const jpgf:array[jf24Bit..jf8Bit] of byte=(24,8);
procedure TForm1.Button1Click(Sender: TObject);
var j:TJpegImage;
begin
     if op1.Execute then
     begin
          j:=TJpegImage.Create;
          j.LoadFromFile(op1.FileName);
          ShowMessage(Format('Jpeg Image: Width %d, Height %d, PixelFormat %d',[j.Width,j.Height,jpgf[j.PixelFormat]]));
          j.Free;
     end;

end;