A method for transmitting five primary color image signals based on standard three-channel

Abstract

The present invention relates to a method for transmitting five-primary-color image signals based on a standard three-channel approach, comprising the following steps: calculating an encoding matrix for an additional CGB color space to encode the CGB signal into a pseudo-YCbCr signal, and calculating a CGB decoding matrix; calculating an encoding matrix for an additional RGY color space to encode the RGY signal into a pseudo-YCbCr signal; and calculating an RGY decoding matrix. At the transmitting end, the five-primary-color signal is divided according to the color space, with each pixel consisting of three color components (RGB, CGB, or RGY). Standard RGB encoding, CGB encoding, or RGY encoding are used, respectively, to encode the signal into a YCbCr signal for transmission. If the C component value is greater than the R component, the CGB encoding format is used; if the Y component value is greater than the B component, the RGY encoding format is used; otherwise, the RGB encoding format is used. Upon receiving the YCbCr data, the receiving end uses a blind recognition scheme to determine the composition of the three primary colors.

Description

Technical Field

[0001] The present invention relates to the technical field of video image transmission, and in particular to a method for transmitting five-primary-color image signals based on a standard three-channel. Background Art

[0002] The currently widely adopted BT.709 / sRGB three-primary color image format only covers 33.25% of the human eye's visible color gamut, far from meeting the demand for faithful reproduction of natural colors. As people's lifestyles, work, entertainment, and consumption patterns change, the application of wide-color-gamut images is expanding, and expectations for them are also rising. Wide-color-gamut image sources and display devices are not only in demand in the video display field, but also in emerging industries such as e-commerce, where high-color-fidelity images are even more pressing.

[0003] Multi-primary color LCDs have already entered the market. For example, the LCD-80XU35A from Japan's Sharp Quattron series uses four primary colors. Japan Semiconductor Energy Laboratory and Taiwan's AU Optronics Corporation have also developed four-primary color OLEDs. In the field of microLED display technology, which is considered the most promising, Japanese researchers have also developed a single-pixel display with a size of only 5×5μm. 2 Four primary color display.

[0004] Multi-primary image sensors have long entered the market and have achieved breakthroughs in recent years. Sony introduced a four-primary image sensor as early as 2003. Its ICX456 and Cyber-Shot DSC-F828 cameras use these sensors, but the output is still RGB because there is no standard supporting four-primary colors. Companies such as Dolby Canada, Israel's Geno Color Technologies Ltd., and Samsung Electronics Co., Ltd. have applied for patents for wide-color gamut display devices and equipment internationally and in my country, proposing four-, five-, and even six-primary color combinations to achieve a wider display color gamut.

[0005] The research work on transmitting wide color gamut video images is mainly divided into three directions: color gamut mapping, "negative" value color light and the selection of pure three primary colors.

[0006] In the gamut mapping direction, mathematical transformations cannot increase the entropy of the image, so gamut mapping technology does not increase color information. On the contrary, if the color gamut range of the signal source is larger than the color gamut range of the display, gamut mapping is necessary to avoid unnatural distortion and loss of detail in the displayed image.

[0007] For the "negative" value color light direction, using a linear matrix to calculate the "negative" value RGB signal will not only affect the signal fidelity, but also make it difficult for the receiving end to recover, affect the accuracy of the data, and cause errors in color reproduction.

[0008] Regarding the direction of selecting the purest RGB primary colors possible, since BT.2020 has such high requirements for the purity of the RGB primary colors that there is no imaging technology that meets its requirements so far, there is no true BT.2020 video source.

[0009] The above analysis demonstrates that current research on wide color gamuts cannot achieve distortion-free reproduction of the source's colors on the display side. Furthermore, since the human eye's visible color gamut is tongue-shaped, the RGB primary colors can only cover a triangular area within it. Therefore, adopting five primary colors is essential for effectively achieving a wide color gamut. Summary of the Invention

[0010] The purpose of the present invention is to provide a method for transmitting five-primary-color image signals based on a standard three-channel method in response to the technical defects in the prior art.

[0011] In order to achieve the above object, the present invention provides the following technical solutions:

[0012] A method for transmitting five-primary-color image signals based on a standard three-channel method comprises the following steps:

[0013] (1) Calculate the encoding matrix of the additional CGB color space to encode the CGB signal into a pseudo YCbCr signal and calculate the CGB decoding matrix;

[0014] The method for calculating the encoding matrix of the CGB color space is as follows:

[0015] Taking Rec.709 as the standard, the pseudo YUV signal in CGB format is expressed as

[0016]

[0017] Among them, C0, G0 and B0 represent the cyan, green and blue primary color signals respectively, and a, b, c are Y CGB 、U CGB and V CGB Compression factor;

[0018] Digitize the pseudo YUV signal to obtain the pseudo YCbCr signal Among them, INT is the rounding operation;

[0019] Calculate the compression coefficients a, b, c that meet the requirements;

[0020] Get the encoding matrix of CGB color space;

[0021] (2) Calculating the encoding matrix of the additional RGY color space to encode the RGY signal into a pseudo YCbCr signal; calculating the RGY decoding matrix;

[0022] The method for calculating the RGY coding matrix is ​​as follows:

[0023] Taking Rec.709 as the standard, the pseudo YUV signal in RGY format is expressed as

[0024]

[0025] Among them, R0, G0 and Y0 represent the red, green and yellow primary color signals respectively; j, k, l represent Y RGY 、U RGY and V RGY Compression coefficient; digitize the pseudo YUV signal to obtain a pseudo YCbCr signal Among them, INT is a rounding operation.

[0026] Calculate the compression coefficients j, k, l that meet the requirements and obtain the RGY encoding matrix;

[0027] (3) The transmitter divides the five primary color signals (red, green, blue, yellow, and cyan) into color space. Each pixel consists of three color components: RGB, CGB, or RGY. Standard RGB encoding, CGB encoding, or RGY encoding are used, respectively, to encode the signal into a YCbCr signal for transmission. If the C component value is greater than the R component, the CGB encoding format is used; if the Y component value is greater than the B component, the RGY encoding format is used; otherwise, the RGB encoding format is used.

[0028] (4) The receiving end receives the YCbCr data and uses a blind recognition scheme to determine the composition of the three primary colors. The YCbCr data is uniformly decoded using the RGB decoding matrix. The decoded signals are X1, X2, and X3. If the decoded values ​​X1, X2, and X3 are all in the range of [0, 255], it means that the pixel is composed of RGB and the decoding is correct; otherwise, if the decoded values ​​X1 and X3 are both less than -128, it means that the pixel is composed of CGB, and the CGB decoding matrix is ​​used to decode the pseudo YCbCr data; otherwise, if the decoded value is negative, it means that the pixel is composed of RGY, and the RGY decoding matrix is ​​used to decode the pseudo YCbCr data. The five primary color signals can be correctly decoded at the receiving end.

[0029] Furthermore, the process of calculating the required compression coefficients a, b, and c is as follows:

[0030] 1) Initialize the number of successfully identified CGBs, 'amount', to zero, and the compression coefficients a, b, and c to 1, 0.5389, and 0.6350, respectively, which are the maximum values;

[0031] 2) Initialize the quantized values ​​of the CGB signal, i.e., C', G', and B', at the encoding end;

[0032] 3) Encode the CGB signal through the CGB encoding matrix to obtain a pseudo YCbCr digital signal;

[0033] 4) Decode the pseudo YCbCr signal through the RGB decoding matrix to reproduce the CGB signal;

[0034] 5) Based on the uncertain color space source, the decoded signal is set to X1, X2, and X3, and it is determined whether X1 and X3 are both less than -128: If so, it is considered that the pseudo YCbCr signal is a mixture of the three primary colors CGB, and 'amount' is increased by 1; if not, it is considered that the YCbCr signal is a mixture of the three primary colors RGB or RGY, and 'amount' remains unchanged;

[0035] Check whether C', G', and B' have increased to 235: If not, increase C', G', and B' by 1 in turn, and then return to step 3); if so, calculate the success rate to determine whether the recognition is successful. If so, output a, b, and c; if not, set 'amount' to 0, set the step size, and decrease the values ​​of a, b, and c in turn, and then return to step 2).

[0036] Furthermore, the compression coefficient values ​​calculated in step (1) are a=0.2534, b=0.2183 and c=0.1006, and the CGB coding matrix is ​​obtained as The CGB decoding matrix is ​​the inverse operation of the encoding, and the result is

[0037] Furthermore, the calculated RGY color space coding compression coefficient values ​​are j = 0.6000, k = 0.5389, l = 0.2126, and the RGY coding matrix is ​​obtained as The RGY decoding matrix is ​​the inverse operation of the encoding, and the result is

[0038]

[0039] In the above technical solution, the present invention provides a method for transmitting five primary color image signals based on a standard three-channel method, which has the following beneficial effects:

[0040] 1. The present invention uses the five primary colors of red, green, blue, cyan, yellow, RGB, and CY to form a pentagonal color gamut. Compared with the triangular color gamut formed by red, green, blue, and RGB, it can better approximate the CIE 1931 or 1976 color space representing the visible range of the human eye, truly reproduce more natural colors, expand the coverage of the color gamut, and improve the display quality of video images;

[0041] 2. This invention uses a method of decomposing the pentagonal color gamut of the five primary colors into three triangular color gamuts of RGB, CGB, and RGY to express the composite color light of nature, while maintaining compatibility with current video transmission and storage formats, providing support for the application of wide color gamut video images.

[0042] 3. Through the special encoding form of the newly added CGB color space and RGY color space at the source end, the universal decoder at the receiving end can blindly identify the pixel composition of the five primary color image, that is, from the RGB color space, CGB color space, or RGY color space, without the need for flag information or additional transmission data, so as to achieve the purpose of expressing more colors without increasing color depth. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the pentagonal color gamut and decomposition method of RGBCY in the CIE 1931 chromaticity diagram;

[0044] Figure 2 Schematic diagram of YCbCr signal formation in the case of five primary colors RGBCY;

[0045] Figure 3 This is a block diagram of a blind identification method for YCbCr signal sources;

[0046] Figure 4 Flowchart for determining the compression coefficients a, b and c of the luminance signal Y and the color difference signals U and V. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings, which are not intended to limit the present invention.

[0048] 1. Representation of composite color light in the case of five primary colors

[0049] For the current three-primary color image system, the color representation in the color gamut covered by the RGB triangle is unique. However, the composite light within the color gamut formed by the RGBCY pentagon may have multiple compositions. This solution decomposes the RGBCY pentagon into three triangles: RGB, CGB, and RGY, to ensure that the transmitter outputs a unique YUV signal, that is, the output YUV signal is composed of only the three primary colors of RGB or the three primary colors of CGB or the three primary colors of RGY. Only three primary colors are transmitted for one pixel, thereby reducing the problem of a significant increase in data volume due to the addition of cyan and yellow components. Taking RGB as the Rec.709 primary color (HDTV colorimetry system) as an example, since the color mixing method within the pentagon is not unique, it is necessary to make a specific analysis of the color light in different areas, such as Figure 1The composite colors C1, C2, C3, C4, C5 and C6 are shown. In order to maintain compatibility with the universal RGB three-primary color system, the RGBCY pentagon is decomposed into three triangles: △RGB, △CGB and △RGY. The colors within △RGB, such as Figure 1 C1, C2 and D65 in the image continue to be mixed by the three RGB primary colors to form a universal YUV signal, which can be correctly displayed by conventional color gamut display devices; although the composite color light C1 is also located in the RGC triangle, in order to ensure the accuracy of color reproduction, taking C1 as an example, all composite color lights inside the RGB triangle (including the edges) are composited and displayed using the three RGB primary colors. Similarly, the composite color light C2 is also located in the RGB triangle and the RBY triangle, and is still composited using the three RGB primary colors. The colors located in △CGB, such as Figure 1 C3 in the image is mixed by the three primary colors of CGB to form a pseudo-YUV signal. For this color, conventional display devices can only display the brightness correctly, while five-primary color wide gamut (WCG) display devices can display both color and brightness correctly. Colors within △RGY, such as Figure 1 The C6 in the image is mixed by the three primary colors RGY to form a pseudo YUV signal; the colors on the BG line, such as Figure 1 C4 in the figure and C5 on the RG line are not restricted by the color gamut division. In order to achieve simplicity and accuracy, they are still classified into the RGB color gamut range that has been studied in depth and expressed through universal YUV signals.

[0050] 2. Five-primary-color video image display recognition solution

[0051] The above transmission scheme decomposes the pentagonal color gamut into three triangles, which raises the question of how the display can identify the source of the YUV signal. Each pixel in the five-primary-color image is represented by RGB, CGB, or RGY. Using different encodings for RGB, CGB, and RGY enables the receiver decoder to blindly identify the source of the YUV signal. After any pixel is encoded with CGB or RGY and decoded with standard RGB, the resulting three-channel signal is denoted as X1, X2, and X3, respectively, as it cannot distinguish between color spaces. Colors within the RGB triangle can be formed by the three primary colors of RGB. Therefore, when the resulting YUV signal is decoded at the receiver, the amplitude of the RGB signal is within the range of 0 to 255 (inclusive). However, colors composed of CGB form a pseudo-YUV signal. If this is still passed through the RGB decoding equation, the resulting signal will have X1 and X3 both less than -128, proving that the color cannot be formed by the additive mixing of the RGB signals, indicating that the pixel is formed by CGB. Otherwise, the color composed of RGY forms a pseudo YUV signal. If it is still passed through the RGB decoding equation, the amplitude of the obtained signal X1, X2, and X3 will be negative, that is, the pixel is formed by RGY. The blind recognition scheme can enable the receiver to accurately identify the source of the YUV signal without transmitting any flag information. The formation and recognition process of the YUV signal is as follows: Figure 2 and Figure 3 As shown, X1, X2, and X3 represent the three-channel signals of the YUV signal after the RGB decoding equation.

[0052] 3. Five primary color video image coding scheme

[0053] To enable the receiver to accurately identify the data source of the YUV signal without any identification information, different YUV encoding schemes are used for RGB, CGB, and RGY color spaces. Specifically, the coefficients and offset values ​​of the YUV encoding equations are different for RGB, CGB, and RGY.

[0054] 3.1 RGB color space encoding and decoding

[0055] For the RGB case, according to ITU-R BT.709, the relationship between the luminance signal and the two color difference signals of the high-definition television (HDTV) signal is as follows:

[0056]

[0057] In equation (1), Y RGB 、U RGB and V RGB Represents the brightness signal and two color difference signals in the RGB case, R0, G0 and B0 represent the red, green and blue primary color signals respectively. The compression coefficients of the red and blue difference signals are kR =0.5 / 0.7874=0.6350, k B =0.5 / 0.9278=0.5389, which is used to compress the red and blue difference signals into the nominal range.

[0058]

[0059] Where R', G' and B' represent the quantized RGB signals, Y' RGB is the quantified Y RGB Signal, Cb' RGB and Cr' RGB It is the quantized U RGB and V RGB Signal, operator INT represents a rounding operation.

[0060] RGB and YCbCr color space data are converted to each other through equations (4) and (5):

[0061]

[0062] Because a guard band is set to prevent the dynamic range from being exceeded, the quantization range of the color signal is limited to 220 levels, which means it is compressed by 219 / 255 = 0.8588. Because the dynamic range of the signal must be reproduced on the display, more precisely, the RGB primary color signal data range that the display must process is 0 to 255, so the compressed color signal should be expanded by 255 / 219 = 1.1644. In this case, the decoding equation can be expressed as:

[0063]

[0064] Where R, G and B represent the reproduced quantized RGB signals respectively.

[0065] 3.2 Encoding and decoding of CGB color space

[0066] In the CGB case, the compression coefficients of the Y and V signals are set to negative values. By adding an offset during digitization, the quantization range of the YUV signal is guaranteed to be the same as that of the RGB case. The color signal is added to the Y signal to ensure decorrelation between the U and V signals, thereby improving the image compression efficiency. Since there is no standard for transmitting CGB primary color images and videos, the YUV signal sent in the CGB case is represented as a linear combination of the three primary colors C, G, and B. Taking the Rec.709 standard as an example, the pseudo-YUV signal in the CGB format is expressed as equation (7):

[0067]

[0068] In equation (7), Y CGB 、U CGB and VCGB They represent the brightness signal and two color difference signals in the CGB case, C0, G0 and B0 represent the cyan, green and blue primary color signals respectively. a, b, c are Y CGB 、U CGB and V CGB In order to make Y CGB 、U CGB and V CGB The nominal range is in [0,1], which is the same as the YUV format signal under the RGB three-primary color system. a, b, c should meet the following conditions:

[0069]

[0070] To comply with Rec.709, when using 8-bit quantization, the same as the RGB case, Y CGB The range is within [16,235], and U CGB and V CGB The range of is within [16,240]. Therefore, the CGB and YCbCr digital signals in the CGB case can be expressed by equations (9) and (10):

[0071]

[0072]

[0073] Where C', G' and B' represent the quantized CGB color signals, Y' CGB Indicates the quantized brightness signal under CGB conditions, Cb' CGB and Cr' CGB Represents the two color difference signals quantized in the CGB case.

[0074] According to equations (7), (9) and (10), we can get Y' CGB , Cb' CGB and Cr' CGB The relationship between C', G' and B' is expressed by equation (11):

[0075]

[0076] The prerequisite for effectively identifying the YUV data source is that the original colors of the YUV signal mixed by CGB in the case of 220×220×220 combination (as mentioned above, the quantization range of the CGB signal is [16,235], with 220 levels) after being decoded by the RGB decoding equation should all meet the blind recognition conditions. Different compression coefficients in the CGB case will lead to different successful recognition rates, so the selection of the compression coefficient is critical. The criteria for selecting the compression coefficient are: first, the successful recognition rate is 100%, that is, the source of the YUV signal data needs to be fully identified; second, the compression coefficient is made as large as possible under the premise of ensuring the successful recognition rate to avoid color distortion caused by excessive compression. According to the above standards, the process of calculating the compression coefficient that meets the requirements is as follows: Figure 4 shown.

[0077] Figure 4 The main steps for calculating the compression coefficients a, b and c are given (the compression coefficients j, k, l are calculated in a similar way) to fully identify the source of the YUV signal data:

[0078] (1) Initialize the number of successful recognitions (if successful recognition is CGB) 'amount' to zero,

[0079] And initialize the compression coefficients a, b and c to 1, which is the maximum value;

[0080] (2) Initialize the quantized values ​​of the CGB signal at the encoding end, i.e., C', G', and B' in equation (9);

[0081] (3) Encode the CGB signal through the CGB encoding matrix, that is, obtain the YUV digital signal according to equation (11);

[0082] (4) Decode the YUV signal through the RGB decoding matrix to reproduce the CGB signal;

[0083] (5) Since the color space source is uncertain, the decoded signal is set to X1, X2, and X3. It is determined whether X1 and X3 are both less than -128: If so, it is considered that the YCbCr signal is a mixture of the three primary colors CGB, and 'amount' is increased by 1; if not, it is considered that the YCbCr signal is a mixture of the three primary colors RGB or RGY, and 'amount' remains unchanged;

[0084] (6) Check whether C', G' and B' have increased to 235: If not, increase C', G' and B' by 1 respectively, and then return to step (3); if so, calculate the success rate (i.e. amount / 220 3), determine whether the successful recognition rate is 100%. If so, output a, b and c and the program ends; if not, set 'amount' to 0, set the step size (a small value, such as 0.0001) and reduce the values ​​of a, b and c in turn, and then return to step (2).

[0085] The final calculated compression coefficients are a = 0.2534, b = 0.2183, and c = 0.1006. Substituting them into equation (11), CGB and YUV color space data can be converted to each other using equations (12) and (13):

[0086]

[0087] Because the range of the CGB three primary color signal data to be processed by the display is 0 to 255, the compressed color signal should be expanded by 255 / 219=1.1644. At this time, the decoding equation can be expressed as follows:

[0088]

[0089] Where C, G and B represent the reproduced quantized CGB signals respectively.

[0090] 3.3RGY color space encoding and decoding

[0091] Similar to the case of CGB color space, this section takes the Rec.709 standard as an example to introduce the encoding and decoding equations of RGY color space. The compression coefficients of the Y and U signals are set to negative values, and the offset is added during digitization to ensure that the quantization range of the YUV signal is the same as that of the RGB case. Equation (15) describes the Y RGY U RGY V RGY Relationship with the primary color signal R0G0Y0.

[0092]

[0093] Where, j, k, and l represent Y RGY 、U RGY and V RGY The compression coefficients are as follows:

[0094]

[0095] The analog signal needs to be digitized before transmission. The digital signals of RGY and YUV can be expressed by equations (17) and (18):

[0096]

[0097] Among them, R', G' and Y' represent the quantized RGY signal, Y' RGYis the quantified Y RGY Signal, Cb' RGY and Cr' RGY It is the quantized U RGY and V RGY Signal. Similarly, considering Y RGY The minimum value of is -j, and Y' in equation (18) is RGY The bias value of is set to j; similarly, Cb' RGY The bias value in is 0.9278jk, Cr' RGY The bias value is 0.7874jl. Integrating equations (15), (17) and (18), we get the quantized Y' RGY Cb' RGY Cr' RGY The relationship between the quantized primary color signal R'G'Y' is shown in equation (19).

[0098]

[0099] Analogously to the CGB color space, we solve the compression coefficients j, k, and l of equation (19) for the RGY color space. The final calculated compression coefficients for the RGY color space encoding are j = 0.6000, k = 0.5389, and l = 0.2126. Substituting these values ​​into equation (19) and writing them in matrix form yields:

[0100]

[0101] Since the maximum value of the quantized signal at the transmitter is compressed from 255 to 219, the display end should expand it by 255 / 219=1.1644. The offset value is calculated according to equation (19) and expressed in matrix form as follows:

[0102]

[0103] Where R, G and Y represent the reproduced quantized RGY signals respectively.

[0104] The following is a summary of the transmission scheme proposed in the present invention:

[0105] 1. A method for transmitting five-primary-color image signals based on a standard three-channel method, comprising the following aspects:

[0106] (1) Calculate the encoding matrix of the additional CGB color space and encode the CGB signal into a pseudo YCbCr signal. Taking Rec.709 as the standard, the pseudo YUV signal in the CGB format is expressed as

[0107]

[0108] Among them, C0, G0 and B0 represent the cyan, green and blue primary color signals respectively. a, b, c are Y CGB 、U CGB and V CGB Compression coefficient. Digitizing the pseudo YUV signal can generate a pseudo YCbCr signal. Among them, INT is a rounding operation.

[0109] At this point, it is necessary to calculate the specific values ​​of the compression coefficients a, b, and c in order to obtain an accurate CGB encoding matrix. The process of calculating the compression coefficients that meet the requirements is as follows:

[0110] 1) Initialize the number of successful recognitions (if successful recognition is CGB) 'amount' to zero, and initialize the compression coefficients a, b, and c to 1, 0.5389, and 0.6350, respectively, which are the maximum values;

[0111] 2) Initialize the quantized values ​​of the CGB signal, i.e., C', G', and B', at the encoding end;

[0112] 3) Encode the CGB signal through the CGB encoding matrix to obtain a pseudo YCbCr digital signal;

[0113] 4) Decode the pseudo YCbCr signal through the RGB decoding matrix to reproduce the CGB signal;

[0114] 5) Since the color space source is uncertain, the decoded signal is set to X1, X2, and X3. Check whether X1 and X3 are both less than -128: If so, it is considered that the YCbCr signal is a mixture of the three primary colors CGB, and 'amount' is increased by 1; if not, it is considered that the YCbCr signal is a mixture of the three primary colors RGB or RGY, and 'amount' remains unchanged;

[0115] 6) Check whether C', G' and B' have increased to 235: If not, increase C', G' and B' by 1 respectively and return to step 3; if so, calculate the success rate (i.e. amount / 220 3 ), determine whether the successful recognition rate is 100%. If so, output a, b and c and the program ends; if not, set 'amount' to 0, set the step size (a small value, such as 0.0001) and reduce the values ​​of a, b and c in turn, and then return to step 2.

[0116] The calculated compression coefficient values ​​are a = 0.2534, b = 0.2183 and c = 0.1006. The final CGB encoding matrix is The CGB decoding matrix is ​​the inverse operation of the encoding, and the result is

[0117]

[0118] (2) Calculate the encoding matrix of the additional RGY color space and encode the RGY signal into a pseudo YCbCr signal. Based on the Rec.709 standard, the pseudo YUV signal in the RGY format is expressed as

[0119]

[0120] Where R0, G0 and Y0 represent the red, green and yellow primary color signals respectively. RGY 、U RGY and V RGY Compression coefficient. Digitizing the pseudo YUV signal can generate a pseudo YCbCr signal. Among them, INT is a rounding operation. At this time, it is necessary to calculate the specific values ​​of the compression coefficients j, k, and l to obtain an accurate RGY encoding matrix. The process of calculating the compression coefficients that meet the requirements is similar to the CGB case. The calculated RGY color space encoding compression coefficient values ​​are j = 0.6000, k = 0.5389, and l = 0.2126. The final RGY encoding matrix is The RGY decoding matrix is ​​the inverse operation of the encoding, and the result is

[0121]

[0122] (3) The transmitter divides the five primary color signals of red, green, blue, yellow, and cyan (RGBCY) according to the color space. Each pixel is composed of three color components, RGB, CGB, or RGY. Standard RGB encoding, CGB encoding, or RGY encoding are used to encode them into YCbCr signals for transmission. If the C component value is greater than the R component, the CGB encoding format is used; if the Y component value is greater than the B component, the RGY encoding format is used; otherwise, the RGB encoding format is used. Among them, the RGB encoding matrix is ​​as follows according to the Rec.709 standard: The CGB encoding matrix is The RGY encoding matrix is

[0123]

[0124] (3) The receiving end receives the YCbCr data and uses a blind recognition scheme to determine the composition of the three primary colors. The YCbCr data is uniformly decoded using the RGB decoding matrix. Decoding, the decoded signal is X1, X2, X3. If the decoded values ​​X1, X2, X3 are all in the range of [0, 255], it means that the pixel is composed of RGB and the decoding is correct; otherwise, if the decoded values ​​X1 and X3 are both less than -128, it means that the pixel is composed of CGB and the CGB decoding matrix is ​​used. Decode the YCbCr data; otherwise, if the decoded value is negative, it means that the pixel is composed of RGY, and the RGY decoding matrix is ​​used. By decoding the YCbCr data, the five primary color signals can be correctly decoded at the receiving end.

[0125] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for transmitting five primary color image signals based on a standard three-channel method, comprising the following steps: (1) Calculate the encoding matrix of the additional CGB color space to encode the CGB signal into a pseudo YCbCr signal and calculate the CGB decoding matrix; The method for calculating the encoding matrix of the CGB color space is as follows: Taking Rec.709 as the standard, the pseudo YUV signal in CGB format is expressed as Among them, C0, G0 and B0 represent the cyan, green and blue primary color signals respectively, and a, b, c are Y CGB 、U CGB and V CGB Compression factor; Digitize the pseudo YUV signal to obtain the pseudo YCbCr signal Among them, INT is the rounding operation; Calculate the compression coefficients a, b, c; Get the encoding matrix of CGB color space; (2) Calculating the encoding matrix of the additional RGY color space to encode the RGY signal into a pseudo YCbCr signal; calculating the RGY decoding matrix; The method for calculating the RGY coding matrix is ​​as follows: Taking Rec.709 as the standard, the pseudo YUV signal in RGY format is expressed as Among them, R0, G0 and Y0 represent the red, green and yellow primary color signals respectively; j, k, l represent Y RGY 、U RGY and V RGY Compression coefficient; digitize the pseudo YUV signal to obtain a pseudo YCbCr signal Among them, INT is the rounding operation; Calculate the compression coefficients j, k, l to obtain the RGY encoding matrix; (3) The transmitter divides the five primary color signals of red, green, blue, yellow, and cyan (RGBCY) according to the color space. Each pixel is composed of three color components: RGB, CGB, or RGY. Standard RGB encoding, CGB encoding, or RGY encoding are used to encode them into YCbCr signals for transmission. If the C component value is greater than the R component, the CGB encoding format is used; if the Y component value is greater than the B component, the RGY encoding format is used; otherwise, the RGB encoding format is used. (4) The receiving end receives YCbCr data and uses a blind recognition scheme to determine the composition of the three primary colors; the YCbCr data is uniformly decoded using the RGB decoding matrix, and the decoded signals are X1, X2, and X3. If the decoded values ​​X1, X2, and X3 are all in the range of [0, 255], it means that the pixel is composed of RGB and the decoding is correct; otherwise, if the decoded values ​​X1 and X3 are both less than -128, it means that the pixel is composed of CGB, and the CGB decoding matrix is ​​used to decode the pseudo YCbCr data; otherwise, if the decoded value is negative, it means that the pixel is composed of RGY, and the RGY decoding matrix is ​​used to decode the pseudo YCbCr data, so that the five primary color signals can be correctly decoded at the receiving end.

2. The method for transmitting five primary color image signals based on a standard three-channel transmission according to claim 1, characterized in that: The process of calculating the compression coefficients a, b, and c is as follows: 1) Initialize the number of successfully identified CGBs, 'amount', to zero, and the compression coefficients a, b, and c to 1, 0.5389, and 0.6350, respectively, which are the maximum values; 2) Initialize the quantized values ​​of the CGB signal, i.e., C', G', and B', at the encoding end; 3) Encode the CGB signal through the CGB encoding matrix to obtain a pseudo YCbCr digital signal; 4) Decode the pseudo YCbCr signal through the RGB decoding matrix to reproduce the CGB signal; 5) Based on the uncertain color space source, the decoded signal is set to X1, X2, and X3, and it is determined whether X1 and X3 are both less than -128: If so, it is considered that the pseudo YCbCr signal is a mixture of the three primary colors CGB, and 'amount' is increased by 1; if not, it is considered that the YCbCr signal is a mixture of the three primary colors RGB or RGY, and 'amount' remains unchanged; Check whether C', G', and B' have increased to 235: If not, increase C', G', and B' by 1 in turn, and then return to step 3); if so, calculate the success rate to determine whether the recognition is successful. If so, output a, b, and c; if not, set 'amount' to 0, set the step size, and decrease the values ​​of a, b, and c in turn, and then return to step 2).

3. The method for transmitting five primary color image signals based on a standard three-channel transmission according to claim 2, characterized in that: Based on the process of calculating the compression coefficients a, b, and c, a calculation method for the compression coefficients j, k, and l is designed.

4. The method for transmitting five primary color image signals based on a standard three-channel transmission according to claim 1, characterized in that: The compression coefficients calculated in step (1) are a=0.2534, b=0.2183 and c=0.1006, and the CGB coding matrix is: The CGB decoding matrix is ​​the inverse operation of the encoding, and the result is 5. The method for transmitting five primary color image signals based on a standard three-channel transmission according to claim 1, characterized in that: The calculated RGY color space coding compression coefficient values ​​are j = 0.6000, k = 0.5389, l = 0.2126, and the RGY coding matrix is The RGY decoding matrix is ​​the inverse operation of the encoding, and the result is

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