通过html字符串迭代查找所有img标记并替换src属性值

Question

我有一个HTML代码作为字符串.我需要在该字符串中找到所有img标记,读取每个src属性的值并将其传递给函数,该函数返回一个整个img标记,需要取代读取的img标记.

它需要遍历整个字符串并为所有img标记执行相同的逻辑.

例如,假设我的html字符串如下所示:

string htmlBody= "<p>Hi everyone</p><img src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAEAAAABACAMAAACdt4HsAAAA..." <p>I am here </p> <img src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAEAAAABAC..." />"

我有以下代码找到的第一个img标签,取src值(这是一个base64字符串)并将其转换成位的阵列,以创建一个流,那么我可以创建新的SRC值链接到该流中.

  //Remove from all src attributes "data:image/png;base64"      
  string res = Regex.Replace(htmlBody, "data:image\\/\\w+\\;base64\\,", "");
  //Match the img tag and get the base64  string value
  string matchString = Regex.Match(res, "<img.+?src=[\"'](.+?)[\"'].*?>", RegexOptions.IgnoreCase).Groups[1].Value;
  var imageData = Convert.FromBase64String(matchString);
  var contentId = Guid.NewGuid().ToString();
  LinkedResource inline = new LinkedResource(new MemoryStream(imageData), "image/jpeg");
  inline.ContentId = contentId;
  inline.TransferEncoding = TransferEncoding.Base64;
  //Replace all img tags with the new img tag 
  htmlBody = Regex.Replace(htmlBody, "<img.+?src=[\"'](.+?)[\"'].*?>", @"<img src='cid:" + inline.ContentId + @"'/>");

正如你可以看到finnaly我有新的img标签要替换:

   <img src='cid:" + inline.ContentId + @"'/>

但代码将使用相同的内容替换所有img标记.我需要能够获取img标记,执行逻辑,替换它然后继续下一个img标记.

希望你能告诉我如何做到这一点.提前致谢.

Answer 1

如果我正确理解您的需要,您可以使用HtmlAgilityPack来实现此目的.使用正则表达式可能会导致不必要的行为 你能试试下面的代码吗？

public static string DoIt()
{
        string htmlString = "";
        using (WebClient client = new WebClient())
            htmlString = client.DownloadString("http://dean.edwards.name/my/base64-ie.html"); //This is an example source for base64 img src, you can change this directly to your source.

        HtmlDocument document = new HtmlDocument();
        document.LoadHtml(htmlString);
        document.DocumentNode.Descendants("img")
                            .Where(e =>
                            {
                                string src = e.GetAttributeValue("src", null) ?? "";
                                return !string.IsNullOrEmpty(src) && src.StartsWith("data:image");
                            })
                            .ToList()
                            .ForEach(x =>
                            {
                                string currentSrcValue = x.GetAttributeValue("src", null);
                                currentSrcValue = currentSrcValue.Split(',')[1];//Base64 part of string
                                byte[] imageData = Convert.FromBase64String(currentSrcValue);
                                string contentId = Guid.NewGuid().ToString();
                                LinkedResource inline = new LinkedResource(new MemoryStream(imageData), "image/jpeg");
                                inline.ContentId = contentId;
                                inline.TransferEncoding = TransferEncoding.Base64;

                                x.SetAttributeValue("src", "cid:" + inline.ContentId);
                            });


        string result = document.DocumentNode.OuterHtml;
}

您可以从https://www.nuget.org/packages/HtmlAgilityPack检索HtmlAgilityPack

希望这可以帮助

Answer 2

我认为你需要为每个img fetched形式的字符串迭代你的代码.以下代码为您提供了所有img标记的列表:

public static List<string> FetchImgsFromSource(string htmlSource)
        {
            List<string> listOfImgdata = new List<string>();
            string regexImgSrc = @"<img[^>]*?src\s*=\s*[""']?([^'"" >]+?)[ '""][^>]*?>";
            MatchCollection matchesImgSrc = Regex.Matches(htmlSource, regexImgSrc, RegexOptions.IgnoreCase | RegexOptions.Singleline);
            foreach (Match m in matchesImgSrc)
            {
                string href = m.Groups[1].Value;
                listOfImgdata.Add(href);
            }
            return listOfImgdata;
        }

在循环中使用此列表和用户逻辑:

foreach (var item in listOfImgdata )
            {
                var imageData = Convert.FromBase64String(item);
                var contentId = Guid.NewGuid().ToString();
                LinkedResource inline = new LinkedResource(new MemoryStream(imageData), "image/jpeg");
                inline.ContentId = contentId;
                inline.TransferEncoding = TransferEncoding.Base64;
                //Replace all img tags with the new img tag 
                htmlBody = Regex.Replace(htmlBody, "<img.+?src=[\"'](.+?)[\"'].*?>", @"<img src='cid:" + inline.ContentId + @"'/>");
            }

希望对你有效.

另外,解析HTML dom的最佳方法是使用其他人提到的HtmlAgilityPack.