Can someone tell me how to find the summation of all the pixel values in an image?

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Sneheet 2014-1-22

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评论： Walter Roberson 2014-1-26

I'm trying to implement a Sum Average Difference (SAD) based code to find the difference between consecutive frames in a video to eliminate those frames which do not contain activity i.e. no motion.

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Bruno Pop-Stefanov 2014-1-22

Do you mean the sum of absolute differences?

Sneheet 2014-1-26

yes, the absolute values of pixel differences.

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Answer 1

Bruno Pop-Stefanov 2014-1-22

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编辑：Bruno Pop-Stefanov 2014-1-22

在 MATLAB Online 中打开

Assuming the frames you want to compare are called img_prev and img_next, both matrices of the same size, the following function computes what you want:

function out = sad(img_prev, img_next)
% First, take the absolute value of the difference at each pixel
myAbsDiff = abs(img_prev - img_next);
% Then, sum over all pixels
out = sum(myAbsDiff(:));
end

Using (:) you can transform matrix myAbsDiff into a vector. Calling sum on a vector computes the sum of all elements in a vector.

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Image Analyst 2014-1-26

编辑：Image Analyst 2014-1-26

在 MATLAB Online 中打开

No, as you can see he just defined it right there above. However, with uint8 images, it will need to be modified to allow negative numbers by casting the numbers to double.

function out = sad(img_prev, img_next)
% First, take the absolute value of the difference at each pixel
myAbsDiff = abs(double(img_prev) - double(img_next));
% Then, sum over all pixels
out = sum(myAbsDiff(:));
end