第一步，添加一個一般處理程序（Handler）,本例是ImageHandler

代碼如下:
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Net.Mime;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;

/// <summary>
/// Summary description for ImageHandler
/// </summary>
public class ImageHandler : IHttpHandler
{
    public ImageHandler()
    {
    }

    public string GetContentType(String path)
    {
        switch (Path.GetExtension(path))
        {
            case ".bmp": return "Image/bmp";
            case ".gif": return "Image/gif";
            case ".jpg": return "Image/jpeg";
            case ".png": return "Image/png";
            default: break;
        }
        return String.Empty;
    }

    public ImageFormat GetImageFormat(String path)
    {
        switch (Path.GetExtension(path).ToLower())
        {
            case ".bmp": return ImageFormat.Bmp;
            case ".gif": return ImageFormat.Gif;
            case ".jpg": return ImageFormat.Jpeg;
            case ".png": return ImageFormat.Png;
            default: return null;
        }
    }

    protected byte[] WatermarkImage(HttpContext context)
    {

        byte[] imageBytes = null;
        if (File.Exists(context.Request.PhysicalPath))
        {
            // Normally you'd put this in a config file somewhere.
            string watermark = "世復檢測";

            Image image = Image.FromFile(context.Request.PhysicalPath);