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.Net generation development WeChat public platform development image processing code analysis

高洛峰
高洛峰Original
2017-03-19 17:39:441896browse

这篇文章主要为大家详细解析了微信公众平台开发之处理图片.Net代码,感兴趣的小伙伴们可以参考一下

举个例子,有人对着我们的公共微信号拍个照片发送过来,然后我们处理这个照片,比如进行ocr识别字(随后就会降到这个例子),或者人脸识别,或者拍照取证等,这些功能都是相当有用的。那么我们现在就要分析一下这个过程。微信平台肯定不能帮助我们OCR或者人脸识别等功能,要做这些功能首先到得到图片!用户拍摄的照片首先被上传到了wenxin的服务器,然后就有了一个mediaID,我们用这个mediaID可以下载到我们自己的服务器上然后处理,把结果给微信平台,由微信平台最终反馈给用户(关注者)。微信的开发文档已经给出了下载资源的办法,我改造为.net的,如下: 

/// <summary>
  /// 下载保存多媒体文件,返回多媒体保存路径
  /// </summary>
  /// <param name="ACCESS_TOKEN"></param>
  /// <param name="MEDIA_ID"></param>
  /// <returns></returns>
  public string GetMultimedia(string ACCESS_TOKEN, string MEDIA_ID)
  {
    string file = string.Empty;
    string content = string.Empty;
    string strpath = string.Empty;
    string savepath = string.Empty;
    string stUrl = "http://file.api.weixin.qq.com/cgi-bin/media/get?access_token=" + ACCESS_TOKEN + "&media_id=" + MEDIA_ID;

    HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(stUrl);

    req.Method = "GET";
    using (WebResponse wr = req.GetResponse())
    {
      HttpWebResponse myResponse = (HttpWebResponse)req.GetResponse();

      strpath = myResponse.ResponseUri.ToString();
      WriteLog("接收类别://" + myResponse.ContentType);
      WebClient mywebclient = new WebClient();
      savepath = Server.MapPath("image") + "\\" + DateTime.Now.ToString("yyyyMMddHHmmssfff") + (new Random()).Next().ToString().Substring(0, 4) + ".jpg";
      WriteLog("路径://" + savepath);
      try
      {
        mywebclient.DownloadFile(strpath, savepath);
        file = savepath;
      }
      catch (Exception ex)
      {
        savepath = ex.ToString();
      }

    }
    return file;
  }

 上面的两个参数很好理解,第一就是ACCESS_TOKEN,之前说过很多了,第二就是在微信服务器上的资源id,即mediaID。如果我们要下载微信服务器上的资源总要知道id吧。但是MEDIA_ID又是怎么产生的呢?我首先改造一下之前的消息实体类,加入MediaId 属性 

 class wxmessage 
  { 
    public string FromUserName { get; set; } 
    public string ToUserName { get; set; } 
    public string MsgType { get; set; } 
    public string EventName { get; set; } 
    public string Content { get; set; }
    public string Recognition { get; set; }
    public string MediaId { get; set; }
    public string EventKey { get; set; } 
  }

然后改造一下GetWxMessage(),给MediaId赋值。


private wxmessage GetWxMessage()
   {
     wxmessage wx = new wxmessage();
     StreamReader str = new StreamReader(Request.InputStream, System.Text.Encoding.UTF8);
     XmlDocument xml = new XmlDocument();
     xml.Load(str);
     wx.ToUserName = xml.SelectSingleNode("xml").SelectSingleNode("ToUserName").InnerText;
     wx.FromUserName = xml.SelectSingleNode("xml").SelectSingleNode("FromUserName").InnerText;
     wx.MsgType = xml.SelectSingleNode("xml").SelectSingleNode("MsgType").InnerText;
     if (wx.MsgType.Trim() == "text")
     {
       wx.Content = xml.SelectSingleNode("xml").SelectSingleNode("Content").InnerText;
     }
     if (wx.MsgType.Trim() == "event")
     {
       wx.EventName = xml.SelectSingleNode("xml").SelectSingleNode("Event").InnerText;
       wx.EventKey = xml.SelectSingleNode("xml").SelectSingleNode("EventKey").InnerText;
     }
     if (wx.MsgType.Trim() == "voice")
     {
       wx.Recognition = xml.SelectSingleNode("xml").SelectSingleNode("Recognition").InnerText;
     }
    if (wx.MsgType.Trim() == "image")
    {
      wx.MediaId = xml.SelectSingleNode("xml").SelectSingleNode("MediaId").InnerText;
    }
     
     return wx;
   }

如果我们在修改一下消息接受的代码,就可以做到,客户发一个照片给微信平台,程序检测到时图片,然后根据MediaId,调用GetMultimedia方法把图片下载到自己的服务器上。后面的工作嘛,你就想干什么干什么了。
 刚才的例子好像是用户(关注者),发图片,然后通过微信平台到我们的服务器中,还有一种情况,用户发一个用户名:例如“hemeng”,然后我需要调用已经存在服务器中的hemeng头像的图片反馈给用户,这怎么办呢?如何把我们的图片传给微信平台,然后传给用户呢?我们就用到了上传得方法: 

/// <summary>
  /// 上传多媒体文件,返回 MediaId
  /// </summary>
  /// <param name="ACCESS_TOKEN"></param>
  /// <param name="Type"></param>
  /// <returns></returns>
  public string UploadMultimedia(string ACCESS_TOKEN, string Type)
  {
    string result = "";
    string wxurl = "http://file.api.weixin.qq.com/cgi-bin/media/upload?access_token=" + ACCESS_TOKEN + "&type=" + Type;
    string filepath = Server.MapPath("image") + "\\hemeng80.jpg";(本地服务器的地址)
    WriteLog("上传路径:" + filepath);
    WebClient myWebClient = new WebClient();
    myWebClient.Credentials = CredentialCache.DefaultCredentials;
    try
    {
      byte[] responseArray = myWebClient.UploadFile(wxurl, "POST", filepath);
      result = System.Text.Encoding.Default.GetString(responseArray, 0, responseArray.Length);
      WriteLog("上传result:" + result);
      UploadMM _mode = JsonHelper.ParseFromJson<UploadMM>(result);
      result = _mode.media_id;
    }
    catch (Exception ex)
    {
      result = "Error:" + ex.Message;
    }
    WriteLog("上传MediaId:" + result);
    return result;
  }

第二个参数如果是图片"image",可以参照微信的文档。函数的返回值就是一个MediaId,这样你就可以利用发送图片的函数,发给客户了,发送图片的函数如下:

protected string sendPicTextMessage(Msg _mode, string MediaId)
  {
    string res = string.Format(@"<xml>
                      <ToUserName><![CDATA[{0}]]></ToUserName>
                      <FromUserName><![CDATA[{1}]]></FromUserName>
                      <CreateTime>{2}</CreateTime>
                      <MsgType><![CDATA[image]]></MsgType>
                      <Image>
                      <MediaId><![CDATA[{3}]]></MediaId>
                      </Image>
                  </xml> ",
      _mode.FromUserName, _mode.ToUserName, DateTime.Now, MediaId);

    return res;
  }

其他视频,语音的操作也类似,就不再冗余介绍了。有了这些知识我们是不是能做不少应用了?当然是肯定的,但是我们的代码还不够优化,结构也不合理,不着急,我们会逐渐介绍到的,因为我们还没有完全了解完微信的强大功能。

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