JP2006173800A - Image processing apparatus and method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a method of computing a color (particular color composite color) obtained by combining two particular colors is not established. <P>SOLUTION: The image processing apparatus is provided with a spectral DB 125 for storing spectral data of particular colors and mixed colors of the particular colors, detects the color mixing region of the particular colors in rendering, refers to a combination table 125a, selects a colorimetry table 125b corresponding to a combination of the particular colors in the color mixing region (S102), acquires spectral data corresponding to the mixed color from the colorimetry table 125b on the basis of a density value of each particular color in the color mixing region (S103), and supplies the spectral data to the rendering processing (S106). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus and method, and, for example, to image processing for reproducing a color mixture region of special colors.

  In general, in printing and publishing work, color proofing is performed using a proof printing machine, an electrophotographic or ink-jet color printer, or a monitor such as a personal computer (PC) before the main printing. Necessary technology in this case is technology relating to color simulation for accurately reproducing the color of the printing press used in the main printing.

  A printing machine generally expresses colors by subtractive color mixing using four color materials of cyan (C), magenta (M), yellow (Y), and black (K), and these four colors are called process colors. A printer or the like that performs color simulation can reproduce color mixing due to process colors of a printing press by color management technology. That is, by using a profile that is a database describing device characteristics, a difference in color reproducibility between devices can be absorbed, and for example, the characteristics of other devices B can be simulated by device A. When applied to color proofing for printing, device A corresponds to a printer or monitor for simulation, and device B corresponds to a printing machine.

  However, a printing machine may use a color material other than a process color called a special color ink in addition to a process color. This is to reduce the cost when it is desired to use a color that is difficult to reproduce in process color synthesis. To simulate this spot color with a printer or the like, first, the spot color is expressed as a color value (Lab value) in a device-independent color space (DIC space) such as L * a * b * based on the name of the spot color. The Lab value is converted to a device-dependent color space value such as a CMYK value.

  Although no method has been established to calculate a color in which two special colors overlap (synthesized) (hereinafter referred to as “special color composite color”), for example, as a method of reproducing a special color composite color, A method of calculating one color value from the color values of the special colors by some method can be considered. However, this calculation may give a correct value in approximation, but it is not an accurate calculation method. For example, if the cyan value when converting a special color to CMYK value is 90%, and the cyan value when converting another special color to CMYK value is 80%, the cyan value when these two special colors are combined The value is 170% if the concentration is simply added, but the upper limit of the concentration value is 100%, and a contradiction arises.

  Even in the case of DIC space, color spaces such as L * a * b * and XYZ, which are often handled in color management, are non-linear, so it is impossible in principle to calculate color composition by summation or multiplication.

Japanese Unexamined Patent Publication No. 4-362869 Japanese Patent Laid-Open No. 2001-136401

  An object of the present invention is to accurately reproduce a color mixture region of special colors.

  The present invention has the following configuration as one means for achieving the above object.

  An image processing apparatus according to the present invention includes: a memory that stores spectral data of spot colors and mixed colors of spot colors; a rendering unit that renders image data; a detection unit that detects a mixed-color region where spot colors are mixed by the rendering; and the mixed color And supplying means for acquiring spectral data corresponding to the color mixture from the memory based on the density value of each spot color in the region and supplying the spectral data to the rendering means.

  An image processing method according to the present invention is an image processing method of an image processing apparatus having a memory for storing spectral data of spot colors and mixed colors of spot colors, and a rendering unit for rendering the image data. An area is detected, spectral data corresponding to the mixed color is acquired from the memory based on the density value of each spot color in the mixed color area, and supplied to the rendering unit.

  According to the present invention, it is possible to accurately reproduce a color mixture region of special colors.

  Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

[Configuration of Printing Server]
FIG. 1 is a block diagram illustrating a configuration example of a printing server according to the embodiment.

  The printing server 120 can be realized, for example, by supplying software that executes processing described later to a computer device having a CPU, RAM, and ROM, but of course, each functional block described later is configured by hardware, It can also be realized by combining these functional blocks.

  The printing server 120 is connected to the network 101 via a network interface card (NIC) 127, and data (hereinafter referred to as “PDL data”) written in a page (or band) description language including information of spot colors from the client PC 100. The CMYK value output data obtained by rendering the PDL data is sent to the printer 102, and printing is executed. Note that the printing server 120 outputs CMYK value data when color calibration is performed by the printer 102, but outputs RGB value data when color calibration is performed by the monitor.

  The print response processing unit 121 of the printing server 120 responds to the print request of the client PC 100 input from the network 101 and performs reception processing of PDL data transmitted by the client PC 100. The spooling processing unit 122 temporarily stores the PDL data received by the print response processing unit 121 in a spool area allocated to a RAM or a hard disk in the printing server 120. As will be described in detail later, the print processing unit 123 reads PDL data from the spool area, analyzes it, and renders it. In addition, the control unit 126 controls the processing of each unit via the system bus 128.

  FIG. 2 is a block diagram illustrating a configuration example of the print processing unit 123.

  The PDL data 134 read by the print processing unit 123 is analyzed by the interprinter 130 and converted into an intermediate code. After the intermediate code processing unit 131 performs necessary processing, for example, rearrangement, imposition processing, etc. Then, rendering processing is performed by the rendering processing unit 132 and output as output data 135. The rendering processing unit 132 examines objects such as characters, line drawings, graphics, and tables of the input intermediate code, and causes the overlapping region processing unit 133 to process a portion where the objects overlap (overlapping region).

  The overlapping region processing unit 133 refers to the intermediate code for the portion where the spot colors overlap in the overlapping region, and instructs the spot color processing unit 124 with the name and density value of those spot colors. Although details will be described later, the spectral database (DB) 125 The color value (for example, Lab value) of the special color composite color is acquired based on the spectral data stored in the. The spectral DB 125 is stored in a memory such as a hard disk of the printing server 120.

  In this way, the rendering processing unit 132 can obtain the color value of the special color composite color of the overlapping region, performs rendering processing based on the obtained color value, and the CMYK value corresponding to the special color composite color of the overlapping region. Output data 135 is generated.

  Note that the conversion from spectral data to Lab values, for example, is described in the Color Engineering Dictionary, etc., but the three color perceptual stimulus characteristics obtained by multiplying the spectral data by the color matching function are each integrated and converted into XYZ values. What is necessary is just to convert a value into Lab value.

[Split area]
FIG. 3 is a conceptual diagram illustrating rendering processing.

  The graphic data included in the intermediate data is applied differently depending on the transparency attribute of the graphic. In the case of an opaque figure, it is not necessary to specify an overlapping area. For example, after drawing the blue rectangle A shown in FIG. 3 and then drawing a red rectangle B on top of it, the overlap area of both rectangles is overwritten with the red color of the rectangle B, so There is no need to process colors. In other words, it is not necessary to identify and divide overlapping areas for opaque figures.

  On the other hand, in the case of a transparent figure, the overlapping area needs to be drawn with overlapping colors (mixed colors), and the area needs to be specified and divided. For example, if the blue triangle D is overlapped with the red triangle C shown in FIG. 3, the color of the overlapping area C + D becomes purple, so the overlapping area C + D needs to be drawn in purple, overlapping Region C + D is identified and divided.

[Get spectral data of special color composite color]
FIG. 4 is a diagram for explaining a method of acquiring the spectral data of the special color composite color.

  In order to check the color mixture state of the two special colors, as shown in FIG. 4, the mixed color patch is printed by changing the density of each special color stepwise. In that case, it is ideally printed with a combination of a printing machine to be color calibrated and recording paper, but it may be approximated by printing with a combination of another printer (for example, the printer 102) and general-purpose recording paper. Good.

  When the density of each spot color is changed in the range of 0 to 100% in increments of 25%, five patches are obtained for one spot color, and a sample chart 301 having 25 patches is obtained by combining the two spot colors. It ’s done. Then, if the sample chart 301 is colorimetrically measured, for example, every 5 or 10 nm in the visible range by the colorimeter 302, spectral data 303 indicating the spectral reflectance of the visible range for the combination of the density values of the two special colors is obtained. Obtainable. Of course, the spectral data between the density values of each patch can also be obtained by interpolation calculation of the spectral data 303.

  FIG. 5 is a diagram for explaining the spectral data interpolation calculation.

  In the sample chart 301 shown in FIG. 5, for example, a special orange color is arranged in the vertical direction and a special green color is arranged in the horizontal direction. In the following, spectral data N of a certain wavelength λ of the special color composite color when the density of the orange color is 60% and the density of the green color is 70% (hereinafter referred to as “OG (0.6, 0.7)”) is calculated. The spectral data of OG (0.5, 0.5) is L1, the spectral data of OG (0.75, 0.5) is L2, the spectral data of OG (0.5, 0.75) is L3, and the spectral data of OG (0.75, 0.75) is L4. What is necessary is just to obtain | require the spectral data of the patch located in the middle of four patches.

  As a method of interpolation calculation, the orange color is 60% according to the orange density change from OG (0.5, 0.5) to OG (0.75, 0.5), that is, the spectral data M1 at OG (0.6, 0.75) is linearly interpolated. Similarly, in accordance with the change in orange density from OG (0.5, 0.75) to OG (0.75, 0.75), the orange color is 60%, that is, spectral data M2 at OG (0.6, 0.75) is obtained by linear interpolation. Then, according to the change in density of the green color from OG (0.6, 0.5) to OG (0.6, 0.75), the green color is 70%, that is, spectral data N of OG (0.6, 0.7) is obtained by linear interpolation.

  As for the special colors, about several thousand colors are used, but there are about several hundred sets mainly used in combination. Create a sample chart 301 of these mainly used special color combinations, register the color measurement result table data as a color measurement table, and register the combinations of the special color names of each table data as a combination table in the spectral DB 125. deep.

[Special Color Processing Section]
FIG. 6 is a flowchart showing the processing of the spot color processing unit 124.

  The spot color processing unit 124 receives the names of two spot colors (for example, names of orange, green, red, etc., Munsell symbol, PANTONE (R) name, etc.) from the overlapping area processing unit 133 (S101). With reference to the combination table 125a registered in the spectral DB 125 shown in FIG. 7, the colorimetric table 125b corresponding to the two spot colors is selected (S102). Then, the density values of the two special colors (or values before and after the density values) are input to the color measurement table 125b to obtain corresponding spectral data (S103). In the case of a density value that matches the step value of the color measurement table 125b, if the density value is input to the color measurement table 125b, spectral data of the spot color composite color can be obtained, but if it does not match the step value, A value that matches the grid value of the table in the vicinity of the density value is input to the color measurement table 125b, and a plurality of spectral data necessary for interpolation calculation of the special color composite color is acquired.

  Then, it is determined whether or not to perform interpolation calculation (S104) .If interpolation calculation is required, the above-described interpolation calculation is performed using the acquired spectral data (S105), and the acquired spectral data or the interpolated spectral data is calculated. The color value of the special color composite color is calculated and output to the overlapping area processing unit 133 (S106).

  In this way, the color value for reproducing the special color composite color when combining each arbitrary special color with an arbitrary density value is accurately calculated by the spectral database storing the spectral data of the color mixture result of the special color and the interpolation calculation. Can be sought.

  In the above, an example in which 25 color patches are used as the sample chart 301 has been described, but of course, a sample chart composed of more patches may be used. Furthermore, the device for color calibration is not limited to a printer, and the same effect can be obtained with other output devices such as a monitor. For print media, subtractive color mixture is applied.For additive color model monitors, etc., the color mixture model is different, but the same effect can be achieved if the purpose of configuring the system matches with color simulation. It is possible to obtain.

[Other embodiments]
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to.

  Also, an object of the present invention is to supply a storage medium (or recording medium) on which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. Needless to say, the CPU of the expansion card or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

  When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above.

Block diagram showing a configuration example of a printing server, Block diagram showing a configuration example of the printing processing unit, A conceptual diagram explaining the rendering process, The figure explaining the method of acquiring the spectral data of a special color composite color, The figure explaining the interpolation calculation of spectral data, A flowchart showing processing of the spot color processing unit; It is a figure which shows an example of a combination table.

Claims (7)

A memory for storing spectral data of spot colors and mixed colors of spot colors;
A rendering means for rendering image data;
Detecting means for detecting a mixed color region in which the special colors are mixed by the rendering;
An image processing apparatus comprising: a supply unit that acquires spectral data corresponding to the color mixture from the memory based on a density value of each spot color in the color mixture region and supplies the spectral data to the rendering unit. Furthermore, input means for inputting image data for color calibration,
2. The image processing apparatus according to claim 1, further comprising an output unit that outputs the print data generated by the rendering unit to a printing apparatus.   3. The image processing apparatus according to claim 1, wherein the memory includes a plurality of color measurement tables and a combination table indicating a correspondence relationship between combinations of the color measurement tables and the spot colors.   The supply unit refers to the combination table, selects a colorimetric table corresponding to a combination of spot colors in the mixed color area, and selects a density value of each spot color or a value before and after the density value. 4. The image processing apparatus according to claim 3, further comprising an acquisition unit that acquires spectral data by inputting to a colorimetry table. An image processing method of an image processing apparatus having a memory for storing spectral data of spot colors and mixed colors of spot colors and a rendering unit for rendering image data,
Detecting the special color mixture area by the rendering,
An image processing method comprising: obtaining spectral data corresponding to the color mixture from the memory based on a density value of each spot color in the color mixture region and supplying the spectral data to the rendering unit.   6. A program for controlling an image processing apparatus to realize the image processing according to claim 5.   7. A recording medium on which the program according to claim 6 is recorded.

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