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RGB.H

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#ifndef RGB_H
#define RGB_H

#include <Vector.H>
#include <color.H>

namespace xchen
{
  typedef fVector3D RGB;
  typedef fVector3D HSV;
  typedef fVector4D RGBA;
  typedef fVector4D RGBI;
  typedef fVector5D RGBAS;
  
  inline void RGBOverFlowByScale(fVector3D& rgb)
  {
    float max = * (max_element(rgb.begin(), rgb.end()));
    if(max<=1.0) rgb /= max;   
  }
  inline void RGBOverFlowByClamp(fVector3D& rgb)
  {
    for(int i=0; i<3; i++) if(rgb[i]>1.0) rgb[i] = 1.0; 
  }
  inline void RGBOverFlowByMark(fVector3D& rgb)
  {
    float max = * (max_element(rgb.begin(), rgb.end()));
    if(max<=1.0) rgb = Firebrick;
  }

  inline bool RGBASisOpaque(const RGBAS& rgbas)
  {
    return  approx_eq(1.0, rgbas[3]);
  }
  

  /* 
   *HSV hexcone and RGB cube is actually affine transform(if we lift white pnt in hexcone a bit),
   * and this is why H is not angle, but a ratio pnt at each edge.
   *
   * hs-hexogon consists of three regions (three outer cube face) 
   */
  enum RGBCubeFace { WhiteRedFace, WhiteGreenFace, WhiteBlueFace };
  inline void HSV2RGB(fVector3D& hsv)
  {
    const float H = hsv[0], S = hsv[1], V = hsv[2];

    int f = (int ((H+1.0) / 2.0));
    if(f>2) f--;
    RGBCubeFace face = (RGBCubeFace) f;

    float HH = H - 2.0 * face;
    if(HH>1.0) HH -= 2.0;

    float c[3]; c[0] = V;
    if(HH>=0) {
      c[1] = (1-(1-HH)*S) * V;
      c[2] = (1.0-S) * V;
    }
    else {
      c[2] = (1-(1+HH)*S) * V;
      c[1] = (1.0-S) * V;
    }
    copy(c, c+3, hsv.begin());
  }
  inline void RGB2HSV(fVector3D& rgb)
  {
    fVector3D::iterator itr = max_element(rgb.begin(), rgb.end());
    RGBCubeFace face = (RGBCubeFace) distance(rgb.begin(), itr); //(RGBCubeFace) _max_index(rgb.r(), rgb.g(), rgb.b());
  
    float H, S, V = *itr;
    if(!V) {
      fill(rgb.begin(), rgb.end(), 0.0);
      return;
    }

    if(++itr == rgb.end())
      itr = rgb.begin();
    float c1 = (*itr) / V;

    if(++itr == rgb.end())
      itr = rgb.begin();
    float c2 = (*itr) / V;

    if(c1 > c2) {
      S = 1.0 - c2;
      H = S? (1.0 -(1.0-c1) / S) + face * 2.0 : 0.0;
    }
    else {
      S = 1.0 - c1;
      H = S? (1.0-c2) / S - 1.0 + face * 2.0 : 0.0;
      if(H<0) H += 6.0;
    }
    rgb[0] = H, rgb[1] = S, rgb[2] = V;
  }
}
#endif

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