frcs-colour-transfer

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%
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%   colour transfer algorithm based on N-Dimensional PDF Transfer 
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%
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%   IR = colour_transfer_IDT(I_original, I_target, nb_iterations);
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%
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%  (c) F. Pitie 2007
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%
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%  see reference:
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%     Automated colour grading using colour distribution transfer. (2007) 
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%     Computer Vision and Image Understanding.
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%
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%  To remove the "grainyness" on the results, you should apply the grain 
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%  reducer proposed in the paper and implemented in regrain.m:
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%
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%  IRR = regrain(I_original, IR);
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%
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function IR = colour_transfer_IDT(I0, I1, nb_iterations)
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if (ndims(I0)~=3)
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    error('pictures must have 3 dimensions');
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end
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nb_channels = size(I0,3);
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%% reshape images as 3xN matrices
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for i=1:nb_channels
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    D0(i,:) = reshape(I0(:,:,i), 1, size(I0,1)*size(I0,2));
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    D1(i,:) = reshape(I1(:,:,i), 1, size(I1,1)*size(I1,2));
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end
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%% building a sequence of (almost) random projections
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% 
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R{1} = [1 0 0; 0 1 0; 0 0 1; 2/3 2/3 -1/3; 2/3 -1/3 2/3; -1/3 2/3 2/3];
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for i=2:nb_iterations
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      R{i} = R{1} * orth(randn(3,3));
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end
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%for i=2:nb_iterations, R{i} = R{1}; end
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%% pdf transfer
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DR = pdf_transfer(D0, D1, R, 1);
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%% reshape the resulting 3xN matrix as an image
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IR = I0;
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for i=1:nb_channels
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    IR(:,:,i) = reshape(DR(i,:), size(IR, 1), size(IR, 2));
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end
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