Background subtraction in an RGB Image
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how can i do a background subtraction on an RGB image?
![image1.jpg](https://www.mathworks.com/matlabcentral/answers/uploaded_files/140969/image1.jpg)
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Image Analyst
2018-11-13
You can't. At best you could crop it down to the object in the image, giving a rectangular image. Images must remain rectangular and not have some ragged irregular shape.
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Adam
2018-11-14
Well, you can do something like this:
rgb = rand( 5, 5, 3 ); % Random image
rgb( 2, 3, : ) = [0 0 0]; % Turn a pixel black
rgb( 4, 3, : ) = [0 0 0]; % Turn a pixel black
mask = sum( rgb, 3 ) > 0;
figure; h = imagesc( rgb );
h.AlphaData = mask;
Obviously in your case you don't need the first 3 lines, they are just for me to create an example of an image with some black pixels.
Bear in mind though that this will make all black pixels transparent so that you see the colour of the axes underneath, so if you have bona fide black pixels elsewhere within your image this will make them transparent too which is not desirable.
In that case you would have to run some kind of algorithm which would work out the boundary of your desired image to segment out the background, but that is not my area of expertise. The remaining part would be the same though - however you create the background mask, just set its inverse as the AlphaData (Note that my mask above is actually the non-mask because we are setting it as AlphaData where 1 means opaque and 0 means transparent).
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