procedure TForm1.Button2Click(Sender: TObject);

var i : integer;

begin
try
  bmp32bit := TGPBitmap.Create('ten.bmp');
  T1 := now;
  for i := 0 to 1000 do begin
      bmp8bit := Create8bitFrom32bitBitmap(bmp32bit, 8);
      bmp8bit.Free;
  end;
  T2 := now;
  DecodeTime(T2-T1,h,m,s,ms);
  Label2.Caption:='Done in:';
  Label3.Caption:=IntTostr(s) +':'+ IntTostr(ms);
finally
  bmp32bit.Free;
end;

end;