CN101764914B - Method of alpha channel boundary corrosion - Google Patents
Method of alpha channel boundary corrosion Download PDFInfo
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- CN101764914B CN101764914B CN2008102394360A CN200810239436A CN101764914B CN 101764914 B CN101764914 B CN 101764914B CN 2008102394360 A CN2008102394360 A CN 2008102394360A CN 200810239436 A CN200810239436 A CN 200810239436A CN 101764914 B CN101764914 B CN 101764914B
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- 238000000034 method Methods 0.000 title claims abstract description 29
- 238000005260 corrosion Methods 0.000 title claims abstract description 16
- 230000007797 corrosion Effects 0.000 title claims abstract description 16
- 235000013399 edible fruits Nutrition 0.000 claims description 12
- 230000000694 effects Effects 0.000 abstract description 8
- 239000011159 matrix material Substances 0.000 description 2
- 230000002950 deficient Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000006748 scratching Methods 0.000 description 1
- 230000002393 scratching effect Effects 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
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Abstract
The present invention relates to a method of alpha channel boundary corrosion, which belongs to the technical field of image and video processing. In the existing method, box blur and Gaussian blur both can soften a boundary, but the whole boundary can be blurred, and the position on an original boundary with small alpha value place can become big now. In the method of alpha channel boundary corrosion, all the pixels in original alpha channel images are described pixels in the boundary and out the boundary by a threshold, and then, different coefficient matrixes are used for the multiplicative summation of pixels in neighborhoods aiming to different categories. By using the method of alpha channel boundary corrosion, ideal alpha channel corrosion effect can be realized; and the method is simple, and is easy to optimize.
Description
Technical field
The invention belongs to image and technical field of video processing, be specifically related to the method for a kind of Alpha (alpha) channel boundary corrosion.
Background technology
In the image/video treatment technology, it is a kind of that often run into and use demand very widely that a certain class color in the image/video is scratched.The given a kind of color of the essence of these class methods (also may add other parameter) all calculates a key assignments to each pixel in the image, the neutralize key assignments of the identical or approaching color pixel of this color of image is zero or smaller, and it is bigger or be 1 that color differs the key assignments of bigger pixel.This key assignments just can be used as this image and the background image alpha passage when synthesizing so, thereby reaches the purpose of scratching picture.
The key image (back is referred to as the alpha channel image) that is drawn by the key method often has more sharp-pointed border, and this border just is made of the very big alpha value of contrast, and very big such as the pixel alpha value of the inside, border, the alpha value of outside is very little.When this alpha channel image of image applications and background image were synthesized, prospect and background also can be bigger in the boundary contrast of alpha passage.But sometimes people wish boundary contrast not so not greatly or so sharp-pointed, this just requires the boundary of alpha passage is carried out the processing of softening.
Box in the existing method fuzzy (box blur) can reach the effect that makes the border softening with Gaussian Blur (gaussian blur).But they all have a problem, be exactly that their are whole border can be thickened unclear, and the very little place of original borderline alpha value can become now very big (this place that just makes the prospect of composograph to occur also appears at final composograph and suffered).And people's demand is: after the softening of border, the border is still more high-visible, but inside, border (place that the alpha value is very big) carries out softening (also can be described as corrosion) to the inside; External boundary (place that the alpha value is very little) is to outside softening, and the alpha value has a certain upgrade, but can not excessive (also can be described as a kind of corrosion to external boundary).
Summary of the invention
At the defective that exists in the prior art, the purpose of this invention is to provide a kind of method of alpha channel boundary corrosion.This method can realize more satisfactory alpha passage corrosive effect, and this method is fairly simple, is very easy to optimize.
For reaching above purpose, the technical solution used in the present invention is: a kind of method of alpha channel boundary corrosion comprises the steps:
(1) at first the alpha value that is in the original alpha channel image between (0,255) is reduced;
(2) try to achieve greater than threshold value weighted sum coefficient;
Calculating is as follows greater than the formula of the weighted sum coefficient of threshold value:
(x y) is not equal to central point (x as fruit dot
0, y
0), then
(x y) equals central point (x as fruit dot
0, y
0), then
Factor (x
0Y
0)=1-∑ (factor (x, y) | x
0-width≤x≤x
0+ width, y
0-width≤y≤y
0+ width, and (x, y) ≠ (x
0, y
0))
In the above-mentioned formula, the span of width is [0,30], and unit is a pixel; X be point (x, abscissa y), y be point (x, ordinate y), e are natural logrithms, σ=3width;
(3) try to achieve less than threshold value weighted sum coefficient;
Calculating is as follows less than the formula of threshold value weighted sum coefficient:
(x y) is not equal to central point (x as fruit dot
0, y
0), then
(x y) equals central point (x as fruit dot
0, y
0), then
(4) each pixel is divided greater than threshold value and is weighted summation less than two kinds of situations of threshold value obtain final result.
Further, in the step (1), will be in the formula that the alpha value between (0,255) all dwindles and be: (alpha/255)
1.6* 255.
Further, in step (2) and the step (3), the span of described threshold value is [max/2-30, max/2+30], and wherein, max is a maximum gradation value.
Further, described threshold value is max/2, and wherein max is a maximum gradation value.
Further, step (4) is achieved in that
1) all pixels in the original alpha channel image are carried out neighborhood territory pixel and the processing of multiplying each other and suing for peace greater than pairing that weighted sum coefficient of threshold value, the result puts into an intermediate images I1;
2) all pixels in the original alpha channel image are carried out neighborhood territory pixel and the processing of multiplying each other and suing for peace less than pairing that weighted sum coefficient of threshold value, the result puts into an intermediate images I2;
3) all pixels of alpha channel image are carried out following processing: if the pixel value of original alpha channel image greater than threshold value, then the respective pixel values among the intermediate images I1 is put into target image; If the pixel value of original alpha channel image is less than threshold value, then the respective pixel values among the intermediate images I2 is put into target image.
Effect of the present invention is: adopt method of the present invention, can realize more satisfactory alpha passage corrosive effect, and this method is fairly simple, be very easy to optimize.Therefore, this method is specially adapted in the special effect processing and synthetic technology of high quality and high efficiency video and image.
Description of drawings
Fig. 1 is the flow chart of step in the specific embodiment of the invention (4);
Fig. 2 is original input picture;
Fig. 3 is the schematic diagram that adopts after the method for the invention is handled input picture.
Embodiment
Below in conjunction with the drawings and specific embodiments the present invention is further described.
Method of the present invention is that all pixels of alpha passage are divided in the border and the border exterior pixel by certain threshold value, uses different coefficient matrixes to the multiply each other process of summation of the pixel in its neighborhood at their different classifications then.
A kind of method of alpha channel boundary corrosion comprises the steps:
(1) at first the alpha value that is in the original alpha channel image between (0,255) is reduced;
In the present embodiment, the alpha passage is 8bit, and wherein 0 and 255 still keep initial value, will be in [0,255) between the alpha value all dwindle, dwindle formula and be: (alpha/255)
1.6* 255;
(1) tries to achieve greater than threshold value weighted sum coefficient;
The span of described threshold value is [max/2-30, max/2+30], and for the 8bit image, the span of threshold value is 98-158, but preferably maximum gradation value half promptly 128, in the present embodiment, threshold value is 128.For the image of other bit wide, be in half adjacent threshold of maximum gradation value, to get threshold value in principle, but from experimental result, it is best to get peaked half effect of gray value.
Calculating is as follows greater than the formula of the weighted sum coefficient of threshold value:
(x y) is not equal to central point (x as fruit dot
0, y
0), then
(x y) equals central point (x as fruit dot
0, y
0), then
Factor (x
0Y
0)=1-∑ (factor (x, y) | x
0-width≤x≤x
0+ width, y
0-width≤y≤y
0+ width, and (x, y) ≠ (x
0, y
0))
In the above-mentioned formula, the span of width is [0,30], and unit is a pixel; X be point (x, abscissa y), y be point (x, ordinate y), e are natural logrithms, σ=3width;
(3) try to achieve less than threshold value weighted sum coefficient;
Calculating is as follows less than the formula of threshold value weighted sum coefficient:
(x y) is not equal to central point (x as fruit dot
0, y
0), then
(x y) equals central point (x as fruit dot
0, y
0), then
In the above-mentioned formula, the span of width is [0,30], and unit is a pixel.Parameter width has determined the degree of softening, and the big more then softening degree of parameter width value is more dark, and promptly boundary corrosion must be dark more.In the present embodiment, the width value is 30.
(4) each pixel divided greater than threshold value and is weighted summation less than two kinds of situations of threshold value obtain final result, concrete steps as shown in Figure 1:
1) all pixels in the original alpha channel image are carried out neighborhood territory pixel and the processing of multiplying each other and suing for peace greater than pairing that matrix coefficient of threshold value (promptly greater than threshold value weighted sum coefficient), the result puts into an intermediate images I1;
2) all pixels in the original alpha channel image are carried out neighborhood territory pixel and the processing of multiplying each other and suing for peace less than pairing that matrix coefficient of threshold value (promptly less than threshold value weighted sum coefficient), the result puts into an intermediate images I2;
3) all pixels of alpha channel image are carried out following processing: if the pixel value of original alpha channel image greater than threshold value, then the respective pixel values among the intermediate images I1 is put into target image; If the pixel value of original alpha channel image is less than threshold value, then the respective pixel values among the intermediate images I2 is put into target image.
As shown in Figures 2 and 3, Fig. 2 is original alpha channel image, and Fig. 3 is the image that adopts after method of the present invention is handled.By the foregoing description as can be seen, adopt method proposed by the invention can realize more satisfactory alpha passage corrosive effect, and this method is fairly simple, is very easy to optimize.
Method and system of the present invention is not limited to the embodiment described in the embodiment, and those skilled in the art's technical scheme according to the present invention draws other execution mode, belongs to technological innovation scope of the present invention equally.
Claims (3)
1. the method for an alpha channel boundary corrosion comprises the steps:
(1) at first the alpha value that is in the original alpha channel image between (0,255) is reduced, will be in the formula that the alpha value between (0,255) all dwindles and be: (alpha/255)
1.6* 255;
(2) try to achieve greater than threshold value weighted sum coefficient;
Calculating is as follows greater than the formula of the weighted sum coefficient of threshold value:
(x y) is not equal to central point (x as fruit dot
0, y
0), then
(x y) equals central point (x as fruit dot
0, y
0), then
Factor (x
0Y
0)=1-∑ (factor (x, y) | x
0-width≤x≤x
0+ width, y
0-width≤y≤y
0+ width, and (x, y) ≠ (x
0, y
0))
In the above-mentioned formula, the span of width is [0,30], and unit is a pixel; X be point (x, abscissa y), y be point (x, ordinate y), e are natural logrithms, σ=3width;
(3) try to achieve less than threshold value weighted sum coefficient;
Calculating is as follows less than the formula of the weighted sum coefficient of threshold value:
(x y) is not equal to central point (x as fruit dot
0, y
0), then
(x y) equals central point (x as fruit dot
0, y
0), then
(4) each pixel is divided greater than threshold value and is weighted summation less than two kinds of situations of threshold value obtain final result, its concrete grammar is:
1) all pixels in the original alpha channel image are carried out neighborhood territory pixel and the processing of multiplying each other and suing for peace greater than pairing that weighted sum coefficient of threshold value, the result puts into an intermediate images I1;
2) all pixels in the original alpha channel image are carried out neighborhood territory pixel and the processing of multiplying each other and suing for peace less than pairing that weighted sum coefficient of threshold value, the result puts into an intermediate images I2;
3) all pixels of alpha channel image are carried out following processing: if the pixel value of original alpha channel image greater than threshold value, then the respective pixel values among the intermediate images I1 is put into target image; If the pixel value of original alpha channel image is less than threshold value, then the respective pixel values among the intermediate images I2 is put into target image.
2. the method for a kind of alpha channel boundary corrosion as claimed in claim 1 is characterized in that: in step (2) and the step (3), the span of described threshold value is [max/2-30, max/2+30], and wherein, max is a maximum gradation value.
3. the method for a kind of alpha channel boundary corrosion as claimed in claim 3 is characterized in that: described threshold value is max/2, and wherein max is a maximum gradation value.
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| CN2008102394360A CN101764914B (en) | 2008-12-10 | 2008-12-10 | Method of alpha channel boundary corrosion |
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| CN105678724A (en) * | 2015-12-29 | 2016-06-15 | 北京奇艺世纪科技有限公司 | Background replacing method and apparatus for images |
| CN107230182B (en) * | 2017-08-03 | 2021-11-09 | 腾讯科技（深圳）有限公司 | Image processing method and device and storage medium |
| CN108198128B (en) * | 2017-12-12 | 2021-12-03 | 北京美摄网络科技有限公司 | Method and device for alpha channel boundary corrosion |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1716311A (en) * | 2004-06-28 | 2006-01-04 | 微软公司 | System and process for generating a two-layer, 3D representation of a scene |
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|---|---|---|---|---|
| CN1716311A (en) * | 2004-06-28 | 2006-01-04 | 微软公司 | System and process for generating a two-layer, 3D representation of a scene |
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