function C=erode(A,B) % A eroded by structuring element B
asize=size(A); % set up to find largest size
bsize=size(B);
csize=max(asize',bsize')';
Apad=zeropad(A,csize); %pad both inputs to be same max size
Bpad=zeropad(B,csize);
maxsum=sum(sum(B))-1; % get maximum sum for complete union
C=abs(ifft2(fft2(Apad).*conj(fft2(Bpad)))); % correlate
C=C-maxsum; % drop off 0 values by making them negative
cmax=max(max(abs(C)))*2; % scale values to be less than unity 
if cmax>0
   C=C./cmax;
end;
C=ceil(C); % binarize final image