Color gamut deviation display method, color gamut deviation display system, and program

Abstract

Provided is a color gamut deviation display method which exhibits excellent convenience to a user. Provided is a color gamut deviation display method executed by a computer system, the color gamut deviation display method comprising: calculating an xy chromaticity coordinate point from a chromaticity value of a pixel of a video signal to be measured; calculating, by using the xy chromaticity coordinate point on a chromaticity diagram of the pixel, the xy chromaticity coordinate point of a white point on the chromaticity diagram, the xy chromaticity coordinate point on a chromaticity diagram of a container color gamut which is a color gamut of the video signal, and the xy chromaticity coordinate point on a chromaticity diagram of a target color gamut which is narrower than the container color gamut, a GER value indicating the degree of deviation of the pixel from the target color gamut; and arranging, in one composite plan view by using the GER value, an H value indicating hue, and a V value indicating lightness for each of at least a part of pixels of the video signal, a plurality of chromaticity plan views in which the H values and the GER values of the at least a part of pixels of the video signal are arranged for each range of the plurality of V values.

Description

Method for displaying color gamut deviations, system for displaying color gamut deviations, and program

[0001] The present invention relates to a method for displaying the degree of color gamut deviation in an image.

[0002] Since the establishment of the ITU-R Recommendation 2020, wide-gamut video formats have become commonplace. On the other hand, the performance of displays used by end users of video is limited to narrow color gamuts, such as DCI P3, which was established by the Digital Cinema Initiatives, a US film industry association. Generally, such displays are equipped with color gamut limiting functions to restrict the color range from wide color gamuts such as ITU-R Recommendation 2020 to narrow color gamuts such as DCI P3. However, video content providers may not be satisfied with these color gamut limiting functions and may perform color gamut limiting on the content before distribution. For example, this might involve restricting a wide color gamut system such as ITU-R Recommendation 2020 to a narrow color gamut system such as DCI P3.

[0003] In response to such demands, conventional tools such as the CIE (International Commission on Illumination) chromaticity diagram have been used as methods for displaying color gamuts (for example, Patent Document 1).

[0004] Japanese Patent Publication No. 2014-129098

[0005] Lakshmanan Gopishankar, “Making the CIE Chart Indispensable for Color Grading!”, the Proceedings of the 2024 NAB Broadcast Engineering and Information Technology (BEIT) Conference, USA, PILOT, April 3, 2024. NHK Public Relations Department, “New Method for Color Gamut Expression, ‘Gamut Rings,’ Becomes an International Standard ~Visualizing the Color Reproduction Range of Displays More Accurately and Clearly~”, Press Release, Japan, NHK Science & Technology Research Laboratories, February 15, 2022.

[0006] However, conventional methods of displaying color gamuts did not fully meet user demands, for example, because the CIE chromaticity diagram was not perceptually uniform. Therefore, there was a need for a tool that was more user-friendly.

[0007] This invention was made in view of these problems.

[0008] To solve the above problems, one aspect of the present invention is a color gamut deviation display method performed by a computer system, which includes calculating xy chromaticity coordinates from the chromaticity values ​​of pixels in a video signal that is a signal under test, calculating a GER value indicating the degree of deviation of the pixel from the target color gamut using the xy chromaticity coordinates which are the coordinates on the chromaticity diagram of the pixel, the xy chromaticity coordinates of the white point on the chromaticity diagram, the xy chromaticity coordinates which are the xy chromaticity coordinates on the chromaticity diagram of the container color gamut which is the color gamut of the video signal, and the xy chromaticity coordinates which are the xy chromaticity coordinates on the chromaticity diagram of the target color gamut which is a narrower color gamut than the container color gamut, and arranging a plurality of chromaticity plane diagrams in which the H values ​​and GER values ​​of at least some pixels of the video signal are arranged for each of a plurality of V value ranges using the GER value for at least some pixels of the video signal, an H value indicating hue, and a V value indicating brightness, into a single composite plane diagram.

[0009] Another aspect of the present invention is the above-described method for displaying color gamut deviations, wherein the chromaticity diagram is a CIE chromaticity diagram.

[0010] Another aspect of the present invention is the above-described method for displaying color gamut deviations, which includes displaying and outputting the synthesized composite plan view.

[0011] Another aspect of the present invention is a method for displaying color gamut deviation, wherein the GER value of the pixel is calculated using a first intersection point on a chromaticity diagram, which is the intersection point of a straight line connecting the pixel and the white point with the boundary line of the region indicating the container color gamut, and a second intersection point, which is the intersection point of the straight line with the boundary line of the region indicating the target color gamut.

[0012] Another aspect of the present invention is the above-described method for displaying color gamut deviations, wherein the chromaticity planar and / or the composite planar are circular or annular in shape.

[0013] Another aspect of the present invention is the above-described method for displaying color gamut deviations, wherein the plurality of chromaticity plane diagrams are arranged in order of magnitude of the V value range from the center to the periphery of the composite plane diagram.

[0014] Another aspect of the present invention is the above-described method for displaying color gamut deviations, wherein the plurality of chromaticity plane diagrams are arranged in the composite plane diagram according to user specifications.

[0015] Another aspect of the present invention is the above-described method for displaying color gamut deviations, wherein only a portion of the plurality of chromaticity planar diagrams is placed in the composite planar diagram.

[0016] Another aspect of the present invention is the above-described method for displaying color gamut deviations, wherein the number of ranges of the plurality of V values ​​is determined according to user input.

[0017] Another aspect of the present invention is a computer system that performs the above-described method for displaying color gamut deviations.

[0018] Another aspect of the present invention is a program for causing a computer system to execute the above-described color gamut deviation display method.

[0019] Another aspect of the present invention is a computer-readable recording medium that stores a program for causing a computer system to execute the above-described color gamut deviation display method.

[0020] This figure shows an example of the configuration of a color gamut deviation display system according to one embodiment of the present invention. This is a flowchart showing an example of processing in a color gamut deviation display method according to one embodiment of the present invention. This is a flowchart showing an example of processing in a color gamut deviation display method according to one embodiment of the present invention. This figure shows an example of a sample color image to illustrate a specific example of a case where a video signal of the container color gamut is restricted to the target color gamut. This figure shows the representation of the sample image on an xy chromaticity diagram. This figure maps the GER value of each pixel of the sample image onto the image. This figure shows the GER value as a histogram. This figure draws the HGV value of each pixel of the sample image according to the HSV color system. This figure shows the HG value of a pixel with a V value range of 0 to 84 (dark area) drawn on a circular two-dimensional plane using polar coordinates. This figure shows the HG value of a pixel with a V value range of 85 to 169 drawn on a circular two-dimensional plane using polar coordinates. This figure shows the HG value of a pixel with a V value range of 170 to 255 (bright area) drawn on a circular two-dimensional plane using polar coordinates. This diagram shows HG values ​​for multiple ranges of V values ​​plotted on a single two-dimensional plane.

[0021] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0022] (Color Gamut Deviation Display System) The color gamut deviation display system according to this embodiment is a device that measures and displays the degree of deviation from the color gamut of a signal under test, such as a video signal. The color gamut deviation display system according to this embodiment is composed of a waveform monitor and a rasterizer as an example. However, it is not limited to this and can be realized by various configurations having hardware and software capable of realizing each function of the color gamut deviation display system. The color gamut deviation display system according to this embodiment can be realized by various configurations such as a general-purpose computer device (a stationary computer device such as a desktop computer, a portable computer device such as a notebook computer, a smartphone, or a tablet computer), a distributed computer system composed of multiple computer devices, a client / server computer system, or a cloud system.

[0023] The color gamut deviation display system according to this embodiment is a color gamut deviation display system that takes the following points into consideration: (1) Handling of the signal under test in a more intuitive color system (2) More quantitative representation of the degree of deviation (3) Two-dimensional representation of three-dimensional information

[0024] The following explains (1) to (3).

[0025] (1) Handling signals in a more intuitive color system The conventionally used CIE color system is not perceptually uniform. The HSV color system is a color system that is easy for engineers and colorists to use. For these reasons, the color gamut deviation display system according to this embodiment adopts a display method that conforms to the HSV color system. HSV stands for "Hue," "Saturation," and "Value," respectively.

[0026] (2) More quantitative representation of the degree of deviation In the color gamut deviation display system according to this embodiment, in order to quantitatively handle the signal under test, the inventors use a novel index called GER (Gamut Excursion Ratio: degree of color gamut deviation). When displaying the signal under test on the CIE chromaticity diagram, it is only possible to determine whether the chromaticity of the signal under test is inside or outside the triangle representing the RGB color space of the target color gamut (a narrow color gamut targeted for conversion for displays, etc.) mapped on the CIE xy plane, and to grasp the distance from the triangle on the xy plane to the point representing the chromaticity of the signal under test. Furthermore, even if the distance is the same, the corresponding perceived amount differs depending on the chromaticity of the signal under test. This distance is not a common index for all colors (Hue) as an index of color gamut deviation. This is because the relationship between the target color gamut and the color gamut of the original color system (container color system) of the signal under test differs for each Hue.

[0027] To address this problem, Non-Patent Document 1 proposes an index called "GEM". The method described in Non-Patent Document 1, as shown in Figure 8 of Non-Patent Document 1, defines the quantification when the test signal P exists between the container color system and the target color system. In the method described in Non-Patent Document 1, on the xy plane of the CIE, the intersection point A of the line connecting the test signal P and the white point W with the triangle of the container color system is defined, and the intersection point B of the line with the triangle of the target color system is defined, and the deviation degree is defined as the value obtained by dividing the distance BP between point B and point P by the distance BA between point B and point A (BP / BA). This provides a common index for all Hues.

[0028] However, Non-Patent Document 1 only describes the case where the signal under test is outside the target color gamut, and does not consider the case where the signal under test is within the target color gamut (including the case where it is on the boundary of the target color gamut; the same applies hereinafter throughout this specification). The novel index GER according to this embodiment is configured to also handle the case where the signal under test is within the target color gamut.

[0029] More specifically, when the signal P under test is within the target color gamut, the index is the value obtained by dividing the negative number -BP (the distance BP between point B and the signal P under test) by the distance WB (the distance between the white point W and point B) (-BP / WB). In this embodiment, GER can be quantified for all pixels of the image (signal under test) between a value of "-1" and "1". GER = -1 indicates achromatic, GER = 0 indicates the boundary of the target color gamut, and GER = 1 indicates the boundary of the container color gamut.

[0030] Furthermore, in this embodiment, GER is used instead of S (saturation) in the HSV color system (GER is abbreviated as "G"), and three-dimensional information is represented as "HGV".

[0031] In this specification, "container" in terms such as "container color system" and "container color gamut" refers to the original color system and color gamut (wide color gamut) of the signal being tested, such as a video signal. Furthermore, "target" in terms such as "target color system" and "target color gamut" refers to the target color system and color gamut (wide color gamut) that should be aimed for in order to maintain image quality under the limitations of the display performance of a display, etc.

[0032] (3) Two-dimensional representation of three-dimensional information: Since color is three-dimensional information, some kind of ingenuity is required to obtain the overall information of the signal under test. For example, one possible method is to check multiple hue-saturation charts that are limited in the brightness direction.

[0033] One method that makes such three-dimensional color information easily visible is the method described in Non-Patent Document 2. The method in Non-Patent Document 2 divides the CIE 1976 L*a*b* color space into 10 slices in the brightness direction, stretches it onto a plane from the lower brightness side, and arranges the color gamut with higher brightness in a ring shape around it to represent the three-dimensional information in two dimensions.

[0034] In the color gamut deviation display system according to this embodiment, three-dimensional information is also represented in two dimensions. The color gamut deviation display system according to this embodiment does not use the L*a*b* color system, but rather a novel HGV color system devised by the inventors, which is an improvement on the HSV color system that is more familiar to engineers and colorists as described above. In this embodiment, the number of sections into which the color gamut is sliced ​​is three: dark areas (Low), midtone areas (Medium), and bright areas (High). When considering a scenario in which a signal under test is converted to a narrow color gamut, it is thought that three sections are a more appropriate number. However, this is not limited to this, and the number of sections may be other. For example, the color gamut deviation display system may determine the number of sections by accepting user input specifying the number of sections.

[0035] Also, in Non-Patent Document 2, the color space is cut into 10 slices in the brightness direction, stretched out flat from the lower brightness side, and color gamuts with higher brightness are arranged in a ring shape around it. In contrast, the color gamut deviation display system according to the present embodiment can be configured to determine whether to arrange the color gamuts in order from the inside starting from the color gamut with lower brightness or the color gamut with higher brightness by receiving an input from a user who specifies that. Further, only any one or more color gamuts specified by the input from the user among the sliced color gamuts may be arranged two-dimensionally.

[0036] (Configuration of Color Gamut Deviation Display System) FIG. 1 is a diagram showing an example of the configuration of the color gamut deviation display system according to the present embodiment. As described above, the color gamut deviation display system according to the present embodiment will be described as being a waveform monitor as an example. However, it is not limited to this, and it can be realized by various configurations having hardware and software capable of realizing each function of the color gamut deviation display system. As shown in FIG. 1, the color gamut deviation display system 1 according to the present embodiment includes a display 102, a key / encoder circuit 104, a serial-parallel converter (or IP-parallel converter; the same applies hereinafter) 106, a picture image generation circuit 108, a vector image generation circuit 110, a waveform image generation circuit 112, a color gamut deviation display image generation circuit 126, a conversion circuit 114, a conversion circuit 116, a selection pixel extraction circuit 118, a display control circuit 120, a drawing memory 122, and a synthesis circuit 124. The serial-parallel converter  106, the image generation circuits 108, 110, 112, and 126, and the conversion circuits 114 and 116 function to generate an image of a video signal. This video signal is a test signal that is the target to be converted from a wide color gamut to a narrow color gamut in the color gamut deviation display image generation circuit 126. The selection pixel extraction circuit 118, the display control circuit 120, and the drawing memory 122 function to perform display control of the image of the video signal.

[0037] In this embodiment, circuits 108, 110, 112, 114, 116, 118, 124, and 126 may be configured using FPGAs. However, this is merely an example and is not limited thereto. Furthermore, the display control circuit 120 may be implemented using a computer and a program. It should be noted that all the various circuits of the color gamut deviation display system 1 in this embodiment can be implemented using hardware, or using a combination of computer and software.

[0038] The display unit 102 may include an input that receives a composite image signal from the synthesis circuit 124, and a screen that displays an image to the user in response to the composite image signal, for example, at a resolution of XGA (Note that XGA is just one example, and other resolutions may be used. The same applies hereinafter). The key / encoder circuit 104 may include a key matrix containing a plurality of keys for operating the monitor 100, and an encoder knob. The key matrix may have, for example, a plurality of function keys and a plurality of other keys (in this description, these will be tentatively called PIC, WFM, VECT, GMT, and MULTI). The keys PIC, WFM, VECT, GMT, and MULTI are used to specify the display mode of the color gamut deviation display system 1 of this embodiment. The PIC key specifies the picture display mode, and when this mode is selected, a raster image composed of the video signal is displayed as a "picture image". The WFM key specifies the waveform display mode, and when this mode is selected, an image showing the time variation of the components contained in the video signal is displayed as a "waveform image". The VECT key specifies the vector display mode, and when this mode is selected, an image similar to that displayed in a conventional vectorscope is displayed as a "vector image". The GMT key specifies the color gamut deviation display mode, and when this mode is selected, an image generated by the color gamut deviation display method according to this embodiment is displayed as a "color gamut deviation display image". The color gamut deviation display image is an image that shows whether the original video signal before conversion to a narrow color gamut deviates from the target color gamut of the narrow color gamut. The MULTI key is a key that specifies the multi-screen mode, and when this mode is selected, the picture image, waveform image, vector image, and color gamut deviation display image are displayed simultaneously on one screen. If the multi-screen mode is not selected, it operates in single-screen mode. In single-screen mode, only the color gamut deviation display image may be displayed. In multi-screen mode, the color gamut deviation display image and one or more of the picture image, vector image, and waveform image may be displayed simultaneously.

[0039] When the key / encoder circuit 104 receives the above user operation input, it generates a key matrix output indicating which key has been pressed, and when the encoder knob is operated, it generates an encoder output representing the operation. The encoder can include, for example, a rotary encoder. In this case, the encoder detects the pulses of the rotary encoder output and generates an encoder output obtained by updating the data representing the operation direction and the moving distance.

[0040] The serial-parallel converter 106 has an input for receiving a video signal as a detected signal, for example, an HD SDI signal (however, this is just an example. It can be various video standards related to SDI and IP such as the SMPTE274M standard), and converts the received HD SDI signal in serial form into a video signal in parallel form having an HD SDI rate and outputs it. In this embodiment, an example of an HD SDI signal (SMPTE274M standard) is described as the video signal, but the present invention is also applicable to video signals of other standards (for example, various video standards such as SD-SDI, 3G-SDI, HDMI, DisplayPort, etc.).

[0041] Next, the picture image generation circuit 108, the vector image generation circuit 110, the waveform image generation circuit 112, and the gamut deviation display image generation circuit 126 each have an input for receiving the output from the serial-parallel converter 106 and an input for receiving a display position / display size setting output from the display control circuit 120, which will be described in detail later. Further, the waveform image generation circuit 112 has an input for receiving a GBR conversion command from the display control circuit 120. The image generation circuits 108, 110, 112, and 126 each represent an image related to the received video signal and generate different forms of images according to the display position and display size settings received from the display control circuit 120.

[0042] In detail, the picture image generation circuit 108 generates an active picture image from the input parallel data, excluding the blanking period. To match the format of the display unit 102, it converts the generated picture image to XGA resolution, reduces the size of this converted picture image according to the set display size, and then shifts the reduced image to the set display position, outputting the resulting XGA-sized picture image. In display modes where a picture image is not required, the image generation circuit 108 masks the picture image output, meaning it does not generate a picture image at output.

[0043] The vector image generation circuit 110 removes the blanking period from the input parallel data, converts the generated picture image into a vector display coordinate system, rasterizes the vector image, converts the resolution of the rasterized vector image to XGA to match the display format, reduces the converted vector image to the set display size, shifts this reduced image so that it is displayed at the set display position, and outputs the resulting XGA-sized vector image. In display modes where a vector image is not required, the image generation circuit 110 masks the vector image output.

[0044] The waveform image generation circuit 112 converts the input parallel data from the serial-to-parallel converter 106 into three waveforms: a Y (luminance) signal, chrominance signals Cb and Cr (or G (green), B (blue), and R (red) signals in the case of GBR display). These three waveforms are rasterized into a single image. The resolution of this rasterized image is converted to XGA to match the display format. The converted image is then scaled down to the set display size, and this scaled-down image is shifted to the set display position. Finally, the resulting XGA-sized waveform image is output. In display modes where a waveform image is not required, the image generation circuit 112 masks the waveform image output.

[0045] The color gamut deviation display image generation circuit 126 may be configured to receive input parallel data from the serial-to-parallel converter 106 and receive a brightness value V, a hue value H, a saturation value S, and a GER value from the display control circuit 120 (or the brightness value V, hue value H, saturation value S, and GER value may be calculated by the color gamut deviation display image generation circuit 126) to generate a color gamut deviation display image. The color gamut deviation display image generation circuit 126 converts the resolution of the color gamut deviation display image generated by the color gamut deviation display method according to this embodiment (for example, the image in Figure 12) to XGA to match the format of the display unit 102, reduces the converted color gamut deviation display image to a set display size, shifts this reduced image so that it is displayed at a set display position, and outputs the resulting XGA-sized color gamut deviation display image. In display modes where a color gamut deviation display image is not required, the color gamut deviation display image generation circuit 126 masks the output of the color gamut deviation display image.

[0046] Next, the conversion circuit 114 has an input connected to the output of the picture image generation circuit 108, and performs picture frame rate conversion to convert the frame rate of the picture image to have an XGA rate, and then generates this converted XGA picture image as an output. Similarly, the conversion circuit 116 has an input connected to the output of the vector image generation circuit 110, an input connected to the output of the waveform image generation circuit 112, and an input connected to the output of the color gamut deviation display image generation circuit 126, and combines the vector image, the waveform image, and the color gamut deviation display image, converts the frame rate of this combined image to an XGA rate to match the display format, and generates this converted XGA combined image as an output.

[0047] Next, the display control circuit 120 has an input connected to the output of the key / encoder circuit 104, and reads the key matrix output and encoder output from the key / encoder circuit by polling, thereby determining the display mode from the operated key. The display control circuit 120 also calculates and outputs the sample number and line number of the input video based on the format of the input video signal from the output of the operated encoder.

[0048] The selected pixel extraction circuit 118 has an input connected to the output of the serial-to-parallel converter 106 and an input connected to the output of the display control circuit 120. By detecting a synchronization signal from the received input parallel data, it monitors the sample number and line number, and extracts and outputs the pixels of the input parallel data corresponding to the sample number and line number received from the display control circuit 120. The selected pixel extraction circuit 118 also detects the luminance value Y, chrominance value Cb, and Cr of the extracted pixels, updates these values, and outputs them together with the extracted pixels as extracted pixel data.

[0049] The display control circuit 120, which has an input to receive this extracted pixel data, obtains the luminance value Y, chrominance values ​​Cb and Cr from the extracted pixel data. The display control circuit 120 also sets the display size and position of the picture image, vector image, waveform image, and color gamut deviation display image according to the determined display mode. That is, in single-screen mode, where only one image is displayed on the screen, the display size and position are set only for the specified image among the picture image, vector image, waveform image, and color gamut deviation display image. In multi-screen mode, the display size and position of each of the picture image, vector image, waveform image, and color gamut deviation display image are set so that they are displayed in, for example, a predetermined layout. Furthermore, when GBR display is specified in relation to the waveform display mode, the display control circuit 120 generates a GBR conversion command. These settings and commands are used in the image generation circuits 108, 110, 112, and 126 as described above.

[0050] Furthermore, the display control circuit 120 performs predetermined calculation processing from the extracted pixel data. Specifically, it calculates G, B, or R values ​​to be added to the picture image from the extracted pixel data for addition to each image. Note that the Y (luminance) value can also be selected as the value to be added to the picture image. It also calculates the display position of the scale to be added to the waveform image according to the extracted pixel data and the display mode. In addition, it calculates the Cb% value, Cr% value, saturation% value (d), and hue angle (deg) to be added to the vector image from the extracted pixel data, and calculates the display position of the scale to be added to the vector image according to the display mode. The display control circuit 120 also calculates the brightness value V, hue value H, saturation value S, and GER value to be added to the color gamut deviation display image from the extracted pixel data. The calculated brightness value V, hue value H, saturation value S, and GER value are output to the color gamut deviation display image generation circuit 126. In this example, the brightness value V, hue value H, saturation value S, and GER value are calculated in the display control circuit 120, but they may also be calculated in the color gamut deviation display image generation circuit 126.

[0051] The display control circuit 120 performs drawing processing in the drawing memory 122. Specifically, in the case of a picture image, the display control circuit 120 outputs the G value, B value, R value, or luminance value Y to be added to the picture image to the drawing memory 122. In the case of a vector image, the display control circuit 120 outputs an image of the numerical values ​​of the Cb value (%), Cr value (%), saturation d (%), and hue angle (deg) to be added to the vector image, along with the scale, to the drawing memory 122. In the case of a waveform image, the display control circuit 120 outputs an image of the scale to be added to the waveform image to the drawing memory 122. In the case of a color gamut deviation display image, the display control circuit 120 outputs the brightness value V, hue value H, saturation value S, and GER value to be added to the color gamut deviation display image to the color gamut deviation display image generation circuit 126. In the case of a multi-screen display, images for the four images—the picture image, the vector image, the waveform image, and the color gamut deviation display image—are combined in the drawing memory 122.

[0052] The drawing memory 122 has inputs that receive the output described above from the display control circuit 120 and the color gamut deviation display image generation circuit 126, stores the data drawn according to the received inputs, and outputs an XGA drawn image (including numerical values ​​and scales) from the drawing data at the XGA rate of the display unit 102.

[0053] The synthesis circuit 124 has inputs connected to the output of the conversion circuit 114, the output of the conversion circuit 116, and the output of the drawing memory 122, respectively. When single screen mode is selected, the synthesis circuit 124 synthesizes the picture image from the conversion circuit 114 with the drawing image from the drawing memory 122, i.e., the G value, B value, or R value image to be added to the picture image. At this time, the vector image is masked by the vector image generation circuit 110, the waveform image is masked by the waveform image generation circuit 112, and the color gamut deviation display image is masked by the color gamut deviation display image generation circuit 126. When waveform display mode is selected, the synthesis circuit 124 synthesizes the waveform image from the conversion circuit 116 with the drawing image from the drawing memory 122, i.e., the scale image to be added to the waveform image. At this time, the picture image is masked by the picture image generation circuit 108, the waveform image is masked by the waveform image generation circuit 112, and the color gamut deviation display image is masked by the color gamut deviation display image generation circuit 126. When the vector display mode is selected, the synthesis circuit 124 synthesizes the vector image from the conversion circuit 116 with the drawing image from the drawing memory 122, that is, the images of the scale, Cb% value, Cr% value, saturation% value (d), and hue angle (deg) to be added to the vector image. At this time, the picture image is masked by the picture image generation circuit 108, the waveform image is masked by the waveform image generation circuit 112, and the color gamut deviation display image is masked by the color gamut deviation display image generation circuit 126. When the color gamut deviation display mode is selected, the synthesis circuit 124 may output the color gamut deviation display image from the conversion circuit 116 as is. At this time, the picture image is masked by the picture image generation circuit 108, the waveform image is masked by the waveform image generation circuit 112, and the vector image is masked by the vector image generation circuit 110. When the multi-screen mode is selected, the synthesis circuit 124 synthesizes the picture image, vector image, waveform image, and color gamut deviation display image, and further synthesizes the above-mentioned additional images to be added to these four images into this synthesized image. The synthesis circuit 124 outputs the synthesis result.The display unit 102, which has an input that receives the output of the synthesis circuit 124, displays the received synthesized image to the user.

[0054] (Flowchart) Figures 2A and 2B are examples of flowcharts of the color gamut deviation display method of this embodiment, which is executed in the color gamut deviation display system 1 according to this embodiment. Figures 2A and 2B mainly describe the processing flow of the color gamut deviation display method according to this embodiment. Figure 3 is a diagram illustrating, as an example, the case in which a video signal in a container color gamut (wide color gamut) format is restricted to a target color gamut (narrow color gamut) format. In Figure 3, the container color gamut is indicated by a dashed triangle 31, and the target color gamut is indicated by a dashed triangle 32. In Figure 3, point P is the point that indicates the chromaticity of each pixel of the video signal before restriction. In Figure 3, if point P is outside the target color gamut, it is indicated by point Po 42a, and if it is within the target color gamut (including the boundary), it is indicated by point Pi 42b. Hereinafter, point Po 42a and point Pi 42b will be collectively referred to as point P 42. Furthermore, point A 45 is defined as the intersection of the line L1 connecting point P 42 and point W 43 (which is the white point) with the container color gamut 31, and point B 46 is defined as the intersection of line L1 with the target color gamut 32. The flowcharts of Figures 2A and 2B will be explained below with reference to Figure 3.

[0055] The color gamut deviation display image generation circuit 126 receives parallel data of the video signal, which is the signal under test, from the serial-to-parallel converter 106 (S102). The display control circuit 120 (or color gamut deviation display image generation circuit 126) calculates the xy chromaticity coordinates of point P 42 from the chromaticity value of point P 42, which indicates the chromaticity of each pixel of the video signal (S104). Specifically, it is calculated as follows.

[0056]

[0057] Here, A is a 3x3 matrix for converting from the RGB color system to the XYZ color system, and it is a matrix that is uniquely determined once the RGB color system and the white point are determined. In the case of a YCbCr signal, xy can be calculated from XYZ after RGB has been converted to YCbCr.

[0058] Furthermore, the display control circuit 120 (or the color gamut deviation display image generation circuit 126) calculates the xy chromaticity coordinates of point A 45 and point B 46 (S106). The calculation in this step can be performed geometrically.

[0059] Next, the color gamut deviation display image generation circuit 126 determines whether the xy chromaticity coordinates of point P 42 calculated in step S104 are located outside the target color gamut 32 or within the target color gamut 32 (including the boundary of the target color gamut 32) (S108).

[0060] In step S108, if the display control circuit 120 (or the color gamut deviation display image generation circuit 126) determines that the xy chromaticity coordinates of point P 42 are located outside the target color gamut 32, the display control circuit 120 (or the color gamut deviation display image generation circuit 126) calculates the GER value (hereinafter sometimes abbreviated as "G value") from the distance between point A 45 and point B 46 (hereinafter referred to as "AB" or "distance AB") and the distance between point P 42 and point B 46 (a positive value; hereinafter referred to as "PB" or "distance PB") using the formula G value = PB / AB (S110).

[0061] In step S108, if the display control circuit 120 (or the color gamut deviation display image generation circuit 126) determines that the xy chromaticity coordinates of point 42 are within the target color gamut 32, the display control circuit 120 (or the color gamut deviation display image generation circuit 126) calculates the GER value (hereinafter sometimes abbreviated as "G value") from the distance between point B 46 and point W 43 (hereinafter referred to as "BW" or "distance BW") and the distance between point B 46 and point P 42 (a positive value; hereinafter referred to as "BP" or "distance BP") using the formula G value = -BP / BW (S112).

[0062] The display control circuit 120 (or the color gamut deviation display image generation circuit 126) replaces the S value among the HSV values calculated for the P point 42 with the G value calculated in step S110 or step S112 (S114). As a result, three-dimensional information can be represented by "HGV" for all pixels (P point 42) of the test signal. The color gamut deviation display image generation circuit 126 draws the HG values of the pixels (P point 42) corresponding to each of the three specific ranges of V values on a circular two-dimensional plane in polar coordinates (S116). In the present embodiment, as an example, the range of 8-bit V values is divided into three: 0 to 84 (dark part: Low), 85 to 169 (midtone part: Medium), and 170 to 255 (bright part: High). Note that in the present embodiment, the range of V values is three, but this is merely an example and is not limited thereto. Also, for example, the color gamut deviation display system 1 may be configured such that the number of ranges of V values is determined by receiving a user input for specifying the number of ranges of V values.

[0063] Next, the color gamut deviation display image generation circuit 126 converts the polar coordinates of each pixel (P point 42) drawn on the two-dimensional plane for the three specific ranges of V values into circular ring-shaped two-dimensional coordinates (hereinafter referred to as "circular ring coordinates") in step S118. The circular ring shape is a shape surrounded by a small concentric circle and a large circle. Specifically, the circular ring coordinates are calculated as follows.

[0064] That is, if the coordinates before conversion are (r ａ , θ ａ ), (where r ａ is a value of 0 or more and 1 or less), the coordinates after conversion are (r ｂ , θ ｂ ), (where r ｂ is a value of 0 or more and 1 or less), the outer diameter of the polar coordinates before conversion is R ａｏ , the outer diameter of the circular ring coordinates after conversion is R ｂｏ , and the inner diameter is R ｂｉ , then r ｂ and θ ｂ can be calculated as follows. r ｂ = R ｂｉ + r ａ * (R ｂｏ - R ｂｉ ) θ ｂ= θ ａ

[0065] The color gamut deviation display image generation circuit 126 arranges the annular coordinates converted in step S118 on concentric circles (S120). The processing result of step S120 is finally output to the display unit 102, either alone or together with at least one of a picture image, a vector image, and a waveform image (step S122).

[0066] (Specific Examples) The color gamut deviation display method of this embodiment described above will be explained below using specific examples.

[0067] In this example, we will describe the case where the image (color image) shown in Figure 4 (Source: Institute of Image Information and Television Engineers) is processed by the color gamut deviation display method of this embodiment. In this example, the container color system of the image in Figure 4 is assumed to be 2020, and the target color system is P3. Figure 5 is a diagram showing the representation of the image in Figure 4 on an xy chromaticity diagram. In Figure 5, the chromaticity values ​​of the image are drawn with black dots. According to Figure 5, it can be seen that some pixels of the image deviate from the target color gamut 32.

[0068] Figure 6 is a diagram that maps the GER values ​​of each pixel in the image from Figure 4 onto the image. Figure 7 is a histogram of the GER values. In the graph in Figure 7, the horizontal axis represents the GER value, and the vertical axis represents the number of pixels corresponding to each GER value. A GER value of -1 indicates achromaticity, a GER value of 0 indicates that it is on the boundary of the target color gamut, and a GER value of 1 indicates that it is on the boundary of the container color gamut. That is, if 0 < GER value ≤ 1, it indicates that the pixel with that GER value is outside the target color gamut, and if -1 ≤ GER value ≤ 0, it indicates that the pixel with that GER value is within the target color gamut.

[0069] Figure 8 shows the HGV values ​​of each pixel, obtained by replacing the S value of each pixel with a G value (corresponding to S110 or S112 and S114 in Figure 2), and plotting the HGV values ​​of each pixel according to the HSV color system. Here, the plan view (chromaticity plan view) 50 in Figure 8 is composed of a circular shape as a whole. The H value is indicated by the central angle (0° to 360°). The position with a central angle of 0° indicates red, and moving clockwise, the hue (H) changes as follows: yellow (central angle = 60°), green (central angle = 120°), cyan (central angle = 180°), blue (central angle = 240°), magenta (central angle = 300°) (the same as the generally well-known color wheel). The GER value is indicated by the distance from the center along the direction from the center toward the circumference, and the GER value increases as you move away from the center. The center of the circle corresponds to a GER value of -1, and the circumference corresponds to a GER value of 1. Furthermore, the circumference of the circle with a radius of half that of the circle in Figure 8 (dashed line 60) corresponds to a GER value of 0. Note that the V value (brightness) is shown perpendicular to the plane of the paper and is therefore not shown in Figure 8. Also, although all of the video signal being tested is processed in Figure 8, only a portion of it may be processed. The specifications of circle 50 described above are the same for circles (chromaticity plane diagrams) 51, 52, and 53 in Figures 9 to 11, which will be explained below.

[0070] Next, in this example, the 8-bit brightness (V value) range is divided into three parts: 0 to 84 (dark areas: Low), 85 to 169 (midtone areas: Medium), and 170 to 255 (bright areas: High). Figure 9 shows the HG values ​​of pixels with a V value range of 0 to 84 (dark areas) plotted in polar coordinates on a circular two-dimensional plan 51. Figure 10 shows the HG values ​​of pixels with a V value range of 85 to 169 (midtone areas) plotted in polar coordinates on a circular two-dimensional plan 52. Figure 11 shows the HG values ​​of pixels with a V value range of 170 to 255 (bright areas) plotted in polar coordinates on a circular two-dimensional plan 53. Also, the circumferences 61, 62, and 63 in Figures 9 to 11 correspond to the circumference 60 in Figure 8 and correspond to a GER value of 0. Figures 9 to 11 correspond to the processing of S116 in Figure 2.

[0071] Next, the circles 51, 52, and 53 generated for each range of V values ​​in Figures 9 to 11 are transformed into annular shapes by expanding the central portion of the circle circumferentially to create a blank area near the center of the circle (corresponding to the process S118 in Figure 2). Then, as shown in Figure 12, the plan views 51a, 52a, and 53a, in which the circles 51, 52, and 53 have been transformed into annular shapes, are arranged so that the centers of each annular shape 51a, 52a, and 53a overlap (center 65) in order of increasing V value range (dark areas, midtone areas, bright areas) from the center towards the circumference, forming concentric circles, and as a whole, a two-dimensional plan view (composite plan view) 70 of an annular shape is constructed. In the two-dimensional plan view 70 of annular shape, the annular shapes 51a, 52a, and 53a may be arranged in order of increasing V value range (bright areas, midtone areas, dark areas) from the center towards the circumference. Additionally, users may be able to input information for these specifications.

[0072] Here, the GER values ​​for the rings 51a, 52a, and 53a in the two-dimensional plan view 70 are the same as for rings 51, 52, and 53. The circumference of the smaller circle (the circle closer to the center) of ring 51a corresponds to a GER value of -1, and the circumference of the larger circle (the circle further from the center) corresponds to a GER value of 1. Also, the circumference of the circle with a radius of half the sum of the radii of the larger and smaller circles that make up ring 51a (dashed line 61a) corresponds to a GER value of 0. Similarly, the circumference of the smaller circle (the circle closer to the center) of ring 52a corresponds to a GER value of -1, and the circumference of the larger circle (the circle further from the center) corresponds to a GER value of 1. Also, the circumference of the circle with a radius of half the sum of the radii of the larger and smaller circles that make up ring 52a (dashed line 62a) corresponds to a GER value of 0. The circumference of the smaller circle (the circle closer to the center) of the ring 53a corresponds to a GER value of -1, and the circumference of the larger circle (the circle further from the center) corresponds to a GER value of 1. Furthermore, the circumference of the circle (dashed line 63a) having a radius of half the sum of the radii of the larger and smaller circles that make up the ring 53a corresponds to a GER value of 0.

[0073] Although the two-dimensional plan view 70 illustrated in Figure 12 is an annular shape, the entire structure may be circular. That is, the annular ring 51a in Figure 12 may be circular in shape, as is the case with the annular rings 52a and 53a arranged around it.

[0074] As described above, by configuring multiple V-value ranges as a single two-dimensional plan 70, users can check the HG values ​​for multiple V-value ranges at a glance, improving visibility. Furthermore, while conventional CIE chromaticity diagrams are not shown in a uniform shape, making them difficult for users to understand, the two-dimensional plan 70 shown in Figure 12 shows the HG values ​​in a uniform annular or circular two-dimensional plan 70, which has the advantage of being easy for users to understand.

[0075] The circles 50 to 53 in Figures 8 to 11 may or may not be displayed by the display unit 102 of the color gamut deviation display system 1. In other words, the circles 50 to 53 in Figures 8 to 11 can also be seen as diagrams showing the processes performed internally in order for the two-dimensional plan view 70 shown in Figure 12 to be displayed by the display unit 102.

[0076] Furthermore, in Figure 12, the rings 51a, 52a, and 53a are arranged in descending order of V-value range from the center in the circumferential direction (dark areas, midtone areas, bright areas), but are not limited to this. The rings 51a, 52a, and 53a may be arranged in descending order of V-value range from the center in the circumferential direction (bright areas, midtone areas, dark areas), or the order of arrangement may be determined according to user input. For example, a GUI (Graphical User Interface) may be displayed and output that allows the user to easily specify the order of arrangement of multiple rings by clicking or dragging each ring.

[0077] Furthermore, while Figure 12 shows three ranges for the V value, it is not limited to these. There may be more or fewer ranges. The number may also be determined based on user input.

[0078] Furthermore, in Figure 12, all of the rings 51a, 52a, and 53a generated based on the circle 51 etc. calculated in Figures 9 to 11 are placed on the ring 70, but only some of them may be placed. Also, the rings 51a etc. to be placed on the ring 70 may be determined according to user input.

[0079] Furthermore, while the above explanation assumes that the CIE color system is used in the original video signal before conversion to a narrow color gamut, it is not limited to this. For example, the color gamut deviation display method according to this embodiment can also be applied to UV chromaticity diagrams.

[0080] Although one embodiment of the present invention has been described so far, it goes without saying that the present invention is not limited to the above-described embodiments and may be implemented in various different forms within the scope of its technical concept.

[0081] Furthermore, the scope of the present invention is not limited to the illustrative and described exemplary embodiments, but also includes all embodiments that produce effects equivalent to those aimed at by the present invention. Moreover, the scope of the present invention is not limited to the combination of features defined by each claim, but can be defined by any desired combination of specific features from all disclosed features.

[0082] 1...Color gamut deviation display system 100...Monitor 102...Display unit 104...Key / encoder circuit 106...Serial-to-parallel converter 108...Picture image generation circuit 110...Vector image generation circuit 112...Waveform image generation circuit 114...Conversion circuit 116...Conversion circuit 118...Selected pixel extraction circuit 120...Display control circuit 122...Drawing memory 124...Composition circuit 126...Color gamut deviation display image generation circuit 31...Container color gamut 32...Target color gamut 42a, 42b...P point 43...White point (W point) 45...A point (intersection of line L1 and container color gamut 31) 46...B point (intersection of line L1 and target color gamut 32) L1...Line connecting P point 42 and W point 43 50, 51, 52, 53...Circle 51a, 52a, 53a...Ring 70...Two-dimensional plan view including rings 51a, 52a, and 53a

Claims

1. A method for displaying color gamut deviations performed by a computer system, comprising: calculating xy chromaticity coordinates from the chromaticity values ​​of pixels in a video signal that is a signal under test; calculating a GER value indicating the degree of deviation of the pixel from the target color gamut using the xy chromaticity coordinates which are the coordinates on the chromaticity diagram of the pixel, the xy chromaticity coordinates of the white point on the chromaticity diagram, the xy chromaticity coordinates which are the xy chromaticity coordinates on the chromaticity diagram of the container color gamut which is the color gamut of the video signal, and the xy chromaticity coordinates which are the xy chromaticity coordinates on the chromaticity diagram of the target color gamut which is a narrower color gamut than the container color gamut; and arranging a plurality of chromaticity plan diagrams in which the H values ​​and GER values ​​of at least some pixels of the video signal are arranged for each of a plurality of V value ranges using the GER value for at least some pixels of the video signal, an H value indicating hue, and a V value indicating brightness, into a single composite plan diagram.

2. The method for displaying color gamut deviations according to claim 1, wherein the chromaticity diagram is a CIE chromaticity diagram.

3. The method for displaying color gamut deviations according to claim 1 or 2, comprising displaying and outputting the synthesized composite plan view.

4. The method for displaying color gamut deviation according to any one of claims 1 to 3, wherein the GER value of the pixel is calculated using a first intersection point on a chromaticity diagram, which is the intersection point of a straight line connecting the pixel and the white point with the boundary line of the region indicating the container color gamut, and a second intersection point, which is the intersection point of the straight line with the boundary line of the region indicating the target color gamut.

5. The method for displaying color gamut deviations according to any one of claims 1 to 4, wherein the chromaticity plan and / or the composite plan are circular or annular in shape.

6. The method for displaying color gamut deviation according to any one of claims 1 to 5, wherein the plurality of chromaticity plan diagrams are arranged in order of magnitude of the V value range from the center to the periphery of the composite plan diagram.

7. The method for displaying color gamut deviations according to any one of claims 1 to 5, wherein the plurality of chromaticity plan diagrams are arranged in the composite plan diagram according to user specifications.

8. A method for displaying color gamut deviations according to any one of claims 1 to 7, wherein only a portion of the plurality of chromaticity plan diagrams is placed in the composite plan diagram.

9. The method for displaying color gamut deviations according to any one of claims 1 to 8, wherein the number of ranges of the plurality of V values ​​is determined according to user input.

10. A computer system that performs the color gamut deviation display method according to any one of claims 1 to 9.

11. A program for causing a computer system to execute the color gamut deviation display method according to any one of claims 1 to 9.

12. A computer-readable recording medium for storing a program for causing a computer system to execute the color gamut deviation display method according to any one of claims 1 to 9.

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