procedure TransparentStretch(const Source, Destination : TBitmap);
  var
    TmpBmp : TBitmap;
  begin
    TmpBmp := TBitmap.Create;
    try
      TmpBmp.Width := Destination.Width;
      TmpBmp.Height := Destination.Height;

      SetStretchBltMode(TmpBmp.Canvas.Handle, HALFTONE);

      if TransparentStretchBlt(
                                TmpBmp.Canvas.Handle, 0, 0, TmpBmp.Width, TmpBmp.Height,
                                Source.Canvas.Handle, 0, 0, Source.Width, Source.Height,
                                Source.Canvas.Handle, 0, 0) then
      begin
        Destination.Assign(TmpBmp);
      end;
    finally
      TmpBmp.Free;
    end;
  end;