Cut a rectangle from an Image to Clipboard

Cutting a graphic to the Clipboard is like copying it, but you also erase the graphic from the source.
 

procedure CutToClipboard
   (AnImage:TImage; ARect:TRect) ;
var b:TBitmap;
begin
  //first copy
  b:=TBitmap:Create;
  try
    b.Width := ARect.Width;
    b.Height := ARect.Height;
    CopyRect(Rect(0,0,b.Height,b.Width),
             AnImage.Canvas, ARect) ;
    Clipboard.Assign(b)
  finally
    b.Free
  end;
  //than cut
  with AnImage.Canvas do
   begin
    CopyMode := cmWhiteness;
    CopyRect(ARect, AnImage.Canvas, ARect) ;
    CopyMode := cmSrcCopy;
   end;
end;