CN109685859B - Three-dimensional color automatic adjustment method based on 3D lookup table - Google Patents
Three-dimensional color automatic adjustment method based on 3D lookup table Download PDFInfo
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Abstract
The invention provides a three-dimensional color automatic adjustment method based on a 3D lookup table, which comprises the following steps: s1, converting the RGB color space into ICtCp color space, and converting the original RGB color space into the ICtCp color space; and S2, performing color adjustment in the ICtCp color space, and performing color adjustment on brightness and color according to the 3D lookup table aiming at the pixel value of each pixel point of each frame image in the ICtCp color space. The invention has the beneficial effects that: three-dimensional color auto-adjustment of the ICtCp video signal format is achieved.
Description
Technical Field
The invention relates to video image processing, in particular to a three-dimensional color automatic adjusting method based on a 3D lookup table.
Background
In the middle of life, large display devices such as liquid crystal televisions, computer screens and projectors which are large to an increasingly large size, small display devices such as smart phones, handheld games and digital cameras, and color displays are closely related to the life of people. Taking a large lcd television as an example, the existing lcd television can not only display color images, but also adjust colors according to the user's preference, thereby improving the viewing experience of the user.
Every revolution in the video field from black and white to color, from analog to digital, is an all-round technical upgrade of the entire ecological chain. In recent years, the high dynamic range has received wide attention from the industry, and manufacturers in different links are actively working for laying out the next generation of video systems, and are facing further upgrading and updating as the video signal standard carrying the complete industry chain. The new generation video signal ICtCp breaks through the bottleneck of the existing signal format in technical reliability and accuracy, and is expected to become the next generation video signal standard. Therefore, in the context of the new generation video signal ICtCp, how to perform color adjustment is a meaningful and to be solved problem.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a three-dimensional color automatic adjustment method based on a 3D lookup table.
The invention provides a three-dimensional color automatic adjustment method based on a 3D lookup table, which comprises the following steps:
s1, converting the RGB color space into ICtCp color space, and converting the original RGB color space into the ICtCp color space;
and S2, performing color adjustment in the ICtCp color space, and performing color adjustment on brightness and color according to the 3D lookup table aiming at the pixel value of each pixel point of each frame image in the ICtCp color space.
As a further improvement of the present invention, in step S1, the specific adjustment values of the brightness and color are obtained by performing trilinear interpolation according to a 3D lookup table.
As a further improvement of the present invention, step S1 includes the following sub-steps:
s11, starting;
s12, updating the frame, reading the current frame data, and preprocessing the data;
s13, updating the pixel points, and reading the current pixel value of the current frame;
s14, converting the RGB pixels into ICtCp values.
As a further improvement of the present invention, step S2 includes the following sub-steps:
s21, performing trilinear interpolation operation according to the data in the 3D lookup table, and calculating a color adjustment value corresponding to the current pixel;
s22, performing color adjustment according to the current pixel ICtCp value and the calculated color adjustment value to obtain a pixel value after color adjustment;
s23, judging whether the current frame has unprocessed pixels, if yes, returning to the step S13, and if not, entering the next step;
s24, judging whether there is unprocessed frame, if yes, returning to step S12, if not, ending.
As a further improvement of the invention, the 3D lookup table comprises an I lookup table, a Ct lookup table and a Cp lookup table, wherein the I lookup table, the Ct lookup table and the Cp lookup table respectively comprise an I dimension, a Ct dimension and a Cp dimension.
The invention has the beneficial effects that: by the scheme, the three-dimensional color automatic adjustment of the ICtCp video signal format is realized.
Drawings
Fig. 1 is an algorithm schematic diagram of a three-dimensional color automatic adjustment method based on a 3D lookup table according to the present invention.
Fig. 2 is a schematic diagram of a 3D lookup table of a three-dimensional color automatic adjustment method based on the 3D lookup table according to the present invention.
Fig. 3 is a schematic diagram of tri-linear interpolation of the three-dimensional color automatic adjustment method based on the 3D lookup table according to the present invention.
Fig. 4 is a flowchart of a three-dimensional color automatic adjustment method based on a 3D lookup table according to the present invention.
Detailed Description
The invention is further described with reference to the following description and embodiments in conjunction with the accompanying drawings.
As shown in fig. 1 to 4, a three-dimensional color automatic adjustment method based on a 3D lookup table first converts an original RGB color space into an ICtCp color space, and performs color adjustment of brightness and color according to the 3D lookup table for pixel values of each pixel point of each frame of image in the ICtCp color space. Wherein, the specific adjustment values of the brightness and the color are obtained by carrying out trilinear interpolation according to a 3D lookup table.
ICtCp is a new video signal format that separates the picture luminance signal from the color signal, where I represents the luminance intensity after encoding, i.e., a black and white signal; ct represents blue-yellow axis chrominance signals, Cp represents red-green axis chrominance signals, and CtCp forms a complete color picture after combination.
Compared with the traditional YCbCr, the ICtCp has a hue shift angle smaller than that of the YCbCr on the whole, and has excellent performance in important areas such as blue, skin color and the like. Secondly, the color linearity and the tone consistency of the ICtCp signal are better than those of YCbCr.
And reading current frame data, performing data preprocessing, and converting the RGB pixel value of the current pixel point into an ICtCp value. The formula for the conversion from RGB space to ICtCp space is as follows:
wherein,
y＝x/10000，m1＝2610/16384 m2＝128×2523/4096,c1＝3424/4096,c2＝32×2413/4096,c3＝32×2392/4096。
the color adjustment in ICtCp space is as follows:
and mapping the pixel values (I, Ct, Cp) of each pixel point of the image in the ICtCp color space to new pixel values (I ', Ct ', Cp ') one by a 3D lookup table method, wherein the new pixel values are the pixel values after color adjustment. The 3D lookup tables are an I lookup table, a Ct lookup table, and a Cp lookup table, respectively. Each having I, Ct, and Cp dimensions. In this way, a three-dimensional mapping can be achieved. Taking 8bits data as an example, the values of the sub-pixel values I, Ct, Cp of the original pixel are all 0-255, and each pixel has 256 × 256 possible situations, each of which corresponds to a three-dimensional color adjustment value (Δ I, Δ Ct, Δ Cp). The look-up table size for the 8bits case is 256 x 3. The adjusted pixel values are:
(I’，Ct’，Cp’)＝(I，Ct，Cp)+(ΔI，ΔCt，ΔCp)
so theoretically, as long as the scale of the lookup table is dense enough and the accuracy of the numerical value is large enough, we can convert any original color into any target color. But the 3D lookup table in this case would be large and consume memory space. The data storage amount of the 3D lookup table is reduced using the trilinear interpolation method here.
The 3D lookup table is illustrated as follows:
taking 8bits data as an example, 0-255 are divided, and nine typical gray levels of 0, 16, 32, 64, 128, 160, 192, 224 and 255 are selected. The resulting 3D lookup table of size 9 × 9 × 9 × 3 is shown in fig. 2. The 3D lookup table has 3 dimensions, 9 × 9 × 9 sampling points, and for writing convenience, nine typical gray levels 0, 16, 32, 64, 128, 160, 192, 224, and 255 are respectively corresponding to integers of 0-8The number and the three dimensions are respectively corresponding to i, j and k. Each representative gray point stores a corresponding color adjustment value (Δ I)i,j,k，ΔCti,j,k，ΔCpi,j,k)。
The trilinear interpolation calculates the target color adjustment value as follows:
taking 8bits data as an example, if the original sub-pixel values are just all the selected typical gray levels 0, 16, 32, 64, 128, 160, 192, 224, 255, the target color adjustment value (Δ I, Δ Ct, Δ Cp) is the color adjustment value (Δ I) corresponding to the 3D lookup tablei,j,k，ΔCti,j,k，ΔCpi,j,k)。
And if the original sub-pixel value is not the selected typical gray level, calculating the target color adjustment value (delta I, delta Ct, delta Cp) by a trilinear interpolation method. The specific way is shown in figure 1:
assuming that the original pixel value is (I, Ct, Cp), I equals I/32, j equals Ct/32, and k equals Cp/32. Where "/" denotes a quotient calculation. Thereby obtaining 8 points P0,0,0，P0,0,1，P0,1,0，P0,1,1，P1,0,0，P1,0,1，P1,1,0，P1,1,1Is defined as:
P0,0,0＝(ΔIi,j,k,ΔCti,j,k,ΔCpi,j,k),P0,0,1＝(ΔIi,j,k+1,ΔCti,j,k+1,ΔCpi,j,k+1)
P0,1,0＝(ΔIi,j+1,k,ΔCti,j+1,k,ΔCpi,j+1,k),P0,1,1＝(ΔIi,j+1,k+1,ΔCti,j+1,k+1,ΔCpi,j+1,k+1)
P1,0,0＝(ΔIi+1,j,k,ΔCti+1,j,k,ΔCpi,j,k),P1,0,1＝(ΔIi+1,j,k+1,ΔCti,j,k+1,ΔCpi,j,k+1)
P1,1,0＝(ΔIi+1,j+1,k,ΔCti,j+1,k,ΔCpi,j+1,k),P1,1,1＝(ΔIi＝1,j+1,k+1,ΔCti,j+1,k+1,ΔCpi,j+1,k+1)
note P0,0，P0,1，P1,0，P1,1The coordinates of (a) are:
P0,0＝(ΔI0,0,ΔCt0,0,ΔCp0,0),P0,1＝(ΔI0,1,ΔCt0,1,ΔCp0,1)，
P1,0＝(ΔI1,0,ΔCt1,0,ΔCp1,0),P1,1＝(ΔI1,1,ΔCt1,1,ΔCp1,1)，
the specific value for each coordinate can be calculated by the following formula, where mod represents the remainder operation.
Note P0，P1Respectively is (Δ I)0,ΔCt0,ΔCp0),(ΔI1,ΔCt1,ΔCp1) Then the specific value of each coordinate can be calculated by the following formula
From P0，P1The point coordinates may calculate a target color adjustment value (Δ I, Δ Ct, Δ Cp)
The adjusted pixel values are:
(I’，Ct’，Cp’)＝(I，Ct，Cp)+(ΔI，ΔCt，ΔCp)
and repeating the operation until all the pixels of all the frames are processed.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (2)
1. A three-dimensional color automatic adjustment method based on a 3D lookup table is characterized by comprising the following steps:
s1, converting the RGB color space into ICtCp color space, and converting the original RGB color space into the ICtCp color space;
s2, color adjustment is carried out in the ICtCp color space, and brightness and color adjustment is carried out according to the 3D lookup table aiming at the pixel value of each pixel point of each frame image in the ICtCp color space;
in step S1, the specific adjustment values of the brightness and color are obtained by performing trilinear interpolation according to the 3D lookup table;
step S1 includes the following substeps:
s11, starting;
s12, updating the frame, reading the current frame data, and preprocessing the data;
s13, updating the pixel points, and reading the current pixel value of the current frame;
s14, converting the RGB pixels into ICtCp values;
step S2 includes the following substeps:
s21, performing trilinear interpolation operation according to the data in the 3D lookup table, and calculating a color adjustment value corresponding to the current pixel;
s22, performing color adjustment according to the current pixel ICtCp value and the calculated color adjustment value to obtain a pixel value after color adjustment;
s23, judging whether the current frame has unprocessed pixels, if yes, returning to the step S13, and if not, entering the next step;
s24, judging whether there is unprocessed frame, if yes, returning to step S12, if not, ending.
2. The method of claim 1, wherein the method comprises: the 3D lookup table comprises an I lookup table, a Ct lookup table and a Cp lookup table, wherein the I lookup table, the Ct lookup table and the Cp lookup table respectively comprise an I dimension, a Ct dimension and a Cp dimension.
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| CN1874410A (en) * | 2005-06-01 | 2006-12-06 | 索尼公司 | Imaging device and method for processing imaging result in imaging device |
| CN107925770A (en) * | 2015-08-04 | 2018-04-17 | 杜比实验室特许公司 | Signal shaping for high dynamic range signal |
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| JP2008085980A (en) * | 2006-08-31 | 2008-04-10 | Sony Corp | Color conversion device, emulation method, formation method of three-dimension lookup table, and image processor |
| US9948916B2 (en) * | 2013-10-14 | 2018-04-17 | Qualcomm Incorporated | Three-dimensional lookup table based color gamut scalability in multi-layer video coding |
| US9756337B2 (en) * | 2013-12-17 | 2017-09-05 | Qualcomm Incorporated | Signaling color values for 3D lookup table for color gamut scalability in multi-layer video coding |
| MX368598B (en) * | 2015-05-20 | 2019-10-08 | Ericsson Telefon Ab L M | Pixel processing and encoding. |
| US10477212B2 (en) * | 2016-10-11 | 2019-11-12 | Dolby Laboratories Licensing Corporation | Adaptive chroma quantization in video coding for multiple color imaging formats |
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