JP2024013728A - Color distribution display device and program of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color distribution display device which can express the color distribution of an image on a color gamut ring by making the expression of saturation clearer.

SOLUTION: A color distribution display device 1 comprises: a reference saturation calculation unit 12 which calculates common reference saturation whose color gamut volume in a unit angle of a hue angle for each predetermined brightness section becomes the same volume as an original color gamut shape from brightness, hue angle and saturation indicating color gamut data of a color gamut solid body; an image data saturation correction unit 14 which multiplies a ratio of the reference saturation to the saturation of the color gamut data by the saturation of the image data for each hue angle in the brightness section and corrects the saturation of the image data; a color gamut ring drawing unit 170 which draws and displays a color gamut ring; and a distribution drawing unit 171 which draws a position of the corrected saturation of the image data on the color gamut ring with a predetermined diagram.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a color distribution display device and a program thereof.

ITU-R Recommendation BT. With the standardization of 4K/8K video formats by Rec. 2020 (Rec. 2020), displays are becoming wider in color gamut, making it important to evaluate the size and shape of the color gamut.
Perceived color is represented in a cylindrical three-dimensional space of brightness, saturation, and hue, and the display color gamut is represented in a three-dimensional perceptually uniform color space. However, the size and shape of a color gamut solid expressed in a three-dimensional color space cannot be understood unless it is observed from a different viewpoint using a PC (personal computer) or the like.

Therefore, a method of expressing a three-dimensional color gamut solid with two-dimensional color gamut rings called Gamut Rings shown in FIG. 14 was proposed and standardized (see Patent Document 1, Non-Patent Documents 1-3). .
The method for generating a color gamut ring is to first divide the color gamut solid (see Figure 3) of the CIE1976 (L ^* , a ^* , b ^* ) (CIELAB) color space from brightness 0.5 to 99.5 in steps of 1. , find 100 boundary polygons. This method involves cutting the color gamut solid into slices at regular brightness intervals, punching holes in each slice of the color gamut solid, stretching them out, and arranging them in a ring shape around the periphery starting from the one with the lowest brightness. do. However, there is no hole in the least bright ring in the center of the color gamut. Note that each ring of the color gamut ring is normally represented by dividing it into 10 polygons, that is, into 10 brightness units.
The area of this ring is proportional to the volume of the three-dimensional color gamut. In addition, the azimuth angle centered at the origin (a ^* _RSS , b ^* _RSS ) = (0, 0) of the color gamut ring is the hue (hue angle) of red (R), blue (B), green (G), etc. ) represents. In addition, the color gamut ring expresses the difference in saturation by the distance from the center.

JP2019-129525A

IEC 62977-2-1:2021 Electronic Displays - Part 2-1: Measurements of Optical Characteristics - Fundamental Measurements Information Display Measurements Standard (IDMS), v1.1, 2021. CIE 246:2021 Color Gamuts for Output Media.

By using the color gamut ring, it is possible to quantitatively evaluate the size per brightness for each hue in the color gamut of a display or printer using a two-dimensional diagram. Therefore, there is a further desire to visually check the distribution of colors contained in an image displayed on a display or printer on a color gamut ring.
However, conventional color gamut rings are generated by overlapping polygons in a ring shape from the center to the periphery for each brightness, so the width of the ring becomes narrow. Therefore, even if the color distribution of an image is simply expressed on a color gamut ring, there is a problem in that it is difficult to distinguish differences in saturation depending on the distance from the center in a narrow ring.
SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a color distribution display device and a program therefor that can express the color distribution of an image on a color gamut ring while making the differences in saturation more clear.

In order to solve the above problem, a color distribution display device according to the present invention displays a color distribution of image data corresponding to a color gamut superimposed on a color gamut ring that displays color gamut data of a three-dimensional color gamut in two dimensions. The present invention is a color distribution display device that includes a reference saturation calculation section, an image data saturation correction section, a gamut ring drawing section, and a distribution drawing section.

In such a configuration, the color distribution display device uses the reference saturation calculation unit to calculate the original color gamut volume within a unit angle of the hue angle for each predetermined brightness interval from the brightness, hue angle, and saturation indicating the color gamut data. Calculate a common reference saturation that has the same volume as the color gamut shape.
The color distribution display device then uses the image data saturation correction unit to multiply the saturation of the image data by the ratio of the reference saturation to the saturation of the color gamut data for each hue angle in the brightness interval where the reference saturation is common. and corrects the saturation of the image data.
As a result, the saturation of the image data is corrected to the saturation based on the common reference saturation for each predetermined brightness interval, without distinguishing the brightness.
Since this reference saturation is common in a predetermined brightness interval, it is possible to express differences in saturation within a wide ring having the width of this brightness interval within the color gamut ring.

Then, the color distribution display device draws and displays the color gamut ring using the color gamut ring drawing section.
Further, the color distribution display device causes the distribution drawing unit to draw a marker at a position on the color gamut ring corresponding to the position of brightness, hue angle, and saturation of the image data corrected by the image data saturation correction unit.
As a result, the color distribution display device can display a color distribution expressing saturation based on the same standard of reference saturation, without distinguishing between brightness, for each ring in a predetermined brightness interval.
Note that the color distribution display device can be operated by a color distribution display program for causing a computer to function as each section described above.

According to the present invention, in a color gamut ring, saturation can be expressed at predetermined brightness intervals without distinguishing brightness.
As a result, the present invention can represent the color distribution of an image by visualizing the expression of saturation more clearly in a color gamut ring that is wider than the conventional ring.

FIG. 1 is a block configuration diagram showing the configuration of a color distribution display device according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining an example of a color distribution image displayed by the color distribution display device according to the first embodiment of the present invention. FIG. 2 is a graph diagram of CIELAB color space showing an example of color gamut data. FIG. 4 is a graph diagram showing an example of color gamut data obtained by converting the color gamut data of FIG. 3 into reference saturation by converting saturation for each hue angle at predetermined brightness intervals. FIG. 6 is an explanatory diagram for explaining a method of calculating a reference saturation for each predetermined brightness section in an image data saturation correction section. FIG. 6 is an explanatory diagram for explaining a method of correcting saturation of color gamut data based on reference saturation for each predetermined brightness section in an image data saturation correction section. FIG. 3 is a diagram showing a DCI-P3 color gamut ring drawn by a color gamut ring drawing unit. Rec. drawn by the color gamut ring drawing unit. 709 is a diagram showing a color gamut ring. Rec. drawn by the color gamut ring drawing unit. 20 is a diagram showing a color gamut ring of 2020; FIG. 3 is a flowchart showing the operation of the color distribution display device according to the first embodiment of the present invention. FIG. 2 is a block configuration diagram showing the configuration of a color distribution display device according to a second embodiment of the present invention. FIG. 7 is an explanatory diagram for explaining an example of a color distribution image displayed by a color distribution display device according to a second embodiment of the present invention. FIG. 3 is an explanatory diagram for explaining a determination method of a device color gamut inside/outside determination section. FIG. 2 is an explanatory diagram for explaining an example of a conventional color gamut ring.

Embodiments of the present invention will be described below with reference to the drawings.
≪First embodiment≫
[Configuration of color distribution display device]
First, with reference to FIG. 1, the configuration of a color distribution display device 1 according to a first embodiment of the present invention will be described.

The color distribution display device 1 superimposes the color distribution of image data whose color gamut corresponds to a color gamut ring (gamut ring) that displays color gamut data of a color gamut solid expressed in a three-dimensional color space in two dimensions. It is displayed as follows.
In other words, the color distribution display device 1 divides the lightness at regular intervals and converts the color gamut solid represented by the cylindrical color space of brightness, saturation, and hue of the color system defined by the image format of the input signal into a two-dimensional image. The color distribution of each pixel of the image data of the input signal is superimposed and displayed on a ring-shaped diagram (color gamut ring).
Specifically, as shown in FIG. 2, the color distribution display device 1 generates a color distribution image CD _I that represents the color distribution of the image data DI with markers M on the color gamut ring GR, and displays it on the monitor 2 _. indicate.
Here, the color distribution display device 1 inputs color gamut data _DC for generating a color gamut ring GR and image data DI, and expresses the color distribution of _the image data _DI on the color gamut ring GR. do.

The color gamut data _DC is data indicating the shape of a color gamut solid that indicates a region of color space in which the image format of the image data _DI can be displayed. Here, the color gamut data D _C is data in the CIE1976 (L ^* , a ^* , b ^* ) (CIELAB) color space (see FIG. 3).
Note that the color gamut data D _C can be specified by four coordinate values: each of the RGB coordinate values of the primary colors in the chromaticity coordinates and the coordinate value of the white point. Techniques for calculating the color gamut from these four coordinate values are described in Non-Patent Documents 1 and 3.

The image data _DI is data of an image whose color distribution is to be displayed on the color gamut ring GR. For example, the image data _DI may be DCI-P3 developed by the American film production industry organization (Digital Cinema Initiatives) or Rec. 709, Rec. This is image data such as 2020. Here, the image data _DI is data in the CIELAB color space, which is the same as the color gamut data _DC .

The color distribution display device 1 includes a color gamut data saturation calculation section 10, an image data saturation calculation section 11, a reference saturation calculation section 12, a color gamut data saturation storage section 13, and an image data saturation correction section. 14, a color gamut ring data generation section 15, a color gamut ring data storage section 16, and a display section 17.

The color gamut data saturation calculation unit 10 calculates saturation ^C * corresponding to lightness L ^* and hue angle h at regular intervals from color gamut data of lightness L ^* and chromaticity a ^* , b ^* . . Note that since this calculation method is a publicly known method (such as Patent Document 1) for generating a color gamut ring, an outline thereof will be explained below.

First, the color gamut data saturation calculation unit 10 divides the lightness L ^* into 100 pieces from 0.5 to 99.5 from the color gamut solid of the (L ^* , a ^* , b ^* ) color space. Calculate the polygon.
Then, ^the color gamut data saturation calculation unit 10 calculates the area A(L ^* , h) are calculated geometrically. Here, the hue angle h is, for example, an angle at 1° intervals from 0° to 359°. Note that if the chromaticities a ^* and b ^* corresponding to the brightness L ^* in steps from 0.5 to 99.5 do not exist, they may be found by linear interpolation. Furthermore, if there are multiple cross sections with the same brightness L ^* , the total area is defined as the area A(L ^* , h).
Then, the gamut data saturation calculation unit 10 calculates an equivalent saturation C ^* (L ^* , h) that is equivalent to the saturation of the lightness L ^* and the hue angle h using the following equation (1). Hereinafter, equivalent saturation will be simply referred to as saturation.

The color gamut data saturation calculation unit 10 calculates saturation for each lightness L ^* (L ^* = 0.5, 1.5,..., 99.5) and hue angle h (h = 0, 1,..., 359). C ^* (L ^* , h) is output to the reference saturation calculation section 12 and the gamut ring data generation section 15.

The image data saturation calculation unit 11 calculates saturation ^C * corresponding to lightness L ^* and hue angle h from image data having lightness L ^* and chromaticity a ^* , b ^* .
Hereinafter, the saturation calculated by the image data saturation calculation unit 11 will be expressed as C ^* _sample to distinguish it from the saturation (equivalent saturation) of equation (1) above.
Specifically, the image data saturation calculation unit 11 calculates the saturation C ^* _sample from the chromaticities a ^* and b ^* using the following equation (2).

Further, the image data saturation calculation unit 11 calculates the hue angle h from the chromaticities a ^* and b ^* using the following equation (3).

The image data saturation calculation section 11 outputs the calculated lightness L ^* and the saturation C ^* _sample (L ^* , h) for each hue angle h to the image data saturation correction section 14.

The reference saturation calculation unit 12 calculates the color gamut volume within the unit angle of the hue angle from the lightness L ^* , hue angle h, and saturation C ^* indicating the color gamut data for each predetermined lightness interval to calculate the original color gamut shape. This is to calculate a common reference saturation that has the same volume as .
Here, the brightness interval is, for example, 10, and the reference saturation calculation unit 12 calculates each hue angle for each brightness interval of 0<L ^* ≦10, 10<L ^* ≦20,..., 90<L ^* ≦100. Calculate the standard saturation.

The reference saturation that does not change the color gamut volume can be obtained by calculating the root mean square of the saturation for each hue angle.
That is, the reference saturation calculation unit 12 calculates the root mean square represented by the following equation (4) to calculate the reference saturation C ^* _mod corresponding to the hue angle h in the lightness interval (0<L ^* ≦10). Calculate (10, h).

The reference saturation calculation unit 12 similarly calculates the index of Σ in the formula (4) for other lightness intervals (10<L ^* ≦20, 20<L ^* ≦30,..., 90<L ^* ≦100). By setting the range of 11-20, 21-30, ..., 91-100, the standard saturation C ^* _mod (20, h), C ^* _mod (30, h), ..., C ^* _mod (100, h).

Setting the saturation of each hue angle to the same reference saturation for each brightness interval means that the color gamut solid shown in Figure 3 is converted to the color gamut solid shown in Figure 4. do. Note that the volume of the color gamut shape for each brightness interval (here, 10) is the same in FIG. 3 and FIG. 4. Therefore, the color gamut solid shown in FIG. 3 and the color gamut solid shown in FIG. 4 have the same shape when expressed as a color gamut ring.

In addition, the polygon connecting the vertices C ^* _RSS10 (h) for each hue angle h in the lightness interval (0<L ^* ≦10) shown in equation (5) below is the polygon of the lightness L ^* =10 of the color gamut ring. It will be the same polygon as the ring.

Furthermore, the polygon connecting the vertices C ^* _RSS20 (h) for each hue angle h in the lightness interval (10<L ^* ≦20) shown in equation (6) below is the polygon that connects the vertices C*RSS20 (h) of the lightness L ^* =20 of the color gamut ring. It will be the same polygon as the outline of the ring.

Similarly, the polygon connecting the vertices C ^* _RSS100 (h) for each hue angle h in the lightness interval (90<L ^* ≦100) shown in equation (7) below is the lightness L ^* =100 of the color gamut ring. It is the same polygon as the outer contour of the ring.

The reference saturation calculation unit 12 calculates the lightness L ^* of the color gamut data and the saturation C ^* (L ^* , h) for each hue angle h, and the reference saturation C ^* _mod (10 , h), C ^* _mod (20, h), C ^* _mod (30, h), . . . , C ^* _mod (100, h) are stored in the color gamut data saturation storage unit 13.

The color gamut data saturation storage unit 13 stores the brightness, hue angle, and saturation (including reference saturation) of color gamut data. The color gamut data saturation storage section 13 can be configured with a general storage medium such as a semiconductor memory.
The color gamut data saturation storage unit 13 stores the color saturation (reference saturation) of the color gamut data in association with the lightness L ^* and the hue angle h, and retains it until new color gamut data is input. be done.

The image data saturation correction unit 14 multiplies the saturation of the image data by the ratio of the reference saturation to the saturation of the color gamut data for each hue angle in the brightness interval where the reference saturation is common, and adjusts the saturation of the image data. This is to correct.
That is, the image data saturation correction unit 14 corrects the coordinate position of a certain color inside the color gamut shape shown in FIG. 3 to the coordinate position of a color inside the color gamut shape shown in FIG.

For example, as shown in FIG. 5, the image data saturation correction unit 14 adjusts the brightness L ^* (L ^* = 0.5, 1.5,..., 9.5) in the brightness interval of 0<L ^* ≦10. For each ^, the ratio ⁽ C ^* _mod ⁽ 10 _, , h)/C ^* (L ^* , h)) is calculated as the saturation ratio. In addition, in FIG. 5, the mark ◯ indicates the saturation C ^* (L ^* , h) at the hue angle h, and the mark □ indicates the reference saturation C ^* _mod (10, h).
Similarly, the image data saturation correction unit 14 calculates C ^* _mod (20, h) in other lightness intervals of 10<L ^* ≦20, 20<L ^* ≦30,..., 90<L ^* ≦100. ^{/C*(L*,h),C*mod(30,h)/C*(L*,h),...,C*mod(100,h)/C*(L*,h )} _is ^{calculated . _ _} _{_} ^{_ _} .

Then, the image data saturation correction unit 14 corrects the brightness L ^* of the image data and the saturation C ^* _sample (L ^* ,h) for each hue angle h by multiplying it by the saturation ratio.At this time, the image data saturation The correction unit 14 corrects the image when the lightness L ^* of the image data is one of 0.5, 1.5, ..., 99.5 and the hue angle h is one of 0, 1, ..., 359. The chroma data C ^* _sample (L ^* , h) is stored in the gamut data saturation storage unit 13 in association with the lightness L ^* and the hue angle ^{h *} , h) by the ratio of the reference saturation.
That is, when the brightness L ^* of the image data satisfies 0<L ^* ≦10, the image data saturation correction unit 14 calculates the corrected saturation C ^* _sample-mod (L ^* ,h ) is calculated.

Similarly, when the lightness L ^* is 10<L ^* ≦20, 20<L ^* ≦30,..., 90<L ^* ≦100, the image data saturation correction unit 14 calculates the C ^* _mod of the equation (8) above. (10, h) as C ^* _mod (20, h), C ^* _mod (30, h), ..., C ^* _mod (100, h), and saturation C ^* _sample-mod (L ^* , h). calculate.

Note that if one or both of the lightness L ^* and the hue angle h of the image data are different from the lightness and hue angle corresponding to the reference saturation calculated by the reference saturation calculation unit 12, that is, the lightness L ^* of the image data is neither 0.5, 1.5, ..., 99.5, and/or the hue angle h is neither 0, 1, ..., 359, the image data saturation correction unit 14 Using the lightness L ^* and hue angle h of the data, the coordinates of C ^* _mod (L ^* , h) and C ^* (L ^* , h) on the color gamut solid are determined by linear interpolation, and the calculation of equation (8) above is performed. All you have to do is

For example, as shown in FIG. 6, when the saturation C ^* of the image data is the saturation indicated by a circle in the brightness interval of 0<L ^* ≦10, the image data saturation correction unit 14 adjusts the standard saturation. Correct the saturation to a value less than or equal to C ^* _mod (10, h), as indicated by the □ mark.
Note that in FIG. 6, the x mark indicates the saturation boundary of the color gamut data. At this time, at a certain lightness (for example, L ^* = 9.5), the ratio of the saturation marked with ○ to the saturation C ^* (9.5, h) is the ratio of the saturation marked with a circle to the standard saturation C ^* _mod (10, h). Equal to the saturation ratio of the mark □.
As a result, the image data saturation correction unit 14 normalizes the saturation based on the reference saturation for each predetermined brightness interval, regardless of the brightness of the image data, so that the distribution drawing unit 171 (described later) Color distribution can be expressed within one link.
The image data saturation correction unit 14 outputs the corrected lightness L ^* of the image data and the saturation C ^* _sample-mod (L ^* , h) for each hue angle h to the display unit 17.

The color gamut ring data generation unit 15 generates saturation C for each lightness L ^* (L ^* = 0.5, 1.5, ..., 99.5) and hue angle h (h = 0, 1, ..., 359). ^* From (L ^* , h), data indicating the ring boundary of the color gamut ring for each lightness L ^* is generated. Note that this generation method is a known method (such as Patent Document 1), so an outline thereof will be explained below.

First, the color gamut ring data generation unit 15 calculates the sum of the saturation C ^* from the minimum lightness (here, 0) to the predetermined lightness L ^* as the root sum of squares (RSS) shown in the following equation (9): The saturation C ^* _RSS (L ^* , h) is calculated for each hue angle h. Here, the lightness L ^* is an integer from 1 to 100.

Then, for each lightness L ^* and hue angle h, the gamut ring data generation unit 15 decomposes the saturation C ^* _RSS (L ^* , h) into two dimensions according to the hue angle using the following equation (10). The two-dimensional coordinate values (a ^* _RSS , b ^* _RSS ) _{L*, h} are calculated.

At the same lightness L ^* , the line connecting the two-dimensional coordinate values (a ^* _RSS , b ^* _RSS ) _{L*, h} calculated by the above formula (10) for each hue angle h forms the ring boundary of the color gamut ring. It will be shown.
The color gamut ring data generation unit 15 stores the generated color gamut ring data (two-dimensional coordinate values (a ^* _RSS , b ^* _RSS ) _{L*, h} ) for each lightness L ^* and hue angle h in the color gamut ring data storage unit. 16.

The color gamut ring data storage section 16 stores color gamut ring data. The color gamut ring data storage section 16 can be configured with a general storage medium such as a semiconductor memory.
The color gamut ring data storage unit 16 stores color gamut ring data (two-dimensional coordinate ^value (a ^* _RSS ,b ^* _RSS ) _L*,h ) are stored and held until new color gamut data is input.

The display unit 17 draws and displays the color distribution of image data on a color gamut ring. Here, the display section 17 includes a color gamut ring drawing section 170 and a distribution drawing section 171.

The color gamut ring drawing unit 170 draws a color gamut ring corresponding to color gamut data.
The gamut ring drawing unit 170 draws gamut ring data (two-dimensional coordinate values (a ^* _RSS , b ^* _RSS ) L ^* _{, h} ) is graphed and displayed on monitor 2.
Here _, the color gamut ring drawing unit 170 plots two ^- _dimensional coordinate values ^{( a *} _RSS ,b ^* _RSS ) _L*,h are connected to generate the gamut ring GR shown in FIG. Note that here, the color gamut ring drawing unit 170 thins out the lightness L ^* in 10 steps of 10, 20, . . . , 100, and paints the rings differently in gray scale.

For example, if the color gamut data _DC is data of DCI-P3, the color gamut ring drawing unit 170 draws the color gamut ring shown in FIG. Also, the color gamut data _DC is Rec. 709, the gamut ring drawing unit 170 draws the gamut ring shown in FIG. Also, the color gamut data _DC is Rec. If the data is 2020, the gamut ring drawing unit 170 draws the gamut ring shown in FIG.

The distribution drawing unit 171 draws a color gamut ring corresponding to the position of the brightness L ^* of the image data corrected by the image data saturation correction unit 14 and the saturation C ^* _sample-mod (L ^* , h) for each hue angle h. This draws a marker at the top position.
The distribution drawing unit 171 calculates the saturation C ^* _sample-mod (L ^* , h) corrected by the image data saturation correction unit 14 by plotting the horizontal axis as a ^* _RSS and the vertical axis as b ^* _RSS , which is the same as the color gamut ring. Convert to two-dimensional coordinate values and draw a marker at the coordinate values.
Specifically, the distribution drawing unit 171 calculates the saturation C ^* _sample-mod (L ^* , h) corresponding to the hue angle h in the lightness interval (0<L ^* ≦10) using the following equation (11). Convert to chroma C ^* _M-RSS (L ^* , h).

Furthermore, the distribution drawing unit 171 stores the saturation C ^* _sample-mod (L ^* , h) corresponding to the hue angle h in the lightness interval (10<L ^* ≦20) in the gamut data saturation storage unit 13. Using the stored reference chroma C ^* _mod , it is converted into chroma C ^* _M-RSS (L ^* , h) according to the following equation (12).

Similarly, for the saturation C ^* _sample-mod (L ^* , h) corresponding to the hue angle h in the lightness interval (90<L ^* ≦100) shown in equation (13) below, the color gamut data saturation storage Using the reference chroma C ^* _mod stored in the unit 13, the chroma is converted into a chroma C ^* _M-RSS (L ^* , h) according to the following equation (13).

The same applies to other brightness sections (20<L ^* ≦30), (30<L ^* ≦40), ..., (80<L ^* ≦90).
Then, the distribution drawing unit 171 converts the lightness L ^* and the saturation C ^* _M-RSS (L ^* , h) for each hue angle h into two-dimensional coordinate values a ^* _RSS for each pixel of the image data according to the hue angle. , b ^* _RSS , and draw markers M (for example, O marks) at coordinate positions on the color gamut ring GR as a color distribution, as shown in FIG.

With the above configuration, the color distribution display device 1 is able to express saturation with a maximum brightness difference of 10 at each hue angle within a ring divided by a predetermined brightness interval (here, 10). can. In the color gamut within this same ring, saturation is expressed without distinguishing lightness, so the expression of saturation can be visualized more clearly.
Note that the color distribution display device 1 can operate a computer (not shown) using a color distribution display program for functioning as each section described above.

[Operation of color distribution display device]
Next, the operation of the color distribution display device 1 according to the first embodiment of the present invention will be described with reference to FIG. 10 (see FIG. 1 as appropriate).

In step S1, the color gamut data saturation calculation unit 10 calculates saturation ^C * corresponding to lightness L ^* and hue angle h at regular intervals from the color gamut data of lightness L ^* and chromaticity a ^* , b ^* . do. Here, the color gamut data saturation calculation unit 10 sets the lightness L ^* at constant intervals of 1 from 0.5 to 99.5, and sets the hue angle h to 0, 1, . . . , 359.

In step S2, the reference saturation calculation unit 12 calculates a hue angle for each predetermined lightness interval (0<L ^* ≦10, 10<L ^* ≦20,..., 90<L ^* ≦100) in the color gamut data. A common reference saturation at which the color gamut volume at the unit angle (1°) is the same as the original color gamut shape is calculated. That is, the reference saturation calculation unit 12 calculates the reference saturation C ^* _mod by calculating the root mean square of the saturation C ^* calculated in step S1 for each hue angle h in a predetermined lightness interval. .

In step S3, the reference saturation calculation unit 12 calculates the brightness L ^* of the color gamut data calculated in step S1 and the saturation C ^* for each hue angle h, and the brightness C* for each hue angle h calculated in step S2. The reference saturation C ^* _mod for each hue angle h is stored in the gamut data saturation storage unit 13.

In step S4, the color gamut ring data generation unit 15 generates lightness L ^* (L ^* =0.5, 1.5,...,99.5) and hue angle h (h=0,1,...,359). From the chroma C ^* (L ^* , h), calculate the chroma C ^* _RSS (L ^* , h) indicating the ring boundary of the color gamut ring, and calculate the two-dimensional coordinate value (a ^* _RSS , b ^* _RSS ) _L By decomposing into _{* and h} , color gamut ring data is generated.

In step S5, the gamut ring data generation unit 15 stores the gamut ring data (two-dimensional coordinate values (a ^* _RSS , b ^* _RSS ) _{L*, h} ) generated in step S4 in the gamut ring data storage unit 16. Remember.

In step S6, the image data saturation calculation unit 11 calculates a saturation C ^* _sample (L ^* , h) corresponding to the lightness L ^* and hue angle h from the image data of the lightness L ^* and chromaticities a ^* , b ^* . Calculate.

In step S7, the image data saturation correction unit 14 converts the saturation C ^* _sample (L ^* , h) corresponding to the lightness L ^* and hue angle h calculated in step S6 into a predetermined lightness interval (0< L ^* ≦10, 10<L ^* ≦20,..., 90<L ^* ≦100), the ratio of the reference saturation to the saturation of the color gamut data stored in the color gamut data saturation storage unit 13 is determined. Correct accordingly, and calculate saturation C ^* _sample-mod (L ^* , h).
Note that the image data saturation correction unit 14 corrects image data when the lightness L ^* is not 0.5, 1.5, ..., 99.5, or the hue angle h is 0, 1, ..., 359. If neither of these is the case, the coordinates of C ^* _mod (L ^* , h) and C ^* (L ^* , h) on the color gamut solid are linearly interpolated using lightness and hue angle, and then corrected.

In step S8, the gamut ring drawing unit 170 of the display unit 17 draws gamut ring data (two ^- dimensional coordinate values (a ^* _RSS ,b ^* _RSS ) _L*,h ) to draw a color gamut ring and display it on the monitor 2.

In step S9, the distribution drawing unit 171 plots the lightness L ^* whose saturation was corrected in step S8 and the saturation C ^* _sample-mod (L ^* , h) for each hue angle h on the same horizontal axis as the color gamut ring. is converted into a two-dimensional coordinate value with a ^* _RSS and the vertical axis is b ^* _RSS (see formula (11), formula (12) to formula (13)), and the two-dimensional coordinate value a ^* _RSS is converted according to the hue angle. , b ^* _RSS , and the color distribution is displayed on the monitor 2 by drawing a predetermined marker (for example, a circle) at the same coordinate position as the color gamut ring.

Through the above operations, the color distribution display device 1 can display the color distribution image _{CD I in} which the color distribution of the image data DI is represented by the markers M on the color gamut ring GR, as shown in FIG.
Note that when there is no change in the color gamut data _DC and only the image data _DI is to be changed and the color distribution is to be displayed on the color gamut ring GR, the color distribution display device 1 performs the following operations after steps S1 to S9. It is only necessary to perform the operations from steps S6 to S9 on other image data _DI .
Moreover, although the single image data _DI input to the color distribution display device 1 has been described here, the input image data may be an image frame inputted as a video. Thereby, the color distribution display device 1 can display the color distribution of a moving image in real time.

≪Second embodiment≫
Next, with reference to FIG. 11, a color distribution display device 1B according to a second embodiment of the present invention will be described.

The color distribution display device 1B superimposes and displays the color distribution of image data on a color gamut ring (gamut rings) that displays color gamut data of a 3D color gamut in two dimensions. This is to determine whether the color distribution of the image data is included in the color gamut of (e.g.).
Specifically, as shown in FIG. 12, the color distribution display device 1B represents the color distribution _of the image data DI with markers M on the color gamut ring GR specified by the color gamut data _DC , and creates a color distribution image. Displayed on monitor 2 as CD _I.
Furthermore, the color distribution display device 1B represents pixels in the color distribution of the image data _DI that do not belong to the color gamut of the device color gamut data _DD with markers M'.

The color gamut data D _C and the image data D _I are the same as the input data of the color distribution display device 1 explained with reference to FIG.
The device color gamut data _DD is data indicating the shape of a color gamut solid that indicates an area of a displayable color space that has been measured in advance on a specific device. Here, the device color gamut data _DD is data in the CIE1976 (L ^* , a ^* , b ^* ) (CIELAB) color space.

The color distribution display device 1B includes a color gamut data saturation calculation section 10, an image data saturation calculation section 11, a reference saturation calculation section 12, a color gamut data saturation storage section 13, and an image data saturation correction section. 14, a color gamut ring data generation section 15, a color gamut ring data storage section 16, a display section 17B, and a device color gamut inside/outside determination section 18.
The configuration other than the display section 17B and the device color gamut inside/outside determination section 18 is the same as the color distribution display device 1 described with reference to FIG. 1, and therefore the description thereof will be omitted.

First, the device color gamut inside/outside determination section 18 will be explained.
The device color gamut inside/outside determination unit 18 determines whether the color of each pixel of the image data _DI belongs to the color gamut of the device color gamut data _DD .
For example, as shown in FIG. 13, the device color gamut inside/outside determination unit 18 determines, for each pixel of the image data _DI , the CIELAB cross section of the device color gamut data _DD at the brightness of the pixel (for example, L ^* =50). A polygon POL is obtained, and it is determined whether the pixel belongs to the color gamut of the device color gamut data _DD depending on whether the pixel falls within the polygon POL. In FIG. 13, pixels marked with ◯ indicate that they belong to the color gamut of the device color gamut data _DD , and pixels marked with an x mark indicate that they do not belong to the color gamut of the device color gamut data _DD .
This determination of the inside and outside of the polygon can be performed using a known determination method such as the inpolygon function of MATLAB (registered trademark).

Note that since the device color gamut data _DD is discrete data, a cross section that matches the brightness of the pixels of the image data _DI cannot be accurately determined. In that case, the device color gamut inside/outside determination unit 18 may make the determination using the cross section closest to the brightness of the pixel, or may linearly interpolate discrete cross sections to generate a cross section corresponding to the brightness of the pixel and make the determination. good.
The device color gamut inside/outside determination unit 18 outputs a determination result indicating whether each pixel of the image data _DI belongs to the color gamut of the device color gamut data _DD to the display unit 17B.

The display unit 17B draws and displays the color distribution of image data on a color gamut ring. Here, the display section 17B includes a color gamut ring drawing section 170 and a distribution drawing section 171B. The color gamut ring drawing unit 170 has the same configuration as the color distribution display device 1 described with reference to FIG. 1, so a description thereof will be omitted.

The distribution drawing unit 171B draws a color gamut ring corresponding to the position of the brightness L ^* of the image data corrected by the image data saturation correction unit 14 and the saturation C ^* _sample-mod (L ^* , h) for each hue angle h. It draws a marker at the upper position, and has the same function as the distribution drawing section 171 described in FIG. 1.
Further, the distribution drawing unit 171B uses the determination result of whether or not the color corresponding to the pixel of the image data belongs to the color gamut specified by the device color gamut data _DD , which is input from the device color gamut inside/outside determination unit 18. Draw markers in different shapes or colors based on
For example, if the color corresponding to the pixel of the image data belongs to the color gamut of the device, the distribution drawing unit 171B places a marker M (for example, a circle mark) at the coordinate position on the color gamut ring GR, as shown in FIG. draw. On the other hand, if the color corresponding to the pixel of the image data does not belong to the color gamut of the device, the distribution drawing unit 171B draws the marker M' in a shape (for example, an x mark) or color (for example, red) that is different from that of the marker M. draw.

Note that the operation of the color distribution display device 1B is such that, in the operation of the color distribution display device 1 described in FIG. What is necessary is to perform the above steps and draw a marker corresponding to the determination result in step S9.

With the above configuration, the color distribution display device 1B has the same effect as the color distribution display device 1 described in _FIG . can be displayed.
Note that the color distribution display device 1B can be operated by a color distribution display program for making a computer (not shown) function as each section described above.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments.
Here, the reference saturation calculation unit 12 sets the brightness interval for calculating the common reference saturation to 10, but the invention is not limited to this. For example, 20, 25, etc. may be used as the brightness interval.

Further, here, the color distribution display device 1 is configured to perform drawing of the color gamut ring and drawing of the color distribution within the same device (program).
However, these drawings may be performed using different devices (programs).
In that case, a conventional color gamut display device (program) such as Patent Document 1 is used to draw the color gamut ring, and from the color distribution display device 1, the color gamut ring data generation unit 15, the color gamut ring data storage unit 16 Also, the color gamut ring drawing section 170 may be omitted.

Furthermore, although the color gamut data D _C and image data D _I have been explained here as data in the (L ^* , a ^* , b ^* ) color space, respectively, these data can be in any color space. Data is fine. In that case, the color gamut data saturation calculation unit 10 and the image data saturation calculation unit 11 may each convert the color space into a (L ^* , a ^* , b ^* ) color space.

Furthermore, if the color gamut data D _C and the image data D _I are data of (L ^* , C ^* , h), respectively, the color gamut data saturation calculation unit 10 and the image data saturation calculation unit 11 are removed from the configuration. May be omitted. However, in that case, the interval of lightness L ^* of color gamut data D _C is set at 1 step from 0.5 to 99.5, and the hue angle h is set at unit angle (1°) from 0° to 359°, for example. ) interval.

Further, here, the color distribution display device 1 displays the color distribution of the image data on the color gamut ring of the color gamut data D _C corresponding to the image data (see FIG. 2), and the color distribution display device 1B Furthermore, the color distribution of image data that is not displayed on the designated device is displayed on the color gamut ring specified by the color gamut data _DC (see FIG. 12).
However, the color distribution of image data is not limited to these displays.
For example, the color distribution display device 1B further includes a color gamut ring generation unit that generates a gamut ring of the device color gamut data _DD , and the distribution drawing unit 171B generates a gamut ring of the device gamut data _DD . The color distribution of the image data _DI that can be displayed on the designated device may be displayed on the ring.

1, 1B Color distribution display device 10 Color gamut data saturation calculation unit 11 Image data saturation calculation unit 12 Reference saturation calculation unit 13 Color gamut data saturation storage unit 14 Image data saturation correction unit 15 Color gamut ring data generation unit 16 Color gamut ring data storage section 17, 17B Display section 170 Color gamut ring drawing section 171, 171B Distribution drawing section 18 Device color gamut inside/outside determination section M, M' marker GR Color gamut ring

Claims (6)

A color distribution display device that superimposes and displays the color distribution of image data corresponding to the color gamut on a color gamut ring that two-dimensionally displays color gamut data of a color gamut solid expressed in a three-dimensional color space. hand,
From the lightness, hue angle, and saturation indicating the color gamut data, a common reference saturation is determined for each predetermined lightness interval so that the color gamut volume within the unit angle of the hue angle is the same volume as the original color gamut shape. a reference saturation calculation unit that calculates;
an image data saturation correction unit that corrects the saturation of the image data by multiplying the saturation of the image data by a ratio of the reference saturation to the saturation of the color gamut data for each hue angle in the brightness interval;
a color gamut ring drawing unit that draws and displays the color gamut ring;
a distribution drawing unit that draws a marker at a position on a color gamut ring corresponding to a position of brightness, hue angle, and saturation of the image data corrected by the image data saturation correction unit;
A color distribution display device comprising: The color distribution display device according to claim 1, wherein the reference saturation calculation unit calculates the reference saturation based on the root mean square of the saturation of the hue angle for each of the lightness intervals. The image data saturation correction unit corrects the image data when one or both of the brightness and hue angle of the image data is different from the brightness and hue angle corresponding to the reference saturation calculated by the reference saturation calculation unit. The saturation corresponding to the lightness and hue angle and the saturation of the color gamut data are determined by linear interpolation from the coordinates on the color gamut solid, and after calculating the ratio, the saturation of the image data is corrected. The color distribution display device according to claim 1. further comprising a gamut ring data generation unit that generates gamut ring data indicating brightness of the gamut ring and saturation for each hue angle from the gamut data,
The color distribution display device according to claim 1, wherein the color gamut ring drawing section draws and displays the color gamut ring generated by the color gamut ring data generation section. further comprising a device color gamut inside/outside determination unit that determines whether the color of each pixel of the image data belongs to a color gamut of color gamut data of a specified device;
The color distribution display device according to claim 1, wherein the distribution drawing section draws the marker in a different shape or color based on the determination result of the device color gamut inside/outside determination section. A color distribution display program for causing a computer to function as the color distribution display device according to claim 1.

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