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R6289/code/computeColor.m
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computeColor.m
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function img = computeColor(u,v)
% computeColor color codes flow field U, V
% According to the c++ source code of Daniel Scharstein
% Contact: schar@middlebury.edu
% Author: Deqing Sun, Department of Computer Science, Brown University
% Contact: dqsun@cs.brown.edu
% $Date: 2007-10-31 21:20:30 (Wed, 31 Oct 2006) $
% Copyright 2007-2010, Brown University, Providence, RI. USA
%
%
% All Rights Reserved
%
% Permission to use, copy, modify, and distribute this software and its
% documentation for any purpose other than its incorporation into a
% commercial product is hereby granted without fee, provided that the
% above copyright notice appear in all copies and that both that
% copyright notice and this permission notice appear in supporting
% documentation, and that the name of the author and Brown University not be used in
% advertising or publicity pertaining to distribution of the software
% without specific, written prior permission.
%
% THE AUTHOR AND BROWN UNIVERSITY DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
% INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR ANY
% PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR OR BROWN UNIVERSITY BE LIABLE FOR
% ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
nanIdx = isnan(u) | isnan(v);
u(nanIdx) = 0;
v(nanIdx) = 0;
colorwheel = makeColorwheel;
ncols = size(colorwheel, 1);
rad = sqrt(u.^2+v.^2);
a = atan2(-v, -u)/pi;
fk = (a+1) /2 * (ncols-1) + 1; % -1~1 maped to 1~ncols
k0 = floor(fk); % 1, 2, ..., ncols
k1 = k0+1;
k1(k1==ncols+1) = 1;
f = fk - k0;
for i = 1:size(colorwheel,2)
tmp = colorwheel(:,i);
col0 = tmp(k0)/255;
col1 = tmp(k1)/255;
col = (1-f).*col0 + f.*col1;
idx = rad <= 1;
col(idx) = 1-rad(idx).*(1-col(idx)); % increase saturation with radius
col(~idx) = col(~idx)*0.75; % out of range
img(:,:, i) = uint8(floor(255*col.*(1-nanIdx)));
end;
%%
function colorwheel = makeColorwheel()
% color encoding scheme
% adapted from the color circle idea described at
% http://members.shaw.ca/quadibloc/other/colint.htm
RY = 15;
YG = 6;
GC = 4;
CB = 11;
BM = 13;
MR = 6;
ncols = RY + YG + GC + CB + BM + MR;
colorwheel = zeros(ncols, 3); % r g b
col = 0;
%RY
colorwheel(1:RY, 1) = 255;
colorwheel(1:RY, 2) = floor(255*(0:RY-1)/RY)';
col = col+RY;
%YG
colorwheel(col+(1:YG), 1) = 255 - floor(255*(0:YG-1)/YG)';
colorwheel(col+(1:YG), 2) = 255;
col = col+YG;
%GC
colorwheel(col+(1:GC), 2) = 255;
colorwheel(col+(1:GC), 3) = floor(255*(0:GC-1)/GC)';
col = col+GC;
%CB
colorwheel(col+(1:CB), 2) = 255 - floor(255*(0:CB-1)/CB)';
colorwheel(col+(1:CB), 3) = 255;
col = col+CB;
%BM
colorwheel(col+(1:BM), 3) = 255;
colorwheel(col+(1:BM), 1) = floor(255*(0:BM-1)/BM)';
col = col+BM;
%MR
colorwheel(col+(1:MR), 3) = 255 - floor(255*(0:MR-1)/MR)';
colorwheel(col+(1:MR), 1) = 255;
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