图片水印

public class WaterImgHandler:IHttpHandler
 2     {
 3 
 4         public bool IsReusable
 5         {
 6             get { return false; }
 7         }
 8 
 9         public void ProcessRequest(HttpContext context)
10         {
11                  // 指定水印图片
12             string water_Url = "~/wImages/logo.gif";
13             // 指定默认图片
14             string default_Url = "~/wImages/error.jpg";
15             // 创建图片对象，用于存放用户读取的图片
16             System.Drawing.Image g;
17             // 判断所请求的图片是否存在，存在就给图片加水印
18             if (File.Exists(context.Request.PhysicalPath))
19             {
20                 g = System.Drawing.Image.FromFile(context.Request.PhysicalPath);
21                 // 加载水印图片
22                 System.Drawing.Image waterImg = System.Drawing.Image.FromFile(context.Request.MapPath(water_Url));
23                 Graphics gh = Graphics.FromImage(g);
24                 gh.DrawImage(waterImg, new RectangleF(0, g.Height - waterImg.Height, 100, 20));
25 
26                 // 加载水印字符串
27                 Font font = new System.Drawing.Font("Arial", 6, System.Drawing.FontStyle.Bold);
28                 gh.DrawString("abcdefg", font, Brushes.White, 2, 2);
29                 gh.Dispose();
30                 waterImg.Dispose();
31             }
32             else { 
33                 // 图片不存在，显示默认图片
34                 g = System.Drawing.Image.FromFile(context.Request.MapPath(default_Url));
35             }
36             context.Request.ContentType = "image/jpeg";
37             g.Save(context.Response.OutputStream,System.Drawing.Imaging.ImageFormat.Jpeg);
38             g.Dispose();
39             context.Response.End();
40 
41         }
42     }
43         // 最后在配置文件Web.config中写
44       <httpHandlers>
45          <add verb="*" path="*.jpg" type="Picture.WaterImgHandler"/>
46      </httpHandlers>