C#判断一个图像是否是透明的GIF图的方法

本文实例讲述了c#判断一个图像是否是透明的gif图的方法。分享给大家供大家参考。具体如下：
1. 使用方法如下：

system.drawing.image objimage = downloadimage("https://www.google.com/images/srpr/logo3w.png");
if (istransparentpalette(objimage.palette)) {//your code....}

2. c#代码如下：

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;
}

希望本文所述对大家的c#程序设计有所帮助。