rgbhsl.hh

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// Copyright (C) 2001, 2002, 2003, 2004  EPITA Research and Development Laboratory
//
// This file is part of the Olena Library.  This library is free
// software; you can redistribute it and/or modify it under the terms
// of the GNU General Public License version 2 as published by the
// Free Software Foundation.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this library; see the file COPYING.  If not, write to
// the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
// MA 02111-1307, USA.
//
// As a special exception, you may use this file as part of a free
// software library without restriction.  Specifically, if other files
// instantiate templates or use macros or inline functions from this
// file, or you compile this file and link it with other files to
// produce an executable, this file does not by itself cause the
// resulting executable to be covered by the GNU General Public
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// reasons why the executable file might be covered by the GNU General
// Public License.


#ifndef OLENA_CONVERT_NRGBHSL_HH
# define OLENA_CONVERT_NRGBHSL_HH

# include <oln/basics.hh>
# include <oln/convert/abstract/colorconv.hh>

# include <ntg/basics.hh>
# include <ntg/color/nrgb.hh>
# include <ntg/color/hsl.hh>

# include <mlc/contract.hh>

# include <cstdlib>
# include <sstream>

namespace oln {

  using namespace ntg;

  namespace convert {
    template<unsigned inbits, unsigned outbits>
    struct f_rgb_to_hsl
      : public abstract::color_conversion<3, inbits, rgb_traits,
                                          3, outbits, hsl_traits, f_rgb_to_hsl<inbits, outbits> >
    {
      color<3, outbits, hsl_traits>
      doit(const color<3, inbits, rgb_traits>& v) const
      {
        vec<3, float> in = v.to_float();
        vec<3, float> out;

        float max_in = ntg::max(in[rgb_R], std::max(in[rgb_B], in[rgb_G]));
        float min_in = ntg::min(in[rgb_R], std::min(in[rgb_B], in[rgb_G]));
        float diff = max_in-min_in;

        out[hsl_L] = (max_in + min_in) / 2;
        if (std::abs(diff) <= FLT_EPSILON){
          out[hsl_S] = 0;
          out[hsl_H] = 0; // undefined
        }
        else {
          if (out[hsl_L] <= 0.5)
            out[hsl_S] = diff / (max_in + min_in);
          else
            out[hsl_S] = diff / (2 - max_in - min_in);


          float r_dist = (max_in - in[rgb_R]) / diff;
          float g_dist = (max_in - in[rgb_G]) / diff;
          float b_dist = (max_in - in[rgb_B]) / diff;

          if (in[rgb_R] == max_in)
            out[hsl_H] = b_dist - g_dist;
          else if(in[rgb_G] == max_in)
            out[hsl_H] = 2 + r_dist - b_dist;
          else if(in[rgb_B] == max_in)
            out[hsl_H] = 4 + g_dist - r_dist;

          out[hsl_H] *= 60;
          if(out[hsl_H] < 0)
            out[hsl_H] += 360;
        }
        return out;
      }

      static std::string
      name()
      {
        std::ostringstream s;
        s << "f_rgb_to_hsl<" << inbits << ", " << outbits << '>';
        s.str();
      }
    };

    template <unsigned inbits, unsigned outbits>
    color<3, inbits, hsl_traits>
    rgb_to_hsl(const color<3, outbits, rgb_traits>& v)
    {
      f_rgb_to_hsl<inbits, outbits> f;
      return f(v);
    }

    namespace internal {
      float
      RGB(float q1, float q2, float hue)
      {
        if (hue >= 360)
          hue -= 360;
        if (hue < 0)
          hue += 360;
        if (hue < 60)
          return q1 + (q2 - q1) * hue / 60;
        else if (hue < 180)
          return q2;
        else if (hue < 240)
          return q1 + (q2 - q1) * (240 - hue) / 60;
        else
          return q1;
      }
    }

    template<unsigned inbits, unsigned outbits>
    struct f_hsl_to_rgb
      : public abstract::color_conversion<3, inbits, hsl_traits,
                                          3, outbits, rgb_traits, f_hsl_to_rgb<inbits, outbits> >
    {
      color<3, outbits, rgb_traits>
      doit(const color<3, inbits, hsl_traits>& v) const
      {
        vec<3, float> in = v.to_float();
        vec<3, float> out;
        float p2;

        if(in[hsl_L] < 0.5)
          p2 = in[hsl_L] * (1+in[hsl_S]);
        else
          p2 = in[hsl_L] + in[hsl_S] - (in[hsl_L] * in[hsl_S]);

        float p1 = 2 * in[hsl_L] - p2;

        if(in[hsl_S] == 0)
          out[rgb_R] = out[rgb_G] = out[rgb_B] = in[hsl_L];
        else
          {
            out[rgb_R] = internal::RGB(p1, p2, in[hsl_H] + 120);
            out[rgb_G] = internal::RGB(p1, p2, in[hsl_H]);
            out[rgb_B] = internal::RGB(p1, p2, in[hsl_H] - 120);
          }

        return out;
      }

      static std::string
      name()
      {
        std::ostringstream s;
        s << "f_hsl_to_rgb<" << inbits << ", " << outbits << '>';
        s.str();
      }
    };

    template<unsigned inbits, unsigned outbits>
    color<3, outbits, rgb_traits>
    hsl_to_rgb(const color<3, inbits, hsl_traits>& v)
    {
      f_hsl_to_rgb<inbits, outbits> f;
      return f(v);
    }

  } // convert
} // oln

#endif // OLENA_CONVERT_RGBHSL_HH

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