I have a 65 x 65 image that i want to down-size to 13 x 13. I am using the command B=resize(A, [13 13]). I expected the pixels in the output image B to be the average of the 5 x 5 windows but they were not. Exactly how does down-sizing work?
Did you look in the documentation for imresize()? That's always a good place to start. You'll see under method that there are bilinear (default), bicubic, and nearest. I think those are rather self explanatory, if not, there's always Wikipedia. And there are further options on the interpolation kernel.