#include <cassert>   //For assert
#include <cmath>     //For std::sqrt
#include <algorithm> //For std::min

//From http://www.richelbilderbeek.nl/CppDrawGlobe.htm
void DrawGlobe(
  TImage * const image,
  const unsigned char rMax,
  const unsigned char gMax,
  const unsigned char bMax)
{
  assert(image!=0);
  const int width  = image->Picture->Bitmap->Width;
  const int height = image->Picture->Bitmap->Height;
  const double midX = static_cast<double>(width ) / 2.0;
  const double midY = static_cast<double>(height) / 2.0;
  const double maxDist = std::min(midX,midY);
  for (int y=0; y!=height; ++y)
  {
    unsigned char * const line
      = static_cast<unsigned char *>(image->Picture->Bitmap->ScanLine[y]);
    const double yD = static_cast<double>(y);
    for (int x=0; x!=width; ++x)
    {
      const double xD = static_cast<double>(x);
      const double dist = std::sqrt( ((xD - midX) * (xD - midX)) + ((yD - midY) * (yD - midY)) );
      if (dist <= maxDist)
      {
        const double relDist = dist / maxDist;
        const int r = relDist * static_cast<double>(rMax);
        const int g = relDist * static_cast<double>(gMax);
        const int b = relDist * static_cast<double>(bMax);
        assert( r >= 0);
        assert( r < 256);
        assert( g >= 0);
        assert( g < 256);
        assert( b >= 0);
        assert( b < 256);
        line[x*3+2] = (r == 0 ? 1 : r); //Never use a zero for red
        line[x*3+1] = (g == 0 ? 1 : g); //Never use a zero for green
        line[x*3+0] = (b == 0 ? 1 : b); //Never use a zero for blue
      }
      else
      {
        line[x*3+2] = 0;
        line[x*3+1] = 0;
        line[x*3+0] = 0;
      }
    }
  }
}