Enter 10.

  Next, in step S907, the CPU 101 creates a color conversion profile based on the color chart data and measurement values of the portion excluding the color conversion profile verification area. In step S908, color conversion is performed on the color conversion profile verification region using the created color conversion profile. Then, the image quality is determined for each region in the L * a * b * color space from the L * a * b * color chart data of the color conversion profile verification area subjected to color conversion and the color chart measurement values of the color conversion profile verification area. An evaluation value is calculated. FIG. 10 is a diagram illustrating an example of region division in the L * a * b * color space. As shown in the figure, each of the a * -axis direction and b * -axis direction is divided into two areas, for a total of four areas.

  In step S909, it is determined for each region in the L * a * b * color space whether or not the calculated image quality evaluation value is below the determination value, and if the image quality evaluation value is below the determination value for all regions. Finish creating the color conversion profile. If the image quality evaluation value is not lower than the determination value, it is determined whether or not all color chart groups have been used (step S910). When all color chart groups are used, creation of the color conversion profile is completed. When all color chart groups are used, color chart groups are created for areas where the image quality evaluation value does not fall below the judgment value. Add (step S912), and if not all color chart groups are used, add color chart groups (step S911) and perform the processing from step S905 onward to create a color conversion profile. For example, when level 2 is designated in S902, color chart groups 1 to 3 are used first. If the average color difference between the color charts is region A: ΔE = 7, region B: ΔE = 4.5, region C: ΔE = 5.5, and region D: ΔE = 3 in S909, region A and region C is not lower than the judgment value ΔE = 5. In step S910, since it is determined that not all color chart groups are used, the color chart groups are changed to color chart groups 1 to 4 in step S912, and a color conversion profile is created again. The average color difference of the color charts obtained using the color conversion profile created again is as follows: area A: ΔE = 6, area B: ΔE = 3.5, area C: ΔE = 4, area D: ΔE = 2.5 As a result, only the region A does not fall below the determination value ΔE = 5. This time, since it is determined in step S910 that all the color chart groups have been used, the color chart group of the area A is created / added, the processing in step S905 and thereafter is performed, and a color conversion profile is created.

  In addition, although the example which uses the average color difference of a color chart as an image quality evaluation value was shown, you may use the function value which combined not only this but the minimum value of the measured value, the maximum value, the standard deviation value, or those. Further, different determination values may be determined for each region. For example, level 1 (region A: ΔE = 8, region B: ΔE = 10, region C: ΔE = 8, region D: ΔE = 6), level 2 (region A: ΔE = 5, region B: ΔE = 6) , Region C: ΔE = 5.5, region D: ΔE = 4, level 3 (region A: ΔE = 2, region B: ΔE = 2.5, region C: ΔE = 2, region D: ΔE = 1) .5) may be determined.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. The third embodiment is characterized in that the conversion from RGB data to CMYK data is performed in two steps. In addition, you may make it implement 3rd Embodiment combining 1st Embodiment or 2nd Embodiment.
FIG. 11 is a diagram showing a procedure for converting RGB data into CMYK data. The input data input to the image input unit is converted into R′G′B ′ data that matches the output color of the image output device 60 by the first profile 31. The R′G′B ′ data is converted into CMYK data by the second profile 32.

なお、上記の方法は第２プロファイルの作成に適用しても良い。 The second profile 32 is created by outputting a color chart group consisting of a plurality of color charts of CMYK and a color chart group consisting of a plurality of color charts of RGB by the image output device 60 and measuring each color chart group. Create based on measured values. The first profile 31 is a combination of RGB → L * a * b * conversion and L * a * b * → R′G′B ′ conversion. The RGB → L * a * b * conversion is for performing conversion processing when a target color is set for each RGB value. When the target color is sRGB, the conversion is as follows.

Note that the above method may be applied to create the second profile.

<Modification>
The present invention is not limited to the form described above, and can be implemented in various forms. For example, the embodiment described above can be modified as follows.
In the above embodiment, the color chart has been described as RGB digital data, but may be CMYK digital data. Moreover, the printed material etc. which recorded these digital data may be sufficient.
Although the above embodiment has been described using an example of evaluation of an image formed using a printer, the present invention can be similarly applied to evaluation of an image displayed as an image display image of a display device or the like.

  A processing accuracy category is provided for density / gradation evaluation, and processing accuracy is verified in the same way as other processing items. If sufficient processing accuracy is not obtained, a color chart group is added for reprocessing. It may be. Further, the processing item may include at least one of density / gradation evaluation, color reproducibility evaluation, and color conversion profile. In the present invention, the processing items are not limited to the above items, and any processing related to image processing is targeted.

  DESCRIPTION OF SYMBOLS 10 ... Image processing apparatus 101 ... CPU, 102 ... ROM, 103 ... RAM, 104 ... Memory | storage part, 105 ... Communication I / F, 106 ... Instruction input part, 107 ... Display part, 20 ... Color chart, 50 ... Image input Device, 60... Image output device.

Claims (4)

Each of a plurality of color chart data groups each consisting of a plurality of color chart data of CMYK, color chart data for verifying color conversion by a profile, and image processing that can be performed using the color chart data group The tone characteristics evaluation for obtaining an evaluation value representing the gradation characteristics of the image output using the color chart data of the color chart data group, and the color chart data of the color chart data group. Color conversion for creating a color conversion profile for an image output device, which is performed on at least one of color reproducibility evaluation for obtaining an evaluation value representing the color reproducibility of an image and color chart data for performing the verification Storage means for storing each processing item of image processing including profile creation and the processing accuracy level achieved by the color chart data group in association with each other;
Input means for designating the processing item and the processing accuracy level;
Image processing means for reading out the color chart data group corresponding to the processing item and processing accuracy level designated by the input means from the storage means and performing image processing corresponding to the processing item using the color chart data group. When the designated processing item is the profile creation, the color chart data group corresponding to the designated processing accuracy level and the measured value of the image output based on the color chart data group are obtained. Using image processing means for creating the profile ;
Based on the color chart data for performing the verification, and the measured value of the image output using the color chart data for performing the color conversion performed by the profile created by the image processing unit, An evaluation value representing the processing accuracy of the profile is obtained, it is determined whether or not the obtained evaluation value satisfies a predetermined criterion, and if the criterion is not satisfied, the color used at the time of creating the profile Re-creating means for adding a color chart data group corresponding to the next higher processing accuracy level to the vote data group and creating a profile again;
An image processing apparatus comprising: The recreating means includes
The color space is divided into a plurality of areas, and for each of the areas, an evaluation value indicating the processing accuracy of the profile created by the image processing means is obtained, and whether or not the evaluation value satisfies a predetermined criterion. If there is an area that does not satisfy the determination criteria, color chart data corresponding to the area and not the same as that used when creating the profile is added to the color chart data used when creating the profile. the image processing apparatus according to claim 1, wherein the benzalkonium create a profile again. The recreating means includes
When all of the color chart data groups stored in the storage unit are used for creating the profile, the color chart data group corresponding to the area that does not satisfy the determination criteria is created to create the profile. The image processing apparatus according to claim 1. The computer,
Each of a plurality of color chart data groups each consisting of a plurality of color chart data of CMYK, color chart data for verifying color conversion by a profile, and image processing that can be performed using the color chart data group The tone characteristics evaluation for obtaining an evaluation value representing the gradation characteristics of the image output using the color chart data of the color chart data group, and the color chart data of the color chart data group. Color conversion for creating a color conversion profile for an image output device, which is performed on at least one of color reproducibility evaluation for obtaining an evaluation value representing the color reproducibility of an image and color chart data for performing the verification Storage means for storing each processing item of image processing including profile creation and the processing accuracy level achieved by the color chart data group in association with each other;
Input means for designating the processing item and the processing accuracy level;
Image processing means for reading out the color chart data group corresponding to the processing item and processing accuracy level designated by the input means from the storage means and performing image processing corresponding to the processing item using the color chart data group. When the designated processing item is the profile creation, the color chart data group corresponding to the designated processing accuracy level and the measured value of the image output based on the color chart data group are obtained. Using image processing means for creating the profile ;
Based on the color chart data for performing the verification, and the measured value of the image output using the color chart data for performing the color conversion performed by the profile created by the image processing unit, An evaluation value representing the processing accuracy of the profile is obtained, it is determined whether or not the obtained evaluation value satisfies a predetermined criterion, and if the criterion is not satisfied, the color used at the time of creating the profile Re-creating means to add a color chart data group corresponding to the next higher processing accuracy level to the vote data group and create a profile again
Program to function as .

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