when i convert PNG picture to BMP picture via routine below, then colors are not same in BMP as they are in original PNG.

procedure TForm1.Button4Click(Sender: TObject);
var
  R: TRect;
  Bmp: TBitmap;
  Png: TPngImage;
begin
  Png := TPngImage.Create;
  try
    Png.LoadFromFile('C:tempSource.png');
    bmp := TBitmap.Create(Png.Width, Png.Height);
    try
      R := Rect(0, 0, Png.Width, Png.Height);
      bmp.Canvas.CopyRect(R, png.Canvas, R);
      bmp.SaveToFile('C:temptarget.bmp')
    finally
      Bmp.Free;
    end;
  finally
    Png.Free;
  end;
end;

Could you provide me a hint how to solve this issue please.

Thank you

JP