JP2006159709A - Image outputting device/method and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image outputting device which outputs an image suited for spectral color matching, only in case image data enabling the spectral color matching to be performed, is entered, and thus can achieve the high precision spectral color matching, fully using the performance of an ink set. <P>SOLUTION: The image outputting device comprises the following components: an input means which inputs color image data, a decision means which decides the attribute of entered image data, a first image outputting means which uses the ink set for the spectral color matching, a plurality of the ink sets including a second image outputting means which uses a different ink set from the first image outputting means, and a selection means which selects the ink set based on the attribute of the image data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a color image output apparatus such as a color facsimile, a color printer, and a color copying machine, and more particularly to an image output apparatus, an image output method, and a recording medium that output an input color image signal with an optimal ink set.

Conventional color printers generally perform color reproduction based on conditional colors on input data. In this color reproduction based on the condition color matching, the color reproduction is performed using the CIE color matching function so that the perceived color is the same even if the spectral waveform is different. There was a problem that the appearance of the color would change if it changed. For example, a product catalog prints image data taken in a specific lighting environment, but does not reflect the spectral reflectance characteristics of the actual product. I didn't know what kind of color it looked like.
In order to overcome this situation, in recent years, there has been an active movement of performing color reproduction that matches spectrally with the progress of input devices and output devices. For example, in terms of imaging technology, multi-channel photographing machines (multi-band cameras), in particular, photographing machines having a number of channels that can restore the spectral waveform to be photographed with sufficient practical accuracy are being put into practical use. This is a camera that captures a subject and obtains a plurality of image data (multiband image data) in a wavelength region (multiband) that transmits a plurality of types (mostly four or more types) of light.
These are described in Non-Patent Document 1 and the like. Since the multiband image data photographed by the multiband camera can estimate the spectral waveform for each pixel, it is possible to accurately simulate the color appearance in various illumination environments.
Further, in terms of the image forming method, in Patent Document 1, a cyan, magenta, and yellow pigment are mixed, a gray ink having a spectral reflectance close to a flat is formed, and this gray ink is added and used. A proposal has been made to eliminate the phenomenon (metamerism) that the color of a printed material viewed using the color and the color of the same printed material viewed using another light source are not the same.

Further, Patent Document 2 describes a method of selectively using spectral waveform chromaticity reproduction and waveform reproduction depending on the application when a multiband image is input. When the spectral waveforms are matched, the original color appearance under various observation illuminations can be reproduced with copies.
In recent printers, various ink sets have been developed for various effects as well as spectral color matching. In particular, there are many types of inkjet printers capable of printing six colors using light cyan or light magenta, and output with high image quality with graininess below the perceptual limit is possible. Patent Document 3 proposes printing in seven colors including cyan, magenta, yellow, black, red, blue, and green in order to prevent bleeding due to an increased amount of ink.
Further, in Patent Document 4, “a resin-containing pigment ink containing a pigment that is dispersible in water via a resin and water” corresponding to the hue, and “a pigment that can be dispersed in water without a dispersant and water A self-dispersing pigment ink containing “,” and a method of performing ink jet recording using a resin-containing pigment ink for inkjet paper and using a self-dispersing pigment ink for plain paper has also been proposed. ing.
In Patent Document 5, the colorant of ink A is mainly a dye, and the colorant of ink B is mainly a pigment. When printing on plain paper, only with ink B, and when printing on glossy paper A technique of printing using ink A and / or ink B is shown.
JP 2003-192967 A JP 2000-333186 A JP 10-44473 A JP 2003-213180 A JP 2004-010640 A "Optics Vol.11, No.6, pp.573-578 (1982), Miyagawa et al."

As described above, in recent years, many ink sets have been actively developed for the purpose of spectral color matching and image quality improvement. However, when many ink sets are used, the method of using them becomes complicated, and the user uses the wrong ink set, which causes a problem that the merit cannot be fully utilized. In particular, when the number of inks in the ink set is limited, it is necessary to set an appropriate ink set depending on whether importance is attached to the accuracy of spectral color matching or image quality aspects such as graininess are considered.
For example, in the case of a gray ink composed of a mixture of cyan, magenta, and yellow colorants as in the technique of Patent Document 1 and a gray ink composed of carbon black as a commonly used colorant, the spectral reflectance characteristics thereof are used. Are different. Therefore, even if there is an image output means that can select and use both gray inks, it has been difficult to determine which ink to use. Furthermore, as can be seen in Patent Document 3, when a large number of chromatic inks can be used, various combinations are possible even if spectral color matching is performed, and the problem becomes more complicated. Therefore, the present invention has been made in consideration of the above-described circumstances, and performs output suitable for spectral color matching only when input with image data capable of spectral color matching, and fully utilizes the performance of the ink set. An object of the present invention is to provide an image output device, an image output method, and a recording medium that can perform spectral color matching with high accuracy.

In order to solve the above-described problems, the invention described in claim 1 includes an input unit that inputs color image data, a determination unit that determines an attribute of the input image data, and an ink set for spectral color matching. A plurality of ink sets including a first image output means to be used and a second image output means to use an ink set different from the first image output means; and the ink set based on the attribute of the image data An image output apparatus having a selection means for selecting is the most important feature.
According to a second aspect of the present invention, the selection means is mainly characterized by an image output apparatus that determines the ink set to be used based on whether or not the image data includes multiband data.
According to a third aspect of the present invention, the chromatic ink included in the spectral color matching ink set is mainly characterized by an image output apparatus having a hue difference of 30 degrees or more.
According to a fourth aspect of the present invention, the spectral color matching ink set is mainly characterized by an image output device including cyan, magenta, yellow, black, orange, and green.
According to a fifth aspect of the present invention, an image output apparatus in which a chromatic ink included in an ink set different from the first image output unit includes an ink having a hue difference of 15 degrees or less is a main feature. To do.
According to a sixth aspect of the present invention, the ink set different from the first image output means is mainly characterized by an image output device including light cyan ink or light magenta ink.

In the invention described in claim 7, the ink set can be replaced,
An image output apparatus including a notification unit that notifies the user of the selected ink set when the output unit selected by the selection unit is unusable is a main feature.
According to an eighth aspect of the present invention, when the image data includes multiband data, an evaluation unit that evaluates metamerism characteristics for each of the plurality of ink sets, and a result of the evaluation unit The main features are a first determination unit that determines an ink set and an image output device that outputs an image using the ink set determined by the first determination unit.
In the invention according to claim 9, the evaluation unit includes a look-up table whose output value is a metamerism characteristic value when the image data is reproduced with the plurality of ink sets. The main feature of the image output apparatus is to execute a memory map interpolation operation to obtain a metamerism characteristic value.
In the invention according to claim 10, input data is color-converted using color conversion parameters corresponding to each of the plurality of ink sets, and a plurality of observations are performed on the color difference between the image data and the reproduced color after color conversion. The main feature is an image output apparatus that obtains conditions and uses statistical values of color differences under a plurality of observation conditions as metamerism characteristic values.
In the invention according to claim 11, the attribute information is color gamut information of the image data, and includes second determination means for determining an ink set to be used based on the read color gamut information. The main feature is an image output device.
According to a twelfth aspect of the present invention, the second determining means is mainly characterized by an image output device including ink set characteristic storage means for storing color gamut information corresponding to each ink set.

According to a thirteenth aspect of the present invention, the second deciding means evaluates the ink gamut relationship between the color gamut of each ink set read from the ink set characteristic storage means and the color gamut of the input image data. The main feature is an image output device for determining a set.
In the invention described in claim 14, the step of determining whether or not the input image data is multiband data. If the image data is multiband data, the image data is used for spectral color matching. An image output that is converted into an ink set control signal and output, and if the image data is not multiband data, the image data is converted into an ink set control signal other than the spectral color matching ink set and output. Features the method.
In the invention according to claim 15, a step of evaluating a metamerism characteristic for each of a plurality of ink sets based on image data, a step of determining an ink set based on an evaluation result of the metalism characteristic, An image output method including a step of outputting an image using the ink set determined by the determination step of determining the ink set is a main feature.
In the invention according to claim 16, a color gamut information acquisition step of reading color gamut information of input image data, a step of determining an ink set based on the color gamut information acquired in the color gamut information acquisition step, An image output method comprising a step of outputting image data using an ink set determined based on the color gamut information.
According to a seventeenth aspect of the present invention, there is provided a recording medium on which a program for converting an output signal based on input image data is recorded, the procedure for reading attribute information of the image data, and the attribute information Recording medium storing a program for causing a computer to execute a procedure for determining whether or not multiband data is included and a procedure for determining an ink set to be used according to a determination result of whether or not multiband data is included Is the main feature.

According to the present invention, since the optimum ink set is determined based on the type and color characteristics of the input image data, high-precision spectral color matching that fully utilizes the performance of the ink set is performed. I can do it. In addition, since different ink sets are used depending on whether multiband data is included in input image data, an image can be output using an optimal ink set when spectral color matching is possible.
Further, since an ink set having chromatic ink having a hue difference of 30 degrees or more is used, the metamerism phenomenon can be faithfully reproduced. Further, since an ink set including cyan, magenta, yellow, black, orange, and green is used, high-precision spectral color matching can be performed.
In addition, since inks having substantially the same hue are included, high-quality image output with excellent gradation and graininess can be performed on image data that does not require spectral color matching. In addition, since light cyan ink or light magenta ink is included, image output with excellent graininess can be performed. In addition, when an ink set that is not suitable for the attribute of the image data is mounted, the user is notified, so that the capability of the image output apparatus can be utilized to the maximum.
In addition, since metamerism characteristics are predicted for a plurality of ink sets, an ink set suitable for input image data can be used even when a large number of ink sets can be used. Further, since the metamerism characteristic value is held in the lookup table, the metamerism characteristic value can be calculated at high speed. In addition, since the ink set is determined using the statistical values of the color differences under a plurality of viewing conditions, high-precision spectral color matching can be performed.
In addition, since the ink set is determined based on the color gamut, it is possible to easily determine an ink set that minimizes colors that cannot be reproduced. In addition, since ink set characteristic storage means for storing color gamut information corresponding to each ink set is provided, the color gamut for each ink set need not be calculated each time. In addition, since the conjugation relationship between the color gamut of each ink set and the color gamut of the input image data is evaluated, an ink set suitable for the color range of the input image can be easily determined.

The best mode for carrying out an image output apparatus, an image output method, and a recording medium of the present invention will be described below in detail with reference to the drawings. The description of the best mode for carrying out the image output apparatus of the present invention includes the description of the best mode for carrying out the image output method of the present invention.
[First Embodiment]
FIG. 1 is a block diagram for explaining a schematic functional configuration of a printer 1 which is a first embodiment of an image output apparatus of the present invention. Here, the printer 1 is an inkjet color printer, but may be a color printer using another method such as an electrophotographic method. The printer 1 includes an input unit that inputs color image data, a determination unit that determines an attribute of the input image data, a first image output unit that uses an ink set for spectral color matching, and a first image. A plurality of ink sets including a second image output means using an ink set different from the output means; and a selection means for selecting an ink set based on an attribute of the image data.
As shown in FIG. 1, the printer 1 is roughly composed of a control device 11 and a printing mechanism unit 12. The control device 11 includes an interface 13, a signal processing unit 14, a drive circuit unit 15, and the like, and performs printing processing on printing paper while controlling the printing mechanism unit 12 based on print job data transmitted from an external host computer. Execute. The interface 13 provides a function for performing communication with a host computer connected via a cable.
The connection with the host computer may be a network connection, a serial or parallel connection, and can be selectively used as appropriate. The printer 1 typically receives print job data from the host computer via the interface 13 and executes print processing. However, the printer 1 reads the print target data from a memory card attached to the printer 1 and prints it. Processing may be executed. In this way, the function of input means for inputting color image data is realized.

The signal processing unit 14 includes a CPU 141, a ROM 142, a RAM 143, and the like that are connected to each other via an internal bus. The CPU 141 executes various control programs stored in the ROM 142 while using the RAM 143 functioning as a main storage device, and controls the printer 1 in an integrated manner. For example, an output image generation function, a print control function, a user interface function, and the like are realized by the control program.
The output image generation function is a function for generating image data that can be sent to the print mechanism unit by performing image processing described later while interpreting print job data received via the interface 13. The generated image data is written into an image buffer memory configured as a part of the RAM 143 and temporarily held.
The print control function is a function for controlling the drive circuit unit 15 based on image data written in the image buffer memory. The drive circuit unit 15 includes control circuits for controlling the print head 121, the carriage 122, and the transport roller 123 of the printing mechanism unit 12, and operates according to control commands from the signal processing unit.
The user interface function is a function that provides an interactive operating environment to the user through the user interface unit 16. The user interface unit 16 typically includes various buttons, an LED display lamp, a liquid crystal panel, and the like. The printing mechanism unit 12 is configured around a mechanical member that operates when printing is performed. Specifically, the printing mechanism unit 12 includes a printing head 121 that records on printing paper, a carriage 122 that mounts the printing head 121, a conveyance roller 123 that conveys the printing paper, and the like.
The drive circuit unit 15 is for driving and controlling the mechanical members of the print mechanism unit 12 based on the generated image data. The print head drive circuit 151 is configured according to the configuration of the print mechanism unit 12. , A carriage driving circuit 152, a conveyance roller driving circuit 153, and the like.

FIG. 2 is a diagram illustrating a schematic configuration of the printing mechanism unit 12. The print head 121 includes a plurality of recording elements arranged in the main scanning direction for each color. The carriage 122 on which the print head 121 is mounted is attached to an endless belt 21 stretched by two pulleys, and the carriage motor 22 is driven to rotate so that the axial direction (mainly along the carriage shaft 23). Reciprocate in the scanning direction). The printing paper P is transported in the sub-scanning direction by a transport roller 123 that is rotationally driven by a transport motor 24.
The carriage 122 is provided with a cartridge slot. The ink cartridges 25 containing the ink liquid for each color are detachably set in the corresponding cartridge slots, and supply the ink liquid to the recording elements of the print head 121. In the printer 1, yellow (Y), magenta (M), cyan (C), light cyan (Lc), light magenta (Lm), black (K), orange (O), and green (G) are used as the ink cartridge 25. It can be attached and detached freely. The carriage 122 has six cartridge slots, and only six types of ink cartridges can be mounted simultaneously.
In the printing mechanism unit 12 configured as described above, the print head 121 performs main scanning on the printing paper P conveyed in the sub-scanning direction in accordance with the rotation operation of the conveyance motor 24 in accordance with the rotation operation of the carriage motor 22. Ink droplets are ejected from the recording elements driven by the print head drive circuit 151 while reciprocating in the direction, and are deposited on the printing paper P to form dots, and the image is reproduced on the printing paper P. Can do.
The ink cartridge 25 includes a rewritable nonvolatile memory (EEPROM) (not shown). This EEPROM stores predetermined cartridge information. The predetermined cartridge information is, for example, type information of the ink (ink cartridge) that is stored. When such an ink cartridge 25 is set in the cartridge slot, the EEPROM of the ink cartridge 25 is connected to the signal processing unit 14, and the signal processing unit 14 accesses the EEPROM to obtain necessary information. Can be read.

Next, the processing operation of the printing system in this embodiment will be described. FIG. 3 is a flowchart for explaining the flow of processing during printing by the printer 1 according to this embodiment. When the printer 1 receives the print request, the print job data is sent to the signal processing unit 14 and converted into an output image according to the procedure of the flowchart of FIG.
The print request is received, for example, in the form of print job data from the host computer. As shown in FIG. 3, the print job data is typically described on the assumption that various attribute information such as the color space attribute, size, and position of the image data is written in the header portion, and then the content of the image data continues. To do. Here, the color space attribute of the print job data is generally RGB format data created by an application on the host computer. However, in this embodiment, various data formats can be handled. In addition to document data in the format, multiband data obtained by shooting with a multiband camera can be printed.
Therefore, as the color signal attribute, in addition to the general monochrome binary, RGB color, and CMYK color, in the present invention, a color signal attribute called Multi color is further defined and processed. In the multi color, the larger the number of channels, the more accurately the spectral reflectance of the object to be photographed can be restored. However, considering the simplicity of the apparatus and the shortening of the photographing time, about 6 to 20 channels are better. According to the computer simulation, the practical number of channels seems to be about six.

First, in step S100, the printer 1 is initialized.
A specific example of the initialization operation will be described with reference to the flowchart of FIG.
In the initialization process, the signal processing unit 14 accesses each of the EEPROMs provided in the ink cartridge 25 in step S101, and obtains ink cartridge type information. Next, based on the information described in the header of the image data included in the received job data, the color space attribute and the output mode information are read, and the operation of the printer 1 is initialized according to the read information. . Specifically, in step S102, all the color space attributes in the job data are read to determine whether multi-color image data is included.
Here, determination of whether or not multi-color image data is included will be described. The received job data is held in the RAM 143 in the signal processing unit 14. A color space attribute is described in the header portion of the job data. The determination of whether the image data is multi color image data is performed by the CPU of the signal processing unit 14 reading the header information of the job data held in the RAM 143 and determining whether there is a description of a multi image in the header. If Multi color is described in the header portion, the job data includes Multi color image data.
When job data consists of multiple objects, the color signal attribute is defined for each object, so the color described in the header of the object data for all object data included in the job data. Read signal attributes. If there is at least one object in which the color signal attribute of Multi color is defined among a plurality of object data, a Multi color image is included. Thereby, a determination means for determining the attribute of the input image data is realized.

Returning to FIG. 4, next, in step S103, the ink set is confirmed. As a method for checking the ink set, it is checked whether or not an ink set suitable for the determination result is mounted based on the type information of the ink cartridge. For example, when spectral color matching is performed in the printer 1, output is recommended with six ink cartridges C, M, Y, K, O, and G. For RGB data, C, M, Y, K, Assume that it is recommended to output with six cartridges of Lc and Lm. In this case, when the input image data includes multi-color image data, it is determined whether or not six ink cartridges C, M, Y, K, O, and G are mounted. In this way, the function of the selection means for selectively using the first image output means using the spectral color matching ink set and the second image output means using a different ink set from the first image output means is provided. It has been realized.
As a result of the determination, if an appropriate ink set is not mounted, a display is made to prompt the user to replace the ink set, and when the user replaces the ink cartridge, the output operation is resumed. At this time, the selected ink set is notified to the user by the notification means. Note that if the user does not have a spectral color matching ink cartridge, for example, and the user wants to output forcibly installed C, M, Y, K, Lc, and Lm ink sets, it is already installed. You may make it permit the output by an ink. It is also possible to set a mode in which the above ink set confirmation operation is not performed on the printer driver. In this case, output is performed using the color conversion parameters for the installed ink set as described later. To do.
When the ink set to be used for output is determined by the above procedure, the color conversion parameter for executing the color conversion process is determined in step S104. The color conversion table is a multidimensional lookup table in which input data and desired printer output data when color reproduction is performed on printing paper are associated, and is typically stored in the ROM 142 of the printer 1 or the like.

When the color conversion parameter is determined, the address of the ROM 143 in which the color conversion parameter is described may be set in a predetermined memory space of the RAM 143 according to the color attribute of the input image data and the ink set to be used. Examples of such combinations are shown below.
(1) When using CMYKOG ink set a) Multi-color image data: color conversion parameter for spectral waveform matching b) Other than multi-color image data: Color conversion parameter for image-oriented mode (2) When using CMYKLmLc ink set All Data: Color conversion parameter for image quality emphasis mode (3) When using other ink sets If CMYK ink is included, color conversion parameter for CMYK output If any ink of CMYK is not included, Stops the output operation.
In the pattern (1), two types of color conversion parameters are used by switching between color conversion parameters for emphasizing image quality and color conversion parameters for spectral waveform matching in image data other than multi-color and multi-color. In Multi color, since the input signal is 6 channels, the color conversion parameter for spectral waveform matching is a 6-input 6-output look-up table, and the CMYKOG output value of the grid point is designed so that the matching between the input waveform and the output waveform is the best. ing.
Here, the design of the CMYKOG output value will be described. In order to match the colors in any observation illumination environment, it is necessary to perform spectral color reproduction that reproduces the same spectral reflectance as that of the input target. When image data is received in multiple colors, the spectral reflectance of the object being photographed can be approximately reproduced, so that the spectral waveform similar to the original spectral reflectance can also be reproduced in the output object, so that it does not depend on the observation light source. Color matching can be realized. Therefore, when the input is multi-color, it is aimed to reproduce the color so that the input and output spectral waveforms match as much as possible. As a specific example of the output value determination method, an error of the output spectral reflectance calculated from the estimated input spectral reflectance and the CMYKOG output value is obtained, and the value of the CMYKOG output value that minimizes the error is obtained by a convergence operation. A method is conceivable.

Now, for input data other than multi-color, if RGB input CMYKOG output is used, a 3-input 6-output look-up table is used, and the CMYKOG output value at that grid point matches the input RGB color value, and ink The parameter design emphasizes image quality, such as using output values that are superior in terms of consumption and graininess. In the case of an input other than the multi color (for example, RGB image), it is impossible to estimate the spectral reflectance of the photographic object, and thus it is impossible to reproduce the color so that the spectral waveforms match.
For this reason, color matching for matching chromaticity values as in the past is performed. However, since there are six types of ink, there are a plurality of ink combinations for matching the chromaticity values. Therefore, parameter design is performed so that output values are combined with an emphasis on image quality.
For example, there are a method of reproducing with green ink and a method of reproducing with CY as green color reproduction. If reproduction is better with CY than with G ink, reproduction is performed with CY. To do. If there is not much difference between the two, reproduction is performed with G ink that requires a small amount of ink.
By the way, the parameters include light cyan (Lc) and light magenta (Lm) in this ink set. Therefore, in the highlighted portion where the graininess is conspicuous, do not use C and M inks as much as possible. Are used to output C and M inks in a high-density color gamut.

In the example of (2), since the effect of performing spectral color matching is poor, color conversion parameters that emphasize the same image quality are used for both multi-color images and non-multi-color images. However, when the input image data is multi-color, since there are 6 inputs, a 6-input 6-output look-up table is used, and for non-multi-color image data, a 3-input 6-output look-up table is used. According to this method, even when the user forcibly uses the CMYKLmLc ink set, the output operation can be continued.
In the above example (3), for example, a case where a combination of ink sets originally not assumed by the printer 1 such as CMYKLmG is mounted is applicable. Even in such a case, if only CMYK is used, the image can be converted to an image without failure, so that the output operation can be continued by printing with CMYK. However, for a combination such as CMLmLcOG, since there is no YK, the color reproducibility is remarkably deteriorated, so basically output is not permitted.

As described above, in the present invention, a color conversion parameter suitable for the input image data is set depending on whether or not the input image data includes the multi-color attribute. However, in step S105, other than the color space attribute is set. In addition, the output mode is also read and initialization is performed. The output mode is various setting information set by the printer driver or the like. For example, the output mode corresponds to information such as the paper type and image quality mode set on the printer driver. With this information, the color conversion parameters can be controlled more precisely according to the paper type, and the mask pattern for dither processing can be switched.
When the initialization is completed, in step S110, the color signal of the job data is converted into a color signal that can be output by the printer 1 using the color conversion parameter set in step S104. As the color conversion method, a color conversion processing device using a known memory map interpolation method can be used. The memory map interpolation method uses a multi-dimensional lookup table set as a color conversion profile. That is, when using the CMYKOG ink set for spectral color matching, the memory map interpolation calculation is performed by switching the color conversion parameter for each of the multiband data and the RGB image data.
When using the CMYKLmLc ink set, after converting data other than Multi data into CMYK, the C and M signals are decomposed into a lookup table into C + Lc and M + Lm. Since the interpolation parameter cannot be used, color conversion is performed using normal color conversion parameters. For example, in spectral color matching, since an ink set composed of six colors of C, M, Y, K, O, and G is used, color conversion is performed using a 6-input 6-output color conversion table. . In the case of an RGB signal, a color conversion parameter with 3 inputs and 3 outputs is used.
When the CMYKLmLc ink set is used, if the input image data is multi data, color conversion cannot be performed as it is. Therefore, the multiband data is once converted into an RGB image or a Lab image, and then converted into a printer signal by memory map interpolation calculation.
Next, in step S120, the job data in the command format is sequentially converted into raster data that matches the resolution of the printer 1. At this time, object data and color space information described in the print job data are simultaneously identified, and raster data having attribute information is also generated. As described above, the rasterization process is performed after the color conversion, so that even when the number of bands of the Multi data is large, there is no shortage of raster development memory.
When the rasterization is completed, halftone processing for reducing the number of gradations that can be reproduced by the printer 1 is performed in step S130, and the halftone processing is written into an image buffer memory configured as a part of the RAM 143. At this time, adaptive processing can be performed by switching the dither matrix of halftone processing by reading the contents of the attribute information bitmap.
When the creation of output data to be output by the printer 1 is completed by the above operation, the data is transmitted to the printing mechanism unit and the above-described output operation is started.
In the above-described embodiment, an example of switching between the CMYKOG ink set and the CMYKLmLc ink set has been described. However, the present invention is not limited to this, but when the spectral waveforms are matched, the chromatic ink hue difference is as much as possible. A larger one is preferable, and an ink set having a hue difference of 30 degrees or more is used. On the other hand, in an ink set in which image quality is emphasized, it is often better to use light ink and the graininess is better, and if two types of ink having the same hue are used, the number of gradations increases, so that the image quality can be improved. Therefore, when the image quality is important, it is desirable to include ink having a hue difference of 15 degrees or less.

As described above, according to the first embodiment, since the optimum ink set is determined based on the type and color characteristics of the input image data, high accuracy that fully utilizes the performance of the ink set. Spectral color matching can be performed. In addition, since different ink sets are used depending on whether multiband data is included in input image data, an image can be output using an optimal ink set when spectral color matching is possible.
Further, since an ink set having chromatic ink having a hue difference of 30 degrees or more is used, the metamerism phenomenon can be faithfully reproduced. Further, since an ink set including cyan, magenta, yellow, black, orange, and green is used, high-precision spectral color matching can be performed. In addition, since inks having substantially the same hue are included, high-quality image output with excellent gradation and graininess can be performed on image data that does not require spectral color matching.
In addition, since light cyan ink or light magenta ink is included, image output with excellent graininess can be performed. In addition, when an ink set that is not suitable for the attribute of the image data is mounted, the user is notified, so that the capability of the image output apparatus can be utilized to the maximum.

[Second Embodiment]
In the first embodiment described above, the output method in which two types of ink sets are switched and used in accordance with the attribute of the input color signal has been described. In this embodiment, an example in which more ink sets can be used will be described. Here, the ink cartridge 25 includes yellow (Y), magenta (M), cyan (C), light cyan (Lc), light magenta (Lm), black (K), orange (O), green (G), A total of 11 types of ink can be used: blue (B), matte gray (Mg), and photo gray (Pg).
However, six types of ink cartridges can be simultaneously mounted, and ten types of usable ink sets are CMYKLcLm, CMYKOG, CMYKOB, CMYKGB, CMYKMgO, CMYKMgG, CMYKMgB, CMYKPgO, CMYKPgG, and CMYKPgB.
Here, the matte gray Mg is a gray ink composed by diluting carbon black, and has a flat spectral reflectance characteristic regardless of the wavelength. On the other hand, photogray Pg is a gray ink composed of CMY and mixed, and the spectral reflectance characteristic is uneven. By using gray ink, it is possible to reproduce gray color that is less affected by ink density fluctuations than when C, M, and Y are overprinted. However, since the spectral reflectance characteristics are different, the light source metamerism is different.
That is, the photo gray Pg appears to change its color when the light source changes, whereas the mat black can always reproduce gray stably regardless of the light source. In other words, if the input signal is a signal that easily changes its light source, color reproduction that matches spectrally can be realized by using photo black. Similarly, when reproducing the same green, mixing Y and C to reproduce the green color and using G ink to reproduce the green color results in better use of different inks depending on the spectral characteristics. Is obtained.
However, if all the inks are installed at the same time, the device becomes large and expensive, and if the number of inks is limited, the cartridge must be replaced so that the most suitable ink set is used according to the output image. Don't be. As described above, since the optimum ink set varies depending on the input multiband data, in this embodiment, the optimum ink set for spectral color matching is determined for each input data.

(Flow of printing operation)
Next, the processing operation will be described.
FIG. 5 is a functional block diagram of the signal processing unit 14.
The signal processing unit 14 includes a metamerism prediction module 40 that calculates metamerism characteristics of various ink sets based on input data, an ink set determination unit 41 that determines an ink set from a metamerism prediction result, and color conversion parameters corresponding to the various ink sets. The stored color conversion parameter storage unit 42, a color conversion processing unit 43 that performs color conversion processing, a color conversion parameter memory 44 that temporarily stores color conversion parameters used for color conversion processing, and the like.
First, when input image data is received, an attribute of the input data is determined. When the input data is multi-color data, the metamerism characteristics are evaluated for a plurality of ink sets, and the ink set is determined so as to minimize the metamerism. When the ink set is determined, the corresponding color conversion parameter is read from the color conversion parameter and loaded into the color conversion parameter memory. Thus, when the color conversion parameter is loaded, the input image data is color-converted using the loaded color conversion parameter.

ここで、Ｐ（λ）は光源の分光輝度であり、Ａ光源、Ｄ６５光源それぞれ異なる。また、ｘ（λ）、ｙ（λ）、ｚ（λ）は、等色関数を意味する。上式でＸＹＺ三刺激値が求まると、色差を求めるためにＣＩＥで標準化されている変換式を用いてＬａｂ或いはＣＩＥＣＡＭなどの信号へ変換する。例えば、Ｌａｂ信号への変換式は以下のとおりである。
Ｌ＊＝１１６（Ｙ／Ｙｗ）^1/3−１６
ａ＊＝５００｛（Ｘ／Ｘｗ）^1/3−（Ｙ／Ｙｗ）^1/3｝
ｂ＊＝２００｛（Ｙ／Ｙｗ）^1/3−（Ｚ／Ｚｗ）^1/3｝
以上の計算により、Ａ光源環境時のＬａｂ値及びＤ６５光源環境時のＬａｂ値をそれぞれ計算する。
同様に、出力の色彩値も各光源ごとに計算する。出力の色彩値を計算するには、まず出力の分光反射率から求める必要がある。 (Description of metamerism characteristic calculation unit)
FIG. 6 is a flowchart for explaining an evaluation method for evaluating metamerism characteristics. Among these, an evaluation means for evaluating metamerism characteristics is realized. As the metamerism characteristic, for example, an average value of color differences under a plurality of observation light source environments can be used. The calculation procedure of the metamerism characteristic value will be described in detail below.
(1) Estimate the spectral reflectance Ri (λ) from the multi-band data. As this estimation method, for example, the method presented in Patent Document 2 can be used.
(2) Next, the color values of the A light source and the D65 light source are calculated based on the estimated spectral reflectance Ri (λ). First, an XYZ stimulus value corresponding to each light source is obtained. The calculation formula is shown below.

Here, P (λ) is the spectral luminance of the light source, and is different for each of the A light source and the D65 light source. Moreover, x (λ), y (λ), and z (λ) mean color matching functions. When the XYZ tristimulus values are obtained from the above equation, they are converted into signals such as Lab or CIECAM using a conversion equation standardized by CIE in order to obtain a color difference. For example, the conversion formula to the Lab signal is as follows.
L * = 116 (Y / Yw) ^1/3 -16
a * = 500 {(X / Xw) ¹ /3-(Y / Yw) ^1/3 }
b * = 200 {(Y / Yw) ¹ /3-(Z / Zw) ^1/3 }
Through the above calculation, the Lab value in the A light source environment and the Lab value in the D65 light source environment are calculated.
Similarly, the output color value is calculated for each light source. In order to calculate the output color value, it is first necessary to obtain the output spectral reflectance.

(3) Calculation of output signal First, an output color signal is obtained using a color conversion parameter corresponding to an ink set for evaluating metamerism. For example, when evaluating the metamerism of a CMYKOG ink set, a color conversion parameter for converting multiband data into a CMYKOG output value is used. The input of color conversion at this time uses the same multiband data as (1) described above.
(4) Estimation of spectral reflectance When the output signal value for multiband data is obtained, the spectral reflectance is obtained. For this reason, a color prediction model is constructed in advance based on colorimetric data obtained by measuring a color by outputting a patch with a combination of representative output values. Then, the output signal value is converted into spectral reflectance data using the constructed color prediction model. As the color prediction model, a Yule Nielsen-Neugebauer model, a Kubelka-Munk model, or the like can be used.
(5) Calculation of output color value After calculating the output spectral reflectance as described above, it is converted into a Lab value in the same manner as in the above (1) and (2).

(6) Calculation of color difference Using the color value obtained in the above procedure, the color difference is calculated for each light source. As the color difference formula, the Delta E2000 color difference formula is desirable, but other color difference formulas such as the CIE94 color difference formula may be used. For example, assuming that the color difference between the Lab value of the input multiband data and the output Lab value in the light source S is δ (S), the metamerism evaluation value is calculated from the color differences obtained by the A light source and the D65 light source, respectively. As the metamerism evaluation value D,
Evaluation value D = (δ (A) ² + δ (D65) ² ) ^1/2
Can be calculated as
As described above, the metamerism evaluation value for arbitrary multiband data is obtained. The above calculation is repeated for each pixel of the input image data, and the average value is used. In the above description, an example of the CMYKOG ink set has been described. When determining an ink set, the above calculation is performed for all ink sets to determine the ink set having the minimum evaluation value. In this way, the first determination unit that determines the ink set based on the result of the evaluation unit is realized.
As the metamerism characteristic value, the statistical value of the color difference of the plurality of light sources can be used. The statistical value may be the maximum value or the average value of the color difference. Here, the average value is used. The above calculation is unsuitable for real-time processing because the calculation load of the metamerism characteristic value is large. Therefore, when actually outputting to a printer or the like, it is desirable to set the calculated metamerism characteristic value in the lookup table in advance and perform the calculation by interpolation.
For example, the metamerism characteristic is calculated by 6-input 10-output interpolation calculation where the input data is 6-band data and there are 10 types of ink sets. Since the metamerism characteristic of each ink set can be predicted by the above calculation, the ink set is determined using the predicted characteristic value. For example, when the metamerism is predicted for each of the 10 types of ink sets, the ink set having the smallest metamerism is used. Further, the confirmation of the ink set does not have to be performed every time, and may be performed only when the user designates a predetermined confirmation.
As described above, according to the second embodiment, since metamerism characteristics are predicted for a plurality of ink sets, an ink set suitable for input image data can be used even when a large number of ink sets can be used. Further, since the metamerism characteristic value is held in the lookup table, the metamerism characteristic value can be calculated at high speed. In addition, since the ink set is determined using the statistical values of the color differences under a plurality of viewing conditions, high-precision spectral color matching can be performed.

[Third Embodiment]
In the third embodiment, a method of analyzing the color distribution of input image data and performing output using an ink set suitable for the color distribution will be described. Color gamut information is stored for each ink set, and the ink set is determined by comparing with the color gamut of the input image.
FIG. 7 is a flowchart for explaining the ink set determination method of the present embodiment, in which the second determination means for determining the ink set to be used based on the read color gamut information is realized. In this embodiment, it is assumed that the color range of the input image data is described in advance as attribute information in the input image data. However, if the attribute information is not described, it may be calculated and obtained. .
The outline of the flowchart of FIG. 7 will be described. First, in step S300, the color gamut of the input image data is read from the attribute information. As the color gamut information, for example, flag information within or outside the color gamut may be described in each of the lattice points obtained by dividing the Lab space by n × m × l. Next, in step S301, comparison with color gamut information for each ink set prepared in advance is performed. Similarly to the input image, the color gamut information for each ink set also has a table in which flag 0 is described when reproducible for each divided space obtained by dividing the three-dimensional color space, and flag 1 is described when reproducible. Then, the number of pixels outside the reproduction region is obtained by multiplying the flag and the frequency of the three-dimensional histogram for each color space region.

Here, the processing based on the flowchart of FIG. 7 will be described in detail. In the third embodiment, color gamut information for each ink set is recorded in advance in the ROM 142 (ink set characteristic storage unit) of the signal processing unit 14 in order to speed up the ink set determination process. As the color gamut information for each ink set, it is assumed that a device-independent color space such as a Lab space is subdivided and a flag for determining whether or not reproduction is possible for each divided space is described.
An example of the above division is shown in FIG. In the example of FIG. 8, the Lab space is divided into 10 axes. In this example, the range of the L axis is L = 0 to 100, and the range of the a and b axes is −150 to 150. Therefore, in one divided space, ΔL is 10, Δa is 30, and Δb is 30. Here, the number of divisions is not particularly limited, and the division number may be divided more finely, or the division number may be different depending on the axis. Here, for convenience of explanation, it is assumed that the predetermined color gamut information is represented by GT (x, y, z). However,
x = (int) (L / 10)
y = (int) ((a + 150) / 30)
z = (int) ((b + 150) / 30)
It is.
In other words, the values of GT (x, y, z) are (10x) <= L <(10 (x + 1)), (30y−150) <= a <(30 (y + 1) −150), (30z− 150) <= b <(30 (z + 1) -150) indicates whether or not the color gamut can be reproduced by the ink set, and 0 is assigned if reproducible and 1 is assigned if reproducible. . These color gamut information tables are prepared for all ink sets that can be printed out.

即ち、ＧＴ（ｘ，ｙ，ｚ）は、再現域外の場合１の値となっているので、上式は入力画像データのうち再現域外の画素数をカウントしていることになる。このようにして、Ｌａｂ空間の全色空間について色域外の画素数をカウントすることにより色域外の総画素数を求めることができる。
上記の演算を全てのインクセットに対して行なった後、ステップＳ３０２においてインクセットを決定する。本実施例では、色再現域外の画素Ｐが最も少ないインクセットを使用することにする。
但し、入力画像データの色域が狭い場合には、色域外の画素がほとんどなくなってしまい色域外の画素数という条件のみではインクセットを決められなくなる可能性がある。このように入力画像の色域が狭く複数のインクセットが候補になる場合には、別の条件（速度、画質、インク消費量など）に基づいて決める。
この条件を自動で判定するようにしても良いが、主観的に決定しても構わない。主観的に決定する場合には、予め画質や速度を考慮して使用するインクセットの優先順位を決めておけば、上記複数の候補となるインクセットから最も優先順位の高いインクセットを使用すればよいことになる。 Next, when image data is input and output is instructed, the color distribution of the input image is obtained in step S300. To find the color distribution:
1) Perform RGB → Lab conversion for each pixel of the input image. For example, if the color characteristic of the RGB signal conforms to sRGB, the Lab value can be calculated by using a conversion formula defined in CIE 61966-2-2.
2) Next, the histogram is updated based on the calculated Lab value. The number of histogram divisions is the same as the color gamut information of the ink set described above. For example, the Lab value calculated from the input pixel value is [40, 20, -30]. At this time, since x = 4, y = 5, and z = 4, the value of GTI (4, 5, 4) is incremented. Here, GTI means a table describing a three-dimensional histogram of an input image, and the table value stores the number of pixels included in the divided space.
Next, in step S301, the number of pixels P of the color that cannot be reproduced by the ink set is calculated by the following formula using the color gamut information table of the ink set described above and the three-dimensional histogram of the input image data.

That is, GT (x, y, z) has a value of 1 when it is outside the reproduction range, so the above expression counts the number of pixels outside the reproduction region in the input image data. In this way, the total number of pixels outside the color gamut can be obtained by counting the number of pixels outside the color gamut for all color spaces in the Lab space.
After the above calculation is performed for all ink sets, ink sets are determined in step S302. In this embodiment, an ink set having the smallest number of pixels P outside the color gamut is used.
However, when the color gamut of the input image data is narrow, there are almost no pixels outside the color gamut, and there is a possibility that the ink set cannot be determined only by the condition of the number of pixels outside the color gamut. In this way, when the color gamut of the input image is narrow and a plurality of ink sets are candidates, they are determined based on other conditions (speed, image quality, ink consumption, etc.).
This condition may be automatically determined, but may be determined subjectively. In the case of subjective determination, if the priority order of the ink set to be used is determined in advance in consideration of the image quality and speed, the ink set having the highest priority among the plurality of candidate ink sets may be used. It will be good.

  As described above, according to the third embodiment, since the ink set is determined based on the color gamut, it is possible to easily determine the ink set that minimizes the color that cannot be reproduced. In addition, since ink set characteristic storage means for storing color gamut information corresponding to each ink set is provided, the color gamut for each ink set need not be calculated each time. In addition, since the conjugation relationship between the color gamut of each ink set and the color gamut of the input image data is evaluated, an ink set suitable for the color range of the input image can be easily determined.

[Fourth Embodiment]
In the above embodiment, the optimum ink set determination method is described as being performed inside the printer 1, but may be performed by an apparatus independent of the printer 1. In the host computer, it may be performed in the form of software with a printer driver. FIG. 9 is a diagram showing an apparatus for realizing the optimum ink set determination method. As shown in FIG. 9, the color signal processing apparatus according to the present embodiment includes an apparatus body 10 including a microcomputer, a mouse 11a and a keyboard 12a for inputting data and commands, and for displaying image data. And a printer 14a as an image forming apparatus such as a color printer.
The apparatus main body 10 includes a CPU 21a, a ROM 22a, a RAM 23a, a hard disk 24a in which a control program for the CPU 21a is stored, a NIC 25a for exchanging data between the main body and another apparatus, and data and commands are input / output to / from these. It consists of buses connected as possible. In this system, the CPU 21a can be provided with a function as the optimum ink set determination method of the present invention.

The function of the CPU 21a as such an optimal ink set determination method can be provided in the form of, for example, a software package, specifically, an information recording medium such as a CD-ROM. For this reason, the example of FIG. Then, when the information recording medium 30 is set, a program reading device 31 is provided as a medium driving device for driving the information recording medium 30.
In other words, the optimum ink set determination method of the present invention causes a general-purpose computer system having a display or the like to read a program recorded on an information recording medium such as a CD-ROM, and causes the microprocessor of the general-purpose computer system to read the program. The present invention can also be implemented in an apparatus configuration that executes the optimum ink set determination method.
In this case, the program for executing the optimum ink set determination method of the present invention, that is, the program used in the hardware system is provided in a state recorded on the medium. The information recording medium on which the program is recorded is not limited to the CD-ROM, and a ROM, RAM, flexible disk, memory card, or the like may be used.
The program recorded on the medium is installed in a storage device incorporated in the hardware system, for example, the hard disk 24a, so that the program can be executed to realize a color conversion function and a color conversion profile generation function. it can. Further, the program for realizing the above-described optimal ink set determination method is not only provided in the form of a medium, but may be provided by, for example, a server through communication.

1 is a block diagram for explaining a schematic functional configuration of a printer 1 according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a schematic configuration of a printing mechanism unit 12. 4 is a flowchart for explaining a flow of processing when the printer 1 performs printing. It is a flowchart of initialization operation | movement. 3 is a functional block diagram of a signal processing unit 14. FIG. It is a flowchart explaining the evaluation method which evaluates a metamerism characteristic. It is a flowchart explaining the ink set determination method. 10 is a diagram illustrating an example of color gamut division according to Embodiment 3. FIG. It is a figure which shows the apparatus which implement | achieves the optimal ink set determination method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Printer, 10 apparatus main body, 11 control apparatus, 11a mouse, 12 printing mechanism part, 12a keyboard, 13 interface, 13a display, 14 signal processing part, 14a image forming apparatus, 15 drive circuit part, 16 user interface part, 21 endless Belt, 21a, 141 CPU, 22 Carriage motor, 22a, 142 ROM, 23 Carriage shaft, 23a, 143 RAM, 24 Transport motor, 24a Hard disk, 25 Ink cartridge, 25a NIC, 30 Information recording medium, 31 Program reader, 121 Print head, 122 carriage, 123 transport roller, 151 print head drive circuit, 152 carriage drive circuit, 153 transport roller drive circuit, P printing paper

Claims (17)

Input means for inputting color image data;
Determining means for determining attributes of input image data;
A plurality of ink sets including a first image output means using an ink set for spectral color matching and a second image output means using an ink set different from the first image output means;
An image output apparatus comprising: selection means for selecting the ink set based on an attribute of the image data.   The image output apparatus according to claim 1, wherein the selection unit determines the ink set to be used based on whether or not the image data includes multiband data.   The image output apparatus according to claim 1, wherein the chromatic inks included in the spectral color matching ink set have a hue difference of 30 degrees or more.   The image output apparatus according to claim 1, wherein the spectral color matching ink set includes cyan, magenta, yellow, black, orange, and green.   2. The image output apparatus according to claim 1, wherein the chromatic ink included in the ink set different from that of the first image output means includes an ink having a hue difference of 15 degrees or less.   2. The image output apparatus according to claim 1, wherein the ink set different from the first image output means includes light cyan ink or light magenta ink. The ink set can be replaced,
The image output apparatus according to claim 1, further comprising a notification unit that notifies the user of the selected ink set when the output unit selected by the selection unit is unusable. When the image data includes multiband data, an evaluation unit that evaluates metamerism characteristics for each of the plurality of ink sets;
First determination means for determining an ink set based on a result of the evaluation means;
2. The image output apparatus according to claim 1, wherein image output is performed using the ink set determined by the first determination means.   The evaluation means includes a look-up table that outputs metamerism characteristic values when the image data is reproduced with the plurality of ink sets, and executes a memory map interpolation operation using the look-up table. 9. The image output apparatus according to claim 8, wherein a metamerism characteristic value is obtained.   The input data is color-converted using color conversion parameters corresponding to each of the plurality of ink sets, the color difference between the image data and the reproduced color after color conversion is obtained for a plurality of viewing conditions, and the color difference of the plurality of viewing conditions is calculated. The image output apparatus according to claim 9, wherein the statistical value is a metamerism characteristic value.   The attribute information is color gamut information of the image data, and comprises second determination means for determining an ink set to be used based on the read color gamut information. Image output device.   12. The image output apparatus according to claim 11, wherein the second determination unit includes an ink set characteristic storage unit that stores color gamut information corresponding to each ink set.   The second determination means determines an ink set by evaluating a conjugation relationship between a color gamut of each ink set read from the ink set characteristic storage means and a color gamut of input image data. 12. The image output device according to 12. Determining whether the input image data is multiband data;
When the image data is multiband data, the image data is converted into a control signal for an ink set for spectral color matching and output,
When the image data is not multiband data, the image data is output after being converted into a control signal of an ink set other than the ink set for spectral color matching. Evaluating metamerism characteristics for each of a plurality of ink sets based on image data;
Determining an ink set based on the evaluation result of the metal rhythm characteristics;
And an image output method using the ink set determined by the determination step of determining the ink set. A color gamut information acquisition step for reading color gamut information of input image data;
A step of determining an ink set based on the color gamut information acquired in the color gamut information acquisition step;
And a step of outputting image data using an ink set determined based on the color gamut information. A recording medium that records a program for converting to an output signal based on input image data,
Reading the attribute information of the image data;
Determining whether multiband data is included from the attribute information;
A recording medium on which a program for causing a computer to execute a procedure for determining an ink set to be used is recorded according to a determination result of whether or not multiband data is included.

Images