JP4640180B2 - Setting the color tone to be added to the image - Google Patents

Description

  The present invention relates to a technique for setting a color tone to be added to an image.

  2. Description of the Related Art Conventionally, a technique for displaying and printing a monochrome image having only brightness information with a desired color tone has been disclosed. Colors to be added to a monochrome image include a cool color tone (hereinafter referred to as “cool tone”), a warm color tone (hereinafter referred to as “warm tone”), and a shade of a photograph (hereinafter referred to as “sepia tone”). )and so on.

  For example, in Patent Document 1, when printing a monochrome image, a one-dimensional lookup table in which an input value is a gray gradation value and an output value is a gradation value of the density of each ink color of the printer is used. Then, image conversion is performed. Then, a one-dimensional lookup table having a plurality of patterns is prepared by changing the maximum value of the chromatic colors cyan, magenta, and yellow among the output values of the one-dimensional lookup table by a predetermined step size. A plurality of monochrome sample images are printed. Then, a sample image having a preferable color tone is selected from the images, and the color tone to be added to the image is determined.

JP 2004-142423 A JP 2002-331893 A

  However, in the above technique, it is necessary to print a plurality of monochrome sample images in order to determine the color tone to be added to the print image, and the procedure for printing the monochrome image with a color tone is complicated.

  The present invention has been made in view of the above points, and a main object of the present invention is to provide a technique capable of obtaining a printed image with a color tone according to a user's wishes by a simple procedure.

  In order to achieve the above object, according to the present invention, the following processing is performed when a tone is given to an achromatic image and displayed on a display unit and printed. That is, first, (a) for each color component of the first color system, a tone curve for modifying the first type gradation value representing the intensity of the color component is generated. Then, (b) referring to each tone curve, the achromatic original image data including the first type of gradation value is converted into display image data to which a color tone is given, and according to the display image data A monotone image is displayed on the display unit.

  On the other hand, for (c) reference gray (N is an integer of 2 or more) that is N achromatic colors represented by the first type of gradation value of each color component, each gradation value after conversion by each tone curve is determined. To do. Then, (d) a second type that has the first type of gradation value as an input value and represents the intensity of ink colors of a plurality of inks as an output value based on the respective gradation values before and after conversion of N reference grays. A one-dimensional ink color look-up table having the following tone values is generated. Thereafter, referring to the (e) one-dimensional ink color look-up table, the original image data is converted into print image data including the second type of gradation value and printed.

  When the color tone of the print image and the color tone of the image displayed on the display unit are different, it is difficult for the user to determine the color tone to be attached to the print image based on the color tone of the image displayed on the display unit. However, if it is set as the above aspects, the user can obtain a print image with a color tone similar to the image displayed on the display unit. For this reason, the user can obtain a print image with a color tone according to the user's wishes by a simple procedure with reference to the color tone of the displayed image.

  When realizing the processing as described above, a display unit that displays an image, a printing unit that receives image data and prints using a plurality of inks including chromatic ink, the display unit, and printing It is preferable to use a printing apparatus including a control unit that controls the printing unit.

  In addition, when generating the one-dimensional ink color lookup table, the lookup table is for performing printing without adding a color tone to an achromatic image, and has a first type gradation value as an input value. The output value of the ink color of the predetermined chromatic ink in the one-dimensional original ink color look-up table having the second type of tone value as the output value is used as the first type of tone value before and after conversion of N reference grays. Is preferably modified to generate a one-dimensional ink color look-up table.

  When generating a one-dimensional ink color look-up table for printing at the time of printing, it is preferable to take care that the generated one-dimensional ink color look-up table can provide a sufficiently high-quality printed image. In the above-described aspect, a one-dimensional primary ink color lookup table is prepared in advance as a lookup table that can provide a high-quality printing result, and based on the one-dimensional primary ink color lookup table. The generated one-dimensional ink color lookup table can also be a lookup table that can provide high-quality printing results.

  When modifying the output value of a predetermined chromatic ink in the one-dimensional original ink color lookup table, it is preferable to perform the following processing. That is, the output value is modified based on the first type gradation value of each color component after conversion of one reference gray Gi (i is any one of 1 to N) of N reference grays G1 to GN A reference modification coefficient determination process is performed to determine a reference modification coefficient Rri corresponding to one reference gray Gi, which is a reference modification coefficient of a predetermined chromatic color ink. Then, the reference modification coefficient determination process is performed for N reference grays G1 to GN, and the N reference grays G1 to GN, which are reference modification coefficients for the predetermined chromatic color ink, respectively. Reference modification coefficients Rr1 to RrN are determined.

  Thereafter, based on the N reference modification coefficients Rr1 to RrN, at least one modification coefficient Rmin to Rmax that is different from the others is determined corresponding to each gradation value of the first type of predetermined chromatic ink. It should be noted that it is preferable to define modification coefficients for all gradation values of the first type. Then, the output value of the predetermined chromatic color ink in the one-dimensional original ink color look-up table is multiplied by the modification coefficients Rmin to Rmax corresponding to the first type gradation values as the respective input values. To generate a one-dimensional ink color lookup table.

  In such an aspect, the one-dimensional ink color look-up table is generated in consideration of the colors before and after the conversion of the plurality of reference grays by the tone curve used when generating the display image data. Therefore, the color tone of the image displayed on the display unit can be made similar to the color tone of the printed image.

  The N reference modification coefficients Rr1 to RrN preferably include reference modification coefficients having different values. If it is such an aspect, the color tone suitable for each can be attached | subjected about the part from which the brightness differs in an image.

  Further, when performing the reference modification coefficient determination process for determining the reference modification coefficient Rri corresponding to one reference gray Gi, the following process is preferably performed. That is, with reference to a three-dimensional reference color lookup table having a combination of the second type of gradation values that can be associated with a combination of the first type of gradation values of each color component, conversion of one reference gray Gi A second type gradation value VIi of a predetermined chromatic color ink whose output value is to be modified is determined from the combination of the first type gradation value later. On the other hand, referring to the one-dimensional original ink color look-up table, the second type gradation value VIbi of a predetermined chromatic color ink is determined from the first type gradation value before conversion of one reference gray Gi. . Then, the ratio (VIi / VIbi) of the second type of chromatic color before and after conversion is determined as the reference modification coefficient Rri corresponding to one reference gray Gi.

  According to such an aspect, the color conversion similar to the conversion along the display tone curve is performed for each reference gray even in the conversion using the print look-up table. Therefore, when the image is printed with a color tone, print image data that reproduces a color tone similar to the image displayed on the display unit can be obtained.

  The three-dimensional reference color look-up table can be N three-dimensional reference color look-up tables associated with the reference grays G1 to GN, respectively. In this aspect, the three-dimensional reference color lookup table corresponding to one reference gray Gi has a combination of the second type of gradation values associated with a predetermined range of colors including the one reference gray Gi. Each of the three-dimensional reference color lookup tables corresponding to the reference grays G1 to GN generally has a second type of gradation value that is associated with a part of the color in the color space of the first color system. Have a combination of In other words, in the color space of the first color system, there is a color in which each three-dimensional reference color lookup table does not have a combination of the second type of gradation values associated with the color. To do.

  In such an aspect, when the output gradation values are provided at the same interval, the aspect in which the three-dimensional reference color lookup table has the output gradation values for the colors in the entire color space. As compared with the above, the data amount of the three-dimensional reference color lookup table can be reduced.

  The three-dimensional reference color look-up table can be a look-up table having gradation values of color components of the second color system independent of the device as input values. In such an aspect, prior to referring to the three-dimensional standard color lookup table, the combination of the first type of gradation values after conversion of one standard gray Gi is used as the color component of the second color system. It is preferable to convert to a combination of gradation values.

  In such an aspect, the color corresponding to the reference gray is once replaced with the expression by the second color system independent of the device. For this reason, it is easy to apply the image processing described above to a plurality of types of printing units that use different basic colors when outputting an image.

  Note that the three-dimensional reference color lookup table may be a lookup table having a first type of gradation value of the first color system as an input value. According to such an aspect, it is possible to obtain a print image with a color tone close to that of the display image by simple processing.

  The N reference grays preferably include the following first to third grays. That is, the first gray is the first type of gradation value of each color component having the same value, and the first type of gradation included in the first range that is 1/3 of the maximum value. Gray represented by a combination of values. The second gray is the first type of gradation value of each color component having the same value, and is the first type of gradation value included in the second range that is 1/3 of the minimum value. It is gray expressed in combination. The third gray is the first type of gradation value of each color component having the same value, and is the first type included in the third range located between the first and second ranges. It is gray represented by a combination of gradation values.

  With such an aspect, it is possible to obtain an elephant by printing with a color tone close to that of the display image for each of the dark part, the bright part, and the intermediate part of the image.

  When generating a tone curve for generating display image data, it is preferable to receive from a user a designation of a color tone to be added to achromatic original image data. It is preferable to generate a tone curve based on the designated color tone. According to such an aspect, a color tone reflecting the user's intention can be added to the image.

  When the designation of the color tone is received from the user, it is a color tone designation region for designating the color tone to be attached to the image at one designated point, and the color tone to be attached to the image is visually recognized from the position in the color tone designation region. In other words, it is possible to display a color tone designation area configured so that it can be recognized visually. In such an aspect, it is preferable to receive the designation of one designated point in the color tone designation area from the user. According to such an aspect, the user can easily select a preferable color tone.

  Further, when generating the one-dimensional ink color look-up table, the following aspects can be adopted. That is, based on the first type gradation value of each color component after conversion of one reference gray Gi (i is any one of 1 to N) of the N reference grays, a predetermined chromatic ink reference A reference output value determination process for determining a reference output gradation value Vri corresponding to one reference gray Gi that is an output gradation value is performed. Then, the reference output value determination process is performed for N reference grays G1 to GN, and N reference grayscale values corresponding to the N reference grays G1 to GN, which are reference output gradation values of predetermined chromatic color inks, respectively. The reference output gradation values Vr1 to VrN are determined.

  Thereafter, based on the N reference output gradation values Vr1 to VrN, output values Vmin to Vmax corresponding to the first gradation values of the predetermined chromatic color ink are determined, and the one-dimensional ink color lookup table is determined. Is generated. With such an aspect, it is possible to generate a one-dimensional ink color lookup table with a simpler process compared to an aspect that uses a modification coefficient.

  The present invention can be realized in various forms, for example, a color tone setting method and apparatus, a color tone setting auxiliary method and apparatus, an image processing method and apparatus, a print control method and apparatus, a printing method and apparatus, The present invention can be realized in the form of a computer program for realizing the functions of these methods or apparatuses, a recording medium on which the computer program is recorded, or the like.

Hereinafter, embodiments of the invention will be described in the following order.
A. First embodiment:
A1. Overall configuration and processing:
A2. Color conversion processing:
B. Second embodiment:
C. Third embodiment:
D. Variations:

A. First embodiment:
A1. Overall configuration and processing:
FIG. 1 is a block diagram illustrating a software configuration of the printing system according to the first embodiment. In the computer 90, an application program 95 operates under a predetermined operating system. In addition, a video driver 91 and a printer driver 96 are incorporated in the operating system.

  The application program 95 converts the original image data ORG composed of the three color components of red (R), green (G), and blue (B) into CD- in accordance with a user instruction input from the mouse 130 or the keyboard 120. Read from R140. Then, in response to a user instruction, processing such as image retouching is performed on the original image data ORG. The application program 95 displays the processed image on the liquid crystal display 21 via the video driver 91. When the application program 95 receives a print instruction from the user, it issues a print instruction to the printer driver 96 and outputs the processed image to the printer driver 96 as initial image data PID.

  The printer driver 96 receives the initial image data PID from the application program 95, and print image data FNL (here, cyan, magenta, yellow, and first to third achromatic inks that can be processed by the printer 22). Multi-valued signal).

  In the example shown in FIG. 1, the printer driver 96 includes a resolution conversion module 97, a color conversion module 98, a color conversion table 104, a halftone module 99, and a rearrangement module 100. .

  The resolution conversion module 97 converts the resolution of the initial image data PID into the resolution used when printing by the printer 22. The color conversion module 98 refers to the three-dimensional lookup table 104a of the color conversion table 104 when printing a color image, and an image in which the color of each pixel is expressed with RGB gradation values of the sRGB color system. The color of each pixel is represented by the gradation values of cyan (C), magenta (M), yellow (Y), and first to third achromatic inks (K1 to K3) used by the printer 22 for the data MID1. The image data MID2 is converted. The first to third achromatic inks are achromatic inks having higher lightness in that order.

  In addition, when printing a monochrome image, the color conversion module 98 refers to the printing one-dimensional lookup table 104c of the color conversion table 104 and converts the image data MID1 in which the color is represented only by lightness to cyan (C). , Magenta (M), yellow (Y), and first to third achromatic inks (K1 to K3) are converted into image data MID2 in which the color of each pixel is represented. In FIG. 1, a table newly generated at the time of printing is indicated by a broken line.

  The halftone module 99 performs halftone processing on the image data MID2 in which the density of each color of each pixel is represented by the gradation value of each color, whereby image data in which the density of each color is represented by the presence or absence of dots in each pixel. Conversion to MID3 (also referred to as “print data” or “dot data”).

  The image data MID3 generated in this way is rearranged in the order of data to be transferred to the printer 22 by the rearrangement module 100, and is output as final print image data FNL. The halftone module 99 and the rearrangement module 100 correspond to a “print processing unit” in the claims.

  The printer 22 includes a mechanism for transporting the paper P by a paper feed motor, a mechanism for reciprocating the carriage 31 in a direction MS perpendicular to the transport direction SS of the paper P by a carriage motor, and ink ejection and dots mounted on the carriage 31. The print head 28 for forming, a P-ROM 42 for storing various setting data, and a CPU 41 for controlling these paper feed motor, carriage motor, print head 28, P-ROM 42 and operation panel 32 are configured. ing. The printer 22 receives the print image data FNL and prints with cyan (C), magenta (M), yellow (Y), and first to third achromatic inks (K1 to K3) according to the print image data FNL. Dots are formed on the medium and printing is performed.

  In the present specification, the “printing apparatus” refers only to the printer 22 in a narrow sense, but represents the entire printing system including the computer 90 and the printer 22 in a broad sense.

A2. Color conversion processing:
FIG. 2 is a flowchart showing a color tone assignment procedure when the initial image data PID output from the application program 95 is monochrome image data and the printer driver 96 prints the monochrome image with a predetermined color tone. It is. The “monochrome image” referred to here may be image data having only lightness information for each pixel constituting the image, or red (R), green (G), and blue (B) for each pixel. May be image data having equal gradation values.

  FIG. 3 is an explanatory diagram showing a color tone setting screen 200 of the printer driver 96. When a print instruction is issued from the application program 95, a predetermined user interface screen of the printer driver 96 is displayed on the liquid crystal display 21. When the user selects a monochrome printing tab (see the upper left in FIG. 3) on the user interface screen of the printer driver 96, the color tone setting screen 200 shown in FIG. 3 is displayed in step S10 of FIG.

  The color tone setting screen 200 designates a color circle 210 for designating a parameter for defining a color tone to be attached to an image, a sample image display area 220 for displaying a color sample image, and a brightness parameter for defining the brightness of the image. And a contrast scale 240 for specifying a contrast parameter that defines the contrast of the image.

  The color tone setting screen 200 also displays the color tone selected by the color tone selection unit 250, the color circle 210, and the color tone selection unit 250 for selecting a parameter setting that defines the color tone to be added to the image from among those prepared in advance. Is provided with a tone emphasis scale 255 for setting the degree of emphasis in the shadow portion (dark portion) and highlight portion (bright portion), and a gamma value specifying portion 260 for specifying a gamma value when performing gamma correction.

  The color tone setting screen 200 is further applied to the initial image data PID according to the parameters set through the color circle 210, the lightness scale 230, the contrast scale 240, the color tone selection unit 250, the color tone enhancement scale 255, and the gamma value designation unit 260. A preview button 270 for displaying the color sample image in the case of performing image conversion in the sample image display area 220 is provided. Then, a cancel button 280 for canceling the printing process and a print button 290 for confirming the set parameters and performing image conversion according to these parameters to execute printing are provided.

  When the color tone setting screen 200 is displayed in step S10 of FIG. 2, an image obtained by performing a predetermined resolution conversion on the initial image data PID is displayed in the sample image display area 220. Note that an image prepared in advance may be displayed in the sample image display area 220 as a color sample image regardless of the initial image data PID input from the application program 95. As an image to be used when printing a monochrome image with a predetermined color tone, it is preferable to prepare a monochrome image expressed only by the brightness of the pixels.

The color circle 210 is an a ^* b ^* plane where L ^* is 55 in the L ^* a ^* b ^* color system, and a circle with a radius of 20 having a ^* = b ^* = 0 as the center point O. It is an included part. In other words, the color circle 210 is a disk having a gray point as the center, and at least one of a ^* and b ^* varies stepwise depending on the position in the color circle 210.

  When the color tone setting screen 200 is displayed, the user operates the mouse 130 to select a color tone to be added to the image via the color tone selection unit 250 in step S20 of FIG. The user can select any one of warm tone, cool tone, and sepia tone. The cool tone is a cool color tone, the warm tone is a warm color tone, and the sepia tone is a shade of a photograph faded. In the example of FIG. 3, the cool tone is selected.

  After the color tone is designated through the color tone selection unit 250 in step S20, when the user presses the preview button 270 (see FIG. 3) via the mouse in step S30, the printer driver 96 sets the initial image data PID. The reduced image data obtained by the resolution conversion is color-converted along the display conversion table 104b.

  The printer driver 96 holds in advance three types of display conversion tables 104b corresponding to the color tone (warm tone, cool tone, sepia tone). A display conversion curve generation unit 98f, which is a functional unit of the color conversion module 98, selects a display conversion table corresponding to the color tone selected in step S20. The display conversion curve generation unit 98f is displayed as “display conversion C generation unit 98f” in FIG. The display conversion table 104b is red, green, and blue color conversion curves Cr, Cg, and Cb in which input values and output values are stored in the form of discrete values.

  FIG. 4 is an explanatory diagram showing color conversion curves Cr, Cg, Cb as the display conversion table 104b. The color conversion curve is a curve that defines how each gradation value of RGB is changed when a tone is added to a monochrome image. The subscripts r, g, and b of the symbol C of the color conversion curve represent RGB colors, respectively. In FIG. 4, the horizontal axis represents RGB gradation values before conversion, and the vertical axis represents RGB gradation values after conversion.

  In the example of FIG. 4, the gradation values of red and green are not modified by the color conversion curves Cr and Cg. On the other hand, the blue tone value is changed to a larger value as a whole. The color conversion curves Cr, Cg, and Cb in FIG. 4 are color conversion curves when a cool tone is applied.

  In step S30, the color conversion module 98 converts the red, green, and blue tone values of the reduced image data obtained by converting the resolution of the initial image data PID along the color conversion curves Cr, Cg, and Cb. . A functional unit of the printer driver 96 having such a function is shown in FIG. 1 as a display image generating unit 98g.

  The display image generation unit 98g displays the color-converted image in the sample image display area 220 via the video driver 91. The display image generation unit 98g and the video driver 91 correspond to a “display image generation unit” in the claims.

  When the initial image data PID input from the application program 95 is image data having only the lightness gradation value for each pixel, the display image generation unit 98g sets the lightness gradation for each pixel. Treated as images having equal red, green, and blue tone values.

  When the color sample image is displayed in step S30 of FIG. 2, the user determines in step S40 whether the color tone of the color sample image is acceptable. If it is desired to change the color tone from the color sample image, the process returns to step S20. If the color tone of the color sample image is acceptable, the process proceeds to step S50.

  In step S50, the user uses the tone emphasis scale 255 to set the enhancement degree modification coefficient Re. The enhancement degree modification coefficient Re varies the color tone applied to a darker shadow portion (dark portion) and a brighter highlight portion (bright portion) with respect to an intermediate portion having intermediate brightness in an image to be printed. It is a coefficient that determines whether or not. The enhancement degree modification coefficient Re is a coefficient related to processing at the time of printing, and thus the value is not reflected in the display image of the sample image display area 220 on the display 21.

  Thereafter, when the print button 290 (see FIG. 3) is pressed in step S60, the image data MID1 of the RGB image is cyan (C), magenta (M), yellow (Y), first to third in step S70. Are converted into image data MID2 in which the color of each pixel is represented by the gradation values of the achromatic inks (K1 to K3). Note that the display of the color tone setting screen 200 and the reception of instructions from the user as described above are performed by the user interface unit 98a as a functional unit of the color conversion module 98. The user interface unit 98a is referred to as a “UI unit” in FIG.

  Image conversion from the image data MID1 to the image data MID2 is performed with reference to the printing one-dimensional LUT 104c (see FIG. 1). After the print button 290 is pressed, the printing one-dimensional LUT 104c is generated by modifying the output values of cyan, magenta, and yellow in the original printing one-dimensional lookup table 104d in step S70 of FIG. Hereinafter, a procedure for generating the printing one-dimensional LUT 104c will be described.

  FIG. 5 is an explanatory diagram showing the original printing one-dimensional lookup table 104d (see FIG. 1). The one-dimensional lookup table 104d for original printing uses cyan (C), magenta (M), and yellow (Y) that the printer 22 uses gray gradation values when printing a monochrome image without color tone. FIG. 6 is a one-dimensional lookup table for converting to gradation values of first to third achromatic inks (K1 to K3). The horizontal axis of the graph of FIG. 5 is the lightness gradation value, and the gray brightness becomes brighter as it goes to the right on the horizontal axis, and darker as it goes to the left. The lightness gradation value can be directly replaced with the achromatic red, green, and blue gradation values. For example, gray having a lightness gradation value of 25 can be represented by a combination of gradation values of red, green, and blue (25, 25, 25).

  The vertical axis in FIG. 5 is the gradation values of C, M, Y, and K1 to K3. A printing conversion table generation unit 98d, which is a functional unit of the color conversion module 98, generates a printing one-dimensional lookup table 104c based on the original printing one-dimensional lookup table 104d. The print conversion table generation unit 98d is represented as “print conversion T generation unit 98d” in FIG.

  FIG. 6 is a flowchart showing a procedure for generating a one-dimensional printing look-up table 104c for image conversion in step S70 of FIG. First, in step S710, it is calculated what color the reference grays G1, G2, and G3, which are the three basic achromatic colors, are converted by the color tone specified in step S20 of FIG. .

  The reference grays G1, G2, and G3 are achromatic colors having different brightness. The achromatic color can be represented by the same gradation values of red, green and blue. Therefore, here, the reference grays G1, G2, and G3 are red, green, and blue input gradation values (V1, V1, V1), (V2, V2, V2), and (V3, V3, V3), respectively. Shall be represented. Note that V1> V2> V3. For example, V1 = 223, V2 = 128, and V3 = 32.

  Further, the reference grays G1 (V1, V1, V1), G2 (V2, V2, V2), G3 (V3, V3, V3) are obtained by the color conversion (see FIG. 4) designated in step S20 of FIG. Are converted into reference colors G1c (Vr1c, Vg1c, Vb1c), G2c (Vr2c, Vg2c, Vb2c), and G3c (Vr3c, Vg3c, Vb3c), respectively, to which colors are assigned. The gradation values representing the reference colors G1c, G2c, G3c are obtained from the color conversion curves Cr, Cg, Cb as the display conversion table 104b in FIG.

Next, in step S720 of FIG. 6, the reference color G1c obtained by converting the reference grays G1, G2, and G3 by the display conversion table 104b with reference to the first reference point conversion table 104g (see FIG. 1). , G2c, and G3c are converted into combinations of gradation values of the L ^* a ^* b ^* color system. The first reference point conversion table 104g is a combination of color tone values (Vr, Vg, Vb) expressed in the sRGB color system and the color gradations expressed in the L ^* a ^* b ^* color system. It is a three-dimensional lookup table for conversion into a combination of values (Vl ^* , Va ^* , Vb ^* ). Note that the reference colors G1c, G2c, and G3c represented by the gradation values of the L ^* a ^* b ^* color system are denoted as reference colors G1cL, G2cL, and G3cL.

In step S720, the combination of gradation values of each reference color represented by the sRGB color system, G1c (Vr1c, Vg1c, Vb1c), G2c (Vr2c, Vg2c, Vb2c), G3c (Vr3c, Vg3c, Vb3c) G1cL (Vl1 ^* , Va1 ^* , Vb1 ^* ), G2cL (Vl2 ^* , Va2 ^* , Vb2 ^* ), G3cL (Vl3 ^* , Va3 ^* ), a combination of gradation values expressed in the L ^* a ^* b ^* color system , Vb3 ^* ).

  In step S730, referring to the second reference point conversion tables 104h, 104i, and 104j (see FIG. 1), the combination of the gradation values representing the reference colors G1cL, G2cL, and G3cL is changed to cyan (C) that is the ink color. , Magenta (M), yellow (Y), and first to third achromatic inks (K1 to K3). Note that the reference colors G1c, G2c, and G3c represented by the gradation values of the ink colors are denoted as reference colors G1cI, G2cI, and G3cI.

In step S730, a combination of gradation values of each reference color expressed in the L ^* a ^* b ^* color system, G1cL (Vl1 ^* , Va1 ^* , Vb1 ^* ), G2cL (Vl2 ^* , Va2 ^* , Vb2 ^* ) , G3cL (Vl3 ^* , Va3 ^* , Vb3 ^* ) are combinations of ink color gradation values, G1cI (Vc1, Vm1, Vy1, Vk1, Vlk1, Vllk1), G2cI (Vc2, Vm2, Vy2, Vk2, Vlk2, Vllk2), G3cI (Vc3, Vm3, Vy3, Vk3, Vlk3, Vllk3).

  In the above gradation value display, the sign next to V has the following meaning. That is, “c” in Vc1 to Vc3 represents cyan. “M” in Vm1 to Vm3 represents magenta. “Y” in Vy1 to Vy3 represents yellow. “K” in Vk1 to Vk3 represents the first achromatic color K1. “Lk” in Vlk1 to Vlk3 represents the second achromatic color K2. “Llk” of Vllk1 to Vllk3 represents the third achromatic color K3. The same applies to other notations relating to ink colors.

FIG. 7 is an explanatory diagram showing the second reference point conversion tables 104h, 104i, and 104j (see FIG. 1). The second reference point conversion tables 104h, 104i, and 104j are obtained by combining color tone value combinations (Vl ^* , Va ^* , Vb ^* ) expressed in the L ^* a ^* b ^* color system, and ink color C. , M, Y, K1 to K3 gradation value combinations (Vc, Vm, Vy, Vk, Vlk, Vllk).

  In this embodiment, the second reference point conversion tables 104h, 104i, and 104j have five input gradation values for each of the RGB color components. The second reference point conversion tables 104h, 104i, and 104j are lookup tables having a total of 5 × 5 × 5 = 125 lattice points. In step S730, when the combination of gradation values of each reference color expressed in the L * a * b * color system is converted into a combination of gradation values of ink colors, the respective second reference point conversions are performed. A gradation value of each ink is obtained by performing an interpolation calculation based on the output gradation values of ink colors at a plurality of grid points included in the table.

The second reference point conversion table 104h shown in the upper part of FIG. 7 is a second reference point conversion table corresponding to the reference gray G1 and the converted reference color G1cL. The second reference point conversion table 104h has output gradation values of ink colors only in the range of lightness of plus or minus 10 centering on Vlg1 ^* which is the lightness of the reference gray G1. The second reference point conversion table 104h, for a ^* for the range of -30 to + 30, for the range of -30 to + 30 for b ^* only has an output tone value of ink color.

The second reference point conversion table 104i shown in the middle of FIG. 7 is a second reference point conversion table corresponding to the reference gray G2, and has a lightness of plus or minus 10 centered on Vlg2 ^* which is the lightness of the reference gray G2. Only the range has the output gradation value of the ink color. Further, the second reference point conversion table 104j shown in the lower part of FIG. 7 is a second reference point conversion table corresponding to the reference gray G3, and is plus or minus 10 centering on Vlg3 ^* which is the brightness of the reference gray G3. Only the lightness range has an output tone value of ink color. The second reference point conversion table 104i, 104Jh also the range of -30 to + 30 for a ^* only, for a range of -30 to + 30 for b ^* only has an output tone value of ink colors .

  That is, the second reference point conversion tables 104h, 104i, and 104j do not have output gradation values for the colors in the entire color space as a whole, and include the corresponding reference grays G1, G2, and G3, and overlap each other. Only some color spaces that do not have ink output tone values.

  According to the color tone designated in step S20 of FIG. 2, the tone is given to each reference gray by the tone curve of FIG. However, when printing is performed with a color tone applied to a monochrome image, the lightness does not change greatly depending on the color tone, and gray is not converted into red itself or green itself. Therefore, even if the second reference point conversion tables 104h, 104i, and 104j do not have output gradation values for all the colors in the color space, the reference grays G1, G2, and the like in step S730 of FIG. It is possible to output gradation values of ink colors corresponding to the colors G1cL, G2cL, and G3cL after the conversion of G3.

  Further, by setting the second reference point conversion tables 104h, 104i, and 104j as described above, the second reference point conversion table holds the output tone values of ink colors for all color spaces. Compared to the above, the data amount of the second reference point conversion tables 104h, 104i, 104j can be reduced.

  Next, in step S740 in FIG. 6, reference modification coefficients Rcr1 to Rcr3, Rmr1 to Rmr3, Ryr1 to Ryr3 corresponding to the reference grays G1, G2, and G3 for cyan, magenta, and yellow are calculated.

  For example, the reference modification coefficient Rcr2 of the cyan reference gray G2 is Vc2 / Vcb2. Vc2 is a cyan gradation value of the reference color G2cI obtained by adding a color tone to the reference gray G2 (see step S730 in FIG. 6 and the middle stage in FIG. 7). This Vc2 is obtained from the gradation value G2cL (Vr2c, Vg2c, Vb2c) of the reference color G2c with the color tone by referring to the second reference point conversion table 104i.

  On the other hand, Vcb2 is a cyan gradation value corresponding to the reference gray G2 (see FIG. 5). This Vcb2 is obtained from the gradation values (V2, V2, V2) of the reference gray G2 with reference to the original printing one-dimensional lookup table 104d. In addition to the cyan gradation value Vcb2 corresponding to the reference gray G2, FIG. 5 also shows the magenta gradation value Vmb2 corresponding to the reference gray G2 and the yellow gradation value Vyb2 corresponding to the reference gray G2.

  That is, the reference modification coefficient Rcr2 is the ratio of the cyan tone value Vc2 after the color tone is applied to the cyan tone value Vcb2 before the tone is applied to the reference gray G2.

  Similarly, the reference modification coefficient Rcr1 of the cyan reference gray G1 is the ratio of the cyan gradation value after the color tone is imparted to the cyan tone value before the tone is imparted to the reference gray G1, and is Vc1 / Vcb1. The reference modification coefficient Rcr3 of the cyan reference gray G3 is a ratio of the cyan gradation value after the color tone is imparted to the cyan tone value before the tone is imparted to the reference gray G3, and is Vc3 / Vcb3.

  The cyan reference modification coefficients Rcr1 to Rcr3 have been described above as examples, but the magenta and yellow reference modification coefficients Rmr1 to Rmr3 and Ryr1 to Ryr3 are similarly calculated. It is the reference modification coefficient determination unit 98b as a function unit of the color conversion module 98 that performs such a function.

  In step S740 of the flowchart of FIG. 6, “c”, “m”, and “y” that represent the ink color in each symbol in the above description are collectively represented by I. That is, RIri represents a reference modification coefficient for each ink color. VIi represents a gradation value of each ink color representing a reference color obtained by adding a color tone to the reference gray Gi (i = 1 to 3). VIbi is a gradation value of each ink color representing the reference gray Gi (i = 1 to 3).

  Next, in step S750, cyan, magenta, and yellow corresponding to gradation values 0 to 255 of cyan, magenta, and yellow based on reference modification coefficients Rcr1 to Rcr3, Rmr1 to Rmr3, and Ryr1 to Ryr3 corresponding to the respective reference grays G1, G2, and G3. The modification coefficients Rc, Rm, Ry to be calculated are calculated.

  FIG. 8 is an explanatory diagram showing modification coefficient tables Tc, Tm, Ty for cyan, magenta, and yellow. The horizontal axis in the figure is lightness gradation values 0 to 255. The minimum gradation value of brightness may be expressed as Vmin and the maximum gradation value may be expressed as Vmax. The vertical axis represents the modification coefficients Rc, Rm, Ry. In the figure, the modification coefficients Rc, Rm, and Ry of the modification coefficient tables Tc, Tm, and Ty are shown as a continuous graph. However, in practice, the modification coefficients Rc, Rm, and Ry are gray. It is determined discretely for each gradation value 0-255.

  As shown in FIG. 8, the modification coefficients Rc, Rm, and Ry are not constant with respect to the lightness gradation value. That is, at least one of the modification coefficients corresponding to the lightness gradation values 0 to 255 is different from the others. For this reason, the tone values of cyan, magenta, and yellow in the original printing one-dimensional lookup table 104d are modified with different modification coefficients according to the lightness tone values as input values. Therefore, a preferable color tone is set according to the lightness. In the following description, the modification coefficient Rc for cyan will be described as an example.

  In step S750 of FIG. 6, the modification coefficient table generation unit 98c calculates the modification coefficients Rc (0) to Rc (255) at the lightness gradations (0 to 255) as values on the following curve. That is, the curve has a point pmax (255, 1.0), a point pc1 (V1, Rcr1), a point pc2 (V2) in a graph in which the horizontal axis represents the lightness gradation value and the vertical axis represents the cyan modification coefficient Rc. , Rcr2), a point pc3 (V3, Rcr3), a curve passing through the point pmin (0, 1.0), for example, a spline curve.

  As a result, the modification coefficient Rc (V1) at the lightness gradation value V1 is Rcr1, the modification coefficient Rc (V2) at the lightness V2 gradation value is Rcr2, and the modification coefficient Rc (V3) at the lightness gradation value V3. Becomes Rcr3. The modification coefficient Rcmax = Rc (255) at the maximum gradation value Vmax = 255 is 1.0. Further, the modification coefficient Rcmin = Rc (0) at the lightness minimum gradation value Vmin = 0 is also 1.0.

  The cyan modification coefficient Rc is uniquely determined with respect to the lightness gradation value. For example, when the spline curve passing through each of the above points is such that the modification coefficient Rc is not uniquely determined with respect to the lightness gradation value, correction is appropriately made.

  As described above, the cyan modification coefficients Rc (0) to Rc (255) are determined for each gradation (0 to 255) of lightness. The cyan modification coefficient Rc of each gradation value is held as a modification coefficient table Tc.

  Although the cyan modification coefficient Rc has been described above as an example, in step S750, the magenta modification coefficient Rm and the yellow modification coefficient Ry are similarly generated (see FIG. 8). In the example of FIG. 8, the cyan modification coefficient Rc is a value of 1 or more, while the magenta modification coefficient Rm and the yellow modification coefficient Ry are both values of 1 or less.

  In step S750 in FIG. 6, the modification coefficient table generation unit 98c generates the modification coefficient tables Tc, Tm, and Ty as described above. In FIG. 1, the modification coefficient tables Tc, Tm, and Ty are collectively referred to as “modification coefficient T (table) 104f”.

  In step S760 of FIG. 6, based on the modification coefficients Rc, Rm, Ry of the modification coefficient tables Tc, Tm, Ty generated as described above, the printing conversion table generation unit 98d performs the one-dimensional look for original printing. The cyan, magenta, and yellow output values of the up table 104d are modified to generate a one-dimensional lookup table 104c for printing.

  FIG. 9 is an explanatory diagram showing the printing one-dimensional lookup table 104c. In FIG. 9, the cyan, magenta, and yellow output values of the one-dimensional lookup table 104d for original printing are indicated by broken lines as Co, Mo, and Yo.

  In step S760 of FIG. 6, for example, the cyan output value for each input gradation value in the original printing one-dimensional lookup table 104d has a modification coefficient Rc (0) having a value between 1.0 and 1.4, respectively. ) To Rc (255) (see the upper part of FIG. 8), the value is equal to or higher than the original value. The output values of magenta and yellow are multiplied by modification coefficients Rm (0) to Rm (255) and Ry (0) to Ry (255) each having a value between 0.8 and 1.0 ( In the middle and lower parts of FIG. As a result, the output values of cyan magenta and yellow are changed from graphs Co, Mo, and Yo indicated by broken lines to graphs C, M, and Y indicated by solid lines.

  For example, when the input gradation value is V2 = 128, the cyan output gradation value of the original printing one-dimensional lookup table 104d is multiplied by Rc (128), that is, Rcr2 (see FIG. 8). As a result, the output gradation value of cyan is changed from Vco2 to Vc2 (see the middle stages of FIGS. 9 and 7). Further, the cyan output gradation value of the original printing one-dimensional lookup table 104d when the input gradation value is V1 = 223 is multiplied by Rc (223), that is, Rcr1. As a result, the output tone value of cyan becomes Vc1 (see the upper part of FIG. 7). The cyan output gradation value of the original printing one-dimensional lookup table 104d when the input gradation value is V3 = 32 is multiplied by Rc (32), that is, Rcr3. As a result, the output tone value of cyan becomes Vc3 (see the lower part of FIG. 7).

  As described above, in step S760 of FIG. 6, the printing one-dimensional lookup table 104c as shown in FIG. 9 is generated.

  In step S770, referring to the printing one-dimensional lookup table 104c generated as described above (see FIG. 9), the image data MID1 in which the color is represented only by lightness is cyan (C), magenta (M ), Yellow (Y), and the first to third achromatic inks (K1 to K3) are converted into image data MID2 in which the color of each pixel is represented (see FIG. 1). Note that such image conversion is executed by an image conversion execution unit 98e as a functional unit of the color conversion module 98.

Note that the color conversion performed with reference to the printing one-dimensional lookup table 104c in step S770 is based on gray on the axis of a ^* = b ^* = 0 in the L ^* a ^* b ^* color space. This is color conversion for conversion to points on a curve (shown by a broken line in FIG. 7) passing through three points representing the colors G1cL, G2cL, and G3cL.

Note that the upper end point of the curve representing the color after conversion in FIG. 7 is “lightness when reproducing the lightness gradation value 255 in FIG. 5” on the L ^* axis, that is, “ink on the print medium”. This is a point representing "lightness" L ^* max when not recorded at all. Then, the lower end point is on the L ^* axis “when the printing uses the one-dimensional lookup table 104d for original printing in FIG. 5 or the one-dimensional lookup table for printing 104c in FIG. "Lightness when reproducing value 0", that is, "the darkest lightness that can be reproduced when using the original one-dimensional lookup table 104d in FIG. 5 or the one-dimensional lookup table 104c in FIG. 9 for printing" This is a point representing L ^* min.

  In the present embodiment, the sample data display area 220 is provided with a color tone with a tone curve (see FIG. 4) along the color tone specified by the user with respect to the image data represented by the gradation value of the sRGB color system. To display. On the other hand, in the printing process, based on the colors before and after conversion of the reference grays G1 to G3 converted by the tone curve, the chromatic colors of the original printing one-dimensional lookup table 104d used when no color tone is given. The ink output value is modified to generate a printing one-dimensional lookup table 104c (see FIG. 9). Then, according to the printing one-dimensional lookup table 104c, the image data represented by the gradation value of the sRGB color system is converted into the image data represented by the gradation value of the ink color system and printed. I do.

  In such an aspect, the color tone of the image printed with ink is close to the color tone of the image displayed on the display 21. For this reason, the user can confirm the color tone by himself / herself on the display and can obtain a print image to which the color tone is attached. Therefore, the user can obtain a print image with a desired color tone by a simple procedure without repeating printing and repeating trial and error or printing many sample images.

B. Second embodiment:
In the first embodiment, the color tone to be added to the image is selected from the color tone prepared in advance via the color tone selection unit 250 (see step S20 in FIG. 2 and FIG. 3). However, the color tone to be added to the monochrome image can be designated by other methods. In the second embodiment, the operation of the color conversion module 98 (see steps S20 and S30 in FIG. 2) when the color tone is designated by a method different from the first embodiment will be described. Other operations and the configuration of each part are the same as those in the first embodiment.

  When the color tone setting screen 200 of FIG. 3 is displayed, the user operates the cursor CS via the mouse 130 and designates one point in the color circle 210. This point is called “designated point Pcc”. The user can designate the color tone to be attached to the monochrome image by designating one point in the color circle 210 in which the intensity of the color component varies stepwise according to the position. Therefore, it is possible to easily and intuitively specify the color tone to be added to the monochrome image.

FIG. 10 is a flowchart showing a procedure for generating the color conversion curves Cr, Cg, Cb based on the designated point Pcc. This process is performed by the display conversion curve generation unit 98f. When the designated point Pcc is designated, the display conversion curve generating unit 98f, in step S302, represents the coordinates of the L ^* a ^* b ^* color system that represents the same color as the designated point Pcc in the color circle 210 (L _{^{0 *, a 1 *, b}} 1 *) is calculated. In step S304, the coordinates (Rs, Gs, Bs) of the sRGB color system representing the same color as the (L ₀ ^* , a ₁ ^* , b ₁ ^* ) are calculated. Incidentally, the specified point Pcc, since L ^* is a point in the color circle 210 is the a ^* b ^* plane is 55, L ₀ ^* is 55.

Further, the display conversion curve generation unit 98f calculates the coordinates (Ro, Go, Bo) of the sRGB color system representing the same color as the center point O of the color circle 210 in step S306. The center point O of the color circle 210 is an achromatic color represented by (55, 0, 0) in the L ^* a ^* b ^* color system. For this reason, Ro = Go = Bo. Thus, according to the parameters input by the user, the coordinates (Rs, Gs, Bs) of the sRGB color system representing the same color as the color of the designated point Pcc and the coordinates of the sRGB color system representing the same color as the center point O are set. (Ro, Go, Bo) is calculated.

  FIG. 11 is an explanatory diagram showing the color conversion curves Cr, Cg, Cb. In step S308, the printer driver 96 generates color conversion curves Cr, Cg, and Cb based on (Rs, Gs, Bs) corresponding to the designated point Pcc and (Ro, Go, Bo) corresponding to the center point O. To do.

  For example, the red color conversion curve Cr is generated as a quadratic curve passing through the origin (0, 0) and the points (255, 255) and (Ro, Rs) in FIG. Similarly, the other color conversion curves Cg and Cb are generated based on Go and Gs and Bo and Bs. The color conversion curves Cr, Cg, and Cb are actually generated as a display conversion table 104b that stores converted gradation values corresponding to the respective gradation values before RGB conversion.

According to the color conversion curves Cr, Cg, and Cb, the gray of (Ro, Go, Bo) corresponding to the center point, that is, the gray of lightness L ^* of 55 is the color (Rs, Gs, Bs) corresponding to the designated point Pcc. ). As described above, the conversion using the color conversion curves Cr, Cg, and Cb converts the color displayed at the center point O of the color circle 210 to the color of the designated point Pcc designated by the user. Therefore, the user can use the color circle 210 to specify the color tone while intuitively grasping the color tone attached to the monochrome image.

  In step S310, the display image generation unit 98g (see FIG. 1) performs color conversion on the reduced image data obtained by converting the resolution of the initial image data PID along the color conversion curves Cr, Cg, and Cb, and the tone setting screen. 200 sample image display areas 220 are displayed. At the same time, a user interface screen displaying color conversion curves Cr, Cg, and Cb as shown in FIG. 11 is displayed in a window different from the color tone setting screen 200.

  In step S312, the user determines whether the color tone of the color sample image is acceptable. If it is desired to change the color tone from the color sample image, the process proceeds to step S314. If the color tone of the color sample image is acceptable, the color conversion curve generation process is terminated, and then the process proceeds to step S50 in FIG. 2 to set the enhancement degree modification coefficient.

  In step 314, the user corrects the color conversion curves Cr, Cg, and Cb displayed on the user interface screen by operating the mouse 130. Specifically, the user places the cursor CS on the points pr1 to pr3, pg1 to pg3, and pb1 to pb3 corresponding to the input gradation values 32, 218, and 223 on the color conversion curves Cr, Cg, and Cb, and drags and drags them. By dropping, these points can be manipulated up and down. The points pr1 to pr3 are points on the red color conversion curve Cr, pg1 to pg3 are points on the green color conversion curve Cg, and pb1 to pb3 are on the blue color conversion curve Cb. Is a point. Each time the point on the color conversion curve of each color is moved, the display conversion curve generation unit 98f corrects the color conversion curve graph so that it passes through each point.

  When the user finishes the operation and presses the preview button 270, the process returns to step S310, and the color sample image is displayed in the sample image display area 220. The user can repeat the correction processing in steps S310 to S314 until the color sample image has a desired color tone.

  In this manner, the user can freely correct the tone curve and set the color tone to be added to the image.

C. Third embodiment:
In the first embodiment, reference is made when determining the gradation value combinations G1cI, G2cI, G3cI of the ink colors corresponding to the reference colors G1c, G2c, G3c obtained by adding color tones to the reference grays G1, G2, G3. The reference point conversion tables 104h, 104i, and 104j convert the combination of gradation values of the L ^* a ^* b ^* color system into the combination of gradation values of ink colors. However, the reference point conversion table referred to when determining the combination of gradation values of the ink color corresponding to the reference color after the color tone is applied can be in another form. In the third embodiment, such an aspect will be described. The third embodiment is the same as the first embodiment except for the process of determining the combination of the reference point conversion table and the gradation value of the ink color of the reference color (see steps S720 and S730 in FIG. 6).

  FIG. 12 is a diagram illustrating the reference point conversion tables 104h3, 104i3, and 104j3. The reference point conversion tables 104h3, 104i3, and 104j3 are combinations of gradation values (Vr, Vg, Vb) of colors represented by the sRGB color system, and gradations of ink colors C, M, Y, and K1 to K3. It is a three-dimensional lookup table for converting into a combination of values (Vc, Vm, Vy, Vk, Vlk, Vllk).

  The reference point conversion tables 104h3, 104i3, and 104j3 have five input gradation values for each of the RGB color components. The reference point conversion tables 104h3, 104i3, and 104j3 are lookup tables having a total of 5 × 5 × 5 = 125 lattice points. When converting a combination of gradation values of each reference color expressed in the RGB color system into a combination of gradation values of ink colors, output of ink colors at a plurality of grid points included in each reference point conversion table The gradation value of each ink is obtained by performing an interpolation calculation based on the gradation value.

  The reference point conversion tables 104h3, 104i3, 104j3 as a whole do not have output gradation values for the colors in the entire color space, and include corresponding reference grays G1, G2, G3 as shown in FIG. Only some color spaces that do not overlap with each other have output gradation values of ink colors.

  When such reference point conversion tables 104h3, 104i3, and 104j3 are used, the reference modification coefficient determination unit 98b can perform the following processing instead of steps S720 and S730 in FIG. That is, with reference to the reference point conversion table 104h3, the gradation values (Vc1, Vm1, Vy1, Vk1, Vlk1, Vllk1) of the ink color of the reference color G1c obtained by adding a color tone to the reference gray G1 are determined. Further, with reference to the reference point conversion table 104i3, the ink color gradation values (Vc2, Vm2, Vy2, Vk2, Vlk2, Vllk2) of the reference color G2c obtained by adding a color tone to the reference gray G2 are determined. Then, with reference to the reference point conversion table 104j3, the gradation values (Vc3, Vm3, Vy3, Vk3, Vlk3, Vllk3) of the ink color of the reference color G3c obtained by adding a color tone to the reference gray G3 are determined.

  With such an aspect, the reference modification coefficient can be determined with a simpler process than in the first embodiment.

D. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

D1. Modification 1:
In the above embodiment, the reference gray is three achromatic colors having different brightness values, and the reference modification coefficient is three for each chromatic color. However, the number of reference grays and corresponding reference modification coefficients can be any number. However, the number thereof is preferably 2 or more. The two or more reference modification coefficients preferably include two reference modification coefficients having different values. With this aspect, the modification coefficient can be changed according to the lightness gradation value, and a more natural color tone can be reproduced in the printed image.

  Further, it is more preferable that the number of the reference gray and the corresponding reference modification coefficient is 3 or more. A combination of the first gray represented by a combination of RGB gradation values included in the range Rg1 that is 1/3 from the maximum value and an RGB gradation value included in the range Rg2 that is 1/3 from the minimum value And a third gray represented by a combination of RGB gradation values included in the range Rg3 located between the range Rg1 and the range Rg2 (see FIG. 4).

  Also, a combination of the first gray represented by a combination of RGB gradation values included in the range Rg4 from the maximum value to 1/6 and an RGB gradation value included in the range Rg5 from the minimum value to 1/6. And a third gray represented by a combination of RGB gradation values included in the entire range Rg6 including the central value.

  In these aspects, the range Rg1 (or Rg4) corresponding to the highlight portion, the range Rg3 (or Rg6) corresponding to the middle portion, and the range Rg2 (or Rg5) corresponding to the shadow portion are displayed for display. Thus, there is a color that can reproduce the color converted along the color conversion curve (see FIG. 4). Therefore, a color tone close to the color tone confirmed on the display can be given to various brightness portions in the image.

D2. Modification 2:
The reference point conversion tables 104h, 104i, 104j of the first embodiment and the reference point conversion tables 104h3, 104i3, 104j3 of the third embodiment have five input gradation values for each color component, for a total of 5 ×. It was a look-up table having 5 × 5 = 125 lattice points. However, the reference point conversion table can be in other forms. The reference point conversion table is, for example, an aspect having 7 × 7 × 7 = 343 grid points in total, 7 for each color component, or 9 × 9 × 9 = 729 grids in total for 9 for each color component. It can be set as the aspect which has a point. In other words, the reference point conversion table may have a positive integer number of grid points with an appropriate density according to the color interpolation accuracy required by the user.

The fineness of the input gradation value on the L ^* axis of the second reference point conversion tables 104h, 104i, 104j of the first embodiment can be as fine as follows. That is, the difference of “1” of the lightness gradation value, which is the input gradation value of the original printing one-dimensional lookup table 104d and the generated printing one-dimensional lookup table 104c, is represented as the input level of the lightness L ^* . It is fine enough to be expressed by differences in key values.

Further, the fineness of the input gradation values of the a ^* axis and b ^* axis of the second reference point conversion tables 104h, 104i, 104j of the first embodiment may be as small as the following. it can. That is, the difference of “1” in the gradation value of the ink color that is the output gradation value of the original printing one-dimensional lookup table 104d and the generated printing one-dimensional lookup table 104c is input to the a ^* axis. It is fine enough to be expressed by the difference between the gradation value and the input gradation value on the b ^* axis.

  Furthermore, the fineness of the input gradation values of the RGB axes in the reference point conversion tables 104h3, 104i3, 104j3 of the third embodiment can be as fine as follows. That is, the difference of “1” in the lightness gradation value which is the input gradation value of the original printing one-dimensional lookup table 104d and the generated printing one-dimensional lookup table 104c is expressed as R, G, B. It is fine enough to be expressed by the difference in the combination of gradation values. Furthermore, the difference of “1” in the gradation value of the ink color that is the output gradation value of the original printing one-dimensional lookup table 104d and the generated printing one-dimensional lookup table 104c is expressed as R, G, B. It is fine enough to be expressed by the difference in the combination of gradation values.

  If it is such an aspect, the output after conversion can be obtained, without performing an interpolation calculation.

D3. Modification 3:
In the first embodiment, when determining the reference modification coefficient, the reference colors G1c, G2c, and G3c are once expressed by the gradation values of the L ^* a ^* b ^* color system, and then the gradation values of the ink colors are changed. It was converted. However, the reference colors G1c, G2c, and G3c can be expressed in other color systems such as the L ^* u ^* v ^* color system and the xyz color system. However, in the middle of processing, once the reference color is replaced with a device-independent color system representation, it is easy to divert to multiple types of output devices that use different basic colors for image output. is there.

D4. Modification 4:
In the first embodiment, the modification coefficients Rc, Rm, and Ry are calculated as values on the spline curve (see FIG. 4). In the second embodiment, the color conversion curve is generated as a quadratic curve (see FIG. 12). However, these curves can be generated as other curves such as a cubic curve, a quartic curve, and a Bezier curve. It is also possible to determine the modification coefficient corresponding to each gradation value by interpolating each point corresponding to the reference modification coefficient by a predetermined method.

  In the above embodiment, the modification coefficients Rc, Rm, and Ry are discretely set for each tone value of brightness, and are retained as modification coefficient tables Tc, Tm, and Ty. However, the modification coefficients Rc, Rm, and Ry may be held as functions that pass through a plurality of designated points such as pc1, pc2, and pc3 (see FIG. 8). In such an aspect, when the output gradation value of the chromatic color of the one-dimensional lookup table for original printing is modified (see step S740 in FIG. 6), the modification is performed with reference to the function.

D5. Modification 5:
In the above embodiment, the modification coefficients Rc, Rm, and Ry are obtained for the chromatic colors of cyan, magenta, and yellow based on the reference grays G1, G2, and G3 (see FIG. 8), and the original printing one-dimensional lookup table 104d is obtained. The output values of cyan, magenta, and yellow are multiplied by the output values of cyan, magenta, and yellow of the one-dimensional LUT 104c for printing. However, it is also possible to generate cyan, magenta, and yellow output values of the printing one-dimensional LUT 104c without using the output values of the original printing one-dimensional lookup table 104d.

  For example, in the case of cyan, the horizontal axis represents the lightness gradation value, and the vertical axis represents the ink color density gradation value. The positions on the horizontal axis represent the reference grays G1, G2, and G3, respectively. The gradation values are V1, V2, and V3, and the points on the vertical axis are Vc1, Vc2, and Vc3. Vc1, Vc2, and Vc3 are cyan tone values of reference colors G1c (G1cI), G2c (G2cI), and G3c (G3cI) obtained by adding color tones to the reference grays G1, G2, and G3. (See FIGS. 7 and 12). Then, the cyan output tone value is calculated as a value on the curve passing through the three points, the point (0, 0), and the point (255, 0). Output tone values are obtained in the same manner for other chromatic ink colors.

  With such an aspect, it is possible to obtain cyan, magenta, and yellow output values of the printing one-dimensional LUT 104c with a simpler procedure. However, the method of obtaining the chromatic color output value of the printing one-dimensional LUT 104c based on the chromatic color output value of the original printing one-dimensional lookup table 104d as in the first embodiment has the following advantages. . That is, if the original printing one-dimensional lookup table 104d for printing without adding color tone is sufficiently adjusted and generated so as not to cause color twist, the printing one generated based on it is generated. Color distortion is less likely to occur in the one-dimensional LUT 104c. Note that the color twist is an unnatural change in the color reproduced with the gradation value of each ink as the output value when the gradation value of the brightness as the input value gradually changes. That is.

D6. Modification 6:
In the above embodiment, the color circle 210 is an a ^* b ^* plane where L ^* is 55. However, the color circle 210 is not limited to such a mode. That is, the color circle has, for example, a gray point that can be expressed only by brightness, and at least one of the color saturation and hue of each position varies stepwise according to the position in the color circle. Can be.

  In the above embodiment, the color tone setting screen 200 has a color circle as an area for the user to specify the color tone to be attached to the monochrome image. However, the area for the user to specify the color tone to be added to the monochrome image is not limited to a circle. For example, a CMY color triangle having 100% cyan, 100% magenta, and 100% yellow at each vertex may be displayed.

D7. Modification 7:
In the above embodiment, the color tone given by the user is selected. However, when the color tone setting screen 200 is displayed, a mode in which a color tone is set in advance, such as a sepia tone, may be used.

D8. Modification 8:
In the above embodiment, the display unit that displays the image to be printed prior to printing is the liquid crystal display 21 (see FIG. 1). However, the display unit can take other forms such as a plasma display, a CRT display, and a liquid crystal projector. In other words, the display unit can be configured to display image data represented by gradation values of intensity of color components different from the ink color used by the printing apparatus.

D9. Modification 9:
In the above embodiment, the color sample image displayed on the liquid crystal display 21 as the display unit is an image generated based on the initial image data PID that is image data to be printed. However, the image displayed on the display unit may be a predetermined sample image. The user can obtain a print image with a desired color tone by selecting a color tone to be added to the image with reference to the color tone of the reference image for the sample.

D10. Modification 10:
In the above embodiment, the printing unit for printing an image is an inkjet printer. However, the printing unit may take other forms such as a bubble jet (registered trademark) printer, a laser printer, a thermal transfer printer, and a dot impact printer. That is, the printing unit can be configured to print an image using a plurality of basic colors including colors different from the color components used by the display unit to display an image.

D11. Modification 11:
In the above embodiment, the printer is a printer that uses cyan (C), magenta (M), yellow (Y), and first to third achromatic inks (K1 to K3). Then, when assigning a color tone to a monochrome image, the output values of cyan, magenta, and yellow in the original printing one-dimensional lookup table 104d used when no color tone is given have been modified. However, the printer may use other chromatic color inks, and may change the output value of these other chromatic color inks when applying a color tone to a monochrome image.

  For example, when the printer uses an ink of light cyan (Lc) and light magenta (Lm) in addition to cyan (C) and magenta (M) ink, a one-dimensional lookup table for original printing is used. Also have output values of those chromatic inks. In such an embodiment, the output values of light cyan, light magenta, and yellow in the original printing one-dimensional lookup table may be modified. “Light cyan” is an ink having the same hue as cyan and lighter than cyan. “Light magenta” is an ink having the same hue as magenta and a lighter color than magenta. With such an aspect, it is possible to reduce graininess in a printed image with a color tone. Note that the output values of a plurality of ink colors having the same hue can be modified.

  That is, when printing is performed with a color tone applied to a monochrome image, the output values of at least some chromatic colors included in the original printing one-dimensional lookup table used when the color tone is not applied are modified. The color tone can be imparted.

D12. Modification 12:
Although not described in each of the above embodiments, in addition to the above-described processing, the lightness scale 230 (see FIG. 3) is used to adjust the lightness or contrast when adding a color tone to a monochrome image. The scale 240 can be used to adjust the contrast.

D13. Modification 13:
In the above embodiment, a part of the configuration realized by hardware may be replaced with software, and conversely, a part of the configuration realized by software may be replaced by hardware. For example, a part of the function of the printer driver 96 (see FIG. 1) may be executed by the printer CPU 41.

  A computer program for realizing such a function is provided in a form recorded on a computer-readable recording medium such as a floppy disk or a CD-ROM. The host computer reads the computer program from the recording medium and transfers it to the internal storage device or the external storage device. Alternatively, the computer program may be supplied from the program supply device to the host computer via a communication path. When realizing the function of the computer program, the computer program stored in the internal storage device is executed by the microprocessor of the host computer. Further, the host computer may directly execute the computer program recorded on the recording medium.

  In this specification, the computer is a concept including a hardware device and an operation system, and means a hardware device that operates under the control of the operation system. The computer program causes such a computer to realize the functions of the above-described units. Note that some of the functions described above may be realized by an operation system instead of an application program.

  In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, An external storage device fixed to a computer such as a hard disk is also included.

  In the above embodiment, the computer 90 is connected to the liquid crystal display 21. However, the display device for displaying the color tone setting screen 200 of the printer driver 96 may be a liquid crystal display, a plasma display, a projector, or a projection screen. It can also be a means.

FIG. 2 is a block diagram illustrating a software configuration of the printing system according to the first embodiment. 6 is a flowchart illustrating a procedure for assigning a color tone when printing with a predetermined color tone added to a monochrome image. FIG. 3 is an explanatory diagram showing a color tone setting screen 200 of the printer driver 96. Explanatory drawing which shows the color conversion curves Cr, Cg, and Cb as the display conversion table 104b. Explanatory drawing which shows the one-dimensional lookup table 104d for original printing. The flowchart which shows the procedure which produces | generates the 1-dimensional lookup table 104c for printing, and performs image conversion. Explanatory drawing showing the 2nd reference point conversion table 104h, 104i, 104j. Explanatory drawing which shows modification coefficient table Tc, Tm, Ty. Explanatory drawing which shows the one-dimensional lookup table 104c for printing. The flowchart which shows the procedure at the time of producing | generating the color conversion curves Cr, Cg, and Cb based on the designated point Pcc. Explanatory drawing which shows color conversion curve Cr, Cg, Cb. The figure which shows the reference point conversion table 104h3, 104i3, 104j3.

Explanation of symbols

21 ... Liquid crystal display 22 ... Printer 28 ... Print head 31 ... Carriage 32 ... Operation panel 41 ... CPU
42 ... ROM
DESCRIPTION OF SYMBOLS 90 ... Computer 91 ... Video driver 95 ... Application program 96 ... Printer driver 97 ... Resolution conversion module 98 ... Color conversion module 98a ... User interface part 98b ... Reference | standard modification coefficient determination part 98c ... Modification coefficient table generation part 98d ... Conversion table for printing Generation unit 98e ... Image conversion execution unit 98f ... Display conversion curve generation unit 99 ... Halftone module 100 ... Rearrangement module 104 ... Color conversion table 104a ... Three-dimensional lookup table 104b ... Display conversion table 104c ... One-dimensional printing Look-up table 104d ... Original printing one-dimensional lookup table 104e ... Parameter correspondence table 104g ... First reference point conversion table 104h, 104i, 104j ... Second reference point conversion test Bull 120 ... Keyboard 130 ... Mouse 200 ... Color tone setting screen 210 ... Color circle 220 ... Sample image display area 230 ... Lightness scale 240 ... Contrast scale 250 ... Color tone selection part 255 ... Color tone enhancement scale 260 ... Gamma value designation part 270 ... Preview Button 280 ... Cancel button 290 ... Print button CS ... Cursor Cr ... Red color conversion curve Cg ... Green color conversion curve Cb ... Blue color conversion curve FNL ... Print image data L ^* ... Lightness MID1 ... Image data after resolution conversion MID2 ... Image data after color conversion MID3 ... Image data after halftone processing MS ... Main scanning direction (carriage movement direction)
O ... Center point of color circle ORG ... Original image data P ... Printing paper PID ... Initial image data Pcc ... Designated point Rcr1-Rcr3 ... Cyan standard modification coefficient corresponding to reference grays G1-G3 Rmr1-Rmr3 ... Reference gray G1- Magenta reference modification coefficient corresponding to G3 Ryr1 to Ryr3 ... Yellow reference modification coefficient corresponding to reference grays G1 to G3 Rc ... Cyan modification coefficient Rm ... Magenta modification coefficient Ry ... Yellow modification coefficient SS ... Transfer of printing paper Direction Tc: Cyan modification coefficient table Tm: Magenta modification coefficient table Ty: Yellow modification coefficient table V1 to V3: Lightness gradation values of reference grays G1 to G3 Vcb1-3: Cyan scale of reference grays G1 to G3 brightness Vr1c~Vr3c of tone value Vlg1 ^* ~Vlg3 ^* ... standard gray G1~G3 Red gradation values of the reference colors G1c to G3c Vg1c to Vg3c ... Green gradation values of the reference colors G1c to G3c Vb1c to Vb3c ... Blue gradation values of the reference colors G1c to G3c Vc1 to Vc3 ... Reference colors G1cI to G3cI Cyan gradation values Vm1 to Vm3 ... Magenta gradation values of reference colors G1cI to G3cI Vy1 to Vy3 ... Yellow gradation values of reference colors G1cI to G3cI Vk1 to Vk3 ... First absence of reference colors G1cI to G3cI Tone values of ink color of chromatic ink K1 Vlk1 to Vlk3 ... Tone values of ink color of second achromatic ink K2 of reference colors G1cI to G3cI Vllk1 to Vllk3 ... Third achromatic ink of reference colors G1cI to G3cI K3 ink color gradation value pc1... Determined by the input gradation value V1 of the reference gray G1 and the cyan reference modification coefficient Rcr1. pc2: Point determined by the input grayscale value V2 of the reference gray G2 and the cyan reference modification coefficient Rcr2 pc3: Point determined by the input grayscale value V3 of the reference gray G3 and the cyan reference modification coefficient Rcr3 pm1: of the reference gray G1 The point determined by the input gradation value V1 and the magenta reference modification coefficient Rmr1 pm2 ... The point determined by the reference gray G2 input gradation value V2 and the magenta reference modification coefficient Rmr2 pm3 ... The input gradation value V3 of the reference gray G3 A point determined by the magenta reference modification coefficient Rmr3. Py1... A point determined by the reference gray G1 input gradation value V1 and the yellow reference modification coefficient Ryr1. Py2... A reference gray G2 input gradation value V2 and the yellow reference modification coefficient Ryr2. Py3: determined by the input grayscale value V3 of the reference gray G3 and the yellow reference modification coefficient Ryr3 pmax ... maximum input gradation value, maximum and pmin ... minimum input tone value that is determined in a modified factor corresponding to the input tone value, the point defined by the modified coefficients corresponding to the minimum input tone value

Claims (13)

A printing apparatus that displays and prints an achromatic image with a color tone,
A display for displaying an image;
A printing unit that receives image data and prints using a plurality of inks including chromatic ink;
A control unit for controlling the display unit and the printing unit,
The controller is
A user interface unit which receives from a user a designation of a color tone to be given to original image data representing an achromatic image by selecting from a plurality of predetermined color tones or designation of one chromatic color;
Based on the specified color tone, for each color component of the first color system that is the RGB color system, a tone curve for modifying the first type of gradation value representing the intensity of each color component is generated. A conversion curve generator for display
Display image generation for converting the resolution of the original image data, converting the image data into display image data to which color tone is given with reference to each tone curve, and displaying a monotone image on the display unit according to the display image data And
Criteria for determining each tone value after conversion by each tone curve for reference gray (N is an integer of 2 or more) which is N achromatic colors represented by the first type tone value of each color component A color determining unit;
Based on the gradation values of the N reference grays before and after the conversion, a second type representing the ink color intensity of the plurality of inks as the output value having the first type gradation value as an input value. An ink color table generation unit for generating a one-dimensional ink color lookup table having gradation values;
An image conversion execution unit that refers to the one-dimensional ink color lookup table and converts the original image data into image data for printing including the second type of gradation values;
A print processing unit that performs predetermined processing on the image data for printing and passes the data to the printing unit. The apparatus of claim 1, comprising:
The ink color table generation unit is a look-up table for performing printing without imparting a color tone to an achromatic image, and has the first type gradation value as an input value and the second type as an output value. The output value of a predetermined chromatic color ink of a one-dimensional original ink color look-up table having the following gradation values is modified based on the respective gradation values before and after the conversion of the N reference grays. A device that generates a dimensional ink color lookup table. The apparatus of claim 2, comprising:
The control unit further includes:
Based on the first type gradation value of each color component after the conversion of one reference gray Gi (i is any one of 1 to N) of the N reference grays G1 to GN, the predetermined gray level A reference modification coefficient determining process for determining a reference modification coefficient Rri corresponding to the one reference gray Gi is performed for the N reference grays G1 to GN, and the predetermined existence coefficient is determined. A reference modification coefficient determination unit that determines N reference modification coefficients Rr1 to RrN of the color ink;
Based on the N reference modification coefficients Rr1 to RrN, modification coefficient generation for determining at least one modification coefficient Rmin to Rmax corresponding to each gradation value of the first type of the predetermined chromatic ink. And comprising
The ink color table generation unit multiplies the output values of the predetermined chromatic color ink of the one-dimensional original ink color look-up table by the modification coefficients Rmin to Rmax corresponding to the respective input values, and outputs the output values. To generate the one-dimensional ink color lookup table. The apparatus of claim 3, wherein
The N reference modification coefficients Rr1 to RrN include reference modification coefficients having different values. An apparatus according to claim 4, wherein
The reference modification coefficient determination unit
Referring to a three-dimensional reference color lookup table having a combination of the second type of gradation values that can be associated with the combination of the first type of gradation values of each color component, the one reference gray Gi The second type gradation value VIi of the predetermined chromatic ink is determined from the combination of the first type gradation values after the conversion of
With reference to the one-dimensional original ink color look-up table, the second type gradation value VIbi of the predetermined chromatic color ink is determined from the first type gradation value before the conversion of the one reference gray Gi. Decide
An apparatus that determines (VIi / VIbi) as the reference modification coefficient Rri corresponding to the one reference gray Gi. The apparatus of claim 5, comprising:
The three-dimensional reference color lookup table is N three-dimensional reference color lookup tables respectively associated with the reference grays G1 to GN.
The three-dimensional reference color lookup table corresponding to the one reference gray Gi has a combination of the second type of gradation values associated with a predetermined range of colors including the one reference gray Gi,
Each three-dimensional reference color lookup table corresponding to each of the reference grays G1 to GN has the second type of gradation associated with a part of the color of the color space of the first color system as a whole. A device having a combination of values. The apparatus of claim 5, comprising:
The three-dimensional reference color lookup table is a lookup table having gradation values of color components of the second color system independent of the device as input values;
Prior to referring to the three-dimensional reference color look-up table, the reference modification coefficient determining unit determines the combination of the first type of gradation values of the one reference gray Gi and the second table. A device that converts to a combination of tone values of color components of a color system. The apparatus of claim 5, comprising:
The three-dimensional reference color lookup table is a lookup table having the first type gradation value of the first color system as an input value. The apparatus of claim 1, comprising:
The N reference grays are
A first type of gradation value of each of the color components having the same value, which is represented by a combination of the first type of gradation value included in the first range that is 1/3 of the maximum value. 1 gray and
A first type of gradation value of each color component having the same value, and represented by a combination of the first type of gradation value included in a second range that is 1/3 from the minimum value. 2 grays,
A first-type gradation value of each of the color components having the same value, represented by a combination of the first-type gradation values included in the third range located between the first and second ranges. And a third gray. The apparatus of claim 1 , comprising:
The user interface unit includes:
A color tone designation area for designating a color tone to be attached to an image at one designated point, the color tone designation area configured such that the color tone to be attached to the image can be visually recognized from a position in the color tone designation area Is displayed,
An apparatus for receiving designation of one designated point in the color tone designation area from a user as designation of the chromatic color of one color . An image processing apparatus that generates a display and print image data by imparting a color tone to an achromatic image of image data,
A user interface unit which receives from a user a designation of a color tone to be given to original image data representing an achromatic image by selecting from a plurality of predetermined color tones or designation of one chromatic color;
Based on the specified color tone, for each color component of the first color system that is the RGB color system, a tone curve for modifying the first type of gradation value representing the intensity of each color component is generated. A conversion curve generator for display
Said original image data to resolution conversion, and converts the image data for display that color tone with reference to the tone curve is applied the display image generation unit,
Criteria for determining each tone value after conversion by each tone curve for reference gray (N is an integer of 2 or more) which is N achromatic colors represented by the first type tone value of each color component A color determining unit;
Based on the respective gradation values before and after the conversion of the N reference grays, a second representing the intensity of a plurality of ink colors including the first type gradation value as an input value and chromatic ink as an output value. An ink color table generation unit for generating a one-dimensional ink color lookup table having various gradation values;
An image conversion execution unit configured to convert the original image data into print image data including the second type of gradation value with reference to the one-dimensional ink color lookup table; A method of adding a color tone to an achromatic image, displaying it on a display unit, and printing,
(A) A specification of a color tone to be given to original image data representing an achromatic image is received from a user by selecting from a plurality of predetermined color tones or specifying a single chromatic color, and the specified color For each color component of the first color system, which is an RGB color system, based on the color tone, generating a tone curve for modifying the first type of tone value representing the intensity of the color component;
(B) the original image data to resolution conversion, the converted image data for display that color tone imparted with reference to each tone curve, and displays the monotone image on the display unit in response to the display image data Process,
(C) For the reference gray (N is an integer of 2 or more) that is N achromatic colors represented by the first type of tone value of each color component, the tone values after conversion by the tone curves are A step of determining;
(D) Based on the gradation values before and after the conversion of the N reference grays, the ink colors of a plurality of inks having the first type gradation value as an input value and chromatic ink as an output value Generating a one-dimensional ink color lookup table having a second type of tone value representing intensity;
(E) referring to the one-dimensional ink color look-up table, converting the original image data into printing image data including the second type gradation value, and printing. A computer program for adding a color tone to an achromatic image, displaying it on a display unit, and printing it,
Specification of the color tone to be given to the original image data representing the achromatic image is received from the user by selecting from a plurality of predetermined color tones or specifying one chromatic color, and based on the specified color tone Te, first for one of the color components of the color system, a function of generating respectively a tone curve for modifying the first type of gradation values representing the intensity of the color components is the RGB color system,
A function of converting the resolution of the original image data, converting the display image data to which color tone is given with reference to each tone curve, and displaying a monotone image on the display unit according to the display image data;
A function for determining each tone value after conversion by each tone curve for reference gray (N is an integer of 2 or more) which is N achromatic colors represented by the first type tone value of each color component. When,
Based on the gradation values of the N reference grays before and after the conversion, the ink color intensities of a plurality of inks including the first type gradation value as an input value and chromatic ink as an output value are represented. A function of generating a one-dimensional ink color look-up table having a second type of gradation value;
A program for causing a computer to realize a function of referring to the one-dimensional ink color look-up table and converting the original image data into image data for printing including the second type of gradation value and printing .

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