获取网页中的验证码图片

首先需要添加mshtml的引用,之后using mshtml;

         public   static  Image GetRegCodePic(WebBrowser wbMail,  string  ImgName,  string  Src,  string  Alt)
         {
            HTMLDocument doc = (HTMLDocument)wbMail.Document.DomDocument;
            HTMLBody body = (HTMLBody)doc.body;
            IHTMLControlRange rang = (IHTMLControlRange)body.createControlRange();
            IHTMLControlElement Img;
            if (ImgName == "") //如果没有图片的名字,通过Src或Alt中的关键字来取
            {
                int ImgNum = GetPicIndex(wbMail, Src,Alt);
                if (ImgNum == -1) return null;
                Img = (IHTMLControlElement)wbMail.Document.Images[ImgNum].DomElement;
            }
            else
                Img = (IHTMLControlElement)wbMail.Document.All[ImgName].DomElement;

            rang.add(Img);
            rang.execCommand("Copy", false, null);
            Image RegImg = Clipboard.GetImage();
            Clipboard.Clear();
            return RegImg;
        }

         public   static   int  GetPicIndex(WebBrowser wbMail,  string  Src,  string  Alt)
         {
            int imgnum = -1;
            for (int i = 0; i < wbMail.Document.Images.Count; i++)　//获取所有的Image元素
            {
                IHTMLImgElement img = (IHTMLImgElement)wbMail.Document.Images[i].DomElement;
                if (Alt == "")
                {
                    if (img.src.Contains(Src)) return i;
                }
                else
                {
                    if (!string.IsNullOrEmpty(img.alt))
                    {
                        if (img.alt.Contains(Alt)) return i;
                    }
                }
            }
            return imgnum;
        }

通过调用GetRegCodePic就可以获得注册码图片了.下面是几个示例.
示例1:
下面是某个站的注册码图片的HTML部分源代码



picturebox1.Image =GetRegCodePic(wbMail, "", "", "Registration Verification Code")


示例2:
下面是某个站的注册码图片的HTML部分源代码



picturebox1.Image =GetRegCodePic(wbMail, "CAPTCHAImage", "", "")  //通过验证码Html元素的名字来取