Don't use image for a variable name since it's the name of a very important built in function. That could be one reason why it doesn't work (but it's not). The reason it doesn't work is that A is a double matrix and all the values are > 1. If imshow() gets a double matrix, it expects it (rightly or wrongly) to be in the range 0-1. To fix, add [] after the (badly-named) A in imshow(). Call A "sumImage" to be more descriptive. To fix:
fullFileName = fullfile(folder, S(i).name, Foty(j).name);
thisImage = double(imread(fullFileName));
[rows, columns, numberOfColorChannels] = size(thisImage);
if numberOfColorChannels > 1 % Only call rgb2gray if it's really RGB, otherwise you'll get an error.
thisImage = rgb2gray(image);
end
if rows == size(sumImage, 1) && columns == size(sumImage, 2)
sumImage = sumImage + thisImage*alpha;
else
message = 'Size mismatch';
uiwait(errordlg(message));
end
After the loop, use
imshow(sumImage, []);
