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

Abstract

A method for displaying color gamut deviation that is user-friendly is provided. To this end, there is provided a gamut deviation display method executed by a computer system, which includes calculating x and y chromaticity coordinates from chromaticity values ​​of pixels of a video signal, which is a signal to be tested; calculating a GER value indicating the degree of deviation of the pixel from the target gamut using the x and y chromaticity coordinates that are the coordinates of the pixel on a chromaticity diagram, the x and y chromaticity coordinates of a white point on the chromaticity diagram, the x and y chromaticity coordinates on a chromaticity diagram of a container gamut that is the gamut of the video signal, and the x and y chromaticity coordinates on a chromaticity diagram of a target gamut that is narrower than the container gamut; and arranging, on a single composite chromaticity diagram, a plurality of chromaticity diagrams in which the H values ​​and GER values ​​of at least some of the pixels of the video signal are arranged for each of a plurality of ranges of V values, using the GER value for at least some of the pixels of the video signal, an H value indicating hue, and a V value indicating lightness.

Description

[Technical Field]

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

[0002] Since the establishment of ITU-R Recommendation 2020, wide-color gamut video formats have become commonplace. However, the performance of end-user displays remains limited to narrow color gamuts, such as DCI-P3, established by the Digital Cinema Initiatives, a U.S. film production industry association. These displays typically include a color gamut restriction function that constrains the color gamut from a wide color gamut, such as ITU-R Recommendation 2020, to a narrow color gamut, such as DCI-P3. However, video content providers may be dissatisfied with the color gamut restriction function and restrict the color gamut of their content before distributing it. For example, a wide-color gamut color system, such as ITU-R Recommendation 2020, may be constrained to a narrow-gamut color system, such as DCI-P3.

[0003] In response to such demands, tools such as the CIE (International Commission on Illumination) chromaticity diagram have conventionally been available as a method for displaying color gamuts (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-129098 [Non-patent literature]

[0005] [Non-Patent Document 1] 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 [Non-patent document 2] NHK Public Relations Department, "Gamut Rings, a new method for color gamut expression, becomes international standard ~ Visualizing the color reproduction range of displays more accurately and clearly ~", Press Release, Japan, NHK Science and Technology Research Laboratories, February 15, 2022 Summary of the Invention [Problem to be solved by the invention]

[0006] However, for reasons such as the CIE chromaticity diagram not being perceptually uniform, conventional methods of displaying color gamuts have not fully satisfied user needs, and therefore a more user-friendly tool has been desired.

[0007] The present invention has been made in view of such problems. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, one aspect of the present invention is a gamut deviation display method executed by a computer system, the method comprising: calculating x and y chromaticity coordinates from chromaticity values ​​of pixels of a video signal, which is a signal to be tested; calculating a GER value indicating the degree of deviation of the pixel from the target gamut using the x and y chromaticity coordinates that are the coordinates of the pixel on a chromaticity diagram, the x and y chromaticity coordinates of a white point on the chromaticity diagram, the x and y chromaticity coordinates on a chromaticity diagram of a container gamut that is the gamut of the video signal, and the x and y chromaticity coordinates on a chromaticity diagram of a target gamut that is narrower than the container gamut; and arranging, on a single composite chromaticity diagram, a plurality of chromaticity diagrams in which the H values ​​and the GER values ​​of at least some of the pixels of the video signal are arranged for each of a plurality of ranges of V values, using the GER value, an H value indicating hue, and a V value indicating lightness for each of at least some of the pixels of the video signal.

[0009] Another aspect of the present invention is the above-mentioned color gamut deviation display method, wherein the chromaticity diagram is a CIE chromaticity diagram.

[0010] Another aspect of the present invention is the above-described color gamut deviation display method, which includes displaying and outputting the synthesized planar view.

[0011] Another aspect of the present invention is the above-mentioned gamut deviation display method, wherein the GER value of the pixel is calculated using a first intersection point on a chromaticity diagram, which is an intersection point between a straight line connecting the pixel and the white point and a boundary line of an area representing the container gamut, and a second intersection point, which is an intersection point between the straight line and a boundary line of an area representing the target gamut.

[0012] Another aspect of the present invention is the above-mentioned color gamut deviation display method, wherein the chromaticity diagram and / or the composite diagram has a circular or toric shape.

[0013] Another aspect of the present invention is the above-mentioned color gamut deviation display method, wherein the plurality of chromaticity plane diagrams are arranged in order of magnitude of the range of V values ​​from the center of the composite plane diagram toward the periphery.

[0014] Another aspect of the present invention is the above-mentioned color gamut deviation display method, wherein the plurality of chromaticity plane diagrams are arranged in the composite plane diagram according to a user's specification.

[0015] Another aspect of the present invention is the above-mentioned color gamut deviation display method, wherein only a portion of the plurality of chromaticity diagrams is arranged in the composite diagram.

[0016] Another aspect of the present invention is the above-described color gamut deviation display method, wherein the number of the plurality of V value ranges is determined in response to a user input.

[0017] Another aspect of the present invention is a computer system that executes the above-described color gamut deviation display method.

[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 storing a program for causing a computer system to execute the above-described color gamut deviation display method. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram showing an example of the configuration of a color gamut deviation display system according to an embodiment of the present invention. [Figure 2A] FIG. 1 is a flowchart showing an example of processing in a color gamut deviation display method according to an embodiment of the present invention. [Figure 2B] FIG. 1 is a flowchart showing an example of processing in a color gamut deviation display method according to an embodiment of the present invention. [Figure 3] FIG. 10 is a diagram illustrating a case where a video signal of a container color gamut is limited to a target color gamut. [Figure 4] FIG. 10 is a diagram showing an example of a sample color image to illustrate a specific example. [Figure 5] FIG. 10 is a diagram showing a representation of a sample image on an xy chromaticity diagram. [Figure 6]This is a diagram in which the GER value of each pixel in a sample video is mapped onto the video. [Figure 7] FIG. 1 is a histogram showing GER values. [Figure 8] This is a diagram in which the HGV values ​​of each pixel in the sample video are plotted in accordance with the HSV color system. [Figure 9] This is a diagram in which the HG values ​​of pixels with a V value range of 0 to 84 (dark area) are plotted on a circular two-dimensional plane using polar coordinates. [Figure 10] This is a diagram in which the HG values ​​of pixels with a V value range of 85 to 169 are plotted on a circular two-dimensional plane using polar coordinates. [Figure 11] This is a diagram in which the HG values ​​of pixels with a V value range of 170 to 255 (bright area) are plotted on a circular two-dimensional plane using polar coordinates. [Figure 12] This is a diagram in which HG values ​​for multiple V value ranges are plotted in a single two-dimensional plane. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail 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 test signal, such as a video signal. The color gamut deviation display system according to this embodiment is configured, for example, by a waveform monitor or a rasterizer. However, the present invention is not limited to these configurations and can be realized by various configurations having hardware and software that can realize 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 fixed 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 consisting of multiple computer devices, a client / server computer system, a cloud system, etc.

[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 test signals in a more intuitive color system (2) A more quantitative expression of the degree of deviation (3) Two-dimensional representation of three-dimensional information

[0024] Below, (1) to (3) will be explained.

[0025] (1) Handling signals in a more intuitive color system The CIE color system, which has been commonly used, is not perceptually uniform. Furthermore, the HSV color system is a color system that is familiar to engineers and colorists. For these reasons, the color gamut deviation display system according to this embodiment employs a display method based on the HSV color system. HSV stands for "hue," "saturation," and "value," respectively.

[0026] (2) A more quantitative expression of the degree of deviation In the gamut deviation display system according to this embodiment, a novel index, Gamut Excursion Ratio (GER), devised by the inventors, is used to quantitatively handle the test signal. Displaying the test signal on the CIE chromaticity diagram only allows us to determine whether the chromaticity of the test signal is inside or outside a triangle representing the RGB color space of the target gamut (a narrow gamut targeted for conversion for displays, etc.) mapped onto the CIE xy plane, and to grasp the distance from the triangle to a point on the xy plane representing the chromaticity of the test signal. Even if the distance is the same, the corresponding perceptual amount varies depending on the chromaticity of the test signal. This distance cannot be used as a common index of gamut deviation for all colors (hues). This is because the relationship between the target gamut and the gamut of the test signal's original color system (container color system) differs for each hue.

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

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

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

[0030] 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 expressed as "HGV."

[0031] In this specification, the term "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 a test signal such as a video signal. Furthermore, the term "target" in terms such as "target color system" and "target color gamut" refers to the color system and color gamut (wide color gamut) that should be targeted to maintain image quality within the limitations of the display performance of a display or the like.

[0032] (3) Two-dimensional representation of three-dimensional information Because color is three-dimensional information, some kind of ingenuity is required to obtain the overall information of the signal under test, such as checking multiple hue-saturation charts limited in the brightness direction.

[0033] One method that makes it easy to visually recognize such three-dimensional color information is described in Non-Patent Document 2. The method in Non-Patent Document 2 slices the CIE1976 L*a*b* color space into ten slices in the brightness direction, stretches them onto a plane starting from the lower brightness side, and arranges the color gamut with higher brightness in a ring shape around it, thereby expressing the three-dimensional information in two dimensions.

[0034] The color gamut deviation display system according to this embodiment also expresses three-dimensional information in two dimensions. Instead of the L*a*b* color system, the color gamut deviation display system according to this embodiment uses the novel HGV color system devised by the inventors, which is an improved version of the HSV color system, which is more familiar to engineers and colorists as described above. Furthermore, in this embodiment, the color gamut solid is sliced ​​into three sections: a dark section (low), a midtone section (medium), and a light section (high). Considering a scenario in which a test signal is converted to a narrow color gamut, a number of slices of approximately three is considered to be a more appropriate number. However, this is not a limitation, and other numbers of slices may be used. For example, the color gamut deviation display system may determine the number of slices by receiving a user input specifying the number of slices.

[0035] Furthermore, in Non-Patent Document 2, the color space is sliced ​​into ten slices in the brightness direction, and the slices are stretched onto a plane starting from the low-lightness one, with the higher-lightness color gamuts arranged in a ring shape around them. In contrast, the color gamut deviation display system according to this embodiment can be configured to determine whether the low-lightness color gamut or the high-lightness color gamut is arranged inward in order by receiving input from a user specifying this. Furthermore, only one or more arbitrary color gamuts designated by user input from among the sliced ​​color gamuts may be arranged two-dimensionally.

[0036] (Configuration of a color gamut deviation display system) FIG. 1 is a diagram showing an example of the configuration of a color gamut deviation display system according to this embodiment. As described above, the color gamut deviation display system according to this embodiment will be described as a waveform monitor, but is not limited to this, and can be realized by various configurations having hardware and software that can realize each function of the color gamut deviation display system. As shown in FIG. 1, the color gamut deviation display system 1 according to this embodiment includes a display 102, a key / encoder circuit 104, a serial-to-parallel converter (or IP-to-parallel converter; the same applies below) 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 selected pixel extraction circuit 118, a display control circuit 120, a drawing memory 122, and a composition circuit 124. The serial-to-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 the video signal. This video signal is a signal to be detected and converted from a wide color gamut to a narrow color gamut in the color gamut deviation display image generation circuit 126. The selected pixel extraction circuit 118, the display control circuit 120, and the drawing memory 122 function to control the display of the image of the video signal.

[0037] In this embodiment, the circuits 108, 110, 112, 114, 116, 118, 124, and 126 may be configured using FPGAs. However, this is merely an example and is not limiting. The display control circuit 120 may be realized using a computer and a program. Note that the various circuits of the color gamut deviation display system 1 of this embodiment may all be realized using hardware, or may be realized using a combination of a computer and software.

[0038] The display 102 may include an input for receiving a composite image signal from the composite circuit 124 and a screen for displaying an image to the user at, for example, XGA resolution in response to the composite image signal (note that XGA is merely an example, and resolutions other than XGA may be used; the same applies below). The key / encoder circuit 104 may include a key matrix including multiple keys for operating the monitor 100 and an encoder knob. The key matrix may include, for example, multiple function keys and multiple other keys (tentatively designated PIC, WFM, VECT, GMT, and MULTI in this description). The keys for specifying the display mode of the color gamut deviation display system 1 of this embodiment include the PIC, WFM, VECT, GMT, and MULTI keys. The PIC key specifies picture display mode, and when this mode is selected, a raster image composed of a video signal is displayed as a "picture image." The WFM key specifies waveform display mode, and when this mode is selected, an image showing the time fluctuations of the components contained in the video signal is displayed as a "waveform image." The VECT key specifies the vector display mode. When this mode is selected, an image similar to that displayed on a conventional vectorscope is displayed as a "vector image." The GMT key specifies the color gamut deviation display mode. 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 indicates whether the original video signal before narrow gamut conversion deviates from the narrow color gamut target color gamut. The MULTI key specifies the multi-screen mode. When this mode is selected, the picture image, waveform image, vector image, and color gamut deviation display image are simultaneously displayed on a single screen. Note that when the multi-screen mode is not selected, the device operates in single-screen mode. Note that 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 simultaneously displayed.

[0039] When the key / encoder circuit 104 receives the above-mentioned user operation input, it generates a key matrix output indicating which key was pressed, and when the encoder knob is operated, it generates an encoder output indicating that operation. The encoder can include, for example, a rotary encoder, in which case the encoder detects pulses of the rotary encoder output and generates an encoder output obtained by updating data indicating the operation direction and movement distance.

[0040] The serial-parallel converter 106 has an input for receiving a video signal to be detected, for example, an HD SDI signal (this is just one example; various video standards related to SDI and IP, such as the SMPTE 274M standard, may be used), and converts the received serial HD SDI signal into a parallel video signal at the HD SDI rate and outputs it. Note that while this embodiment will be described using an HD SDI signal (SMPTE 274M standard) as an example of the video signal, the present invention is also applicable to video signals of other standards (for example, various video standards such as SD-SDI, 3G-SDI, HDMI, Display Port, etc.).

[0041] Next, the picture image generation circuit 108, the vector image generation circuit 110, the waveform image generation circuit 112, and the color gamut deviation display image generation circuit 126 each have an input that receives the output from the serial-to-parallel converter 106 and an input that receives a display position / display size setting output from the display control circuit 120, which will be described in detail later. Furthermore, the waveform image generation circuit 112 has an input that receives a GBR conversion command from the display control circuit 120. The image generation circuits 108, 110, 112, and 126 each generate images of different forms that represent an image associated with the received video signal and that comply with 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 by removing blanking periods from the input parallel data, converts the generated picture image to XGA resolution to match the format of the display 102, reduces the converted generated picture image according to the set display size, shifts the reduced image to the set display position, and outputs the resulting XGA-sized picture image. Note that in display modes where a picture image is not required, the image generation circuit 108 masks the picture image output, i.e., does not generate a picture image as an output.

[0043] The vector image generation circuit 110 removes blanking periods 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 format of the display device, reduces the converted vector image to a set display size, shifts the reduced image so that it is displayed at a set display position, and outputs the resulting XGA-sized vector image. Note that in display modes where vector images are 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-parallel converter 106 into three waveforms: a Y (luminance) signal and color difference signals Cb and Cr (in the case of GBR display, a G (green) signal, a B (blue) signal, and an R (red) signal), rasterizes these three waveforms into a single image, converts the resolution of this rasterized image to XGA to match the format of the display, reduces the converted image to a set display size, shifts this reduced image to be displayed at a set display position, and outputs the resulting XGA-sized waveform image. 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 the lightness value V, hue value H, saturation value S, and GER value from the display control circuit 120 (or the lightness value V, hue value H, saturation value S, and GER values ​​may be calculated by the color gamut deviation display image generation circuit 126), and 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 (e.g., the image of FIG. 12) generated by the color gamut deviation display method according to this embodiment to XGA to match the format of the display device 102, reduces the converted color gamut deviation display image to a set display size, shifts the reduced image so that it is displayed at a set display position, and outputs the resulting XGA-sized color gamut deviation display image. Note that in display modes in which a color gamut deviation display image is not required, the color gamut deviation display image generation circuit 126 masks the color gamut deviation display image output.

[0046] Next, conversion circuit 114 has an input connected to the output of 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 the converted XGA picture image at its output. Similarly, conversion circuit 116 has an input connected to the output of vector image generation circuit 110, an input connected to the output of waveform image generation circuit 112, and an input connected to the output of gamut deviation display image generation circuit 126, and combines the vector image, waveform image, and gamut deviation display image, converts the frame rate of the combined image to an XGA rate to match the format of the display, and generates the converted XGA combined image at its 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. In addition, the display control circuit 120 calculates and outputs the sample number and line number of the input video from the output from the operated encoder based on the format of the input video signal.

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

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

[0050] The display control circuit 120 then performs a predetermined calculation process on the extracted pixel data. Specifically, it calculates the G, B, or R values ​​to be added to the picture image from the extracted pixel data for inclusion in each image. The Y (brightness) value can also be selected as the value to be added to the picture image. The display control circuit 120 also calculates the display position of the scale to be added to the waveform image based on the extracted pixel data and the display mode. The display control circuit 120 also 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 based on 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 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 gamut deviation display image generation circuit 126. In this example, the lightness value V, the hue value H, the saturation value S, and the 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 processing for drawing in the drawing memory 122. That is, 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 ​​and scales of the Cb value (%), Cr value (%), saturation d (%), and hue angle (deg) to be added to the vector image 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 lightness 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, images for the four images, the picture image, the vector image, the waveform image, and the color gamut deviation display image, are synthesized in the drawing memory 122.

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

[0053] The composition circuit 124 has inputs respectively connected to the output of the conversion circuit 114, the output of the conversion circuit 116, and the output of the drawing memory 122. When the single-screen mode is selected, the composition circuit 124 combines the picture image from the conversion circuit 114 with the drawing image from the drawing memory 122, i.e., the image of the G, B, or R values ​​to be added to the picture image, when the picture display mode is selected. 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 the waveform display mode is selected, the composition circuit 124 combines the waveform image from the conversion circuit 116 with the drawing image from the drawing memory 122, i.e., the image of the scale 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 composition circuit 124 combines the vector image from the conversion circuit 116 with the drawing image from the drawing memory 122, i.e., the image 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 composition 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 composition circuit 124 combines the picture image, vector image, waveform image, and color gamut deviation display image, and further combines this combined image with the above-mentioned additional image to be added to these four images. The composition circuit 124 generates the combined result as an output.A display 102 having an input that receives the output of the compositing circuit 124 displays the received composite image to a user.

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

[0055] The color gamut deviation display image generation circuit 126 receives input of parallel data of the video signal, which is the signal to be detected, from the serial-parallel converter 106 (S102). The display control circuit 120 (or the color gamut deviation display image generation circuit 126) calculates the x and y chromaticity coordinates of the P point 42 from the chromaticity value of the P point 42, which indicates the chromaticity of each pixel of the video signal (S104). Specifically, the calculation is performed as follows:

[0056]

number

[0057] Here, A is a 3x3 matrix for converting from the RGB color system to the XYZ color system, and is uniquely determined once the RGB color system and white point are determined. In the case of a YCbCr signal, xy can be calculated from XYZ after converting RGB 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] If in step S108 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] If in step S108 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 located 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 generating circuit 126) replaces the S value of the HSV values ​​calculated for the P point 42 with the G value calculated in step S110 or step S112 (S114). This allows three-dimensional information to be expressed in "HGV" for all pixels (P points 42) of the signal to be detected. The color gamut deviation display image generating circuit 126 plots the HG values ​​of the pixels (P points 42) corresponding to each of three specific ranges of V values ​​on a circular two-dimensional plane using polar coordinates (S116). In this embodiment, as an example, the range of 8-bit V values ​​is divided into three: 0 to 84 (dark area: low), 85 to 169 (midtone area: medium), and 170 to 255 (light area: high). Although three ranges of V values ​​are used in this embodiment, this is merely an example and is not limiting. Furthermore, for example, the color gamut deviation display system 1 may receive a user input for specifying the number of ranges of V values, thereby determining the number of ranges of V values.

[0063] Next, in step S116, the color gamut deviation display image generation circuit 126 converts the polar coordinates of each pixel (P point 42) drawn on a two-dimensional plane for the three specific ranges of V values ​​into two-dimensional coordinates of a ring shape (hereinafter referred to as "ring coordinates") (S118). A ring shape is a shape surrounded by concentric small and large circles. Specifically, the ring coordinates are calculated as follows:

[0064] That is, the coordinates before transformation are (r a ,θ a )(r a is a value between 0 and 1), and the transformed coordinates are (r b ,θ b )(r b is a value between 0 and 1), and the outer radius of the polar coordinate before conversion is R ao , the outer radius of the transformed circular coordinate is R bo , 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 gamut deviation display image generation circuit 126 arranges the converted circular coordinates on concentric circles (S120) in step S118. The processing result of step S120 is finally displayed and output on the display 102 alone or together with at least one of the picture image, vector image, and waveform image (step S_{122}).

[0066] (Specific example) A specific example of the gamut deviation display method of the present embodiment described above will be described below using a specific example.

[0067] In this example, a case where a video (color video) shown in FIG. 4 (source: The Society of Motion Picture and Television Engineers) is processed by the gamut deviation display method of the present embodiment will be described. In this example, it is assumed that the container color system of the video in FIG. 4 is 2020 and the target color system is P3. FIG. 5 is a diagram showing the representation of the image in FIG. 4 on the xy chromaticity diagram. In FIG. 5, the chromaticity values of the video are drawn as black dots. According to FIG. 5, it can be seen that some pixels of the video deviate from the target gamut 32.

[0068] FIG. 6 is a diagram in which the GER values of each pixel of the video in FIG. 4 are mapped on the video. FIG. 7 is a diagram showing the GER values in a histogram. The horizontal axis of the graph in FIG. 7 indicates the GER value, and the vertical axis indicates the number of pixels corresponding to each GER value. GER value = -1 indicates achromatic color, GER value = 0 indicates on the boundary of the target gamut, and GER value = 1 indicates on the boundary of the container gamut. That is, when 0 < GER value ≤ 1, it indicates that the pixels having the GER value deviate from the target gamut, and when -1 ≤ GER value ≤ 0, it indicates that the pixels having the GER value are within the target gamut.

[0069] FIG. 8 shows the HGV values ​​of each pixel, plotted according to the HSV color system, after the S value of each pixel is replaced with a G value (corresponding to S110, S112, and S114 in FIG. 2). The plan view (chromaticity plan view) 50 in FIG. 8 is generally circular. The H value is indicated by the central angle (0° to 360°). Red is indicated at a central angle of 0°, and the hue (H) changes clockwise from yellow (central angle = 60°), green (central angle = 120°), cyan (central angle = 180°), blue (central angle = 240°), and magenta (central angle = 300°) (similar to the commonly known color wheel). The GER value is indicated by the distance from the center along the circumference, increasing with distance 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 a circle (dashed line 60) having a radius half that of the circle in Fig. 8 corresponds to a GER value of 0. Note that the V value (brightness) is shown in the direction perpendicular to the paper surface and is therefore not shown in Fig. 8. Also, although Fig. 8 shows the entire video signal, which is the signal under test, as the processing target, it is also possible to process only a portion of it. The above specifications of circle 50 also apply to circles (chromaticity plane diagrams) 51, 52, and 53 in Figs. 9 to 11, which will be described below.

[0070] Next, in this example, the 8-bit brightness (V value) range is divided into three: 0 to 84 (dark area: low), 85 to 169 (midtone area: medium), and 170 to 255 (bright area: high). FIG. 9 is a diagram in which the HG values ​​of pixels whose V value range is 0 to 84 (dark area) are plotted in polar coordinates on a circular two-dimensional plane diagram 51. FIG. 10 is a diagram in which the HG values ​​of pixels whose V value range is 85 to 169 (midtone area) are plotted in polar coordinates on a circular two-dimensional plane diagram 52. FIG. 11 is a diagram in which the HG values ​​of pixels whose V value range is 170 to 255 (bright area) are plotted in polar coordinates on a circular two-dimensional plane diagram 53. Furthermore, circumferences 61, 62, and 63 in FIGS. 9 to 11 correspond to circumference 60 in FIG. 8 and correspond to a GER value of 0. FIGS. 9 to 11 correspond to the processing of S116 in FIG. 2.

[0071] Next, the circles 51, 52, and 53 in FIGS. 9 to 11 generated for each range of V values ​​are transformed into annular shapes by expanding the center portions of the circles in the circumferential direction and providing a blank area near the center of the circle (corresponding to the process of S118 in FIG. 2). Then, as shown in FIG. 12, plan views 51a, 52a, and 53a, resulting from the transformation of the circles 51, 52, and 53 into annular shapes, are arranged concentrically from the center toward the circumferential direction in order of decreasing V value range (in order of dark areas, midtone areas, and light areas), with the centers of the circles 51a, 52a, and 53a overlapping (center 65), to form a single annular two-dimensional plan view (composite plan view) 70. Note that in the annular two-dimensional plan view 70, the circles 51a, 52a, and 53a may be arranged from the center toward the circumferential direction in order of increasing V value range (in order of light areas, midtone areas, and dark areas). Furthermore, the user may be able to input these specifications.

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

[0073] Although the two-dimensional plan view 70 illustrated in Fig. 12 has a circular shape, it may be configured to have a circular shape as a whole. That is, the circular ring 51a in Fig. 12 may be circular like the circle 51 in Fig. 9, and the circular rings 52a and 53a may be arranged around it.

[0074] As described above, by configuring a plurality of V value ranges as one two-dimensional diagram 70, the user can check the HG values ​​for a plurality of V value ranges at a glance, improving visibility. Furthermore, conventional CIE chromaticity diagrams have the problem of being difficult for users to understand because they are not displayed in uniform shapes, but the two-dimensional diagram 70 shown in Fig. 12 displays the HG values ​​in a two-dimensional diagram 70 with a uniform ring or circular shape overall, which has the advantage of being easy for users to understand.

[0075] 8 to 11 may or may not be displayed by the display 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 understood as diagrams showing the processing that is executed internally in order for the two-dimensional plan view 70 shown in Figure 12 to be displayed by the display 102.

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

[0077] 12, the range of V values ​​is three, but this is not limiting. There may be a greater or lesser number. The number may also be determined according to user input.

[0078] 12, all of the circular rings 51a, 52a, and 53a generated based on the circle 51 etc. calculated in FIGS. 9 to 11 are arranged on the circular ring 70, but only some of them may be arranged. Also, the circular rings 51a etc. to be arranged on the circular ring 70 may be determined in accordance with a user input.

[0079] In addition, although the above description has been made on the assumption that the CIE color system is used in the original video signal before it is converted into a narrow color gamut, this is not limiting. For example, the color gamut deviation display method according to this embodiment can also be applied to the case of a UV chromaticity diagram.

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

[0081] Furthermore, the scope of the present invention is not limited to the exemplary embodiments shown and described, but includes all embodiments that achieve equivalent effects to those intended by the present invention. Furthermore, the scope of the present invention is not limited to the combination of inventive features defined by each claim, but can be defined by any desired combination of specific features from among all the respective disclosed features. [Explanation of symbols]

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

Claims

1. 1. A method for displaying color gamut deviations executed by a computer system, comprising: Calculating x and y chromaticity coordinates from the chromaticity values ​​of pixels of the video signal being the signal to be tested; calculating a GER value indicating a degree of deviation of the pixel from the target color gamut using x and y chromaticity coordinates, which are coordinates on a chromaticity diagram of the pixel, the x and y chromaticity coordinates of a white point on the chromaticity diagram, the x and y chromaticity coordinates on a chromaticity diagram of a container gamut, which is the color gamut of the video signal, and the x and y chromaticity coordinates on a chromaticity diagram of a target color gamut, which is a color gamut narrower than the container gamut; Using the GER value for at least some pixels of the video signal, an H value indicating a hue, and a V value indicating a brightness, a plurality of chromaticity plane diagrams in which the H values ​​and the GER values ​​of at least some pixels of the video signal are arranged for each of a plurality of ranges of V values ​​are arranged on one composite plane diagram. A color gamut deviation display method including:

2. The method of claim 1 , wherein the chromaticity diagram is a CIE chromaticity diagram.

3. A color gamut deviation display method as described in claim 1, which includes displaying and outputting the composite plan view.

4. 2. The color gamut deviation display method according to claim 1, wherein the GER value of the pixel is calculated using a first intersection point on a chromaticity diagram, which is an intersection point between a straight line connecting the pixel and the white point and a boundary line of an area representing the container color gamut, and a second intersection point on a chromaticity diagram, which is an intersection point between the straight line and a boundary line of an area representing the target color gamut.

5. The method for displaying color gamut deviation according to claim 1 , wherein the chromaticity diagram and / or the composite diagram are circular or toric.

6. The color gamut deviation display method according to claim 1 , wherein the plurality of chromaticity diagrams are arranged in order of magnitude of the range of V values ​​from the center of the composite diagram to the periphery.

7. The method for displaying a color gamut deviation according to claim 1 , wherein the plurality of chromaticity diagrams are arranged in the composite diagram according to a user's specification.

8. The method of claim 1 , wherein only a portion of the plurality of chromaticity diagrams is arranged in the composite diagram.

9. The color gamut deviation display method according to claim 1 , wherein the number of the plurality of V value ranges is determined according to a user input.

10. A computer system that executes the method for displaying color gamut deviations 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 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.

Images