JP2002223367A - Method and device for processing picture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a picture processing method and a picture processor for setting a color reproduction characteristic in the neighborhood of a gray axis and reproducing a color which is provided with the color reproduction characteristic closer to that in the neighborhood of the gray axis in the silver salt photography. SOLUTION: When color matching with a printer is applied for RGB-type picture data, a gray mode selected by a user is judged from a plurality of color reproduction modes being different in color reproduction in the neighborhood of the gray axis in a step S101, a one-dimensional LUT based on the gray mode is generated in steps S102-104, the RGB-type picture data are converted into RGB-type picture data based on 1DLUT in a step S108 and, then, the RGB-type picture data are converted into picture data corresponding to the ink colors of the printer based on prescribed 3DLUT in steps S109 and S110.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and an image processing apparatus, and more particularly to an image processing method and an image processing apparatus for performing color matching on RGB format image data.

[0002]

2. Description of the Related Art In particular, in a computer employing Windows (registered trademark) 98 as an OS, Hewlett-Packard Company, a US company, and a US company, perform color matching processing for matching color reproduction between a plurality of devices such as a connected monitor and a printer. It is based on the sRGB color space (hereinafter simply referred to as sRGB) proposed by Microsoft Corporation. In color matching based on sRGB, a user does not need to make profiles and various settings, so that even a user who is not familiar with color processing can obtain an appropriate color matching result.

Accordingly, many image input devices in recent years are sR
In order to realize color matching based on GB, image design is performed by default for sRGB or similar monitors. For example, many printer drivers
A color design targeting an sRGB monitor (or a monitor characteristic close thereto) has been made, and therefore, the color reproduction results for each model are similar. As a feature of such a color reproduction result, since sRGB is a color space designed using a D65 light source as a white reference, the color of the gray axis is slightly bluer.

Here, the color processing performed in a conventional printer driver for an ink jet printer will be briefly described.

[0005] Input image data converted to sRGB, which is a reference color space, is converted from data on sRGB to data on a device RGB color space based on a three-dimensional lookup table (hereinafter referred to as 3DLUT). When the process (referred to as a pre-stage process) is performed, a conversion process (referred to as a post-stage process) from the data in the device RGB color space to the ink color data based on another 3DLUT is performed, and then sent to the inkjet printer. Note that 3D used in pre-processing and post-processing
LUT is the output media (paper, film, etc.)
It must be prepared for each printing mode and printing mode.

[0006] Not only the above-mentioned ink-jet printers but also printers capable of outputting high-quality images have become widespread in recent years.
Opportunities to print photographic images instead of silver halide photographs are increasing. However, as described above, in such a high-quality printer, since the color reproduction in the sRGB mode is designed with the D65 light source as the white reference, the color on the gray axis is reproduced with a slight blue shift. Therefore, the color reproduction of the gray axis, which is used as a reference in silver halide photography, is not reddish to some extent than when the D65 light source is used as a white reference.

Therefore, if a high-quality printer intends to express a slightly reddish gray color peculiar to a silver halide photograph, a light source (D55 to D6) as a standard in the silver halide photograph is used.
It is necessary to prepare a 3DLUT dedicated to the color space designed based on 5) as a white reference separately from the default sRGB mode in each of the pre-stage and post-stage processing.

As another method for performing color reproduction unique to silver halide photography, there is a method of performing color conversion processing on sRGB image data based on a von Kreis color adaptation prediction formula. The chromatic adaptation prediction formula is shown below.

[0009]

(Equation 2) Here, the tristimulus values of white before conversion are X, Y, Z, and R at that time.
The GB values are R ₀ , G ₀ , and B ₀ , and the converted white tristimulus values are X ′,
Y ′, Z ′, and the RGB values at that time are R ₁ , G ₁ , and B ₁ .

Here, the RGB values and the XYZ values are interchangeable by the following conversion formula. In the following equation, (M) is a transformation matrix, and (M) ^-1 is its inverse matrix, and its elements are determined from the chromaticity coordinates of the three basic primary colors.

[0011]

(Equation 3)

That is, the color conversion based on the chromatic adaptation prediction formula is executed by the following procedure. First, X from RGB value
Based on the conversion formula to YZ value, input sRGB data is temporarily
X′Y′Z ′ is obtained by converting the data into XYZ tristimulus value data and applying the chromatic adaptation prediction formula (1) to the XYZ data. Next, the obtained X'Y'Z 'data is subjected to conversion from XYZ values to RGB values to obtain RGB values after color correction. According to the corrected RGB values, it is possible to perform a conversion process using a default 3DLUT prepared for the preceding and subsequent processes in the sRGB mode.
If printing is performed after the conversion by the 3DLUT, color reproduction of a somewhat reddish gray axis unique to silver halide photography can be achieved.

[0013]

However, in the above-mentioned conventional printer driver, for example, "photograph"
Although it was possible to select a color mode such as "Graphic" or "Grayscale" that makes the color of the entire image different, for example, when the "Photo" mode is selected, the color reproduction of the gray axis and its surroundings is further performed. There were no features for high-end users that allowed selection or setting of characteristics. That is, the color reproduction near the gray axis was set slightly closer to blue, and there was no function of expressing the color of the gray axis slightly reddish than the D65 light source unique to silver halide photography.

In order to realize the color reproduction of the reddish gray axis as described above, it is conceivable to perform conversion based on a chromatic adaptation prediction formula on the input image. Therefore, appropriate color conversion is performed for the gray axis of the halftone and its surroundings, but there is a problem that a color that does not exist originally is added to the white portion. That is, when white (8-bit data, R = 255, G = 255, B = 255) in sRGB data is converted by the above method, it is converted into data such as R = 255, G = 253, B = 238. As a result, the area that is supposed to be plain is colored a little.

According to the conversion method based on such a chromatic adaptation prediction formula, the RGB data is once converted into XYZ data, and then the conversion based on the formula (1) is performed and the RGB data is returned to the RGB data again. There is a problem that the amount is large and a long processing time is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and has as its object to provide an image processing method and an image processing apparatus capable of setting a color reproduction characteristic near a gray axis.

It is another object of the present invention to provide an image processing method and an image processing apparatus capable of reproducing colors closer to the color reproduction characteristics near the gray axis in silver halide photography.

[0018]

As one means for solving the above problem, the image processing method of the present invention comprises the following steps.

That is, this is an image processing method for performing color matching on image data in RGB format with a target device, and selects one of a plurality of color reproduction modes having different color reproduction near the gray axis as a gray mode. A mode selection step; and a color conversion step of performing a color conversion on the image data so as to reproduce colors according to the gray mode.

For example, in the color conversion step, a first conversion step of performing a conversion based on the gray mode on the RGB image data to output RGB image data; A second conversion step of converting the RGB format image data output in the step into image data in a color space dependent on the target device.

Further, based on the gray mode, RGB
The method further comprises a table creation step of creating a one-dimensional conversion table for each, and in the first conversion step, conversion based on the one-dimensional conversion table is performed.

Alternatively, the method further comprises a matrix calculation step of calculating a masking matrix for each pixel of the RGB format image data based on the gray mode, and the first conversion step is based on the masking matrix. The conversion is performed.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below in detail with reference to the drawings.

<First Embodiment> In this embodiment, an example in which the present invention is applied to an ink jet printer will be described. The ink jet printer of the present embodiment can print on various recording media such as paper and film, and can print cyan,
An image is formed with six color inks of magenta, yellow, black, light cyan, and light magenta.

FIG. 1 is a diagram showing a block configuration of an image processing system for realizing color matching particularly in the present embodiment. In the system shown in FIG. 1, an ink-jet printer (hereinafter, printer) 200 and a monitor 300 are connected to a host computer (hereinafter, PC) 100, and image data stored in the image memory 120 in the PC 100 is stored in sRGB format. Are displayed on the monitor 300 and printed out by the printer 200 via the color conversion unit 130 described later.

When a print command to the printer 200 is generated in an application (not shown) on the PC 100, a printer driver (not shown) of the printer is started. Then, after the user makes various settings via the operation unit 110 using the setting screen of the printer driver, when a print command is generated again on the screen, when a print command is issued again by the application, for example, the RGB data stored in the image memory 120 is stored. Processing is started for image data of the format.
After the RGB image data is expanded by the color conversion unit 120 into data corresponding to the six ink colors, the printer 20
Transferred to 0 and printing is performed. That is, the color conversion unit 120
Is controlled by a printer driver (not shown).

In the printer driver of the present embodiment, there are an sRGB mode and a silver halide photographic mode as a color reproduction mode (hereinafter referred to as a gray mode) around the gray axis and the user selects one of them from a setting screen. You can choose. The sRGB mode is a mode in which color reproduction is designed with the sRGB monitor (or a monitor characteristic close to it) as the target.The gray axis is set to match the chromaticity coordinates under the D65 light source, and slightly It is characterized by being reproduced. On the other hand, the silver halide photographic mode is a mode in which color reproduction is designed with the color reproduction of silver halide photographs as a target.
It is set so as to be matched to the chromaticity coordinates under 65 light sources, and is characterized in that color reproduction with a slightly reddish color can be obtained compared to the color reproduction set under D65 light source.

The operation unit 110 in this embodiment is
The gray mode is selected by a user selecting a radio button or the like as appropriate on a printer driver setting screen, for example, a pointing device such as a mouse or a keyboard. In the gray mode, for example, an sRGB mode is set as a default.

In the color conversion unit 130, a 1DLUT creation unit 131
Creates a one-dimensional lookup table (1DLUT), which will be described later, based on the gray mode selected via the operation unit 110. Then, the 1DLUT conversion unit 132 converts the 1D
The input sRGB image data is converted on the same color space based on the LUT. The pre-processing unit 133 converts the converted sRGB data into device RGB, and the post-processing unit 134 converts the data into data corresponding to the ink color. Is made. It should be noted that in the pre-stage and post-stage processing units 133 and 134, the same 3DLUT conversion as in the past is performed.

The present embodiment is characterized in that the gray mode can be set, and that the 1DLUT conversion unit 132 can reproduce a silver halide photographic gray color.

Hereinafter, the color conversion processing in the color conversion section 130 of the present embodiment will be described in detail. FIG. 2 is a flowchart illustrating color processing performed in the printer driver according to the present embodiment. Here, it is assumed that the input image data has already been converted into the sRGB color space and stored in the image memory 120, and that the gray mode has already been selected by the user, and each processing content will be described below.

First, in step S101, it is determined whether the gray mode specified by the user via the operation unit 110 is the sRGB mode or the silver halide photography mode. When the sRGB mode is selected, the process proceeds to step S102, and when the silver halide photo mode is selected, the process proceeds to step S103.

In step S102, the 1DLUT creation unit 131 creates a one-dimensional lookup table (hereinafter, referred to as 1DLUT) for each of the RGB channels in the sRGB mode. Here, since sRGB is a general reference color space, a linear 1DLUT whose input value and output value are the same is created. On the other hand, in step S103, the 1DLUT creation unit 1
At 31, a 1DLUT is created for each of the RGB channels in the silver halide photographic mode. Specifically, 1DLUT is created based on the print mode of the printer 200 and the parameters specified by the recording medium. The conversion based on the 1DLUT created here makes it possible to reproduce a silver halide photographic gray color. The creation method will be described later.

Next, in step S104, step S1
In 02 or S103, the 1DLU created by the 1DLUT creation unit 131
T is set in the 1DLUT conversion unit 132. That is, the 1DLUT created in step S102 when the sRGB mode is selected, and the 1DLUT created in step S103 when the silver halide photographic mode is selected.
Are set in the 1DLUT conversion unit 132, respectively.

With the above, 1DLUT setting processing (steps S101 to S101)
104) is finished and then stored in the image memory 120
Color conversion processing for sRGB image data (steps S108 to S1
10) is performed, but the color conversion process is executed for every pixel of the image data one by one as shown in steps S105 to S107.

In step S108, 1DL in which 1DLUT is set
The UT conversion unit 132 performs a conversion process on the input sRGB image data. Since the 1DLUT set when the sRGB mode is selected has a linear characteristic, the pixel value does not change before and after this conversion.

In step S109, the image data in the sRGB color space converted in step S108 is
Is converted into a color space unique to the printer 200 (device RGB) based on the For example, if the number of data bits of each channel of RGB is 8 bits, this 3DLUT is 0 to 255 for each of R, G, B axes.
Is a table that holds N ³ representative points and their correction values obtained by engraving the range in N steps. If the RGB value of each pixel of the input image data is the same value as the representative point of the 3DLUT, the correction value of the representative point is output as a converted value. And performs an interpolation operation based on the representative points surrounding. And outputs the converted value.

In step S110, the device RGB data converted in step S109 is converted into color component data corresponding to the ink color. This conversion is performed in 3D as in step S109.
Performed based on LUT. The 3DLUT includes ink color data corresponding to input RGB values for each representative point, that is, in this embodiment, six channels of cyan, magenta, yellow, black, light cyan, and light magenta corresponding to the ink colors of the printer 200. Holds data for minutes. This 3DL
The ink color data converted based on UT is
And a visible image is formed on the recording medium.

As described above, in this embodiment,
Conversion in 1DLUT conversion section 132, that is, 1DLUT creation section 131
The feature is that 1DLUT created by this makes it possible to reproduce silver halide photographic gray color. Below, 1D
1DLU when silver halide photo mode is selected in the LUT creation unit 131
The T creation method (step S103) will be described in detail.

First, as described in the above-mentioned conventional example, the von Kreis color adaptation prediction equation is given by the following equation (1).

[0041]

(Equation 4)

By using this, a 3 × 3 matrix for performing the RGB to RGB conversion is obtained as follows.

[0043]

(Equation 5)

In equation (2), the RGB values of the white color under the light source before the conversion are R ₀ , G ₀ , and B _0, and the RGB values of the white color under the light source after the conversion are R ₁ , G ₁ , and G ₁ . B ₁

According to equation (2), for example, if each of the RGB values is 8-bit data, the input RGB value becomes white (R =
255, G = 255, B = 255), the converted value is, for example, R = 2
55, G = 253, B = 238. That is, as described above in the related art, when the conversion result based on the chromatic adaptation prediction formula is simply printed out by a printer, some color is added to a white area where nothing should be printed originally. There was a problem.

Therefore, in the present embodiment, when the input RGB value is white (R = 255, G = 255, B = 255), the output value is also white (R = 25
5, G = 255, B = 255), and a conversion formula instead of the above formula (2) is set as follows so as to prevent a rapid change in gradation.

[0047]

(Equation 6)

In the equation (3), R ₀ , G ₀ , B ₀ and R ₁ , G
_1, B _1, like (2), showing a white RGB values in the light source of a original and translated, respectively. Α _k is the input value k
(K = R, G, or B), and changes as follows.

[0049] if (0 ≦ k ≦ N) α k = 0; else α k = (k-N) / (255-N); (N is a constant of 0 ≦ N <255) As the value of alpha _k If RGB data is 8 bits for each color, then 0 ≦ α _k ≦ 1.0 for each input value 0 to 255, and if the input value 255 indicates white, α _k = 1.0. Such a value may be used.

According to equation (3), when R ≦ N, G ≦ N and B ≦ N, the converted RGB values are the same as equation (2), and the input value k
If (R, G, or B) is larger than N, that is, for data near white, the value is white (R = 255, G = 255, B = 2
As the distance approaches 55), the amount of change during conversion becomes smaller. When the input RGB values are white (R = 255, G = 255, B = 255), the output RGB values are also white (R = 255, G = 255, B = 25).
5) is maintained.

Further, since the transformation matrix in equation (3) has only diagonal components, each of the RGB channels can be made independent, and it is easy to generate a 1DLUT for each channel.

As described above, when creating the 1DLUT in the silver halide photographic mode in step S103, the light source before the conversion is set to the D65 light source, which is the light source in the sRGB color space, according to the equation (3). If the latter light source is set to D55 light source and the constant N is set to 220, the following conversion formula for performing light source color conversion is created. FIG. 3 shows a graph based on this conversion formula.

[0053] _{R_out = (1.104 - 0.104α R)} × R_in G_out = (0.987 + 0.013α G) × G_in ··· (4) B_out = (0.823 + 0.177α B) above, as can be seen from × B - IN Figure 3 1DLUT expressed by conversion formula (4)
According to the above, for data near white (R = 255, G = 255, B = 255), the change amount decreases as the value approaches white, and the value of white (R = 255, G = 255, B = 255) data (R = 255, G = 255, B = 255) is maintained after conversion.

In the expression (4), the same color reproduction is performed in the silver halide photographic tone mode regardless of the print mode of the printer or the recording medium. White under the light source
It is necessary to adjust the RGB value and the constant N.

As described above, according to the present embodiment,
For color reproduction of the gray axis of a color printer and its surroundings, the color of the sRGB monitor
An sRGB mode that matches the chromaticity coordinates of the light source and reproduces a slightly bluer gray color, and a grayish color that is slightly redder than the D65 light source, such as the standard for silver halide photography, are used. It becomes possible to select one of the silver halide photographic tone modes to be performed.

In the silver halide photography mode, a color conversion table (3DLUT in the first and second processing units 133 and 134) in the sRGB mode is prepared without preparing a color conversion table (3DLUT) dedicated to the silver halide photography mode. As it is, the 1DLUT conversion unit 132 performs 1DLUT conversion processing for each of the RGB channels created by applying a well-known chromatic adaptation prediction formula to the input image data as preprocessing, thereby obtaining a silver halide photographic tone. Gray color reproduction can be easily realized.

According to the gray color reproduction in the silver halide photographic tone mode of the present embodiment, the output data becomes white if the input data is white while maintaining the gradation of the image data near the highlight. Conversion is performed. Therefore, the problem that the white background is printed with some coloring is solved.

Further, since the conversion using the 1DLUT is performed as the pre-processing, the processing time is reduced as compared with the conversion using the 3DLUT.

<Second Embodiment> Hereinafter, a second embodiment according to the present invention will be described.
An embodiment will be described.

FIG. 4 shows a system configuration for realizing color matching in the second embodiment. FIG.
In the figure, the same components as those in FIG. 1 shown in the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted. In the first embodiment, an example is described in which image data to be subjected to color matching is first converted using a 1DLUT. However, the second embodiment is characterized in that a masking matrix operation is performed instead of the 1DLUT. And Specifically, the matrix calculation unit 141 calculates a masking matrix based on the gray mode and the RGB values of the input image data, and the masking unit 142 performs a masking process on the input image data based on the masking matrix.

Hereinafter, the color conversion processing in the color conversion section 140 of the second embodiment will be described in detail. FIG.
6 is a flowchart illustrating color processing performed in the printer driver according to the embodiment. Also in the second embodiment, it is assumed that the input image data has already been converted into the sRGB color space and stored in the image memory 120, and that the gray mode has already been selected by the user. explain.

First, in step S201, it is determined whether the gray mode specified by the user via the operation unit 110 is the sRGB mode or the silver halide photograph mode, and the step is performed only when the gray mode is the silver halide photograph mode. The processing of S202 to S206 is executed. That is, in the silver halide photographic mode, for each input pixel, a masking matrix is calculated in the matrix calculating unit 141 in step S205, and the masking matrix is multiplied by the input RGB value in the masking unit 142 in step S206 to perform masking conversion. Processing is performed. Details of the masking matrix calculation processing will be described later. When the sRGB mode is selected from the operation unit 110, the matrix calculation unit 141 does not operate, and the masking unit 142
Outputs the input sRGB data through, or prepares a masking matrix that is substantially through as default, and performs masking conversion based on the default matrix.

On the other hand, when the sRGB mode is selected, or when the above-described masking processing is completed for all pixels in the silver halide photographic mode, the first and second steps of color matching are performed in steps S207 to S211. It is. That is, in step S210, the input image data in the sRGB color space is converted into a color space (device RGB) unique to the printer 200 based on the pre-processing 3DLUT similar to the first embodiment described above in step S210. I do. Then, in step S211, the device RGB data is stored in the first
Based on the 3DLUT for post-processing similar to the embodiment, the data is converted into color component data corresponding to the ink color and transferred to the printer 200.

As described above, in the second embodiment,
The feature is that the masking conversion processing in the masking unit 142 enables the reproduction of a silver halide photographic gray color. That is, the gray color reproducibility depends on the masking matrix created by the matrix calculation unit 141. Hereinafter, the masking matrix calculation method (step S205) in the matrix calculation unit 141 will be described in detail.

As in the first embodiment, based on the von Kleis chromatic adaptation prediction formula (1), 3 ×
Although three matrices are obtained as shown in equation (2), according to this conversion equation (2), even if the input RGB value is white (R = 255, G = 255, B = 255), There is a problem that it does not become white. Therefore, in the second embodiment, when the input RGB value is white, the expression (2) is replaced so that the output value becomes the same white, and a rapid change in gradation does not appear. Set the conversion formula as follows.

[0066]

(Equation 7)

In the equation (5), R ₀ , G ₀ , B ₀ and R ₁ ,
G ₁ and B ₁ indicate the RGB values of white under the light source before and after the conversion, respectively, as in Equation (2).

Further, a, b, c, d, e, and f are constants satisfying the following relationship.

R ₁ / R ₀ + a + b = 1.0 G ₁ / G ₀ + c + d = 1.0 B ₁ / B ₀ + e + f = 1.0 Further, α _k is an input value k (k = R, G , B), it changes as follows.

[0070] if (0 ≦ k ≦ N) α k = 0; else α k = (k-N) / (255-N); (N is a constant of 0 ≦ N <255) As the value of alpha _k If RGB data is 8 bits for each color, then 0 ≦ α _k ≦ 1.0 for each input value 0 to 255, and if the input value 255 indicates white, α _k = 1.0. Such a value may be used. That is, the value of the masking matrix may be changed with respect to an input RGB value close to white at a certain threshold.

According to equation (5), when R ≦ N, G ≦ N and B ≦ N, the RGB values after conversion are the same as equation (2), and the input value k
If (R, G, or B) is larger than N, that is, for data near white, the value is white (R = 255, G = 255, B = 2
As the distance approaches 55), the amount of change during conversion becomes smaller. When the input RGB values are white (R = 255, G = 255, B = 255), the output RGB values are also white (R = 255, G = 255, B = 25).
5) is maintained.

In equation (5), regardless of the print mode of the printer or the recording medium, the same color reproduction is performed in the silver halide photographic tone mode. White under the light source
It is necessary to adjust RGB values and constants N, a, b, c, d, e, and f.

As described above, according to the second embodiment, the color conversion table (3DLUT) dedicated to the silver halide photograph mode is not prepared in the silver halide photograph mode, and the color conversion table (previous stage) in the sRGB mode is prepared. And the post-processing unit 133,
The 3D LUT in 134 is used as it is, and the masking unit 142 performs a masking conversion process using a masking matrix created by applying a well-known chromatic adaptation prediction formula to the input image data as a pre-process, thereby obtaining a first process.
Similar to the embodiment, gray-scale reproduction of silver halide photographic tone can be easily realized.

In the first and second embodiments described above, an example in which an image is output to the ink jet printer 200 has been described.
A printer using another image forming method, such as a laser beam printer or a sublimation printer, may be used as long as the printer enables B input.

[0075]

[Other embodiments] The present invention relates to a plurality of devices (for example, a host computer, an interface device, a reader,
Printer, etc.)
The present invention may be applied to an apparatus including one device (for example, a copying machine, a facsimile machine, and the like).

Another object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (or CPU or MPU) of the system or the apparatus. Can also be achieved by reading and executing the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

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

Further, when the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) Do some of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, The CPU provided in the function expansion board or function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

[0081]

As described above, according to the present invention, it is possible to set the color reproduction characteristics near the gray axis.

Further, color reproduction closer to the color reproduction characteristics near the gray axis in silver halide photography can be performed easily and at high speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating color processing in a printer driver according to the embodiment.

FIG. 3 is a diagram showing a graph of 1DLUT for each RGB in the embodiment.

FIG. 4 is a block diagram illustrating a system configuration according to a second embodiment.

FIG. 5 is a flowchart illustrating color processing in a printer driver according to the second embodiment.

[Explanation of symbols]

 100 PC 110 Operation unit 120 Image memory 130 Color conversion unit 131 1DLUT creation unit 132 1DLUT conversion unit 133 Pre-processing unit 134 Post-processing unit 140 Color conversion unit 141 Matrix calculation unit 142 Masking unit 200 Printer 300 Monitor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B057 AA11 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CC01 CE17 5C077 LL19 MP08 PP32 PP37 PQ08 PQ23 PQ25 TT05 5C079 HB01 LA31 LB02 LB04 MA05 MA11 NA03 NA11 NA27 PA03

Claims (19)

[Claims] 1. An image processing method for performing color matching of image data in RGB format with a target device, wherein one of a plurality of color reproduction modes having different color reproduction near a gray axis is selected as a gray mode. An image processing method, comprising: a mode selection step; and a color conversion step of performing color conversion on the image data so that color reproduction according to the gray mode is performed. 2. In the color conversion step, a first conversion step of performing conversion based on the gray mode on the RGB image data and outputting RGB format image data; 2. The method according to claim 1, further comprising the step of: performing a conversion on the image data in RGB format output in the step to convert the image data into image data in a color space dependent on the target device. Image processing method. 3. The image processing apparatus according to claim 1, further comprising:
3. The image processing method according to claim 2, further comprising a table creation step of creating a one-dimensional conversion table for each B, wherein in the first conversion step, conversion based on the one-dimensional conversion table is performed. 4. The image processing method according to claim 3, wherein in the table creation step, a one-dimensional lookup table for performing light source color conversion is created. 5. The image processing method according to claim 4, wherein in the table creation step, the one-dimensional look-up table is calculated based on the following equation. R_out = (R ₁ / R ₀ − (R ₁ / R ₀ -1) × α _R ) × R_in G_out = (G ₁ / G ₀ − (G ₁ / G ₀ -1) × α _G ) × G_in B_out = (B ₁ / B ₀ − (B ₁ / B ₀ -1) × α _B ) × B_in where R_in, G_in, and B_in are input RGB values to the table, R_out, G_out, and B_out are output RGB values of the table, R ₀ , G ₀ , B ₀ are the RGB values of the white color under the reference light source, R ₁ , G ₁ , B ₁ are the RGB values of the white color under the target light source in the gray mode, and α _k is the input value k (k = R, G, or B), and satisfies the following condition. 0 ≦ f (k) ≦ 1.0, f (2 ⁿ⁻ 1) = 1.0 where 0 ≦ k ≦ 2 ⁿ⁻ 1, n indicates the number of data bits. 6. A matrix calculating step of calculating a masking matrix for each pixel of the RGB format image data based on the gray mode, wherein the first converting step is based on the masking matrix. 3. The image processing method according to claim 2, wherein the conversion is performed. 7. The image processing method according to claim 6, wherein in the matrix calculation step, a masking matrix for performing light source color conversion is calculated. 8. The image processing method according to claim 7, wherein, in the matrix calculating step, the masking matrix is calculated based on the following equation. (Equation 1) Here, R_in, G_in, B_in are input RGB values, R_out, G_out, B_out are output RGB values, R ₀ , G ₀ , B ₀ are white RGB values under a reference light source, R ₁ , G ₁ , B ₁ Is the RGB value of white under the target light source in the gray mode, a, b, c, d, e, and f are constants satisfying the following relationship: R ₁ / R ₀ + a + b = 1.0 G ₁ / G ₀ + c + d = 1.0 B ₁ / B ₀ + e + f = 1.0 α _k is a continuous function f (k) that is converted based on the input value k (k = R, G, or B), The following conditions are satisfied. 0 ≦ f (k) ≦ 1.0, f (2 ⁿ⁻ 1) = 1.0 where 0 ≦ k ≦ 2 ⁿ⁻ 1, n indicates the number of data bits. 9. The image data of the RGB format is sRG
2. The image processing method according to claim 1, wherein the image data is image data on a B reference color space. 10. The second conversion step includes: a pre-processing step of converting image data in the RGB format to generate image data in an RGB color space dependent on the target device; 3. The image processing method according to claim 2, further comprising: performing a conversion process on the image data to generate image data in a color space dependent on the target device. 11. The image processing method according to claim 10, wherein in the pre-processing step and the post-processing step, conversion based on mutually different three-dimensional lookup tables is performed. 12. An image processing apparatus for performing color matching on image data in RGB format with a connected target device, wherein one of a plurality of color reproduction modes having different color reproductions near a gray axis is grayed out. An image processing apparatus comprising: a mode selection unit that selects a mode; and a color conversion unit that performs color conversion on the image data so that color reproduction according to the gray mode is performed. 13. The first conversion unit, wherein the color conversion unit performs conversion based on the gray mode on the RGB format image data and outputs RGB format image data. Second conversion means for converting the output RGB image data into image data in a color space dependent on the target device,
13. The image processing apparatus according to claim 12, comprising: 14. The image processing apparatus according to claim 1, further comprising:
14. The image processing apparatus according to claim 13, further comprising table creation means for creating a one-dimensional conversion table for each GB, wherein the first conversion means performs conversion based on the one-dimensional conversion table. 15. Further, based on the gray mode,
14. The image processing apparatus according to claim 13, further comprising: a matrix calculating unit that calculates a masking matrix for each pixel of the image data in the RGB format, wherein the first converting unit performs conversion based on the masking matrix. apparatus. 16. In an image processing system in which an image processing apparatus and a target device are connected, in order to execute color matching on image data in RGB format, one of a plurality of color reproduction modes having different color reproductions near a gray axis is used. Image processing comprising: mode selection means for selecting one of the image data as a gray mode; and color conversion means for performing color conversion on the image data so as to reproduce color according to the gray mode. system. 17. The first conversion unit, wherein the color conversion unit performs conversion based on the gray mode on the RGB format image data to output RGB format image data, and the first conversion unit. Second conversion means for converting the output RGB image data into image data in a color space dependent on the target device,
17. The image processing system according to claim 16, comprising: 18. A program having a code for executing the image processing method according to claim 1 when executed on a computer. 19. A recording medium on which the program according to claim 18 is recorded.