code:

---

/*BltRastPortTrans  
  Blittet RastPort-Ausschnitt halbtransparent zu 50% */

int BltRastPortTrans(struct RastPort *SrcRP ,UWORD SrcX,UWORD SrcY,struct RastPort *DestRP,
                     UWORD DestX, UWORD DestY,UWORD SizeX,UWORD SizeY)
{
int i;
UBYTE *MyArray;
UBYTE *TempArray;

if( (SizeX<1)||(SizeY<1)||(SrcX<0)||(SrcY<0)||(SrcRP==NULL) )return(0);
if( (DestX<0)||(DestY<0)||(DestRP==NULL) )return(0);

 if(MyArray=malloc((int)SizeX*(int)SizeY*3))
 {
 if(TempArray=malloc((int)SizeX*(int)SizeY*3))
 {
  ReadPixelArray(MyArray,0,0,SizeX*3,SrcRP,SrcX,SrcY,SizeX,SizeY,RECTFMT_RGB);
  ReadPixelArray(TempArray,0,0,SizeX*3,DestRP,DestX,DestY,SizeX,SizeY,RECTFMT_RGB);
  
  for(i=0;i<=SizeX*SizeY*3;i++)
   {
    //MyArray[i]=(MyArray[i]+TempArray[i])/2;
    MyArray[i]=(MyArray[i]+TempArray[i])>>1;
   }
 
  WritePixelArray(MyArray,0,0,SizeX*3,DestRP,DestX,DestY,SizeX,SizeY,RECTFMT_RGB);
 
 free(TempArray);
 }
   else{free(MyArray);return(0);
 }
 free(MyArray);
 }
 else{return(0);}
 return((int)(SizeX*SizeY));
}

---