Graphics code snippet to draw a lymphocyte
View an example image of an image created by 'DrawLymphocyte'

#include <cassert>   //For assert

#include <cmath>     //For std::sqrt

#include <algorithm> //For std::min



//From http://www.richelbilderbeek.nl/CppDrawLymphocyte.htm

void DrawLymphocyte(

  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); //Distance to end

  const double edgeDist = maxDist * 0.7; //Distance to edge



  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 <= edgeDist)

      {

        const double relDist = dist / edgeDist;

        const int r = (0.5 + (0.5 * relDist)) * static_cast<double>(rMax);

        const int g = (0.5 + (0.5 * relDist)) * static_cast<double>(gMax);

        const int b = (0.5 + (0.5 * 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 if (dist <= maxDist)

      {

        const double relDist = (dist - edgeDist) / (maxDist - edgeDist);

        const int r = (0.5 + (0.5 * (1.0 - relDist))) * static_cast<double>(rMax);

        const int g = (0.5 + (0.5 * (1.0 - relDist))) * static_cast<double>(gMax);

        const int b = (0.5 + (0.5 * (1.0 - 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;

      }

    }

  }

}
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(C++) DrawLymphocyte
