C#写爬虫，版本V2.0

Posted 2020-07-27 张杨

这个版本主要是以百度图片为对象，对其进行爬虫操作，实现了最基本的下载功能，但是缺陷非常多，日后还会对其进行改进。

打开百度图片，同时打开开发者工具，我们会发现，百度图片是通过如下的一段ajax来加载图片的。

http://image.baidu.com/search/index?tn=baiduimage&ipn=r&ct=201326592&cl=2&lm=-1&st=-1&fm=result&fr=&sf=1&fmq=1466428638972_R&pv=&ic=0&nc=1&z=&se=1&showtab=0&fb=0&width=&height=&face=0&istype=2&ie=utf-8&word=%E5%94%90%E5%AB%A3&f=3&oq=tangyan&rsp=0

这里，我们只需了解word后面就是我们的关键字，那么，这个就比较好弄了，结合一部分V1.0的代码，很快就可以开发出来，原理和V1.0类似。

后台代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Newtonsoft.Json.Linq;
using Newtonsoft.Json;
using System.Text.RegularExpressions;

namespace 针对百度图片的动态网页爬虫
{
    public partial class Form1 : Form
    {
        static int count = 0;
        public Form1()
        {
            InitializeComponent();
        }

        private void btnDo_Click(object sender, EventArgs e)
        {
            int pageCount=2;
            string keyword = this.keyWords.Text;
            for (int i = 0; i <pageCount; i++)
            {
                HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("http://image.baidu.com/search/index?tn=baiduimage&ipn=r&ct=201326592&cl=2&lm=-1&st=-1&fm=result&fr=&sf=1&fmq=1466307565574_R&pv=&ic=0&nc=1&z=&se=1&showtab=0&fb=0&width=&height=&face=0&istype=2&ie=utf-8&word="+keyword.ToString());
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                {
                    if (response.StatusCode == HttpStatusCode.OK)
                    {
                        using (Stream stream = response.GetResponseStream())
                        {
                            try
                            {
                                // 下载指定页的所有图片
                                DownloadPage(stream);
                            }
                            catch (Exception ex)
                            {
                                // 跨线程访问UI线程的txtLogs
                               
                            }
                        }
                    }
                    else
                    {
                       // MessageBox.Show("获取第" + pageCount + "页失败：" + response.StatusCode);
                    }
                }
            }
            MessageBox.Show("执行成功，共"+count.ToString()+"图片");
        }
        private static string[] getLinks(string html)
        {
            const string pattern = @"http://([\\w-]+\\.)+[\\w-]+(/[\\w- ./?%&=]*)?";
            Regex r = new Regex(pattern, RegexOptions.IgnoreCase); //新建正则模式
            MatchCollection m = r.Matches(html); //获得匹配结果
            string[] links = new string[m.Count];
            int count=0;
            for (int i = 0; i < m.Count; i++)
            {
                if(isValiable(m[i].ToString()))
                {
                      links[count] = m[i].ToString(); //提取出结果
                    count++;
                }
              
            }
            return links;
        }
        private void DownloadPage(Stream stream)
        {
            using(StreamReader reader=new StreamReader(stream))
            {
                string r1;
                StringBuilder sb = new StringBuilder();
                while((r1=reader.ReadLine())!=null)
                {
                    sb.Append(r1);
                }
                FileStream aFile = new FileStream("../../txt.txt", FileMode.OpenOrCreate);
                StreamWriter sw = new StreamWriter(aFile);//将网页存储到了txt文本文件中
                sw.WriteLine(sb.ToString());
                sw.Close();
                string[] s;
                s = getLinks(sb.ToString());
                int i = 0;
               
                for(i=0;i<s.Count();i++)
                {
                    if(s[i]!=null||s[i]!="")
                    {
                        count++;
                        savePicture(s[i]);
                    }
                   
                }
                this.label2.Text = count.ToString();
            }
        }
        private static bool isValiable(string url)
        {
            if (url.Contains(".jpg") || url.Contains(".gif") || url.Contains(".png"))
            {
                return true; //得到一些图片之类的资源
            }
            return false;
        }
        private static void savePicture(string path)
        {
            DataClasses1DataContext db = new DataClasses1DataContext();
            Uri url = new Uri(path);
            HttpWebRequest webRequest = (HttpWebRequest)HttpWebRequest.Create(url);
            webRequest.Referer = "http://image.baidu.com";
            HttpWebResponse webResponse = (HttpWebResponse)webRequest.GetResponse();

            if (isValiable(path))//判断如果是图片，就将其存储到数据库中。
            {
                Bitmap myImage = new Bitmap(webResponse.GetResponseStream());

                MemoryStream ms = new MemoryStream();
                myImage.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
                var p = new pictureUrl
                {
                    pictureUrl1 = ms.ToArray()
                };
                db.pictureUrl.InsertOnSubmit(p);
                db.SubmitChanges();
            }

        }
    }
}

演示效果：

这个程序只是解决了有无得问题，还有许多问题，以后会继续解决。