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..." />"

我有以下代码找到第一个img标记，获取src值（这是一个base64字符串）并将其转换为一个位数组来创建一个流，然后我可以创建一个新的src值链接到那条小溪。

  //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 + @"'/>");

正如你所看到的那样，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标签，执行逻辑，替换它，然后继续使用下一个img标签。

希望你能告诉我如何做到这一点。提前谢谢。

Answer 1

如果我理解你的需要，你可以使用HtmlAgilityPack来达到这个目的。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

希望这有帮助

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：

-(void)viewDidLoad
{
[super viewDidLoad];

self.textField = [[UITextField alloc]initWithFrame:CGRectMake(97,     150, 200, 29)];
self.textField.backgroundColor = [UIColor lightGrayColor];
self.textField.placeholder = @"Enter Numbers only";
self.textField.textAlignment = NSTextAlignmentCenter;
[self.view addSubview:self.textField];


self.addButton = [UIButton buttonWithType:UIButtonTypeContactAdd];
self.addButton.frame = CGRectMake(310, 160, 20, 20);
[self.addButton addTarget:self action:@selector(addingNum) forControlEvents:(UIControlEventTouchDown)];
[self.view addSubview:self.addButton];


self.resultSegment = [[UISegmentedControl alloc]init];
self.resultSegment.frame = CGRectMake(10, 200, 395, 29);
self.resultSegment.tintColor = [UIColor whiteColor];
[self.view addSubview:self.resultSegment];


self.refreshBtn = [UIButton buttonWithType:UIButtonTypeCustom];
self.refreshBtn.frame = CGRectMake(350, 160, 20, 20);
[self.refreshBtn setImage:[UIImage imageNamed:@"images.jpeg"] forState:UIControlStateNormal];
[self.refreshBtn addTarget:self action:@selector(removeAllSegments) forControlEvents:UIControlEventTouchDown];
[self.view addSubview:self.refreshBtn];
}


-(void)addingNum
{
[self.resultSegment insertSegmentWithTitle:[NSString  stringWithFormat:@"%@",self.textField.text] atIndex:0 animated:YES];
}


-(void)removeAllSegments
{
    [self.resultSegment removeAllSegments];
}

在循环中使用此列表和用户逻辑：

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;
        }

希望它适合你。

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

通过html字符串迭代查找所有img标记并替换src属性值

2 个答案: