You need two loops. One to read in all the images and see what sizes they are and to store the size of the smallest. Then another one where you read them all in and resize them according to the smallest, and sum them. Something like this (untested):
smallestRows = inf;
smallestColumns = inf;
for i = 1:nargin
thisImage = imread(varargin{i});
[rows, columns, numberOfColorChannels] = size(thisImage);
if rows < smallestRows
smallestRows = rows;
end
if columns< smallestColumns
smallestColumns= columns;
end
end
theSum = zeros(smallestRows, smallestColumns, numberOfColorChannels);
for i = 1:nargin
thisImage = imread(varargin{i});
theSum = theSum + double(imresize(thisImage, [smallestRows, smallestColumns]));
end
imshow(theSum, []);
To make it more robust, check to make sure that all images have the same number of color channels, and if they don't convert the gray scale images to color before summing.
