CN109685859B - 3D Color Automatic Adjustment Method Based on 3D Lookup Table - Google Patents

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

3D Color Automatic Adjustment Method Based on 3D Lookup Table

technical field

The invention relates to video image processing, in particular to a three-dimensional color automatic adjustment method based on a 3D look-up table.

Background technique

In today's life, from large display devices such as LCD TVs, computer screens and projectors, which are becoming larger and larger, to small display devices such as smart phones, handheld games and digital cameras, color displays have been closely related to people's lives. Taking a large LCD TV as an example, today's LCD TVs can not only display color images, but also adjust colors according to the user's preference, so as to improve the user's viewing experience.

From black and white to color, from analog signal to digital signal, every change in the video field is an all-round technological upgrade of the entire ecological chain. In recent years, high dynamic range has received extensive attention in the industry. Manufacturers in different links are actively taking action to deploy the next-generation video system. As a video signal standard that carries a complete industrial chain, it is also facing further upgrades. The new generation of video signal ICtCp breaks through the existing signal format and gradually encounters bottlenecks 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 yet to be solved problem.

SUMMARY OF THE INVENTION

In order to solve the problems in the prior art, the present invention provides a three-dimensional color automatic adjustment method based on a 3D look-up table.

The present invention provides a three-dimensional color automatic adjustment method based on a 3D look-up table, comprising the following steps:

S1, RGB color space to ICtCp color space conversion, convert the original RGB color space to ICtCp color space;

S2. Perform color adjustment in the ICtCp color space, and perform color adjustment of brightness and color respectively according to the 3D lookup table according to the pixel value of each pixel of each frame of image in the ICtCp color space.

As a further improvement of the present invention, in step S1, the specific adjustment values of brightness and color are obtained by trilinear interpolation according to the 3D look-up table.

As a further improvement of the present invention, step S1 includes the following sub-steps:

S11, start;

S12, update the frame, read the current frame data, and perform data preprocessing;

S13, update the pixel point, and read the current pixel value of the current frame;

S14. Convert the RGB pixels into ICtCp values.

As a further improvement of the present invention, step S2 includes the following sub-steps:

S21, perform trilinear interpolation operation according to the data in the 3D lookup table, and calculate the 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 color-adjusted pixel value;

S23, determine whether the current frame has unprocessed pixels, if so, return to step S13, if not, enter the next step;

S24, determine whether there are unprocessed frames, if yes, return to step S12, if not, end.

As a further improvement of the present invention, the 3D lookup table includes an I lookup table, a Ct lookup table, and a Cp lookup table, and the I lookup table, the Ct lookup table, and the Cp lookup table all include the I dimension, the Ct dimension, and the Cp dimension.

The beneficial effects of the present invention are: through the above scheme, the three-dimensional color automatic adjustment of the ICtCp video signal format is realized.

Description of drawings

FIG. 1 is an algorithm principle diagram of a three-dimensional color automatic adjustment method based on a 3D look-up table of the present invention.

FIG. 2 is a schematic diagram of a 3D lookup table of a three-dimensional color automatic adjustment method based on a 3D lookup table of the present invention.

3 is a schematic diagram of trilinear interpolation of a three-dimensional color automatic adjustment method based on a 3D look-up table of the present invention.

FIG. 4 is a flow chart of a three-dimensional color automatic adjustment method based on a 3D look-up table of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

As shown in Figures 1 to 4, a three-dimensional color automatic adjustment method based on a 3D lookup table, firstly converts the original RGB color space into the ICtCp color space, and aims at the pixel value of each pixel of each frame of the image in the ICtCp color space. , according to the 3D look-up table to adjust the brightness and color respectively. The specific adjustment values of brightness and color are obtained by trilinear interpolation according to the 3D look-up table.

ICtCp is a new video signal format, which separates the picture brightness signal from the color signal, where I represents the encoded brightness intensity, that is, the black and white signal; Ct represents the blue-yellow axis chrominance signal, and Cp represents the red-green axis chrominance signal. , CtCp combined to form a complete color picture.

Compared with traditional YCbCr, the hue shift angle of ICtCp is generally smaller than that of YCbCr, and it also has excellent performance in important areas such as blue and skin tones. Secondly, the color linearity and tone consistency of ICtCp signal are better than YCbCr.

Read the current frame data and perform data preprocessing, and convert the RGB pixel value of the current pixel point to the ICtCp value. The conversion formula from RGB space to ICtCp space is as follows:

y＝x/10000，m₁＝2610/16384 m₂＝128×2523/4096,c₁＝3424/4096,c₂＝32×2413/4096,c₃＝32×2392/4096。in,

y=x/10000, m1 ₌ 2610/16384 _m2 =128×2523/4096, c1 ₌ 3424/4096, _c2 =32×2413/4096, c3 ₌ 32×2392/4096.

Color adjustment in ICtCp space is as follows:

The pixel value (I, Ct, Cp) of each pixel of the image in the ICtCp color space is mapped one by one to the new pixel value (I', Ct', Cp') by the method of the 3D lookup table. The pixel value is the pixel value after color adjustment. The 3D lookup tables are an I lookup table, a Ct lookup table, and a Cp lookup table, respectively. And each lookup table has three dimensions of I, Ct, and Cp respectively. This enables three-dimensional mapping. Taking 8bits data as an example, the sub-pixel values I, Ct, and Cp of the original pixel are in the range of 0 to 255, then each pixel has 256*256*256 possible situations, and each situation corresponds to a three-dimensional color adjustment value (ΔI, ΔCt, ΔCp). Then the size of the lookup table in the case of 8bits is 256*256*256*3. The adjusted pixel value is:

(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 numerical precision is large enough, we can convert any original color into any target color. However, the 3D lookup table in this case will be very large and consume storage space. Therefore, the trilinear interpolation method is used here to reduce the data storage amount of the 3D lookup table.

The 3D lookup table is explained as follows:

Taking 8bits data as an example, divide 0 to 255, and select nine typical gray levels of 0, 16, 32, 64, 128, 160, 192, 224, and 255. The resulting 3D lookup table of size 9×9×9×3 is shown in Figure 2. The 3D lookup table has 3 dimensions and 9×9×9 sampling points. For the convenience of writing, the nine typical gray levels 0, 16, 32, 64, 128, 160, 192, 224, and 255 are respectively corresponding to An integer from 0 to 8, the three dimensions correspond to i, j, and k respectively. Then each typical gray point stores the corresponding color adjustment value (ΔI _i,j,k , ΔCt _i,j,k , ΔCp _i,j,k ).

Trilinear interpolation calculates the target color adjustment value as follows:

Taking 8bits data as an example, if the original sub-pixel values are just the selected typical gray levels of 0, 16, 32, 64, 128, 160, 192, 224, 255, the target color adjustment value (ΔI, ΔCt, ΔCp) That is, the corresponding color adjustment values of the 3D look-up table (ΔI _i,j,k , ΔCt _i,j,k , ΔCp _i,j,k ).

If the original sub-pixel value is not the selected typical gray level, a trilinear interpolation method is used to calculate the target color adjustment value (ΔI, ΔCt, ΔCp). The specific method is shown in Figure 1:

Assuming that the original pixel value is (I, Ct, Cp), i=I/32, j=Ct/32, k=Cp/32. Where "/" represents the quotient operation. This results in 8 points P _0,0,0 , P _0,0,1 , P _0,1,0 , P _0,1,1 , P _1,0,0 , P _1,0,1 , P _{1 ,1,0} , P _1,1,1 is defined as:

P _0,0,0 =(ΔI _i,j,k ,ΔCt _i,j,k ,ΔCp _i,j,k ),P _0,0,1 =(ΔI _i,j,k+1 ,ΔCt _{i, j,k+1} ,ΔCp _i,j,k+1 )

P _0,1,0 =(ΔI _i,j+1,k ,ΔCt _i,j+1,k ,ΔCp _i,j+1,k ),P _0,1,1 =(ΔI _{i,j+1 ,k+1} ,ΔCt _i,j+1,k+1 ,ΔCp _i,j+1,k+1 )

P _1,0,0 =(ΔI _i+1,j,k ,ΔCt _i+1,j,k ,ΔCp _i,j,k ),P _1,0,1 =(ΔI _{i+1,j,k +1} ,ΔCt _i,j,k+1 ,ΔCp _i,j,k+1 )

P _1,1,0 =(ΔI _i+1,j+1,k ,ΔCt _i,j+1,k ,ΔCpi _,j+1,k ),P _1,1,1 =(ΔI _{i=1 ,j+1,k+1} ,ΔCt _i,j+1,k+1 ,ΔCp _i,j+1,k+1 )

Note the coordinates of P _0,0 , P _0,1 , P _1,0 , P _1,1 are:

P _0,0 =(ΔI _0,0 ,ΔCt _0,0 ,ΔCp _0,0 ),P _0,1 =(ΔI _0,1 ,ΔCt _0,1 ,ΔCp _0,1 ),

P _1,0 =(ΔI _1,0 ,ΔCt _1,0 ,ΔCp _1,0 ),P _1,1 =(ΔI _1,1 ,ΔCt _1,1 ,ΔCp _1,1 ),

Then the specific value of each coordinate can be calculated by the following formula, where mod represents the remainder operation.

Note that the coordinates of P ₀ and P ₁ are respectively (ΔI ₀ , ΔCt ₀ , ΔCp ₀ ), (ΔI ₁ , ΔCt ₁ , ΔCp ₁ ), then the specific values of each coordinate can be calculated by the following formula

The target color adjustment value (ΔI, ΔCt, ΔCp) can be calculated from the coordinates of P ₀ and P ₁

The adjusted pixel value is:

(I', Ct', Cp')=(I, Ct, Cp)+(ΔI, ΔCt, ΔCp)

Repeat the above operation until all pixels of all frames are processed.

The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deductions or substitutions can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (2)

1. a three-dimensional color automatic adjustment method based on 3D look-up table, is characterized in that, comprises the following steps: S1, RGB color space to ICtCp color space conversion, convert the original RGB color space to ICtCp color space; S2, performing color adjustment in the ICtCp color space, according to the pixel value of each pixel point of each frame of the image in the ICtCp color space, according to the 3D look-up table, respectively adjusting the color of brightness and color; In step S1, the specific adjustment values of brightness and color are obtained by trilinear interpolation according to the 3D look-up table; Step S1 includes the following sub-steps: S11, start; S12, update the frame, read the current frame data, and perform data preprocessing; S13, update the pixel point, and read the current pixel value of the current frame; S14, convert RGB pixels into ICtCp values; Step S2 includes the following sub-steps: S21, perform trilinear interpolation operation according to the data in the 3D lookup table, and calculate the 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 color-adjusted pixel value; S23, determine whether the current frame has unprocessed pixels, if so, return to step S13, if not, enter the next step; S24, determine whether there are unprocessed frames, if yes, return to step S12, if not, end. 2. the three-dimensional color automatic adjustment method based on 3D look-up table according to claim 1, is characterized in that: described 3D look-up table comprises I look-up table, Ct look-up table and Cp look-up table, described I look-up table, Ct look-up table Both the table and the Cp lookup table include the I dimension, the Ct dimension and the Cp dimension.

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