www.pudn.com > ms_segmenter.rar > Rgb_to_luv.m

function Luv_back = Rgb_to_luv (Im_rgb, Type) 
% takes an image in Rgb coords and returns either a vector or an image 
% in Luv coords, depending on Type (Image or vector). 
 
Vector = shiftdim(Im_rgb, 2); 
Vector = double(reshape(Vector, [3, size(Im_rgb, 1)*size(Im_rgb, 2)])); 
Vector_nz = 4096*(sum(Vector, 1) > 0); 
Vector_z = not(Vector_nz); 
Vector = max(Vector, [Vector_z; Vector_z; Vector_z]);	% to avoid all zero pixels 
 
Matrix = [... 
      0.490 0.310 0.200; ... 
      0.177 0.812 0.011; ... 
      0.000 0.010 0.990]; 
 
XYZ = Matrix*Vector;		% now get a vector in XYZ coords 
 
Y0 = 1;		% is it true? 
X0 = 1; 
Z0 = 1; 
 
u0 = 4*X0/(X0+15*Y0+3*Z0); 
v0 = 9*Y0/(X0+15*Y0+3*Z0); 
 
Luv_back = zeros(size(Vector)); 
Luv_back(1, :) = 25*(100*XYZ(2, :)/Y0).^(0.333)-16; 
Zeros = zeros(size(Luv_back(1, :))); 
Luv_back(1, :) = max(Luv_back(1, :), Zeros); 
u = 4*XYZ(1, :) ./ (XYZ(1, :)+15*XYZ(2, :)+3*XYZ(3, :)); 
v = 9*XYZ(2, :) ./ (XYZ(1, :)+15*XYZ(2, :)+3*XYZ(3, :)); 
Luv_back(2, :) = 13*Luv_back(1, :).*(u-u0); 
Luv_back(2, :) = max(Luv_back(2, :), Zeros); 
Luv_back(3, :) = 13*Luv_back(1, :).*(v-v0); 
Luv_back(3, :) = max(Luv_back(3, :), Zeros); 
Luv_back = min(Luv_back, [Vector_nz; Vector_nz; Vector_nz]);	% zeroing out 
Luv_back = Luv_back/(718.3176/256); 
if strcmp(Type, 'Image') 
   Luv_back = reshape(Luv_back, [3, size(Im_rgb, 1), size(Im_rgb, 2)]); 
   Luv_back = shiftdim(Luv_back, 1); 
end