前言

很多微信公众号中需要生成推广海报的功能，粉丝获得专属海报后可以分享到朋友圈或发给朋友，为公众号代言邀请好友即可获取奖励的。海报自带渠道二维码，粉丝长按二维码即可关注微信公众号，从而达到吸粉的目的。

效果如下：

代码实现：

1.获取临时二维码ticket

 /// <summary>
 /// 获取临时二维码ticket
 /// </summary>
 /// <param name="scene_str">场景值ID openid做场景值ID</param>
 /// <returns></returns>
 public static string CreateTempQRCode(string scene_str,string access_token)
 {
  var result = HttpUtility.SendPostHttpRequest($"https://api.weixin.qq.com/cgi-bin/qrcode/create?access_token={access_token}", "application/json", "{\"expire_seconds\": 2592000, \"action_name\": \"QR_STR_SCENE\", \"action_info\": {\"scene\": {\"scene_str\": \"" + scene_str + "\"}}}");

  JObject jobect = (JObject)JsonConvert.DeserializeObject(result);

  string ticket = (string)jobect["ticket"];

  if (string.IsNullOrEmpty(ticket))
  {
   LogHelper.WriteLog(typeof(WeixinHelper), "获取临时二维码ticket失败" + result);
   return null;
  }
  return ticket;
 }

使用openid作为场景值的好处是通过扫A推广的二维码关注用户的场景值便是A的openid。

2. 生成带二维码的专属推广图片

 /// <summary>
 /// 生成带二维码的专属推广图片
 /// </summary>
 /// <param name="user"></param>
 /// <returns></returns>
 public string Draw(WxUser user)
 {
  //背景图片
  string path = Server.MapPath("/Content/images/tg.jpg");

  System.Drawing.Image imgSrc = System.Drawing.Image.FromFile(path);

  //处理二维码图片大小 240*240px
  System.Drawing.Image qrCodeImage = ReduceImage("https://mp.weixin.qq.com/cgi-bin/showqrcode?ticket="+user.ticket, 240, 240);

  //处理头像图片大小 100*100px
  Image titleImage = ReduceImage(user.headimgurl, 100, 100);

  using (Graphics g = Graphics.FromImage(imgSrc))
  {
   //画专属推广二维码
   g.DrawImage(qrCodeImage, new Rectangle(imgSrc.Width - qrCodeImage.Width - 200,
   imgSrc.Height - qrCodeImage.Height - 200,
   qrCodeImage.Width,
   qrCodeImage.Height),
   0, 0, qrCodeImage.Width, qrCodeImage.Height, GraphicsUnit.Pixel);

   //画头像
   g.DrawImage(titleImage, 8, 8, titleImage.Width, titleImage.Height);

   Font font = new Font("宋体", 30, FontStyle.Bold);

   g.DrawString(user.nickname, font, new SolidBrush(Color.Red), 110, 10);
  }
  str【自由互联：韩国服务器 转载请保留连接】ing newpath = Server.MapPath(@"/Content/images/newtg_" + Guid.NewGuid().ToString() + ".jpg");
  imgSrc.Save(newpath, System.Drawing.Imaging.ImageFormat.Jpeg);
  return newpath;
 }


 /// <summary>
 /// 缩小/放大图片
 /// </summary>
 /// <param name="url">图片网络地址</param>
 /// <param name="toWidth">缩小/放大宽度</param>
 /// <param name="toHeight">缩小/放大高度</param>
 /// <returns></returns>
 public Image ReduceImage(string url, int toWidth, int toHeight)
 {
  WebRequest request = WebRequest.Create(url);
  WebResponse response = request.GetResponse();
  Stream responseStream = response.GetResponseStream();

  Image originalImage = Image.FromStream(responseStream);
  if (toWidth <= 0 && toHeight <= 0)
  {
   return originalImage;
  }
  else if (toWidth > 0 && toHeight > 0)
  {
   if (originalImage.Width < toWidth && originalImage.Height < toHeight)
    return originalImage;
  }
  else if (toWidth <= 0 && toHeight > 0)
  {
   if (originalImage.Height < toHeight)
    return originalImage;
   toWidth = originalImage.Width * toHeight / originalImage.Height;
  }
  else if (toHeight <= 0 && toWidth > 0)
  {
   if (originalImage.Width < toWidth)
    return originalImage;
   toHeight = originalImage.Height * toWidth / originalImage.Width;
  }
  Image toBitmap = new Bitmap(toWidth, toHeight);
  using (Graphics g = Graphics.FromImage(toBitmap))
  {
   g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
   g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
   g.Clear(Color.Transparent);
   g.DrawImage(originalImage,
      new Rectangle(0, 0, toWidth, toHeight),
      new Rectangle(0, 0, originalImage.Width, originalImage.Height),
      GraphicsUnit.Pixel);
   originalImage.Dispose();
   return toBitmap;
  }
 }

3.将图片上传微信服务器，并发送给用户

string imagePath = Draw(user);
         
string result = HttpUtility.UploadFile($"https://api.weixin.qq.com/cgi-bin/material/add_material?access_token={access_token}&type=image", imagePath);

JObject jObject = (JObject)JsonConvert.DeserializeObject(result);
         
string media_id = (string)jObject["media_id"];
if (!string.IsNullOrEmpty(media_id))
{
          
  string resxml = "<xml><ToUserName><![CDATA[" + xmlMsg.FromUserName + "]]></ToUserName><FromUserName><![CDATA[" + xmlMsg.ToUserName + "]]></FromUserName><CreateTime>" + nowtime + "</CreateTime><MsgType><![CDATA[image]]></MsgType><Image><MediaId><![CDATA[" + media_id + "]]></MediaId></Image></xml>";
  return resxml;
}
LogHelper.WriteLog(typeof(WechatController), "上传专属推广图片素材失败" + result);

总结

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