Question

Is there a way in Java or OpenCv ; preferably Java, that i can have an HSV histogram give RGB image.

I tried exploring JAI but it creates histogram for RGB image.
Thanks
Harshit

Answer 1

Here is the pseudocode for a simple RGB to HSV converter. It will give a H of UNDEFINED if the color is a shade of gray, otherwise H is between 0 and 6.

x = min(R, G, B);
V = max(R, G, B);
if (V == x) {
  H = UNDEFINED
  S = 0
}
else {
  if( R == x ) {
    f = G - B;
    i = 3;
  } else if( G == x ) {
    f = B - R;
    i = 5;
  } else {
    f = R - G;
    i = 1;
  }
  H = i - f /(V - x);
  S = (V - x)/V;
}

Now you can either convert all your pixels and bin them to construct your HSV histogram, or you can convert each bin of your RGB histogram to an HSV bin.