[C#基础实例]指定地址解析图片并下载

需求：查找页面图片并下载至本地；

实现:

首先：读取通过网络html内容，并用正则表达式查找图片地下。

其次：使用WebRequest.Create创建图片请求。

最后：把获取图片网络流数据通过FileStream创建本地文件并写入数据。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net;
using System.IO;
using System.Text.RegularExpressions;

namespace StreamDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            string url = "http://www.wzfzl.cn/fzl/mm/2013/0429/7092.html";

            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            request.Timeout = 5000;
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream s = response.GetResponseStream();

            StreamReader sr = new StreamReader(s, Encoding.GetEncoding("gb2312"), true);
            string html = sr.ReadToEnd();

            //Console.Write(html);

            // 定义正则表达式用来匹配 img 标签
            Regex regImg = new Regex(@"<img\b[^<>]*?\bsrc[\s\t\r\n]*=[\s\t\r\n]*[""‘]?[\s\t\r\n]*(?<imgUrl>[^\s\t\r\n""‘<>]*)[^<>]*?/?[\s\t\r\n]*>", RegexOptions.IgnoreCase);

            // 搜索匹配的字符串
            MatchCollection matches = regImg.Matches(html);

            int foreachIndex = 1;
            foreach (Match match in matches)
            {
                string imageUrl = "http://www.wzfzl.cn/" + match.Groups["imgUrl"].Value;
                if (imageUrl.IndexOf("uploads") > 0)
                {
                    download(imageUrl, foreachIndex);
                }
                foreachIndex++;
            }
            sr.Close();
            sr.Dispose();

            Console.ReadKey();
        }

        /// <summary>
        /// 下载图片
        /// </summary>
        /// <param name="imageUrl"></param>
        /// <param name="index"></param>
        static void download(string imageUrl, int index)
        {
            string filename = DateTime.Now.Second.ToString() + new Random().Next();
            string filepath = @"F:\uploads\" + filename + "_" + index + ".jpg";

            //FileStream FileMode.OrenOrCreate 使用写模式可以省略下面创建文件语句
            //if (!File.Exists(filepath))
            //{
               // File.Create(filepath).Dispose();  //创建文件并关闭创建对象资源。
            //}           

            //请求图片
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(imageUrl);
            request.Timeout = 5000; //请求超时时间
            request.Method = "GET";
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream s = response.GetResponseStream();  

            //创建文件并写入数据
            FileStream fs = new FileStream(filepath, FileMode.OpenOrCreate, FileAccess.Write);
            byte[] buffer = new byte[1024];
            while (true)
            {
                int r = s.Read(buffer, 0, buffer.Length);
                if (r == 0)
                {
                    break;
                }
                fs.Write(buffer, 0, r);
            }
            fs.Close();
            fs.Dispose();
            response.Close();

            Console.Write("Success : ");
            Console.WriteLine(imageUrl);

        }
    }
}

运行效果如下：