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- % RES = ZCONV2(MTX1, MTX2, CTR)
- %
- % Convolution of two matrices, with boundaries handled as if the larger mtx
- % lies in a sea of zeros. Result will be of size of LARGER vector.
- %
- % The origin of the smaller matrix is assumed to be its center.
- % For even dimensions, the origin is determined by the CTR (optional)
- % argument:
- % CTR origin
- % 0 DIM/2 (default)
- % 1 (DIM/2)+1 (behaves like conv2(mtx1,mtx2,'same'))
- % Eero Simoncelli, 2/97.
- function c = zconv2(a,b,ctr)
- if (exist('ctr') ~= 1)
- ctr = 0;
- end
- if (( size(a,1) >= size(b,1) ) & ( size(a,2) >= size(b,2) ))
- large = a; small = b;
- elseif (( size(a,1) <= size(b,1) ) & ( size(a,2) <= size(b,2) ))
- large = b; small = a;
- else
- error('one arg must be larger than the other in both dimensions!');
- end
- ly = size(large,1);
- lx = size(large,2);
- sy = size(small,1);
- sx = size(small,2);
- %% These values are the index of the small mtx that falls on the
- %% border pixel of the large matrix when computing the first
- %% convolution response sample:
- sy2 = floor((sy+ctr+1)/2);
- sx2 = floor((sx+ctr+1)/2);
- clarge = conv2(large,small);
- c = clarge(sy2:ly+sy2-1, sx2:lx+sx2-1);
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