wolffd@0: function [overlap, normoverlap] = rectintSparse(A,B)
wolffd@0: %
wolffd@0: % A(i,:) = [x y w h]
wolffd@0: % B(j,:) = [x y w h]
wolffd@0: % overlap(i,j) = area of intersection
wolffd@0: % normoverla(i,j)
wolffd@0: %
wolffd@0: % Same as built-in rectint, but uses less memory.
wolffd@0: % Use rectintSparseC for a faster version.
wolffd@0: %
wolffd@0: 
wolffd@0: leftA = A(:,1);
wolffd@0: bottomA = A(:,2);
wolffd@0: rightA = leftA + A(:,3);
wolffd@0: topA = bottomA + A(:,4);
wolffd@0: 
wolffd@0: leftB = B(:,1)';
wolffd@0: bottomB = B(:,2)';
wolffd@0: rightB = leftB + B(:,3)';
wolffd@0: topB = bottomB + B(:,4)';
wolffd@0: 
wolffd@0: numRectA = size(A,1);
wolffd@0: numRectB = size(B,1);
wolffd@0: 
wolffd@0: %out = rectintSparseLoopC(leftA, rightA, topA, bottomA, leftB, rightB, topB, bottomB);
wolffd@0: 
wolffd@0: nnz = ceil(0.2*numRectA*numRectB); % guess of number of non-zeroes
wolffd@0: overlap = sparse([], [], [], numRectA, numRectB, nnz);
wolffd@0: normoverlap = sparse([], [], [], numRectA, numRectB, nnz);
wolffd@0: for j=1:numRectB
wolffd@0:   for i=1:numRectA
wolffd@0:     tmp = (max(0, min(rightA(i), rightB(j)) - max(leftA(i), leftB(j)) ) ) .* ...
wolffd@0: 	(max(0, min(topA(i), topB(j)) - max(bottomA(i), bottomB(j)) ) );
wolffd@0:     if tmp>0
wolffd@0:       overlap(i,j) = tmp;
wolffd@0:       areaA = (rightA(i)-leftA(i))*(topA(i)-bottomA(i));
wolffd@0:       areaB = (rightB(j)-leftB(j))*(topB(j)-bottomB(j));
wolffd@0:       normoverlap(i,j) = min(tmp/areaA, tmp/areaB);
wolffd@0:     end
wolffd@0:     %fprintf('j=%d, i=%d, overlap=%5.3f, norm=%5.3f\n',...
wolffd@0:     %	    j, i, overlap(i,j), normoverlap(i,j));
wolffd@0:   end
wolffd@0: end
wolffd@0: 
wolffd@0: 
wolffd@0: if 0
wolffd@0: N = size(bboxDense01,2); % 1000;
wolffd@0: rect = bboxToRect(bboxDense01)';
wolffd@0: A = rect(1:2,:);
wolffd@0: B = rect(1:N,:);
wolffd@0: 
wolffd@0: tic; out1 = rectint(A, B); toc
wolffd@0: tic; out2 = rectintSparse(A, B); toc
wolffd@0: tic; out3 = rectintSparseC(A, B); toc
wolffd@0: tic; out4 = rectintC(A, B); toc
wolffd@0: assert(approxeq(out1, out2))
wolffd@0: assert(approxeq(out1, full(out3)))
wolffd@0: assert(approxeq(out1, out4))
wolffd@0: end