%也就是说进行Frankle_mccann算法处理彩色图像时，需要对三个颜色通道图像分别进行处理，然后在进行合并
function [ Retinex ] = retinex_frankle_mccann( L, nIterations )
global RR IP OP NP Maximum
RR = L;
Maximum = max(L(:)); % maximum color value in the image
[nrows, ncols] = size(L);
shift = 2^(fix(log2(min(nrows, ncols)))-1); % initial shift
OP = Maximum*ones(nrows, ncols); % initialize Old Product
while (abs(shift) >= 1)
for i = 1:nIterations
CompareWith(0, shift); % horizontal step
CompareWith(shift, 0); % vertical step
end
shift = -shift/2; % update the shift
end
Retinex = NP;
end
function CompareWith(s_row, s_col)
global RR IP OP NP Maximum
IP = OP;
if (s_row + s_col > 0)
IP((s_row+1):end, (s_col+1):end) = OP(1:(end-s_row), 1:(end-s_col)) + ...
RR((s_row+1):end, (s_col+1):end) - RR(1:(end-s_row), 1:(end-s_col));
else
IP(1:(end+s_row), 1:(end+s_col)) = OP((1-s_row):end, (1-s_col):end) + ...
RR(1:(end+s_row),1:(end+s_col)) - RR((1-s_row):end, (1-s_col):end);
end
IP(IP > Maximum) = Maximum; % The Reset operation
NP = (IP + OP)/2; % average with the previous Old Product
OP = NP; % get ready for the next comparison
end
