HSV or RGB for Lips detection?

[tommy_chai]

Dear all,

I have HSV algorithm posted under "color detection algorithm" but i failed to locate the lips as i did by using RGB algorithm. I set the H to 0.1 but still with the same result.
My color image is in pgm format, so i didn't use ind2rgb but straight away to call colorDetectHSV(), will this be a problem?
This is the colorDetectHSV():

function I = colorDetectHSV(RGB, hsvVal, tol)

HSV = rgb2hsv(RGB);

% find the difference between required and real H value:
diffH = abs(HSV(:,:,1) - hsvVal(1));

[M,N,t] = size(RGB);
I1 = zeros(M,N); I2 = zeros(M,N); I3 = zeros(M,N);

T1 = tol(1);

I1( find(diffH < T1) ) = 1;

if (length(tol)>1)
    % find the difference between required and real S value:
    diffS = abs(HSV(:,:,2) - hsvVal(2));    
    T2 = tol(2);
    I2( find(diffS < T2) ) = 1;    
    if (length(tol)>2)
        % find the difference between required and real V value:
        difV = HSV(:,:,3) - hsvVal(3);    
        T3 = tol(3);
        I3( find(diffS < T3) ) = 1;
        I = I1.*I2.*I3;
    else
        I = I1.*I2;
    end
else
    I = I1;    
end

subplot(2,1,1),imshow(RGB); title('Original Image');
subplot(2,1,2),imshow(I,[]); title('Detected Areas');

This is my main program:

a = imread('m-013-1.pgm');
b = colorDetectHSV(a, [0.1 1.0 0.5], [0.5 0.5 0.5]);

The original images is in my attachment below "image.zip".
However, i failed to allocate lips which is in red color. Please help, any comment will be appreciated.

Thank you.

Best regards,
Tommy