JP2005205812A - Color recording method, image processing apparatus and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the color reproduction range of a low lightness region is reduced owing to a color material of a high chroma as a second color material group in color recording which uses a first color material group for expressing base colors including cyan, magenta, yellow and black, and the second color material group for expressing other than the base colors. <P>SOLUTION: The color recording method is provided, which uses the first color material group for expressing the base colors including black, and the second color material group for expressing other than the base colors. The first color material group, which is a recording color material, has a color reproduction range expressible by a combination of the first color material group and the second color material group smaller than a color reproduction range expressible by a combination of the first color material group because of effects of the second color material group. As black is expressed from color, the first color material group which expresses a secondary color by reducing the second color material group is increased, and the first color material group is reduced thereafter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a color recording method, an image processing apparatus, and a method thereof, for example, color recording using a color material other than a basic color.

  Recording agents (color materials) such as color toners and color inks used in image output devices such as color printers are cyan (C), magenta (M), and yellow, which are subtractive three primary colors. There are many cases where four colors (Y) are the basic colors and black (K) is added. In other words, the image output device converts the input signal (R, G, B) into three colors of C, M, Y or four colors including black (BK), and forms an image with the recording agent of three or four colors. .

  In recent years, with the widespread use of color printers, there is an increasing demand for higher image quality. However, the four colors of C, M, Y, and BK have a problem that there is a limit to the colors that can be reproduced due to the color development characteristics of the colorants such as dyes of recording agents, and it is difficult to reproduce more vivid colors.

  Use special colors such as red (R), orange (O), green (G), blue (B) and violet (V) in addition to C, M, Y, BK to solve the above problem Technology has been proposed.

  For example, in Japanese Patent Laid-Open No. 06-237351, the color data of pixels constituting a color image is compared with reference color data reproducible with four basic colors of YMCK, and the color of each pixel is basically It is judged whether or not it can be reproduced with the four color materials, and if it cannot be reproduced with the basic four color materials, the pixel is assigned a basic four color material and a predetermined spot color other than the basic four colors. Techniques for using and printing are disclosed.

  This is a technology that uses special colors only in the color areas that cannot be reproduced with the basic four colors, and the area that can be reproduced with the basic four colors and the non-reproducible area become discontinuous and the image quality is impaired. There is.

  In Japanese Patent Laid-Open No. 2003-11432, if a high-saturation color material is used in the high-lightness region, the saturation in the high-lightness region can be increased, but conversely, the saturation in the low-lightness region is higher than when the basic color is combined. Is determined when a color image is recorded using the first color material group that expresses the basic color and the second color material group that expresses a color other than the basic color. This is solved by expressing the color that gives the maximum saturation of the hue by a combination of the color selected from the first color material group and the color selected from the second color material group.

(How to use color materials in conventional technology)
Hereinafter, red will be described as an example of how to use a color material (ink) in the prior art.

  FIG. 5 is a diagram showing the color reproduction range.

  The horizontal axis represents saturation, the vertical axis represents lightness, and the broken line 502 represents the color reproduction range of the red hue when C, M, Y, and BK color materials are used. A solid line 501 is a color reproduction range when an R color material is used in addition to the C, M, Y, and BK color materials.

  FIG. 3 is a diagram for explaining the amount of ink used (ink ejection amount) in the red hue of the present embodiment, from R, G, B data to C, M, Y, BK, R, G, B data. This corresponds to the color conversion processing table, that is, the three-dimensional LUT of the color conversion processing unit 102. Note that the G and B inks are not used in the red hue, so those curves are omitted in FIG.

  First, the usage of the ink with the highest saturation (R, G, B = 255, 0, 0) of red is arbitrarily determined by the combination of the R ink as the special color and the MY ink as the basic color. In accordance with this, the ink usage method is determined by multiplying white (R, G, B = 255, 255, 255) to red (R, G, B = 255, 0, 0).

  In this process, as disclosed in Japanese Patent Laid-Open No. 2003-011432, the amount of R ink used is increased from white to red, and when the amount of R ink used reaches the maximum value (signal value 255), thereafter A method of adding M and Y inks may be used.

  Next, a method of using ink from red (R, G, B = 255, 0, 0) to black (R, G, B = 0, 0, 0) will be described.

  First, preferable black is set arbitrarily. Here, black is composed of BK ink and C, M, Y ink.

  From red to black, increase the amount of C ink that is complementary to red. Then, the amount of black ink used is increased later. During this time, even if there is a slight decrease in the amount of R ink used, it will not be significantly reduced. R ink is drastically reduced from black to black until the usage is zero.

  The color reproduction range expressed in this way has a problem that a part of the color reproduction range of the low brightness portion is cut as indicated by 501 in FIG.

  This is due to the fact that R ink with high brightness increases the brightness of the low brightness portion.

  In the aforementioned Japanese Patent Application Laid-Open No. 2003-11432, although a specific technical disclosure has been made regarding the use of color materials from white to color, color to black CMY and special colors, and setting of maximum saturation, the technology using black color materials Does not disclose specific technology.

  In the present invention, the first color material group expressing basic colors including cyan (C), magenta (M), yellow (Y), and black (BK), and the second color expressing other than the basic colors In color recording using a group of materials, the problem of a decrease in the color reproduction range of the low lightness region caused by the high-saturation color material, which is the second group of color materials, is solved, and high-quality printing is maintained. For the purpose.

  The present invention includes the following configuration as one means for solving the above-described problems.

  The color recording method according to the present invention is a color recording method using a first color material group expressing a basic color including black and a second color material group expressing a color other than the basic color. Due to the influence of the color material group, the color reproduction range that can be expressed by the combination of the first color material group and the second color material group is a color reproduction range that can be expressed by the combination of the first color material group. A smaller recording color material, wherein the second color material group is decreased and the first color group representing the secondary color is increased as black is represented from the color; The color group is reduced.

  As described above, according to the present invention, a wide range of color reproduction is possible while maintaining high image quality.

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

  In addition, this embodiment is only an example for demonstrating invention, and does not restrict | limit this invention.

(Constitution)
FIG. 7 is an example of an embodiment of a printing apparatus to which the present invention is applied. In FIG. 7, a plurality (seven colors) of head cartridges (recording units) 1 </ b> A, 1 </ b> B, 1 </ b> C, 1 </ b> D, 1 </ b> E, 1 </ b> F, and 1 </ b> G are mounted on the inkjet printer 13 so as to be replaceable. In addition, when referring to the whole or any one of the plurality of recording units 1A to 1G, the recording unit (recording head or head cartridge) 1 is simply indicated.

  Each head cartridge 1 has an ink tank portion at the upper portion and a recording head portion (ink discharge portion) at the lower portion, and has a structure in which the recording head and the ink tank are integrated. Each recording unit 1 is mounted on the carriage 2 so as to be replaceable. Each recording unit 1 has a connector (not shown) for receiving a signal for driving the recording head unit. Is provided. On the other hand, the carriage 2 is provided with a connector holder (electrical connection part) for transmitting a drive signal or the like to each recording part 1 through the connector.

  Each recording unit 1 on the carriage 2 and the control circuit on the apparatus main body side are connected by a flexible cable for flowing a signal pulse current and a temperature control current.

  Each head cartridge has 1 BK ink, 1B, 1C, 1D respectively C, M, Y ink, 1E, 1F, 1G respectively R, G, B ink in the upper ink tank part. The ejection ports for ejecting ink droplets are formed in a predetermined arrangement on the surface of the recording head portion facing the print medium 8 (downward ejection port surface in the illustrated example). The stored ink is ejected.

  The carriage 2 is guided and supported so as to reciprocate along a guide shaft 3 that extends in the main scanning direction and is installed in the apparatus main body. The carriage 2 is driven by the main scanning motor 4 via the motor pulley 5, the driven pulley 6, and the timing belt 7, and the position and movement of the carriage 2 are controlled. A print medium 8 such as paper or a plastic sheet is sandwiched between two pairs of transport rollers 9, 10 and 11, 12, and is positioned opposite to the discharge port surface of the recording head 1 (recording) by the rotation of these transport rollers. Part) is conveyed (paper feed).

  The back surface of the print medium 8 is supported by a platen (not shown) so as to form a flat recording surface in the recording unit. In this case, the head cartridges 1 mounted on the carriage 2 are held so that their discharge port surfaces protrude downward from the carriage 2 and are parallel to the print medium 8 between the two pairs of transport rollers. Yes.

  The ink jet printer 13 configured integrally with these is connected to a host computer 14 via a cable 15 and is controlled by driver software installed in the host computer 14.

FIG. 2 is a block diagram illustrating the image processing system according to the embodiment.
The host computer 201 includes a CPU 202, a memory 203 such as RAM and ROM, an external storage 204 such as a hard disk, an input unit 205 to which input devices such as a keyboard and a mouse are connected, and an interface to which peripheral devices such as a printer can be connected. A face 206 is provided, and these are connected to each other via a system bus.

  The CPU 202 executes a color process and a quantization process described later by executing a program stored in the memory 203.

  This program is stored in the external storage 204 or the like, and is supplied from the external device 204 to the memory 203.

  The host computer 201 is connected to a color recording device 207 such as a printer via an interface 206, sends image data subjected to color processing to the color recording device 207, and prints an image.

  In the following description, the color recording device 207 is assumed to be a color ink jet printer provided with C, M, Y, BK, R, G, and B inks.

  Figure 1 shows the main functions of the image processing system. Input R, G, B color 8-bit (256 gradations) image data is C, M, Y, BK, R, G, B 1-bit color data. It is a block diagram which shows the structure which implement | achieves the function to output as.

  The configuration shown in FIG. 1 is realized as a printer driver that operates on the host computer 201 for controlling the color recording apparatus 207.

  The 8-bit image data of R, G, B colors that is input data is converted into the output color of the color recording device 207 by the three-dimensional lookup table (3D LUT) of the first color conversion processing unit 101, that is, the color conversion table. The image data is converted into 8-bit image data for each R, G, B color.

  Further, the data is converted into 8-bit image data of each color of C, M, Y, BK, R, G, and B by the three-dimensional LUT of the second color conversion processing unit 102.

  These processes are processes for converting the R, G, and B colors of the input system to the C, M, Y, BK, R, G, and B colors of the output system.

  That is, input image data is often the additive primary color (R, G, B) of a light emitter such as a display, but the color recording device 207 has C, M, Y, BK, R, G, B. Therefore, such a conversion process is necessary.

  The three-dimensional LUT is a table that holds data discretely, and data between discrete data is obtained by a known interpolation process such as tetrahedral interpolation.

  The output gamma correction is performed by the one-dimensional LUT of the output gamma correction unit 103 on the 8-bit image data of each color C, M, Y, BK, R, G, B obtained by the color conversion processing. Output gamma correction often corrects the relationship between the number of recorded dots per unit area that is not linear and the output characteristics (reflection density, etc.), and inputs C, M, Y, BK, R, G, B Assures a linear relationship between 8-bit image data for each color and the output characteristics of the formed image.

  By the above processing, the input 8-bit image data for each color of R, G, B is 8-bit image data for each color of C, M, Y, BK, R, G, B corresponding to the color material of the color recording device 207. Is converted to The C, M, Y, BK, R, G, B color 8-bit image data is quantized by the quantization processing unit 104 according to the color recording device 207.

  That is, if the color recording device 207 is a binary printer, it is quantized (binarized) into 1-bit data for each color of C, M, Y, BK, R, G, and B. As a quantization method at that time, a known error diffusion method or dither method is used.

(How to use coloring materials in the embodiment)
Hereinafter, the usage of the color material (ink) in the embodiment for solving the problems of the prior art will be described using red as an example.

The color recording device and the color material are the same as those used in the prior art.
The method of using ink from white (R, G, B = 255, 255, 255) to red (R, G, B = 255, 0, 0) is also the same as in the prior art, and is therefore omitted.

  FIG. 6 is a diagram showing the color reproduction range.

  The horizontal axis represents saturation, the vertical axis represents lightness, and the broken line 602 represents the color reproduction range of red hue when C, M, Y, and BK color materials are used.

  A solid line 601 represents a color reproduction range when an R color material is used in the usage method of the present invention in addition to CMY and BK color materials.

  FIG. 4 is a diagram for explaining the amount of ink used (ink ejection amount) in the red hue of this embodiment, from R, G, B data to C, M, Y, BK, R, G, B data. This corresponds to the color conversion processing table, that is, the three-dimensional LUT of the color conversion processing unit 102.

  Since the G and B inks are not used in the red hue, those curves are omitted in FIG.

  Next, a method of using ink from red (R, G, B = 255, 0, 0) to black (R, G, B = 0, 0, 0) will be described.

  First, preferable black is set arbitrarily. Here, black is composed of BK ink and C, M, Y ink as in the prior art.

  From red to black, increase the amount of C ink that is complementary to red. At the same time, the amount of M and Y ink used to express the secondary color is increased. Here, the amount of R ink used is gradually reduced toward black. This is not done because the saturation drops drastically when R ink is suddenly reduced. Later, the amount of black ink used is increased, and M and Y inks are used up to the maximum amount that can be printed on recording paper, and are reduced in front of black.

  The reduction of M and Y inks here means that the amount of black ink increases will not exceed the maximum ink amount that can be used for recording paper, and the ink usage amount will be changed smoothly toward black. Thus, there are two effects of preventing the generation of pseudo contours.

  The color reproduction range expressed in this way is free from the problem that a part of the color reproduction range of the low brightness portion is cut as shown by the solid line in FIG.

  In the above, a technique has been described in which the R color material is reduced and the amount of M and Y color materials used to express the secondary color is increased and then reduced as the color is expressed from red to black.

  By lowering the R color material and making the M and Y color materials chevron as shown in FIG. 4, the problem that the color reproduction range is cut can be solved while maintaining a smooth gradation.

  In the above embodiment, only red has been described, but the same applies to other colors. Pure color green (R, G, B = 0, 255, 0) may use C, Y and G color materials, and pure color blue (R, G, B = 0, 0, 255) may be C, M and B colors. It is recommended to use a coloring material.

(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.

  Another object of the present invention is to supply a storage medium (or recording medium) in 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 CPU) of the system or apparatus. 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. It goes without saying that the CPU or the like provided in 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.

The block diagram which shows the structure which implement | achieves the main functions of an image processing system. 1 is a block diagram illustrating an image processing system according to an embodiment. Prior art red hue ink usage. A method for using red hue ink according to an embodiment of the present invention. The color reproduction range of the red hue of the prior art. The color reproduction range of the red hue of embodiment of this invention. 1 is an example of an embodiment of a printing apparatus to which the present invention is applied.

Claims (6)

  A color recording method using a first color material group that expresses a basic color, including black, and a second color material group that expresses a color other than the basic color, under the influence of the second color material group, The color reproduction range that can be expressed by the combination of the first color material group and the second color material group is a recording color material that is smaller than the color reproduction range that can be expressed by the combination of the first color material group. Reducing the second colorant group as the color represents black, increasing the first color group representing the secondary color, and then reducing the first color group Characteristic color recording method.   The recording method according to claim 1, wherein the first color material group includes cyan, magenta, yellow, and black.   The recording method according to claim 2, wherein the second color material group includes at least one of red, green, and blue.   A color recording method using a first color material group that expresses a basic color, including black, and a second color material group that expresses a color other than the basic color, under the influence of the second color material group, The color reproduction range that can be expressed by the combination of the first color material group and the second color material group is a recording color material that is smaller than the color reproduction range that can be expressed by the combination of the first color material group. Reducing the second colorant group as the color represents black, increasing the first color group representing the secondary color, and then reducing the first color group A characteristic color recording apparatus.   The recording apparatus according to claim 4, wherein the first color material group includes cyan, magenta, yellow, and black.   6. The recording apparatus according to claim 5, wherein the second color material group includes at least one of red, green, and blue.

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