#include <stdlib.h>
   #include <math.h>

   inline int round (const float a)  { return int (a + 0.5); }

   void lineDDA (int x0, int y0, int xEnd, int yEnd)
   {
      int dx = xEnd - x0,  dy = yEnd - y0,  steps,  k;
      float xIncrement, yIncrement, x = x0, y = y0;

      if (fabs (dx) > fabs (dy))
         steps = fabs (dx);
      else
         steps = fabs (dy);
      xIncrement = float (dx) / float (steps);
      yIncrement = float (dy) / float (steps);

      setPixel (round (x), round (y));
      for (k = 0; k < steps; k++) {
         x += xIncrement;
         y += yIncrement;
         setPixel (round (x), round (y));
      }
   }