With imnoise, no, because it adds noise to every pixel, so the answer is "every pixel". With some other method, if some pixels remain untouched, you can find the changed pixels as a binary image, which is almost always the most convenient form like this:
binaryImage = originalImage ~= noisyImage;
If, for some reason, you want that in a list of coordinates, you can do that with find, like Azzi showed you
if ndims(binaryImage) == 2
[rows, columns] = find(binaryImage
else
[rows, columns, colorChannels] = find(binaryImage);
end
Though this is usually less convenient. For example if you were doing a modified median filter or something, you'd use the binaryImage only, not the coordinates. What are you going to do when you say you need "the locations" so I can tell you what form of "locations" will work best for you?
