asp.net如何在图片上加水印文字具体实现

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 = "世复检测";

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

            Graphics graphic;
            if (image.PixelFormat != PixelFormat.Indexed && image.PixelFormat != PixelFormat.Format8bppIndexed && image.PixelFormat != PixelFormat.Format4bppIndexed && image.PixelFormat != PixelFormat.Format1bppIndexed)
            {
                // Graphic is not a Indexed (GIF) image
                graphic = Graphics.FromImage(image);
            }
            else
            {
                / Cannot create a graphics object from an indexed (GIF) image.
                 So we're going to copy the image into a new bitmap so
                 we can work with it. /
                Bitmap indexedImage = new Bitmap(image);
                graphic = Graphics.FromImage(indexedImage);

                // Draw the contents of the original bitmap onto the new bitmap.
                graphic.DrawImage(image, 0, 0, image.Width, image.Height);
                image = indexedImage;
            }
            graphic.SmoothingMode = SmoothingMode.AntiAlias & SmoothingMode.HighQuality;

            Font myFont = new Font("Arial", 15);
            SolidBrush brush = new SolidBrush(Color.FromArgb(255, Color.Red));

            / This gets the size of the graphic so we can determine
             the loop counts and placement of the watermarked text. /
            SizeF textSize = graphic.MeasureString(watermark, myFont);

            //// Write the text across the image.
            //for (int y = 0; y < image.Height; y++)
            //{
            //    for (int x = 0; x < image.Width; x++)
            //    {
            //        PointF pointF = new PointF(x, y);
            //        graphic.DrawString(watermark, myFont, brush, pointF);
            //        x += Convert.ToInt32(textSize.Width);
            //    }
            //    y += Convert.ToInt32(textSize.Height);
            /