text: // Copyright (c) 2009 libmv authors.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to
  // deal in the Software without restriction, including without limitation the
  // rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
  // sell copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  // IN THE SOFTWARE.
  
  #ifndef LIBMV_IMAGE_IMAGE_CONVERTER_H
  #define LIBMV_IMAGE_IMAGE_CONVERTER_H
  
  #include "libmv/image/array_nd.h"
  
  namespace libmv{
  
  // The factor comes from http://www.easyrgb.com/
  // RGB to XYZ : Y is the luminance channel
  // var_R * 0.2126 + var_G * 0.7152 + var_B * 0.0722
  template<typename T>
  inline T RGB2GRAY(const T r,const T g, const T b) {
    return static_cast<T>(r * 0.2126 + g * 0.7152 + b * 0.0722);
  }
  
  /*
  // Specialization for the uchar type. (that do not want to work...)
  template<>
  inline unsigned char RGB2GRAY<unsigned char>(const unsigned char r,
                                               const unsigned char g,
                                               const unsigned char b) {
    return (unsigned char)(r * 0.2126 + g * 0.7152 + b * 0.0722 +0.5);
  }*/
  
  template<class ImageIn, class ImageOut>
  void Rgb2Gray(const ImageIn &imaIn, ImageOut *imaOut) {
  
    assert( imaIn.Depth() == 3 );
  
    imaOut->Resize(imaIn.Height(), imaIn.Width(), 1);
    // Convert each RGB pixel into Gray value (luminance)
  
    for(int j = 0; j < imaIn.Height(); ++j) {
      for(int i = 0; i < imaIn.Width(); ++i)  {
        (*imaOut)(j,i) = RGB2GRAY(imaIn(j,i,0) , imaIn(j,i,1), imaIn(j,i,2));
      }
    }
  }
  
  } // namespace libmv
  
  #endif  // LIBMV_IMAGE_IMAGE_CONVERTER_H
  