colorhist提取颜色直方图

function colorhist = colorhist(rgb) % CBIR_colorhist() --- color histogram calculation % input: MxNx3 image data, in RGB % output: 1x256 colorhistogram <== (HxSxV = 16x4x4) % as the MPEG-7 generic color histogram descriptor % [Ref] Manjunath, B.S.; Ohm, J.-R.; Vasudevan, V.V.; Yamada, A., "Color and texture descriptors" % IEEE Trans. CSVT, Volume: 11 Issue: 6 , Page(s): 703 -715, June 2001 (section III.B) % check input if size(rgb,3)~=3 error('3 components is needed for histogram'); end % globals H_BITS = 4; S_BITS = 2; V_BITS = 2; % convert to hsv为什么要用hsv hsv = uint8(255*rgb2hsv(rgb)); imgsize = size(hsv); % get rid of irrelevant boundaries i0=round(0.05*imgsize(1)); i1=round(0.95*imgsize(1)); j0=round(0.05*imgsize(2)); j1=round(0.95*imgsize(2)); hsv = hsv(i0:i1, j0:j1, :); % histogram for i = 1 : 2^H_BITS for j = 1 : 2^S_BITS for k = 1 : 2^V_BITS colorhist(i,j,k) = sum(sum( ... bitshift(hsv(:,:,1),-(8-H_BITS))==i-1 &... bitshift(hsv(:,:,2),-(8-S_BITS))==j-1 &... bitshift(hsv(:,:,3),-(8-V_BITS))==k-1 )); end end end colorhist = reshape(colorhist, 1, 2^(H_BITS+S_BITS+V_BITS)); % normalize colorhist = colorhist/sum(colorhist);