JP2008154175A - Information processing apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To create a high-precision color profile by enabling a colorimetric value corresponding to a lining material for utilization to be calculated. <P>SOLUTION: Spectral reflectance and spectral transmittance of a plurality of patches output onto a recording medium by an output device are acquired, spectral reflectance of a lining material is acquired, colorimetric values of the plurality of patches are calculated from the spectral reflectance and the spectral transmittance of the plurality of patches and the spectral reflectance of the lining material, and a color profile of the output device corresponding to the lining material is created from the estimated colorimetric values of the plurality of patches. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for creating a color profile considering a backing material.

  A color management system (CMS) is used to obtain an intended color reproduction between various color devices (color scanner, color display, color printer, etc.) that handle color images. The CMS realizes consistent color reproduction by exchanging color data between devices via device-independent color data. In CMS, color data such as a device-dependent RGB color system or YMCK color system is converted into color data in a color space independent of a device such as CIEXYZ or CIELAB based on device profile information. The color data of CIEXYZ and CIELAB is color measurement data (color measurement values) obtained by measuring a color image. Such device-independent CIEXYZ or CIELAB color data is converted into device-dependent color data such as an RGB color system or a CMYK color system. Then, color reproduction is performed by the device based on the device-dependent color data. For example, if the device-dependent color data is RGB data, the color is reproduced by a color display. If the device-dependent color data is YMCK data, the color is reproduced by a color printer. In general, color measurement of a color image is performed using a color measurement device equipped with a spectrophotometer. However, even if the same print sample is measured, if the color measurement conditions change, the resulting color measurement data will be different. It will be a thing. Therefore, Patent Document 1 describes a technique for correcting a difference in geometric conditions of an optical system during colorimetry.

  The color measurement conditions include the geometric conditions of the optical system at the time of color measurement, the characteristics of the backing material laid under the substrate, and particularly the color difference of the backing material. Regarding the color of the backing material used during colorimetry, black is recommended by the ISO (International Organization for Standardization) standard, and many standards adopt colorimetric data measured in accordance with the ISO standard. Yes.

  In practice, however, it may be preferable to use a white backing material as a colorimetric condition (backing condition) based on the color difference of the backing material. For example, when a plurality of printed materials printed by a color printer are viewed in layers, a white surface that is the background of the paper is often overlaid on the back side of each printed surface, so a color close to the visual impression is reproduced. It is preferable to create a profile using colorimetric data measured using a white backing material. On the other hand, it may be preferable to use a black backing material. For example, in the case of a printed matter output by double-sided printing, if the color of the backing material is black, the colorimetric data when the color image of the front surface is measured is not affected by the backside printing.

If the paper thickness of the printed material is thin, the transmitted light that has passed through the printed material is reflected by the backing material and reaches the light receiver of the colorimeter, so the colorimetric value is affected by the color of the backing material. Change.
JP-A-9-214786

  Conventionally, a profile was created based on colorimetric values without considering the type of backing material. Then, color conversion is performed by selecting a profile regardless of the type of backing material at the time of use. Therefore, if the backing conditions at the time of profile creation differ from the backing conditions at the time of use, the color reproduction accuracy is lowered.

  It is an object of the present invention to realize highly accurate color reproduction by making it possible to calculate colorimetric values according to the backing conditions during use.

  In order to achieve the above object, an information processing apparatus according to the present invention includes first acquisition means for acquiring spectral reflectances and spectral transmittances of a plurality of patches output on a recording medium by an output device, and a backing material. Second acquisition means for acquiring spectral reflectance, calculation means for calculating colorimetric values of the plurality of patches from spectral reflectance and spectral transmittance of the plurality of patches, and spectral reflectance of the backing material And creating means for creating a color profile of the output device corresponding to the backing material from the estimated colorimetric values of the plurality of patches.

  According to the present invention, it is possible to calculate a colorimetric value corresponding to a backing condition at the time of use, and to create a color profile that realizes highly accurate color reproduction.

(Example 1)
In this embodiment, the user selects an appropriate condition for the backing material according to his / her purpose of use. The profile creation device creates a color profile from data obtained by correcting the colorimetric values using the selected backing condition. According to this embodiment, it is possible to create a print image using a color profile that always reflects the purpose of use.

[Basic configuration of profile creation device]
FIG. 1 is a block diagram illustrating a functional configuration of the profile creation apparatus according to the present embodiment. Reference numeral 10 denotes a UI unit for setting a print mode. A color measurement unit 11 measures the spectral reflectance and spectral transmittance of the printed image and the spectral reflectance of the backing material. Reference numeral 12 denotes an arithmetic unit that calculates correction data using the spectral colorimetric values of the colorimetric unit 11 in accordance with the print mode designated by the UI unit 10. A color profile creation unit 12 creates an output image color profile from the input image data and the colorimetric values calculated by the calculation unit 12.

[Processing procedure of profile creation device]
A procedure for creating a color profile in the profile creation apparatus will be described with reference to the flowchart of FIG. Each process in the flowchart of FIG. 2 is executed by reading a control program stored in a computer as a profile creation device and using the RAM as a work memory by the CPU. This computer controls a colorimeter, which is a colorimetric unit 11 that is an external device, and a UI unit 10 including, for example, a display device, as necessary.

  In step S20, information on the backing material, which is a profile creation condition instructed by the user using the UI unit 10, is acquired. That is, the information instructed by the user is acquired using the user interface shown in FIGS.

  In step S21, the spectral reflectance Rm (λ) of the printed matter measured by the spectrophotometer that is the colorimetric unit 11 is acquired. The printed matter is a plurality of color patches necessary for creating a profile, and the plurality of patches are patches formed on a recording medium corresponding to the profile by an output device corresponding to the profile to be created. The spectral reflectance to be acquired is the spectral reflectance of each patch. The spectral reflectance of the printed material can be determined by measuring the printed material with a spectrophotometer using a black backing material. Since black has the property of absorbing light, it is possible to obtain a measurement result equivalent to that measured without using a backing material. Moreover, when measuring a printed matter, a return light may not be generated by providing a space after the printed matter.

  In step S22, the spectral transmittance Tm (λ) of the printed matter measured by the spectrophotometer is acquired. As in step S21, the printed matter to be measured is a plurality of color patches necessary for creating a profile, and the acquired spectral transmittance is the spectral transmittance of each patch.

  In step S23, the spectral reflectance Rb (λ) of the backing material measured by the spectrophotometer is acquired. The backing material has a uniform color. Therefore, the spectral reflectance of the backing material acquired in step S23 is one. The spectral reflectance of the backing material is acquired based on the information acquired in step S20. For example, when the type selected in advance by the profile creation device is selected by the user, the spectral reflectance held by the profile creation device is read out.

  Next, in step S24, from the Rm (λ) and Tm (λ) of the plurality of patches acquired by the calculation unit 12 of FIG. 1 in step S21 and step S22, and one Rb (λ) acquired in step S23. The colorimetric values (XYZ values) of a plurality of patches are calculated. This XYZ value is a colorimetric value corresponding to the specified backing material. Note that the color space of the calorimetric value to be calculated is not limited to XYZ, and other color spaces such as Lab may be used.

  Next, in step S25, from the plurality of XYZ values calculated in step S24, the profile creating unit 13 creates a color profile corresponding to the output device on which the patch is formed and the recording medium on which the patch is formed. The color profile for color correction is color return data for realizing conversion between a device-dependent color space and a device-independent color space. For example, when the color conversion data is in the LUT format, the color conversion data stores the correspondence between the color data in the device-dependent color space and the color data in the device-independent color space. Examples of the color profile format include an ICC profile proposed by the Intercolor Consortium.

  According to the present embodiment, a color profile corresponding to the color of the backing material according to the purpose of use can be created. Then, by performing image output based on color data color-converted using a color profile corresponding to the color of the backing material, highly accurate color reproduction can be realized. Further, according to this embodiment, it is not necessary to measure a plurality of patches for each backing material. When changing the backing material, it is possible to create a color profile corresponding to the changed backing material by acquiring only the spectral reflectance of the backing material.

[Description of reflection model]
The reflection model used when calculating the XYZ value corresponding to the specified backing material in step S24 will be described. FIG. 3 is a diagram for explaining a reflection model of a printed material in a state where a backing material is applied. Reference numeral 30 denotes a light source that irradiates the sample during colorimetry, and reference numeral 31 denotes a light receiving unit that receives reflected light from the printed matter. The light source 30 and the light receiving unit 31 are components of a spectrophotometer that is the color measuring unit 11 of FIG.

  Reference numeral 32 denotes a printed matter in which an image is printed on a recording medium by an output device such as a printer. The spectral reflectance of the printed material 32 is Rm (λ) measured in step S21, and the spectral transmittance of the printed material 32 is Tm (λ) measured in step S22.

  Reference numeral 33 denotes a backing material that is applied to the back of the printed matter 32 when the printed matter 32 is subjected to color measurement using the color measuring unit 11 of FIG. The spectral reflectance of the backing material is Rb (λ) measured in step S23.

  Reference numeral 34 denotes incident light I (λ) from the light source 30 to the printed matter 32. Reference numeral 35 denotes reflected light obtained by reflecting the incident light 34 on the surface of the printed matter 32. Reference numeral 36 denotes transmitted light through which the incident light 34 passes through the printed matter 32. Reference numeral 37 denotes reflected light obtained by reflecting the transmitted light 36 by the backing material. Reference numeral 38 denotes transmitted light in which the reflected light 37 is transmitted through the printed matter 32. Reference numeral 39 denotes a total amount Q (λ) of light incident on the light receiving unit 31 and corresponds to the sum of the reflected light 35 and the transmitted light 38.

  Incident light I (λ) emitted from the light source 30 is reflected light 35 (I (λ) Rm (λ)) reflected by the surface of the printed matter 32 and transmitted light 36 (I) passing through the paper of the printed matter 32. (Λ) T (λ)). The transmitted light 36 is reflected by the backing material 33, and the reflected light 37 (I (λ) T (λ) Rm (λ)) is returned to the back surface of the printed matter as return light. The reflected light 37 is transmitted through the paper from the back surface to the front surface of the printed matter 32 to become transmitted light 38 (I (λ) T (λ) Rm (λ) T (λ)).

Finally, in the light receiving unit 31, the total light quantity Q (λ) in which the reflected light 35 from the surface of the printed matter 32 and the transmitted light 38 reflected from the backing material and emitted from the printed matter surface are superimposed. ) 39 is received. When this is expressed by an equation, equation (1) is obtained.
Q (λ) = I (λ) Rm (λ) x (λ) + I (λ) T (λ) Rb (λ) T (λ) (2)
Incident light: I (λ)
Spectral reflectance of printed matter: Rm (λ)
Spectral transmittance of printed matter: T (λ)
Spectral reflectance of backing material: Rb (λ)
When a black backing material is used as the backing material, “I (λ) T (λ) Rm (λ) T (λ)” in Equation (2) can be considered as 0. Black has the property of absorbing light. Therefore, the spectral reflectance Rb (λ) of the backing material can be considered as 0.

Then, the XYZ value of the total light quantity Q (λ) can be obtained by Expression (2).
X = ∫I (λ) Rm (λ) x (λ) d (λ) + ∫I (λ) T (λ) Rb (λ) T (λ) x (λ) d (λ)
Y = ∫I (λ) Rm (λ) y (λ) d (λ) + ∫I (λ) T (λ) Rb (λ) T (λ) y (λ) d (λ)
Z = ∫I (λ) Rm (λ) z (λ) d (λ) + ∫I (λ) T (λ) Rb (λ) T (λ) z (λ) d (λ)
x (λ), y (λ), z (λ): color matching function
... (3)

[First UI]
A user interface displayed on the UI unit 10 for setting the profile creation conditions will be described with reference to FIG.

  In the profile creation apparatus of the present embodiment, spectral reflectance data of the backing material corresponding to the white backing material is held in advance. Therefore, the UI includes a radio button 40 for designating a black backing material and a radio button 41 for designating a white backing material.

  Further, in order to be able to use an arbitrary backing material, a radio button 42 for reading spectral reflectance data of an arbitrary backing material measured in advance by a user is provided. It has a box 43 for designating a file of spectral reflectance data of an arbitrary backing material, and a reference button 44 for referring to spectral reflectance data of the designated backing material.

[Second UI]
Another example of the user interface displayed on the UI unit 10 for setting the profile creation conditions is shown in FIG.

  In the case of FIG. 5, spectral reflectance data of a proof standard backing material and a colorimetric standard backing material is held in advance in the profile file creation device. The radio buttons 50 and 51 can then be used to select one of a proof standard backing material and a colorimetric standard backing material.

  Furthermore, a plurality of backing materials can be arbitrarily registered by the user, and one of the registered backing materials can be selected. The radio button 52 is used to select use of a backing material arbitrarily registered by the user. The pull-down menu 53 is for selecting one from the registered backing materials.

It is a block diagram which shows the function structure of a profile creation apparatus. It is a flowchart explaining operation | movement of a profile production apparatus. It is a figure which shows an example of a reflection model. It is an example of a user interface. It is an example of a user interface.

Claims (5)

First acquisition means for acquiring spectral reflectances and spectral transmittances of a plurality of patches output on a recording medium by an output device;
A second acquisition means for acquiring the spectral reflectance of the backing material;
Calculating means for calculating colorimetric values of the plurality of patches from the spectral reflectance and spectral transmittance of the plurality of patches and the spectral reflectance of the backing material;
An information processing apparatus comprising: a creation unit configured to create a color profile of the output device corresponding to the backing material from the calculated colorimetric values of the plurality of patches.   2. The information processing apparatus according to claim 1, wherein when the color of the backing material is black, the spectral reflectance of the backing material obtained by the second obtaining unit is zero. The information processing apparatus according to claim 1, wherein the calculation unit calculates a colorimetric value of the patch from a total light amount obtained based on the following expression.
Q (λ) = I (λ) Rm (λ) x (λ) + I (λ) T (λ) Rb (λ) T (λ)
Total light quantity from the patch: Q (λ)
Incident light incident on the patch: I (λ)
Spectral reflectance of the patch: Rm (λ)
Spectral transmittance of the patch: T (λ)
Spectral reflectance of the backing material: Rb (λ)   The program for implement | achieving the information processing apparatus in any one of Claim 1 thru | or 3 using a computer. A first acquisition step of acquiring spectral reflectances and spectral transmittances of a plurality of patches output on a recording medium by an output device;
A second acquisition step of acquiring the spectral reflectance of the backing material;
A calculation step of calculating colorimetric values of the plurality of patches from the spectral reflectance and spectral transmittance of the plurality of patches and the spectral reflectance of the backing material;
And a creation step of creating a color profile of the output device corresponding to the backing material from the estimated colorimetric values of the plurality of patches.

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