ASP.NET为图片加上水印

为我们发布的图片加上一个水印，也是我们经常要做的事情，那怎么样来做呢，下面就一步步开始吧

首先是一个制作水印的类：ImageHandler,代码如下：

using System;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

/// <summary>
///ImageHandler 的摘要说明
/// </summary>
public class ImageHandler:IHttpHandler
{
    private const string waterMark_URL = "~/Images/waterMark.jpg";
    private const string defaultImage_URL = "~/Images/Default.jpg";

    public ImageHandler()
    {
        //
        //TODO: 在此处添加构造函数逻辑
        //
    }

    public void ProcessRequest(HttpContext context)
    {
        System.Drawing.Image ImageConver;
        if (File.Exists(context.Request.PhysicalPath))
        {
            //加载文件
            ImageConver = Image.FromFile(context.Request.PhysicalPath);
            //加载水印图片
            Image waterMark = Image.FromFile(context.Request.MapPath(waterMark_URL));
            //重新画布
            Graphics g = Graphics.FromImage(ImageConver);
            g.DrawImage(waterMark, new Rectangle(ImageConver.Width - waterMark.Width, ImageConver.Height - waterMark.Height, waterMark.Width, waterMark.Height), 0, 0, waterMark.Width, waterMark.Height, GraphicsUnit.Pixel);
            g.Dispose();
            waterMark.Dispose();
        }
        else
        {
            ImageConver=Image.FromFile(context.Request.MapPath(defaultImage_URL));
        }

        //设置输出格式
        context.Response.ContentType="image/jpeg";
        ImageConver.Save(context.Response.OutputStream,System.Drawing.Imaging.ImageFormat.Jpeg);
        ImageConver.Dispose();
        context.Response.End();
    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }
}

接下来，我们要做一个很关键的配置，那就是在Web.Config文件中加入如下一句话

<httpHandlers>

<!--图片水印-->
      <add verb="*" path="Images/*.jpg" type="ImageHandler"/>

</httpHandlers>