function out = pyr7( in )

pyrR = [1 1 1 0 -1 -1 -1; 1 2 2 0 -2 -2 -1; 1 2 3 0 -3 -2 -1; 
1 2 3 0 -3 -2 -1; 1 2 3 0 -3 -2 -1; 1 2 2 0 -2 -2 -1; 1 1 1 0 -1 -1 -1];
pyrR = pyrR / 34;
pr = filter2(pyrR,in); 
pc = filter2(pyrR',in);
out = sqrt(pr .* pr + pc .* pc);

