MATLAB >> RGB -> HSV

by nik » Mon, 01 Mar 2010 00:52:03 GMT

Hi,

I had to build a function that converts RGB to HSV. This is what I've
done so far but I am not sure if it is correct or not. Plus, I am
stuck with Hue conversion.. can someone help me to verify if I am on
the right track or at least give a hint. I've tried to verify it using
the built in function rgb2hsv in matlab, but when I plot it
separately, there was only a blue image appeared. To verify it, this i
did H=rgb2hsv(I); image(H(:,:,1)); image(H(:,:,2)) etc2..

%
---------------------------------------------------------------------------------------------------------
% This function converts RGB truecolor image to HSV
function [H,S,V] = rgbTOhsv(T)

[R C B] = size(T);

% ------ V -------
ro = T(:,:,1);
go = T(:,:,2);
bo = T(:,:,3);

for i = 1:R
for j = 1:C
c(i,j) = ro(i,j) + go(i,j) + bo(i,j);

V(i,j) = (1/3)*c(i,j);
end
end

% ------- S -------
for m = 1:R
for n = 1:C
rs(m,n) = double((ro(m,n) - V(m,n))^2);
gs(m,n) = double((go(m,n) - V(m,n))^2);
bs(m,n) = double((bo(m,n) - V(m,n))^2);

S(m,n) = sqrt(rs(m,n) + gs(m,n) + bs(m,n));
end
end

S = uint8(S);

% ------- H -------
V = double(V);

for p = 1:R
for q = 1:C
x = V(p,q)*[2; -1; -1];
so = [(ro(m,n) - V(m,n)); (go(m,n) - V(m,n)); (bo(m,n) -
V(m,n))];
end
end


H = acos(dot(double(so),double(x))/(length(so)*length(x)));

V = uint8(V);
return;

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