HSV to RGB

hsv2rgb.ino

void hsv2rgb(byte h/*0-252*/,byte s/*0-255*/,byte v/*0-255*/, unsigned char *r, unsigned char *g, unsigned char *b){
   byte i=h/42;
   byte f=h%42;
   word tw,p1,p2,p3;
   
   tw=255*42-s*42;
   p1=((unsigned long)tw*v+21*255)/42/255;
   tw=255*42-s*f;
   p2=((unsigned long)tw*v+21*255)/42/255;
   tw=255*42-s*(42-f);
   p3=((unsigned long)tw*v+21*255)/42/255;
   if(255<p1)p1=255;
   if(255<p2)p2=255;
   if(255<p3)p3=255;
   if(p1<0)p1=0;
   if(p2<0)p2=0;
   if(p3<0)p3=0;
   
   switch(i){
   case 0:
     {*r = v ;*g = p3 ;*b = p1;} 
     break;
   case 1:
     {*r = p2 ;*g = v ;*b = p1;}
     break;
   case 2:
     {*r = p1 ;*g = v;*b = p3;}
     break;
   case 3:
     {*r = p1 ;*g = p2 ;*b = v;}
     break;
   case 4:
     {*r = p3 ;*g = p1 ;*b = v;}
     break;
   default:
     {*r = v ;*g = p1 ;*b = p2;}
     break;
   }
   
}