Megah,
I'd also recommend that you use the MATLAB minus operator instead of imsubtract to perform elementwise subtraction on two images:
image3 = im2double(image1) - im2double(image2)
The imadd and imsubtract functions are old and predate support for integer math in base MATLAB.
The MATLAB math operators are better maintained and in general will exhibit better performance:
>> a = rand(4000,4000); >> b = rand(4000,4000);
>> tic; for i = 1:100; imsubtract(a,b); end; toc
Elapsed time is 17.827151 seconds.
>> tic; for i = 1:100; a-b; end; toc
Elapsed time is 8.206314 seconds.
- Alex.
