asp.net如何给每张图片动态添加水印方法（一）

前台

 <asp:ImageButton ID="imgBtn2" runat="server" ImageUrl="~/imageHandler.ashx?isbn=7115147353" Width="128" Height="135"/>

httpHandle后台

<%@ WebHandler Language="C#" Class="imageHandler" %>

using System;

using System.Web;

using System.Drawing;

using System.Drawing.Imaging;

using System.IO;

using System.Text;

public class imageHandler : IHttpHandler {

    

    public void ProcessRequest (HttpContext context) {

        string isbn = context.Request.QueryString["isbn"];

        string path = context.Server.MapPath("~/Images/BookCovers/"+isbn+".jpg");

        string defaultImg = context.Server.MapPath("~/Images/default.jpg");

        string waterImg = context.Server.MapPath("~/Images/WaterMark.jpg");

        Image cover;

        if (File.Exists(path))

        {

            //加载水印

            Image water = Image.FromFile(waterImg);

            //加载文件

            cover = Image.FromFile(path);

            //实例化画布

            Graphics g = Graphics.FromImage(cover);

            //在Images上绘制水印

            g.DrawImage(

                water, cover.Width - water.Width,

                cover.Height - water.Height,

                water.Width, water.Height

                );

            g.Dispose();

        }

        else//图片不存在时加载默认图片

        {

            cover = Image.FromFile(defaultImg);

        }

        //设置输出类型为jpeg图片

        context.Response.ContentType = "image/jpeg";

        //将修改的图片存入输出流

        cover.Save(context.Response.OutputStream, ImageFormat.Jpeg);

        cover.Dispose();

        context.Response.End();

        

            }

    public bool IsReusable {

        get {

            return true;

        }

    }

}