图片防盗链

 

首先看看IhttpHandler接口都有哪些成员

1：添加ISAPI扩展名映射（完成iis对jpg等图片的注册，如果只是通过vs2008浏览网站，就不需要注册）

2：实现继承IhttpHandler接口的类 比如JpgHandler.cs

Code
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;
using System.IO;
using System.Globalization;

namespace CustomHandler
{
    public class JpgHandler : IHttpHandler
    {
        public void ProcessRequest(HttpContext context)
        {
            //获取当前Request对象
            HttpRequest req = context.Request;
            //从Request对象中获取所请求文件的物理路径
            string IMG_Path = req.PhysicalPath;
            string ContentType;

            //判断请求的URL是否为本站内的URL
            if (req.UrlReferrer != null && req.UrlReferrer.Host.Length > 0)
            {
                if (CultureInfo.InvariantCulture.CompareInfo.Compare(req.Url.Host, req.UrlReferrer.Host, CompareOptions.IgnoreCase) != 0)
                {
                    IMG_Path = context.Server.MapPath("~/images/error.jpg");
                }
            }

            //根据路径名获取输出内容类型
            ContentType = GetContentType(IMG_Path);

            //判断文件是否存在
            if (File.Exists(IMG_Path))
            {
                context.Response.StatusCode = 200;
                context.Response.ContentType = ContentType;
                context.Response.WriteFile(IMG_Path);
            }
            else
            {
                context.Response.StatusCode = 404;
                context.Response.Status = "无法找到您请求的文件";
            }
        }

        public bool IsReusable
        {
            get { return true; }
        }
         

        /// <summary>
        /// 此方法用于从路径获取输出的MIME类型
        /// </summary>
        /// <param name="path">文件路径</param>
        /// <returns>对应的MIME类型</returns>
        private string GetContentType(string path)
        {
            //获取文件的扩展名
            string extension = Path.GetExtension(path);
            string contentType;
            //判断扩展名对应的Mime类型
            switch (extension)
            {
                case ".gif":
                    contentType = "image/gif";
                    break;
                case "image/jpeg":
                    contentType = "image/jpeg";
                    break;
                case ".png":
                    contentType = "image/png";
                    break;
                default:
                    contentType = "";
                    break;
            }
            //返回mime类型
            return contentType;
        }
    }

}

3：在web.config

<httpHandlers>

<add verb="*" path="*.jpg" type="CustomHandler.JpgHandler,CustomHandler"/>

</httpHandlers>

Type 逗号前是类的名称，逗号后类生成后的程序集名称(如果是code内的类就不需要写程序集)

测试方法：通过vs浏览网站下的图片可以正常显示，copy img的url。发布个网站下 img将出现图片无法访问