System.Drawing.Image objImage = DownloadImage("https://www.google.com/images/srpr/logo3w.png");if (IsTransparentPalette(objImage.Palette)) {//your code....}

public bool IsTransparentPalette(System.Drawing.Imaging.ColorPalette palette){  if (palette.Flags!= 1 )    return false;  int total_colors = palette.Entries.GetLength(0);  for (int i = 0; i < total_colors - 1; i++)  {    if (palette.Entries[i].A != 0)    {      return false;    }  }  return true;}public System.Drawing.Image DownloadImage(string url){  System.Drawing.Image tmpImage = null;  try  {    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);    request.AllowWriteStreamBuffering = true;    request.UserAgent = UserAgent;    request.Accept = "GET HTTP/1.1";    request.Timeout = 2000;    System.Net.WebResponse webResponse = request.GetResponse();    System.IO.Stream webStream = webResponse.GetResponseStream();    if (webStream != null) tmpImage = System.Drawing.Image.FromStream(webStream);    webResponse.Close();    webResponse.Close();  }  catch (Exception exception)  {    return null;  }  return tmpImage;}