DEFINE_UI_PARAMS(ratio, Percent, DCTLUI_SLIDER_FLOAT, 2.35, 1.0, 100.0, 0.01)
DEFINE_UI_PARAMS(r, Red, DCTLUI_SLIDER_FLOAT, 1, 0.0, 1.0, 0.1)
DEFINE_UI_PARAMS(g, Green, DCTLUI_SLIDER_FLOAT, 0, 0.0, 1.0, 0.1)
DEFINE_UI_PARAMS(b, Blue, DCTLUI_SLIDER_FLOAT, 0, 0.0, 1.0, 0.1)

__DEVICE__ float3 transform(int p_Width, int p_Height, int p_X, int p_Y, float p_R, float p_G, float p_B)
{  
   float percent = ratio / 100;
   float letterbox_width = (p_Width * percent) / 2 ;
   int size = round(letterbox_width);
   if ((p_X < size) || (p_X > p_Width-size)) {
      return (make_float3(r, g, b));
   } else {
      return (make_float3(p_R, p_G, p_B));
   }
}