JP2011124859A - Image processing device, and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform highly precise color conversion in consideration of orientations of fiber of paper when an output object is observed. <P>SOLUTION: Occurrence of inconvenience that color changes according to the orientations (a longitudinal direction, a lateral direction) of the paper when the output object is observed is reduced even in the case of the output object such as Japanese paper with large orientation characteristics of the fiber by holding a plurality of conversion parameters in consideration of the orientations of the fiber of the paper, and acquiring a conversion parameter to be used for performing color conversion processing of image data from among the plurality of conversion parameters to generate print data according to output conditions to be given from a user when the output object to be printed by an image output device is observed. <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 suitable for use in performing color conversion processing on image data using conversion parameters corresponding to output conditions.

  In general, in an image output device such as a printer in which a color management system is introduced, high-precision color reproduction is realized by performing color conversion processing using a color reproduction characteristic profile of the image output device. As color conversion processing using this profile, a method using a look-up table (hereinafter referred to as LUT) capable of realizing highly accurate color reproduction is generally used.

  The method using the LUT is based on an LUT in which a printer driver connected to a printer associates input color reproduction characteristic data (RGB data) with output color reproduction characteristic data (RGB data or CMYK data). Convert image data. A plurality of LUTs are created and stored in advance in the printer driver so as to realize high image quality according to the type of printing resolution and printing paper.

  The accuracy of color conversion processing using such a profile greatly depends on how accurately the profile reflects the color reproduction characteristics of the image output apparatus. In the printer driver of Patent Document 1, in order to accurately reproduce the appearance of the color of a print due to a difference in illumination light source, an output is observed by holding LUTs corresponding to a plurality of illumination light sources in advance. High-accuracy color conversion processing corresponding to the illumination light source is realized.

JP 2007-150399 A

When printing is performed after the color conversion processing with high accuracy as described above is performed, various output products are used. For example, the color reproduction characteristics of printing paper with a large fiber orientation such as Japanese paper as an output product have the following problems. That is, an output product using printing paper with a large fiber orientation changes the color appearance according to the fiber orientation. For this reason, even if it is the same output thing, the subject that a color changes with directions (vertical direction, horizontal direction) at the time of observing an output thing occurs. However, conventionally, the fiber orientation of such printing paper has not been taken into consideration, and thus there has been a case where an appropriate output cannot be performed on a printing paper having a large fiber orientation.
In view of the above-described problems, an object of the present invention is to enable high-accuracy color conversion in consideration of the fiber orientation of a sheet when an output is observed.

  An image processing apparatus according to the present invention is an image processing apparatus that performs color conversion processing on image data to be printed to generate print data that can be printed by the image output apparatus, and an output product printed by the image output apparatus is observed. A plurality of conversion parameters in consideration of the fiber orientation of the paper is stored, and the image data is subjected to color conversion processing from among the plurality of conversion parameters in accordance with output conditions given by the user. The print data is generated by acquiring the conversion parameters used in the above.

  According to the present invention, a plurality of output profiles are provided according to the orientation of the output material at the time of observation, and these output profiles are switched according to the user's output conditions. High-accuracy color conversion processing can be performed in consideration of the above. Thereby, an appropriate output can be performed on a printing paper having a large fiber orientation.

It is a block diagram which shows the structural example of an image processing apparatus. It is a flowchart which shows the example process sequence in an image processing apparatus. It is a figure which shows the example of UI displayed to a user in an output condition acquisition part. It is a figure which shows the example of the file format of LUT. It is a block diagram which shows the structural example of a conversion parameter production apparatus. It is a flowchart which shows the example process sequence which produces a conversion parameter. It is a figure which shows a mode that each color of a color chart image is measured with a spectrometer. It is a figure which illustrates the data hold | maintained at a conversion parameter holding part.

(First embodiment)
FIG. 1 is a block diagram showing a configuration example of a system according to the first embodiment of the present invention.
In FIG. 1, reference numeral 101 denotes an image processing apparatus. Reference numeral 102 denotes an image data acquisition unit that acquires image data. A conversion parameter holding unit 103 holds a look-up table (LUT) used for color conversion as a parameter for color conversion. Reference numeral 104 denotes a conversion parameter acquisition unit that acquires conversion parameters. Reference numeral 105 denotes a print data output unit that generates and outputs print data that can be printed by the image output apparatus 109. Reference numeral 106 denotes an output condition acquisition unit that acquires output conditions. A color conversion processing unit 107 performs color conversion processing on the acquired image data using color conversion parameters. Reference numeral 108 denotes a buffer memory that temporarily stores image data and calculation results for performing calculation processing. An image output apparatus 109 prints image data on a recording medium. Note that the hardware configuration of the image processing apparatus 101 in the present embodiment can be configured by a known technique such as a computer, and thus detailed description of the hardware is omitted.

<Operation in Image Processing Apparatus 101>
FIG. 2 is a flowchart for explaining an exemplary processing procedure executed in the image processing apparatus 101.
In S21, the output condition acquisition unit 106 displays a user interface as a means for an operator of the image processing apparatus 101 in the present embodiment to input information necessary for image output. FIG. 3 shows an example of a user interface.

  The user interface includes an image data instruction unit 301 for instructing input image data, an output condition instruction unit 302 for instructing conditions for outputting image data, and an output instruction unit 303 for instructing output of image data. In the present embodiment, the output condition instruction unit 302 includes an interface for setting the paper type, print quality (print resolution), color mode, and document size in a pull-down menu format. Furthermore, as output information for considering the fiber orientation of the paper, an interface for setting the paper orientation and the observation orientation in a radio button format is provided.

  As the paper type, for example, glossy paper, matte paper, plain paper, Japanese paper, or the like can be set. In print quality, for example, high quality (600 dpi), standard (300 dpi), and the like can be set. In the color mode, for example, preferable, minimum color difference, monochrome, etc. can be set. As the document size, for example, ISOA3, ISOA4, etc. can be set. The paper orientation can be set to the vertical direction or the horizontal direction. In the observation direction, the vertical direction or the horizontal direction can be set.

In S22, the image data acquisition unit 102 acquires image data with reference to the image file name set by the operator from the image data instruction unit 301 of the user interface displayed in S21. The acquired image data is stored in the buffer memory 108.
In S23, the output condition acquisition unit 106 acquires the output condition by referring to the item set by the user from the output condition instruction unit 302 of the user interface displayed in S21. The output condition is stored in the buffer memory 108.

  In S <b> 24, the conversion parameter acquisition unit 104 acquires the output condition acquired in S <b> 23 from the buffer memory 108. Then, the conversion parameter is acquired from the conversion parameter holding unit 103 based on the acquired output condition. The format and creation method of the conversion parameter stored in the conversion parameter storage unit 103, and details of the conversion parameter storage unit 103 and the conversion parameter acquisition unit 104 will be described later.

In S25, the color conversion processing unit 107 acquires the image data acquired in S22 from the buffer memory 108 using the conversion parameter acquired in S24, and performs color conversion processing on the image data.
In S26, the print data output unit 105 receives the image data converted in S25. Then, halftone processing is performed to express the gradation value of each pixel of the received image data as an ink value. Furthermore, print data is created by adding predetermined information such as resolution. Then, the created print data is transmitted to the image output device 109.
In step S27, the image output apparatus 109 receives the print data transmitted in step S26, performs print processing based on the received print data, and outputs image data corresponding to the print data to a print sheet.

<Conversion parameter format>
In this embodiment, an LUT that describes the correspondence between input color reproduction characteristic data and output color reproduction characteristic data is used as the format of conversion parameters used when color conversion processing is performed on input image data. In the LUT, for example, output RGB data corresponding to input RGB data arranged in uniform grid points as in the format of FIG. 4 is described. When color conversion processing is performed, based on this correspondence relationship, input RGB data is subjected to interpolation processing such as tetrahedral interpolation using a four-point grid surrounding the RGB data. Convert RGB data into output RGB data.

<LUT creation method used for color conversion processing>
Here, a method of creating an LUT corresponding to the orientation of the paper will be described. As already explained, on paper with a large fiber orientation, such as Japanese paper or plain paper, whether the output is output in the vertical direction or in the horizontal direction, even if it is output with the same signal value The way colors look depends For this reason, in order to realize highly accurate color reproduction using a paper having a large fiber orientation, it is necessary to create an LUT according to the viewing direction of the paper.

  FIG. 5 is a block diagram illustrating a configuration example of a system used for creating an LUT. In FIG. 5, reference numeral 501 denotes a conversion parameter creation device. Reference numeral 502 denotes a spectrophotometer for measuring a color chart. Reference numeral 503 denotes a spectral data acquisition unit that acquires measurement data obtained by the spectrophotometer 502. Reference numeral 504 denotes a measurement value calculation unit that calculates measurement values from the spectral data. Reference numeral 505 denotes a target color data holding unit that holds target design values for each paper type and color mode. A data output unit 506 transmits image data to the image output device 509. Reference numeral 507 denotes a conversion parameter creation unit that creates an LUT from the measurement value obtained by the spectrophotometer 502 and target color data. Reference numeral 508 denotes a buffer memory. Reference numeral 509 denotes an image output device for outputting a color chart used for measurement.

FIG. 6 is a flowchart for explaining an exemplary processing procedure executed by the conversion parameter creation device 501.
In the conversion parameter creation device 501, an image based on a predetermined color signal is output by the image output device 509, and a conversion parameter is created based on the relationship between this color signal and the measured value of this image.
In step S61, the image output device 509 receives the color chart image output data from the data output unit 506, and outputs the color chart. The color chart image is, for example, 729 (9 ³ = 729) color (R, R) of uniform grid points obtained by sampling each channel of RGB in 9 steps (0, 32, 64, 96, 128, 160, 192, 224, 255). G, B 9 Grid data). That is, {RGB} = {0, 0, 0}, {0, 0, 32}, ..., {0, 0, 224}, {0, 0, 255}, {0, 32, 0}, {0, 32, 32},..., {255, 255, 255}.

  In step S <b> 62, the conversion parameter creation unit 507 acquires target color data corresponding to each of RGB data of 729 uniform grid points from the target color data holding unit 505. The target color data is data in which design values intended for each paper type and color mode are described as CIE-XYZ values.

  In S63, each color of the color chart image output in S61 is measured by the spectrophotometer 502. The measurement conditions are shown in FIG. In S63, as shown in FIG. 7A, the illumination light source is incident in the 45 degree direction and the spectrophotometer 502 receives the light in the 0 degree direction with the paper placed in the longitudinal direction which is the same direction as the fiber orientation. And measure.

In S64, the conversion parameter creation unit 507 creates an LUT from the target color data acquired in S62 and the measurement value measured in S63. The spectroscopic data acquisition unit 503 acquires spectroscopic data measured by the spectrophotometer 502, and the measurement value calculation unit 504 calculates an equation (1) from the acquired spectroscopic data, the spectral distribution of the illumination light source, and the color matching function. ) To calculate the CIE-XYZ value.
Formula (1): CIE-XYZ value calculation formula

  The conversion parameter creation unit 507 uses the iterative method or the like to calculate the RGB corresponding to the measured value from the calculated measured value (CIE-XYZ value) and the target color data (correspondence relationship between the RGB data and the CIE-XYZ value). Calculate the data. The calculated RGB data is stored in the buffer memory 508 as the LUT 1 for vertical orientation.

  Next, in S65, the color chart image used for the measurement in S63 is rotated by 90 degrees and measured by the spectrophotometer 502. FIG. 7 shows the measurement conditions. In S65, as shown in FIG. 7B, the illumination light source is incident in the 45 degree direction with the color chart image measured as the vertical direction rotated by 90 degrees and placed in the horizontal direction, and the spectrometer 502 is set. Measurement is performed by receiving light in the 0 degree direction.

Next, in S66, the conversion parameter creation unit 507 performs processing similar to the processing in S64, creates a horizontal LUT2 from the target color data and the measured value measured in S65, and buffers the created LUT. Save in memory 508.
In step S <b> 67, LUT <b> 1 and LUT <b> 2 created by the conversion parameter creation device 501 are read from the buffer memory 508 and stored in the conversion parameter holding unit 103 of the image processing device 101.

<Conversion parameter holding unit 103>
The conversion parameter holding unit 103 stores a plurality of conversion parameters used for color conversion in the color conversion processing unit 107. The present embodiment is characterized in that a plurality of conversion parameters corresponding to the fiber orientation of the paper are stored. FIG. 8 is a diagram illustrating data held in the conversion parameter holding unit 103.

  As shown in FIG. 8, the conversion parameter holding unit 103 is created corresponding to an identification ID for identifying an output condition for observing the paper in the vertical direction or in the horizontal direction, and this identification ID. A correspondence table for referring to the LUT is held. For example, when an output condition for portrait orientation is acquired as identification ID1, identification ID1 is associated with LUT1 created for portrait orientation, and when an output condition for landscape orientation is acquired as identification ID2, identification ID2 is for landscape orientation. Are associated with the LUT2 created in the above.

  The conversion parameter holding unit 103 holds an LUT for performing highly accurate color conversion processing for each output condition. In the present embodiment, not only the LUT corresponding to the fiber orientation of the paper but also the LUT corresponding to each of a plurality of printing papers (paper type), printing resolution (printing quality), and color mode are held.

  For example, assume a case corresponding to four types of paper (glossy paper, matte paper, plain paper, Japanese paper), two types of resolution (600 dpi, 300 dpi), and three types of modes (preferable, minimum color difference, monochrome). In this case, 2 × 2 × 3 × 1 = 12 types (ignoring the fiber orientation of glossy paper and matte paper), and 2 × 2 × 3 × 2 = 24 types (plain paper and Japanese paper) 36 types of LUTs are stored in the conversion parameter holding unit 103 in consideration of the fiber orientation of the paper.

<Conversion parameter acquisition unit 104>
The conversion parameter acquisition unit 104 transmits an identification ID to the conversion parameter holding unit 103 based on the output condition acquired by the output condition acquisition unit 106, and the identification ID is selected from a plurality of LUTs stored in the conversion parameter holding unit 103. LUT corresponding to is acquired.

Here, an LUT acquisition method corresponding to the observation direction will be described.
As described in the LUT creation method, there are two types of LUTs corresponding to the observation direction: a vertical LUT and a horizontal LUT. Which of these two types of LUT is used is determined by the direction of the sheet and the direction of observation instructed by the output condition instruction unit 302.

  When the portrait orientation is selected as the set orientation of the paper and the portrait orientation is selected as the observation orientation, the LUT for portrait orientation is acquired. Further, when the landscape orientation is selected as the paper orientation, and the landscape orientation is selected as the observation orientation, the LUT for portrait orientation is acquired. In addition, when different orientations are selected for the paper orientation and the observation orientation, the observation conditions are different from the conditions for creating the LUT for the portrait orientation, and thus the landscape orientation LUT is acquired. Correct the color difference due to the difference in the direction of observing the paper.

  As described above, in the present embodiment, a plurality of output profiles are provided in accordance with the orientation of the output material at the time of observation. When the color conversion process is performed, a plurality of output profiles are switched in accordance with the user's output conditions, so that the color conversion process can be performed with high accuracy in consideration of the fiber orientation of the paper.

Next, an embodiment different from the above-described embodiment will be described.
<Conversion parameter format>
In the first embodiment, an LUT is used as a conversion parameter. However, other conversion parameters such as a matrix may be used, and any method can be used as long as input data can be accurately converted to output data.

<Setting output conditions>
In the first embodiment, a function for setting the paper orientation and the observation orientation on the UI is provided, and the LUT for portrait orientation and the LUT for landscape orientation are selected and acquired. However, if the orientation of the paper is limited to a certain direction when setting the paper by roll paper or manual feed, the LUT for portrait orientation and the LUT for landscape orientation can be selected by providing only the function for setting the observation orientation. It is possible to get it.

  In addition, there are items other than paper orientation (paper type, print quality, color mode, document size) as output condition setting items. If these settings are known in advance, the fiber orientation of the paper is taken into consideration. It is also possible to set only the paper orientation condition.

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (computer program) that implements the functions of the above-described embodiments is supplied to a system or apparatus via a network or various computer-readable storage media. The system or apparatus computer (or CPU, MPU, or the like) reads and executes a program for control.

DESCRIPTION OF SYMBOLS 101 Image processing apparatus, 102 Image data acquisition part, 103 Conversion parameter holding part, 104 Conversion parameter acquisition part, 105 Print data output part, 106 Output condition acquisition part, 107 Color conversion process part, 108 Buffer memory, 109 Image output apparatus

Claims (11)

An image processing device that performs color conversion processing on image data to be printed and generates print data that can be printed by an image output device,
When an output printed by the image output device is observed, a plurality of conversion parameters are stored in consideration of the fiber orientation of the paper, and the plurality of conversion parameters are determined according to output conditions given by the user. An image processing apparatus, wherein the print data is generated by acquiring conversion parameters used for color conversion processing of the image data. Image data acquisition means for acquiring image data;
Conversion parameter holding means for holding a plurality of conversion parameters corresponding to the fiber orientation of the paper;
An output condition acquisition means for acquiring an output condition input by a user;
Conversion parameter acquisition means for acquiring a conversion parameter used for performing color conversion processing from among a plurality of conversion parameters held in the conversion parameter holding means based on the output condition acquired by the output condition acquisition means; ,
Color conversion processing means for performing color conversion processing on the image data using the conversion parameter acquired by the conversion parameter acquisition means to the image data acquired by the image data acquisition means;
An image processing apparatus comprising:   The image processing apparatus according to claim 1, wherein the conversion parameter is stored as a lookup table.   The image processing apparatus according to claim 2, wherein the output condition acquisition unit acquires an observation direction as an output condition.   The image processing apparatus according to claim 2, wherein the output condition acquisition unit acquires a paper direction and an observation direction as output conditions. An image processing method for performing color conversion processing on image data to be printed to generate print data that can be printed by an image output device,
When an output printed by the image output device is observed, a plurality of conversion parameters are stored in consideration of the fiber orientation of the paper, and the plurality of conversion parameters are determined according to output conditions given by the user. An image processing method characterized in that conversion data used for color conversion processing of the image data is acquired from the image data to generate the print data. An image data acquisition process for acquiring image data;
Holding step for holding a plurality of conversion parameters corresponding to the fiber orientation of the paper in the conversion parameter holding means;
An output condition acquisition step of acquiring an output condition input from a user;
A conversion parameter acquisition step for acquiring a conversion parameter used for performing color conversion processing from among a plurality of conversion parameters held in the conversion parameter holding means based on the output condition acquired in the output condition acquisition step; ,
A color conversion processing step of performing color conversion processing on the image data using the conversion parameter acquired in the conversion parameter acquisition step to the image data acquired in the image data acquisition step;
An image processing method comprising: A computer program that causes a computer to execute an image processing method for performing color conversion processing on image data to be printed and generating print data that can be printed by an image output apparatus,
When an output printed by the image output device is observed, a plurality of conversion parameters are stored in consideration of the fiber orientation of the paper, and the plurality of conversion parameters are determined according to output conditions given by the user. A computer program for controlling a computer to acquire conversion parameters used for performing color conversion processing on the image data from the image data and generate the print data. An image data acquisition process for acquiring image data;
Holding step for holding a plurality of conversion parameters corresponding to the fiber orientation of the paper in the conversion parameter holding means;
An output condition acquisition step of acquiring an output condition input from a user;
A conversion parameter acquisition step for acquiring a conversion parameter used for performing color conversion processing from among a plurality of conversion parameters held in the conversion parameter holding means based on the output condition acquired in the output condition acquisition step; ,
A computer program for causing a computer to execute a color conversion processing step of performing color conversion processing on the image data using the conversion parameter acquired in the conversion parameter acquisition step on the image data acquired in the image data acquisition step. . A spectroscopic measuring means for measuring a color chart for measuring the fiber orientation of the paper;
Spectral data acquisition means for acquiring measurement data by the spectral measurement means;
A measurement value calculation means for calculating a measurement value from the spectral data acquired by the spectral data acquisition means;
Target color data holding means for holding a target design value for each paper type and color mode;
An image output device for outputting the color chart;
Data output means for transmitting image data to the image output device;
A conversion parameter creation device, comprising: conversion parameter creation means for creating a look-up table from values measured by the spectroscopic measurement means and target color data. A spectroscopic measurement process for measuring a color chart for measuring the fiber orientation of the paper;
A spectroscopic data acquisition step for acquiring measurement data in the spectroscopic measurement step;
A measurement value calculation step of calculating a measurement value from the spectral data acquired in the spectral data acquisition step;
A target color data holding process for holding a target design value for each paper type and color mode;
An output step of outputting the color chart from the image output device;
A data output step of transmitting image data to the image output device;
A conversion parameter creation method comprising: a conversion parameter creation step of creating a look-up table from the measured value and target color data in the spectroscopic measurement step.

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