网站CSS背景图片抓取工具

工具介绍：
　　1）分析网页，获取页面图片。
　　2）分析网页引用CSS文件，获取背景图片。
　　3）批量下载。
要点：
　　1）正则

　　　　LINK_PATTERN：获取页面所有连接

　　　　BACKGROUND_IMAGE_PATTERN：获取CSS中背景图片地址
　　　　CHECK_URL_PATTERN ：检测URL是否有效

        private const string LINK_PATTERN = @"(href|src)=['""]?(?<link>[^'""\s]*)['""]?";
        private const string BACKGROUND_IMAGE_PATTERN = @"(url)\(['""]?(?<url>[^'""\s]*)['""]?\)";
        private const string CHECK_URL_PATTERN = @"^http(s)?://+([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?";

　　2）线程

        /// <summary>
        /// 线程
        /// </summary>
        private void DoWork()
        {
            //网页路径
            string url = txtUrl.Text.Trim();
            //保存路径
            string saveDir = txtSaveDir.Text.Trim();

            lvLog.Items.Clear();
            tsslStatus.Text = DESC_ANALYSISING;
            tsslTime.Text = string.Format(DESC_SPAND_TIME,0);
            tsslCount.Text = string.Format(DESC_IMAGES_COUNT,0);
            tsslTotalTime.Text = string.Format(DESC_DOWNLOAD_TOTAL_TIME,0);
            btnDownload.Enabled = false;

            Application.DoEvents();
            AnalyzeAndDownload(url, saveDir);
        }

      3）网页分析：

        /// <summary>
        /// 根据网站URL获取CSS
        /// 分析CSS获取背景图片地址
        /// </summary>
        /// <param name="url"></param>
        /// <returns></returns>
        protected List<Uri> FetchCSSWithSite(string url)
        {
            StringBuilder sourceCSS = new StringBuilder();
            List<Uri> list = new List<Uri>();
            using (WebClient client = new WebClient())
            {
                _basicUri = new Uri(url);
                string sourceHtml = client.DownloadString(_basicUri);
                sourceCSS.Append(sourceHtml);
                Regex regex = new Regex(LINK_PATTERN, RegexOptions.IgnoreCase);
                MatchCollection collection = regex.Matches(sourceHtml);
                if (collection == null) return null;
                string extension = string.Empty;
                string link = string.Empty;
                foreach (Match match in collection)
                {
                    link=match.Groups["link"].Value;
                    lvLog.Items.Add(new ListViewItem(new string[] { new Uri(_basicUri, link).AbsoluteUri, DateTime.Now.ToString(TIME_FORMAT), STATUS_ANALYSIS, string.Empty, link.Contains(".") ? link.Substring(link.LastIndexOf('.')) : string.Empty }));

                    if (!link.Contains(".")) continue;
                    extension = link.Substring(link.LastIndexOf('.'));
                    switch (extension.ToUpper())
                    {
                        case ".CSS":
                            sourceCSS.Append(client.DownloadString(new Uri(_basicUri, link)));
                            break;
                        case ".GIF":
                        case ".PNG":
                        case ".JPG":
                        case ".JPEG":
                            list.Add(new Uri(_basicUri, link));
                            break;
                        default:
                            break;
                    }
                }
            }
            list.AddRange(FetchBGImageUrlsWithCSS(sourceCSS.ToString()));

            return list;
        }

 　  4）效果图

下载地址：/Files/olartan/BID.zip