JP2007166402A - Image processing method and image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing method and an image processing apparatus for evaluating a color reproduction characteristic by taking into account an observation environment of an output image. <P>SOLUTION: The image processing apparatus for evaluating the color reproduction characteristic of an image output apparatus on the basis of lighting information designated on a UI by a user is characterized in to include: a spectral data acquisition means for acquiring spectral data from the output image of the image output apparatus; a colorimetric value calculation means for calculating the color reproduction characteristic of the image output apparatus under the observation environment on the basis of the lighting information designated on the UI by the user and the spectral data; and a color reproduction characteristic calculation means that realizes the color reproduction characteristic satisfying a desired condition designated by the user under the plurality of lighting information items designated on the UI by the user on the basis of the colorimetric value calculated by the colorimetric value calculation means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image processing method for calculating color reproduction characteristics that satisfy a condition specified by a user under a plurality of illuminations in which an output image of the image output apparatus is specified on the UI by the user.

In general, in an image output apparatus incorporating a color management system (CMS), advanced color reproduction is achieved by performing color conversion using a color profile (hereinafter referred to as a profile) that stores the color reproduction characteristics of the apparatus. (Patent Document 1). The accuracy of such color reproduction largely depends on how accurately the profile reflects the color reproduction of the image output apparatus.
JP 2005-62915 A

  However, in general, a profile of an image output apparatus that handles printed materials is created based on color reproduction characteristics under a standard illumination environment. Therefore, since the color reproduction characteristics in the environment where the output image is actually observed is not reflected, appropriate color reproduction characteristics cannot be obtained depending on the observation environment. SUMMARY An advantage of some aspects of the invention is that it provides an image processing method and an image processing apparatus that evaluate color reproduction characteristics in consideration of an observation environment of an output image.

  In order to achieve the above object, an image processing apparatus according to claim 1 of the present invention is an image processing apparatus that evaluates color reproduction characteristics of an image output apparatus based on illumination information designated by a user on a UI, and Spectral data acquisition means for acquiring spectral data from an output image of the output device, and colorimetry for calculating color reproduction characteristics of the image output device under an observation environment based on the illumination information and the spectral data specified by the user on the UI And a color difference calculating unit for displaying the colorimetric value calculated by the colorimetric value calculating unit on a display device.

  The image processing method according to claim 2 is an image processing method for evaluating the color reproduction characteristics of an image output device based on illumination information designated by a user on a UI, and obtains spectral data from an output image of the image output device. A spectral data acquisition step, a colorimetric value calculation step of calculating color reproduction characteristics of the image output device under an observation environment based on the illumination information and the spectral data specified by the user on the UI, and the colorimetric value calculation And a color difference calculation step of displaying the colorimetric value calculated in the step on a display device.

  For example, the illumination information is information representing a spectral distribution of illumination in the observation environment.

  For example, the spectral data is data indicating spectral reflectance of the output image.

  For example, when executed by a computer, the computer is operated as the image processing apparatus according to claim 1.

Example 1
Hereinafter, the present embodiment will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of an image processing apparatus according to the present embodiment, and the apparatus includes a spectral data acquisition unit 10, a UI unit 11, and a color constancy value calculation unit 13. FIG. 2 is a flowchart showing a processing procedure of the image processing apparatus represented by the block diagram of FIG. The operation of the image evaluation apparatus of FIG. 1 will be described below with reference to the flowchart of FIG. First, the spectral data acquisition unit 10 measures the output image of the image output device with a spectrocolorimeter to acquire spectral data (S200). Next, the UI unit 11 acquires illumination information necessary for the user to calculate a desired color difference on the UI by a method described later (S201). Next, a plurality of light sources to be considered at the time of image design are selected by a method described later (S202). The colorimetric value calculation unit 12 uses the illumination information S (λ) acquired by the UI unit 11 and the spectral reflectance R (λ) of the output image, according to the equation (1) defined in JIS Z 8701, and the tristimulus of the object color. Values X, Y, and Z are calculated (S203).

ただし、ｘ（λ）、ｙ（λ）、ｚ（λ）は、ＪＩＳ Ｚ８７８２に示されている等色関数である。つぎに、このＸＹＺの値からＪＩＳ Ｚ８７２９で示されているＣＩＥＬＡＢの値を算出する（Ｓ２０４）。つぎに、色差計算部１３は、前記ＵＩ部で指定された複数個（ここではｎとする）光源情報から、式（２）、（３）、（４）に従って算出する（Ｓ２０５）。

However, x (λ), y (λ), and z (λ) are color matching functions shown in JIS Z8782. Next, the value of CIELAB shown in JIS Z8729 is calculated from the value of XYZ (S204). Next, the color difference calculation unit 13 calculates from the plurality of (here, n) light source information specified by the UI unit according to the equations (2), (3), and (4) (S205).

次に、Ｓ２０５で算出した（Ｌ'＊、ａ'＊、ｂ'＊）が、画像設計でのターゲット（ここでは、Ｄ５０）の光源におけるＲ，Ｇ，Ｂ、均等３２分割の格子点でのＬ＊、ａ＊、ｂ＊を満足するデバイスＲＧＢを四面体補間などによって算出してファイルに保存して終了する（ステップＳ２０６）。ただし、式（２）、（３）、（４）によって算出される（Ｌ'＊、ａ'＊、ｂ'＊）がＤ５０の色域外である場合には、最外郭の点に線形的に貼り付けを行う。

Next, (L ′ *, a ′ *, b ′ *) calculated in S205 are R, G, B in the light source of the target (here, D50) in the image design, and lattice points of equal 32 divisions. The device RGB satisfying L *, a *, and b * is calculated by tetrahedral interpolation or the like, stored in a file, and the process ends (step S206). However, when (L ′ *, a ′ *, b ′ *) calculated by the equations (2), (3), and (4) is outside the color gamut of D50, it is linearly set to the outermost point. Paste.

  Next, the setting of the illumination information performed by the user of the UI unit 11 will be described in detail. FIG. 3 is a diagram showing an example of UI in the UI unit 11 for acquiring the illumination data S (λ) of the printed matter observation environment in the present embodiment, and a radio button 31 for designating a reference light source, and color constancy A radio button 32 for selecting whether or not to select a designated light source for calculating a value from existing light source data, or whether to read data measured by a user from a file, and a radio button 33 for designating a designated light source A text box 34 for designating light source data measured by the user from the file, a reference button 35 for selecting the light source data measured by the user from the file, and a file in which the device RGB is calculated from the color constancy value and the target A text box 36 for designating the storage location of the device, and a device RGB calculated from the color constancy value and the target. A reference button 37 for specifying the Le destination consists OK button 38 and a cancel button 39. The UI designation method in FIG. 3 will be described with reference to the flowchart in FIG. First, a UI for color constancy value calculation is selected on the display device (S400). Next, a reference light source for evaluating the color constancy value is selected from the radio box 31 (S401). Next, the counter I of the plurality of light sources is initialized to 0 (S402). Next, it is determined whether or not L *, a *, and b * are calculated under all light source data. If all are calculated, the process proceeds to S406. If not all have been calculated, the process proceeds to S403. Next, one type of light source information to be considered for the color constancy value is selected (S403). Here, if the data separately measured by the user is used, the color measurement data of the light source is designated and read in the text box 34, and the process proceeds to step S404. Next, the color conversion unit 12 performs color conversion to the tristimulus values X, Y, Z and CIELAB of the object color (S404). Next, the counter I is incremented (S405). Next, the color constancy value obtained by the above formulas (2), (3), and (4) is calculated from the reference light source data and the plurality of light source data specified in S401 (S406). Next, a desired file storage destination is specified by a text box 36 for specifying a file storage destination for which the device RGB is calculated from the color constancy value calculated in S406 and a reference button 37, and the data is stored in the file. And finishes (S407).

  As described above, according to the present embodiment, the target value is satisfied by the color constancy value calculated based on the plurality of illumination data S (λ) in the environment that the user actually assumes the output image from the image output apparatus. Since the device RGB is calculated, it is possible to output an image with little color shift on average under a light source specified on the UI. As a result, it is possible to easily obtain an image with little color change visible to the observer under various illuminations without changing the color material or media.

It is a block diagram which shows the structure of the image processing apparatus of this embodiment. It is a flowchart which shows the process sequence of the image processing apparatus of this embodiment. It is a figure which shows the example of illumination data acquisition UI in this embodiment. It is a flowchart which shows the process sequence of the example of illumination data acquisition UI in this embodiment.

Claims (6)

  An image processing device that evaluates the color reproduction characteristics of an image output device based on illumination information specified by the user on the UI, a spectral data acquisition unit that acquires spectral data from the output image of the image output device, and the user on the UI Based on the specified illumination information and the spectroscopic data, a colorimetric value calculating means for calculating the color reproduction characteristics of the image output device under an observation environment, and the user can perform a UI from the colorimetric values calculated by the colorimetric value calculating means. An image processing apparatus comprising: a color reproduction characteristic calculating unit that realizes a color reproduction characteristic that satisfies a condition specified by a user under the plurality of illumination information specified above.   An image processing method for evaluating color reproduction characteristics of an image output device based on illumination information designated by a user on a UI, a spectral data acquisition step for acquiring spectral data from an output image of the image output device, and a user on the UI Based on the specified illumination information and the spectroscopic data, the user can calculate a colorimetric value calculation step for calculating the color reproduction characteristics of the image output device under an observation environment, and the user can perform a UI from the colorimetric values calculated in the colorimetry value calculation step. An image processing method comprising: a color reproduction characteristic calculation step that realizes a color reproduction characteristic that satisfies a condition specified by a user under a plurality of previous illumination information specified above.   The image processing apparatus according to claim 1, wherein the illumination information is information representing a spectral distribution of illumination under the observation environment.   The image processing apparatus according to claim 1, wherein the spectral data is data indicating a spectral reflectance of the output image.   A program that, when executed by a computer, causes the computer to operate as the image processing apparatus according to claim 1.   A recording medium on which the program according to claim 5 is recorded.

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