Luminance adjustment system

1. A luminance adjustment method, comprising:

receiving original image data and dividing image into M×N blocks in X-direction and Y-direction; wherein M and N are both positive integers; each block comprising a plurality of pixels arranged in an array, the original image data of each pixel comprising: red original image data, green original image data, and blue original image data;

obtaining a luminance representative value for each block;

analyzing the original image data of each block to obtain an edge information amount of each block;

calculating a luminance adjustment coefficient of each block based on the luminance representative value and the edge information amount of each block;

performing calibration of the luminance adjustment coefficient of each block to obtain a luminance adjustment calibration value of each block so as to performing smooth processing on each pixel in each block to prevent luminance at borders between blocks from mutating; and

performing modulation on the original image data based on the luminance adjustment calibration value of each block to obtain a modulated image data of each block so as to perform individual luminance modulation on each block;

wherein Sobel operator is used for edge detection to obtain the edge information amount of each block;

wherein the edge information amount of each block is obtained as follows:

calculating an X-direction grayscale value G x and a Y-direction grayscale G Y of each pixel in a block:

G X =Sobel X ×f ( a,b );

G Y =Sobel Y ×f ( a,b );

wherein f(a,b) is the luminance value of the original image data corresponding to the pixel with X-direction coordinate a and Y-direction coordinate b in the block, Sobel X is an X-direction Sobel operator and Sobel Y is a Y-direction Soble operator;

calculating a gradient G of each pixel in the block:

G =√{square root over ( G X 2 +G Y 2 )};

comparing the gradient G of each pixel in the block with a default threshold; if the gradient G of a pixel being greater than the default threshold, determining the pixel as an edge point; and

summing the number of the pixels determined as edge points in the block as the edge information amount of the block; and

wherein the luminance adjustment coefficient of each block is calculated as follows:

presetting a target luminance for grayscale 255 at different luminance representative value APL so that the target luminance decreasing as the grayscale corresponding to the luminance representative value increasing, calculating a normal luminance adjustment coefficient K APL of each block as follows:

K APL =target luminance/luminance before adjustment;

presetting a relation between the edge information amount and an edge luminance adjustment coefficient K edge , so that the edge luminance adjustment coefficient K edge decreasing as the edge information amount increasing, looking for the corresponding edge luminance adjustment coefficient K edge based on the edge information amount of each block; and

calculating the luminance adjustment coefficient K as follows:

K=K APL ×K edge .

2. The luminance adjustment method as claimed in claim 1 , wherein the luminance representative value of each block is obtained as follows:

obtaining a luminance feature value TBP of each pixel in a block; and

calculating an average of the luminance feature values TBP of all the pixels in the block as the luminance representative value (average picture level, APL) of the block.

3. The luminance adjustment method as claimed in claim 2 , wherein the luminance feature value TBP of each pixel in the block is obtained as follows:

extracting a maximum luminance value corresponding to the red original image data, green original image data, and blue original image data of a pixel as the luminance feature value TBP, which is:

TBP =Max( R,G,B ).

4. The luminance adjustment method as claimed in claim 2 , wherein the luminance feature value TBP of each pixel in the block is obtained as follows:

translating the red original image data, green original image data, and blue original image data of a pixel to YCbCr color space, and then calculating the luminance feature value TBP with the following:

TBP= 0.299 R+ 0.587 G+ 0.114 B.

5. The luminance adjustment method as claimed in claim 1 , wherein each block comprises 3×3 pixels, the X-direction Sobel operator Sobel X and Y-direction Soble operator Sobel Y are respectively as:

Sobel

X

=

[

-

1

0

+

1

-

2

0

+

2

-

1

0

+

1

]

Sobel

Y

=

[

+

1

+

2

+

1

0

0

0

-

1

-

2

-

1

]

.

6. The luminance adjustment method as claimed in claim 1 , wherein calibration of the luminance adjustment coefficient of each block is performed as follows:

selecting a block, calculating a horizontal gain K H of an X-direction adjacent block, and a vertical gain K V of a Y-direction adjacent block for the selected block as follows:

K H =K 1 +( K 2 −K 1 )× x/X;

K V =K 1 +( K 3 −K 1 )× y/Y;

wherein K 1 is the luminance adjustment coefficient of the selected block, K 2 is the luminance adjustment coefficient of X-direction adjacent block of the selected block, K 3 is the luminance adjustment coefficient of Y-direction adjacent block of the selected block, x and y are X-direction and Y-direction coordinates of each pixel with respect to a center pixel of the selected block, X is the horizontal distance between the center pixel of the selected block and the center pixel of the X-direction adjacent block, and Y is the vertical distance between the center pixel of the selected block and the center pixel of the Y-direction adjacent block;

then, calculating the luminance adjustment calibration value K′ of each pixel in the selected block as follows:

K ′=( K H +K V )/2.

7. The luminance adjustment method as claimed in claim 6 , wherein the modulated image data of each block is obtained as follows:

the modulated image data of a block=the luminance adjustment calibration value K′ of each pixel in the block×the original image data of the corresponding pixel in the block, wherein:

R′=K′×R;

G′=K′×G;

B′=K′×B;

wherein R′, G′, and B′ are modulated red image data, modulated green image data, and modulated blue image data respectively.

8. A luminance adjustment method, comprising:

receiving original image data and dividing image into M×N blocks in X-direction and Y-direction; wherein M and N are both positive integers; each block comprising a plurality of pixels arranged in an array, the original image data of each pixel comprising: red original image data, green original image data, and blue original image data;

obtaining a luminance representative value for each block;

analyzing the original image data of each block to obtain an edge information amount of each block;

calculating a luminance adjustment coefficient of each block based on the luminance representative value and the edge information amount of each block;

performing calibration of the luminance adjustment coefficient of each block to obtain a luminance adjustment calibration value of each block so as to performing smooth processing on each pixel in each block to prevent luminance at borders between blocks from mutating; and

performing modulation on the original image data based on the luminance adjustment calibration value of each block to obtain a modulated image data of each block so as to perform individual luminance modulation on each block;

wherein the luminance representative value of each block is obtained as follows:

obtaining a luminance feature value TBP of each pixel in a block; and

calculating an average of the luminance feature values TBP of all the pixels in the block as the luminance representative value (average picture level, APL) of the block;

wherein Sobel operator is used for edge detection to obtain the edge information amount of each block;

wherein the edge information amount of each block is obtained as follows:

calculating an X-direction grayscale value G x and a Y-direction grayscale G Y of each pixel in a block:

G X =Sobel X ×f ( a,b );

G Y =Sobel Y ×f ( a,b );

wherein f(a,b) is the luminance value of the original image data corresponding to the pixel with X-direction coordinate a and Y-direction coordinate b in the block, Sobel X is an X-direction Sobel operator and Sobel Y is a Y-direction Soble operator;

calculating a gradient G of each pixel in the block:

G =√{square root over ( G X 2 +G Y 2 )};

comparing the gradient G of each pixel in the block with a default threshold; if the gradient G of a pixel being greater than the default threshold, determining the pixel as an edge point; and

summing the number of the pixels determined as edge points in the block as the edge information amount of the block;

wherein each block comprises 3×3 pixels, the X-direction Sobel operator Sobel X and Y-direction Soble operator Sobel Y are respectively as:

Sobel

X

=

[

-

1

0

+

1

-

2

0

+

2

-

1

0

+

1

]

Sobel

Y

=

[

+

1

+

2

+

1

0

0

0

-

1

-

2

-

1

]

wherein the luminance adjustment coefficient of each block is calculated as follows:

presetting a target luminance for grayscale 255 at different luminance representative value APL so that the target luminance decreasing as the grayscale corresponding to the luminance representative value increasing, calculating a normal luminance adjustment coefficient K APL of each block as follows:

K APL =target luminance/luminance before adjustment;

presetting a relation between the edge information amount and an edge luminance adjustment coefficient K edge , so that the edge luminance adjustment coefficient K edge decreasing as the edge information amount increasing, looking for the corresponding edge luminance adjustment coefficient K edge based on the edge information amount of each block;

calculating the luminance adjustment coefficient K as follows:

K=K APL ×K edge .

9. The luminance adjustment method as claimed in claim 8 , wherein the luminance feature value TBP of each pixel in the block is obtained as follows:

extracting a maximum luminance value corresponding to the red original image data, green original image data, and blue original image data of a pixel as the luminance feature value TBP, which is:

TBP =Max( R,G,B ).

10. The luminance adjustment method as claimed in claim 8 , wherein the luminance feature value TBP of each pixel in the block is obtained as follows:

translating the red original image data, green original image data, and blue original image data of a pixel to YCbCr color space, and then calculating the luminance feature value TBP with the following:

TBP= 0.299 R+ 0.587 G+ 0.114 B.

11. The luminance adjustment system as claimed in claim 8 , wherein calibration of the luminance adjustment coefficient of each block is performed as follows:

selecting a block, calculating a horizontal gain K H of an X-direction adjacent block, and a vertical gain K V of a Y-direction adjacent block for the selected block as follows:

K H =K 1 +( K 2 −K 1 )× x/X;

K V =K 1 +( K 3 −K 1 )× y/Y;

wherein K 1 is the luminance adjustment coefficient of the selected block, K 2 is the luminance adjustment coefficient of X-direction adjacent block of the selected block, K 3 is the luminance adjustment coefficient of Y-direction adjacent block of the selected block, x and y are X-direction and Y-direction coordinates of each pixel with respect to a center pixel of the selected block, X is the horizontal distance between the center pixel of the selected block and the center pixel of the X-direction adjacent block, and Y is the vertical distance between the center pixel of the selected block and the center pixel of the Y-direction adjacent block;

then, calculating the luminance adjustment calibration value K′ of each pixel in the selected block as follows:

K ′=( K H +K V )/2.

12. The luminance adjustment method as claimed in claim 11 , wherein the modulated image data of each block is obtained as follows:

the modulated image data of a block=the luminance adjustment calibration value K′ of each pixel in the block×the original image data of the corresponding pixel in the block, wherein:

R′=K′×R;

G′=K′×G;

B′=K′×B;

wherein R′, G′, and B′ are modulated red image data, modulated green image data, and modulated blue image data respectively.