JP2006262346A - Apparatus and method for image processing and storage medium therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus and the like for generating a look-up table (LUT) which reduces computational complexity and suppresses a pseudo contour by inputting a representative line on the LUT. <P>SOLUTION: The image processing apparatus comprises: a control line setting means for setting at least seven control lines connecting white points and back points in a first color space in accordance with the scale of the LUT; a tetrahedron forming means for forming a tetrahedron in the first color space by selecting four of said control lines; a triangle forming means for forming a triangle using three sides of said tetrahedron; a three-dimension interpolating means for interpolating the triangle formed in said triangle forming means using signal information of two sides holding top-most vertices therebetween in three directions in total from three top-most vertices to opposite sides thereof; a lattice point weight computing means for computing a weight for each of lattice points interpolated in said three-direction interpolating means; and a weight averaging means for averaging the computed weights of lattice point data, wherein the tetrahedron is formed by combining triangles, the first color space is formed by combining the tetrahedrons and the LUT is completed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus, an image processing method, and a storage medium for a color printer, and more particularly, to an image output process for converting a first color space into a second color space using an LUT (lookup table). Is.

  In general, as a look-up table (LUT) generation method for converting the RGB color space into the ink color space of the printer, a color separation control line connecting the white point and the primary color of the printer and the primary vertex of the secondary color and the black point, and white A method of interpolating other grid points using a color space control line connecting points and black points has been studied.

  For example, as disclosed in Patent Document 1, color separation of a W-Bk line connecting a white point (W) and a black point (Bk) and cyan (C), magenta which is a primary color secondary color of a printer color space (M), yellow (Y), red (R), green (G), and blue (B) having the primaries as vertices W-C-Bk, W-M-Bk, W-Y-Bk, W -R-Bk, W-G-Bk, W-B-Bk, using a total of seven lines, divided into tetrahedrons, further divided into triangles, and the interior of the triangle is divided into peak values and contour lines of the ink values on its three sides. There has been proposed a method of performing interpolation calculation using the method.

As a specific method, as shown in FIG. 9, the ink value of each side of the triangle ABC is (1) for the side AB, (2) for the side AC, and (3) for the side BC. If given, the line connecting the vertex A of the ink values (1) and (2) and the vertex I of the ink values (3) is interpolated first, and for the triangle ACI, the ink value and the side CI of the side AC Is interpolated using the ink value contours shown in the figure as a guide, and the triangle ABI is interpolated using the ink values of the side AB and ink values of the side BI using the ink value contours shown in the figure as a guide. Is done. Such interpolation is repeated for the number of ink colors, and a tetrahedron is formed by forming a collection of triangles, and the tetrahedron is connected to finally complete the LUT.
JP 2002-033930 A

  However, in the method disclosed in the above publication, as shown in FIG. 9, the direction of the contour line that serves as a guide is reversed at the side AI, and a pseudo contour near the side AI is likely to be generated due to the effect. Therefore, it becomes difficult to design the signal value lines (1), (2), and (3) that serve as control lines in order to suppress this.

  The present invention has been made paying attention to the above points, and by inputting representative lines (White-Primary-Black and Gray) on the LUT, the LUT that reduces the calculation amount and suppresses pseudo contours. An object of the present invention is to provide an image processing apparatus, an image processing method, and a storage medium that can be generated.

To achieve the above object, according to the color separation image processing apparatus of the color printer of the present invention, the control for setting at least seven control lines connecting the white point and the black point of the first color space according to the scale of the LUT. A tetrahedron forming means for selecting a line setting means and four of the control lines and forming a tetrahedron in a first color space; and a triangle forming means for forming a triangle using three sides of the tetrahedron; Three-way interpolation means for interpolating the triangle formed in the triangle forming means from three vertices toward the opposite side in a total of three directions using signal information of two sides sandwiching the vertex;
Weighting each grid point data calculated by the grid point weighting calculation means, the three-way interpolation means and the grid point weighting calculation means for calculating the weight for each grid point to be interpolated by the three-way interpolation means. A weighted average means for averaging,
A tetrahedron is formed by combining triangles, a first color space is formed by combining the tetrahedron, and the LUT is completed.

  According to the color separation image processing apparatus of the present invention, by inputting representative lines (White-Primary-Black and Gray) on the LUT, it is possible to generate an LUT with a small amount of calculation and suppressing pseudo contours. .

  Hereinafter, preferred embodiments of the present invention will be described.

(First embodiment)
FIG. 1 is a block diagram showing the overall configuration of a color separation system of a color printer according to an embodiment of the present invention.

  As shown in FIG. 1, the color separation system of the color printer according to the present embodiment has a control line setting for setting at least seven control lines connecting the white point and the black point of the first color space according to the LUT scale. A tetrahedron forming means 102 for selecting four of the means 101 and the control line and forming a tetrahedron in a first color space, and a triangle forming means 103 for forming a triangle using three sides of the tetrahedron. The triangle formed by the triangle forming means 103 is interpolated by using the signal information of two sides sandwiching the vertex from three vertices toward the opposite side from the three vertices, and the three-way interpolation means For each grid point to be calculated, each of the points calculated by the grid point weight calculation unit 105, the three-way interpolation unit, and the grid point weight calculation unit is calculated. Composed of the weighted average unit 106. weighted averaging child point data.

  FIG. 2 shows a color separation image processing system as an example of an embodiment of the present invention. In the figure, 201 is a spectrophotometer as an image signal input device, and 202 is a personal computer as a computer system, which can input an image signal read from the spectrophotometer 201 and edit / store it. Further, the image signal information obtained here can be displayed on the display 203 or output from the printer 204.

  FIG. 3 is a block diagram in which the main part in the configuration of FIG. 2 is expressed by blocks as functional modules.

  In the figure, 301 is an interface (I / F) for connecting a mouse and keyboard 313 and a computer system 202 for inputting various manual instructions and the like, and 302 is an image input such as a computer system 202 and a spectrophotometer 201. This is an interface (I / F) for connecting devices.

  Reference numeral 303 denotes a CUP capable of controlling the operation of each internal block or executing a program stored therein.

  A ROM 304 stores necessary image processing and the like in advance.

  A RAM 305 temporarily stores a program and image data to be processed for processing by the CPU.

  Reference numeral 306 denotes a display control device that controls the display device 203 that displays an image to be processed or displays a message to the operator.

  Reference numeral 307 denotes an interface (I / F) that connects the computer system 202 and the color printer 204.

  A hard disk (HD) 308 can store a program and image data to be transferred to the RA 0405 or the like in advance and can store the processed image data.

  Reference numeral 309 denotes a computer system and a transmission device 314 such as a modem or a network card that can transmit various data held in various parts of the computer system to an external device and receive various data from the external device. This is an interface (I / F) to be connected.

  Reference numeral 310 denotes a CD drive capable of reading or writing data stored in a CD (CD-R / CD-RW / DVD) which is one of external storage media.

  Reference numeral 311 denotes an FD drive capable of reading from the FD and writing to the FD as in the case of 310. If an image editing program or printer information is stored on a CD, FD, DVD, etc., these programs are installed on the HD 308 and transferred to the RAM 305 as necessary. ing.

  Reference numeral 312 denotes a sound interface (I / F) to which an external line input 315 and a microphone 316 are connected and external audio data can be input.

  FIG. 4 is a flowchart showing an operation procedure for carrying out the present invention on the configuration shown in FIGS. A computer-executable program that describes the procedure shown in the flowchart of FIG. The present invention is implemented by executing a program.

  Below, the flow of the process in this Embodiment is demonstrated using the flowchart shown in FIG.

  First, in step S401, the color separation of the W-Bk line connecting the white point (W) and the black point (Bk) in the RGB color solid shown in [5-1] of FIG. 5 and the primary color secondary of the printer color space. W-C-Bk, W-M- having the primaries of six primaries of cyan (C), magenta (M), yellow (Y), red (R), green (G), and blue (B) as colors. A total of seven lines Bk, W-Y-Bk, W-R-Bk, W-G-Bk, and W-B-Bk are set as control lines as shown in [5-2] of the figure, A color conversion table such as RGB → CMYK, RGB → CMYKLcLm, etc. of the seven control lines is acquired. This control line color conversion table is pre-defined, and the table is stored on the external storage device 308, CD drive 310, FD drive 311 or receives various data from external devices. It is acquired via a transmission device 314 such as a modem or a network card that can be used.

  Next, in step S402, the cube shown in [5-1] in FIG. 5 is changed from [6-1] to [-6] in FIG. 6 using the seven control lines shown in [5-2] in FIG. 6-6], and is divided into six tetrahedrons. In the following description, the processing from step S403 to step S408 is limited to the processing of one tetrahedron, but it goes without saying that the same processing may be performed for each tetrahedron. The data of each divided tetrahedron is stored in the RAM 305, or when the capacity is large, the external storage device 308 or the like is also used, and the process proceeds to step S403.

  In step S403, the tetrahedron is divided into a plurality of triangles. The dividing method in this case is to create several LUT grid triangles on a plane parallel to one side of the tetrahedron. The number of grids refers to the number of steps when creating an LUT with a minimum value of 2 and a maximum value of 256, for example, when creating an 8-bit RGB LUT. The method of dividing the triangle will be specifically described using the tetrahedron shown in [6-1] of FIG. 6. For example, a triangle parallel to the triangle of the tetrahedron plane WR-Bk is pointed to the point M at the LUT. Create as many grids as possible. Further, the tetrahedron has four faces, and a parallel triangle group can be created from each of the four faces. In order to process all the triangles in the four directions, the following step S404 including this step S403 is performed. To step S407 is repeated four times.

  In step S404, for example, interpolation is performed in the direction of the arrow from the vertex A to the opposite side BC shown in FIG. 7 using the signal values of the sides AB and BC, and similarly in the direction from the vertex B to the opposite side AC. The signal values of the sides AB and BC are used, and interpolation is performed in three directions using the signal values of the sides AC and BC in the direction from the vertex C toward the opposite side AB. The calculated interpolation results in the three directions are stored in the RAM 305, or when the capacity is large, the external storage device 308 is also used.

  Next, in step S405, the weight of each grid is calculated for the three-way interpolation calculated in step S404. For example, as shown in FIG. 8, the calculated weight of each grid is obtained by integrating the area obtained by integrating the signal value of each side used for interpolation into the distance from each vertex as the viewpoint in the interpolation direction. Realized by using the results. The calculated three-way weight result is stored in the RAM 305, or the external storage device 308 is used when the capacity is large.

  Next, in step S406, a weighted average is obtained based on the interpolation result in the three directions calculated in step S404 and the weight for each grid in each direction calculated in step S405, and the signal of the divided inner grid of the triangle is obtained. Calculate the value. The calculated triangle weight average result is stored in the RAM 305, or when the capacity is large, the external storage device 308 or the like is also used. When step S406 ends, the process proceeds to step S407.

  In step S407, a tetrahedron is formed by combining the triangles divided in step S403 with the number of grids. The combined tetrahedron signal value result is stored in the RAM 305, or when the capacity is large, the external storage device 308 or the like is also used.

  Next, in step S408, as with the weights calculated in step S405 for the four directions based on the interpolation results in the four directions repeated in steps S403 to S404, the vertex and the surrounding three triangles are displayed. Weighting is performed based on the volume obtained by integrating the signal values, and one tetrahedron is formed based on the calculated four tetrahedrons based on the weighted average.

  Finally, in step S409, the six tetrahedrons divided in step S402 are combined to complete a cube, thereby forming an LUT.

  When step S409 ends, the series of operations ends.

(Second embodiment)
In the first embodiment, the weighting calculation performed in step S405 integrates the distance from the vertex and the area, but the present invention is not limited to this. That is, only the weight calculation according to the distance from the vertex may be performed, or only the calculated signal value area of each side may be used. Furthermore, the signal value magnitudes of two of the two sides used when interpolating each grid point may be used as a weight reference, or the magnitude of the signal value of the two points and the distance from the vertex. Of course, the integration may be weighted.

(Third embodiment)
In the first embodiment and the second embodiment, in step S408, for each tetrahedron, triangles were divided in four directions from each plane, and the average was taken. It is not limited to. That is, the triangular division need not be in four directions, but may be limited to one direction, or may be two directions or three directions.

(Modification)
Further, the present invention is not limited to only the apparatus and method for realizing the above-described embodiment, but the software for realizing the above-described embodiment on a computer (CPU or MPU) in the system or apparatus. A case in which the above-described embodiment is realized by supplying a software program code and causing the system or apparatus computer to operate the various devices according to the program code is also included in the scope of the present invention.

  In this case, the program code of the software itself realizes the function of the above embodiment, and the program code itself and means for supplying the program code to the computer, specifically, the program code Is included in the scope of the present invention.

  As a storage medium for storing such a program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, magnetic tape, nonvolatile memory card, ROM, or the like can be used.

  The computer controls various devices according to only the supplied program code so that the functions of the above-described embodiments are realized, and the OS (operating system) on which the program code is running on the computer is also provided. Such program code is also included in the scope of the present invention even when the above embodiment is realized in cooperation with a system) or other application software.

  Further, after the supplied program code is stored in the memory of the function expansion board of the computer or the function expansion unit connected to the computer, the program code is stored in the function expansion board or function storage unit based on the instruction of the program code. A case where the CPU or the like provided performs part or all of the actual processing and the above-described embodiment is realized by the processing is also included in the scope of the present invention.

  In addition, any configuration including at least one of the various feature points described above is included in the scope of the present invention.

The figure which shows an example of the color separation image processing system in embodiment of this invention The figure which shows a part of example of the color separation image processing system in embodiment of this invention The figure which shows each module of the color separation image processing system shown in FIG. The flowchart which shows the operation | movement of the color separation image process in 1st embodiment of this invention. The figure which shows the shape of LUT in embodiment of this invention The figure which shows six tetrahedrons in embodiment of this invention The figure which shows the interpolation direction of the triangle in embodiment of this invention Triangular weighting explanatory diagram in the embodiment of the present invention Prior art illustration

Explanation of symbols

101 setting means 102 tetrahedron forming means 103 triangle forming means 104 three-way interpolation means 105 grid point weighting calculating means 106 weighted averaging means 201 spectrophotometer 202 personal computer 203 display 204 printer

Claims (8)

An image processing apparatus in color adjustment of a color separation image processing apparatus that generates a lookup table for converting a first color space into a second color space,
Control line setting means for setting at least seven control lines connecting the white point and black point of the first color space according to the scale of the lookup table;
Tetrahedron forming means for selecting four of the control lines and forming a tetrahedron in the first color space;
Triangle forming means for forming a triangle using three sides in the tetrahedron,
Three-way interpolation means for interpolating the triangle formed in the triangle forming means from three vertices toward the opposite side in a total of three directions using signal information of two sides sandwiching the vertex;
Grid point weight calculation means for calculating a weight for each grid point to be interpolated in the three-way interpolation means;
A weighted average means for weighted averaging the respective grid point data calculated by the three-way interpolation means and the grid point weight calculation means;
An image processing apparatus characterized by combining a triangle to form a tetrahedron, combining the tetrahedron to form a first color space, and completing a lookup table.   The image processing apparatus according to claim 1, wherein the grid point weighting unit varies according to a distance from an interpolation start vertex of the triangle.   The image processing apparatus according to claim 1 or 2, wherein the grid point weighting means varies in accordance with signal amounts of two points sandwiching an interpolation start vertex among triangles. An image processing method for generating a lookup table for converting a first color space to a second color space,
A control line setting step for setting at least seven control lines connecting the white point and the black point of the first color space according to the scale of the lookup table;
Selecting four of the control lines and forming a tetrahedron in the first color space;
A triangle forming step of forming a triangle using three sides in the tetrahedron;
A three-way interpolation step of interpolating the triangle formed in the triangle formation step from three vertices toward the opposite side in a total of three directions using signal information of two sides sandwiching the vertex;
A grid point weighting calculation step of calculating a weight for each grid point to be interpolated in the three-way interpolation step;
A weighted average step of weighted averaging the respective lattice point data calculated in the three-way interpolation step and the lattice point weighting calculation step,
An image processing method comprising: combining a triangle to form a tetrahedron; combining the tetrahedron to form a first color space; and completing a lookup table.   The image processing method according to claim 4, wherein the grid point weighting step varies according to a distance from an interpolation start vertex of the triangle.   6. The image processing method according to claim 4, wherein the grid point weighting step varies according to the signal amount of two points sandwiching an interpolation start vertex among triangles.   A computer program storage medium readable by a computer storing a computer program showing a processing procedure for realizing each step in the color separation image processing method for a color printer according to any one of claims 4 to 6.   The computer program which showed the process sequence which implement | achieves each process in the image processing method of the color printer in any one of Claim 4 thru | or 6.

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