一般处理程序上传图片打水印

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.IO;
using System.Drawing;

namespace CZBK.ItcastProject.WebApp._2015_5_27
{
    /// <summary>
    /// ProcessFileUp 的摘要说明
    /// </summary>
    public class ProcessFileUp : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/html";
            HttpPostedFile file = context.Request.Files[0];//获取上传的文件
            if (file.ContentLength > 0)
            {
                //对上传的文件类型进行校验
                string fileName = Path.GetFileName(file.FileName);//获取上传文件的名称，包含扩展名
                string fileExt = Path.GetExtension(fileName);//获取用户上传的文件扩展名
                if (fileExt == ".jpg")
                {
                    //对上传文件进行重命名
                    string newfileName = Guid.NewGuid().ToString();
                    //将上传的文件放在不同目录下
                    string dir = "/ImageUpload/" + DateTime.Now.Year + "/" + DateTime.Now.Month + "/" + DateTime.Now.Day + "/";
                    //创建文件夹
                    if (!Directory.Exists(context.Request.MapPath(dir)))
                    {
                        Directory.CreateDirectory(context.Request.MapPath(dir));
                    }
                    //文件的完整路径
                    string fullDir = dir + newfileName + fileExt;
                    //注意：保存一定要用context.Request.MapPath来回去路径
                    file.SaveAs(context.Request.MapPath(fullDir));


                    //创建图片的水印
                    //using (Image img = Image.FromStream(file.InputStream))//或者下面的
                    //根据上传成功的图片创建一个Image
                    using (Image img=Image.FromFile(context.Request.MapPath(fullDir)))
                    {
                        //根据画布的高度与宽度创建画布
                        using (Bitmap map =new Bitmap(img.Width,img.Height))
                        {
                            //为画布创建画笔
                            using (Graphics g=Graphics.FromImage(map))
                            {
                                g.DrawImage(img, 0, 0, img.Width, img.Height);
                                g.DrawString("图片加水印", new Font("宋体", 30.0f, FontStyle.Bold), Brushes.Red, new PointF(map.Width - 400, map.Height - 200));
                                string waterImageName="water"+Guid.NewGuid().ToString();
                                map.Save(context.Request.MapPath("/ImageUpload/"+waterImageName+".jpg"),System.Drawing.Imaging.ImageFormat.Jpeg);
                                context.Response.Write("<html><body><img src='" + fullDir + "'></br><img src='/ImageUpload/" + waterImageName + ".jpg' /></body></html>");
                            }
                        }
                    }
                    
                    //context.Response.Write("<html><body><img src='" + fullDir + "'></body></html>");
                    //file.SaveAs(context.Request.MapPath("/ImageUpload/"+fileName));//完成文件的保存
                    //context.Response.Write("<html><body><img src='/ImageUpload/" + fileName + "'></body></html>");
                }
                else
                {
                    context.Response.Write("只能上传图片文件");
                }
            }
            else
            {
                context.Response.Write("请选择上传文件");
            }
        }

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

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title></title>
</head>
<body>
    <form action="ProcessFileUp.ashx" method="post" enctype="multipart/form-data">
        <input type="file" name="fileup" />
        <input type="submit" value="上传" />
    </form>
</body>
</html>