使用WebBrower实现ASP.NET抓图 但不知为何出现空白

Question

代码如下：GetImage.cs
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Windows.Forms;
using System.IO;/// <summary>
/// GetImage 的摘要说明
/// </summary>
namespace Wap.Map
{
    public class GetImage
    {
        int F_Width;
        string MyURL;
        /// <summary>
        /// 宽度
        /// </summary>
        public int ImageWidth
        {
            get
            {
                return F_Width;
            }
            set
            {
                F_Width = value;
            }
        }
        /// <summary>
        /// URL地址
        /// </summary>
        public string WebSite
        {
            get
            {
                return MyURL;
            }
            set
            {
                MyURL = value;
            }
        }
        /// <summary>
        /// 构造
        /// </summary>
        /// <param name="WebSite"></param>
        /// <param name="ImageWidth"></param>
        public GetImage(string WebSite, int ImageWidth)
        {
            this.WebSite = WebSite;
            this.ImageWidth = ImageWidth;
        }
        /// <summary>
        /// 获得图片
        /// </summary>
        /// <returns></returns>
        public byte[] GetBitmap()
        {
            WebPageBitmap Shot = new WebPageBitmap(this.WebSite);
            Shot.GetIt();
            Bitmap Pic = Shot.DrawBitmap(this.ImageWidth);
            return imageToByteArray(Pic);
        }
        /// <summary>
        /// 获得输出
        /// </summary>
        /// <param name="bitMap"></param>
        /// <returns></returns>
        private byte[] imageToByteArray(System.Drawing.Bitmap bitMap)
        {
            MemoryStream ms = new MemoryStream();
            bitMap.Save(ms, System.Drawing.Imaging.ImageFormat.Bmp);
            return ms.ToArray();
        }
        /// <summary>
        /// 获得图片类型
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        private System.Drawing.Imaging.ImageFormat getImgFormat(string fileName)
        {
            fileName = Path.GetExtension(fileName).TrimStart('.').ToLower();
            if (fileName.Equals("bmp"))
            {
                return System.Drawing.Imaging.ImageFormat.Bmp;
            }
            if (fileName.Equals("gif"))
            {
                return System.Drawing.Imaging.ImageFormat.Gif;
            }
            if (fileName.Equals("jpg") || fileName.Equals("jpeg"))
            {
                return System.Drawing.Imaging.ImageFormat.Jpeg;
            }
            if (fileName.Equals("png"))
            {
                return System.Drawing.Imaging.ImageFormat.Png;
            }
            if (fileName.Equals("tiff"))
            {
                return System.Drawing.Imaging.ImageFormat.Tiff;
            }
            return System.Drawing.Imaging.ImageFormat.Jpeg;
        }    }
    /// <summary>
    /// 抓网页
    /// </summary>
    public class WebPageBitmap
    {
        System.Windows.Forms.WebBrowser MyBrowser;
        string URL;
        public WebPageBitmap(string url)
        {
            this.URL = url;
            MyBrowser = new System.Windows.Forms.WebBrowser();
            MyBrowser.ScrollBarsEnabled = false;
            MyBrowser.Visible = false;
            MyBrowser.Size = new Size(1, 1);
        }        public void GetIt()
        {
            MyBrowser.Navigate(this.URL, false);
            while (MyBrowser.ReadyState != WebBrowserReadyState.Complete)
            {
                Application.DoEvents();
                System.Threading.Thread.Sleep(500);
            }
        }        public Bitmap DrawBitmap(int imgWidth)
        {
            int DocumentHeight = MyBrowser.Document.Window.Size.Height;
            int DocumentWidth = MyBrowser.Document.Window.Size.Width;
            MyBrowser.Size = new Size(DocumentWidth, DocumentHeight);
            if (DocumentWidth < imgWidth)
            {
                imgWidth = DocumentWidth;
            }
            int imgHeight = System.Convert.ToInt32(Math.Ceiling(DocumentHeight * imgWidth / System.Convert.ToDouble(DocumentWidth)));
            Bitmap MyBitmap = new Bitmap(DocumentWidth, DocumentHeight);
            Rectangle DrawRect = new Rectangle(0, 0, DocumentWidth, DocumentHeight);
            /*
             * System.Windows.Forms.WebBrowser继承了System.Windows.Forms.WebBrowserBase
             * 而
             * System.Windows.Forms.WebBrowserBase继承了System.Windows.Forms.Control
             * 
             * System.Windows.Forms.Control.DrawToBitmap(bitmap,targetBounds)
             * 支持呈现到指定的位图
             * bitmap         要绘制到的位图。
             * targetBounds   呈现控件时的边界。
             * 
             * DrawToBitmap 方法具有下列局限性：
             * 可能会针对大位图引发 ArgumentException。允许使用的最大大小因计算机而异。
             * DrawToBitmap 不支持 Windows XP Tablet PC Edition 2005 操作系统的 Ink 控件。
             * 如果 TextBox 的 Visible 属性设置为 false，则 DrawToBitmap 不绘制子 TextBox。
             * 容器内部的控件按相反的顺序呈现。
             * 对于 RichTextBox，DrawToBitmap 不能完全发挥作用；只绘制位图的边框
             */
            try
            {
                MyBrowser.DrawToBitmap(MyBitmap, DrawRect);
                System.Drawing.Bitmap oThumbNail = new Bitmap(imgWidth, imgHeight, MyBitmap.PixelFormat);
                Graphics g = Graphics.FromImage(oThumbNail);
                g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighSpeed;
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighSpeed;
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;
                Rectangle oRectangle = new Rectangle(0, 0, imgWidth, imgHeight);
                g.DrawImage(MyBitmap, oRectangle);
                g.Dispose();
                return oThumbNail;
            }
            catch
            {
                return null;
            }
            finally
            {
                MyBitmap.Dispose();
                MyBrowser.Dispose();
                MyBrowser = null;
            }
        }
    }
}

Answer 1

形成图片页面：
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="GetMap.aspx.cs" Inherits="Wap.Map.GetMap" %>
后台代码
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Threading;
namespace Wap.Map
{
    public partial class GetMap : System.Web.UI.Page
    {
        private AutoResetEvent autoEvent = new AutoResetEvent(false);        private byte[] content = null;        protected void Page_Load(object sender, EventArgs e)
        {
            Response.Clear();
            Response.Buffer = true;            ThreadStart start = new ThreadStart(getContent);
            Thread t = new Thread(start);
            t.SetApartmentState(ApartmentState.STA);
            t.Priority = ThreadPriority.Highest;
            t.Start();            autoEvent.WaitOne(1000, false);
            while (content == null)
            {
                //等待线程结果;
                autoEvent.WaitOne(500, false);
            }
            Response.BinaryWrite(content);
            Response.End();
        }        private void getContent()
        {
            string url = "http://www.baidu.com"; 
            GetImage image = new GetImage(url, 230);
            content = image.GetBitmap();
            autoEvent.Set();
        }
    }
}

Answer 2

测试页面：
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Test.aspx.cs" Inherits="Wap.Test" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <img src="Map/GetMap.aspx" />
    </div>
    </form>
</body>
</html>

Answer 3

看看这个有帮助吗？
http://topic.csdn.net/u/20070512/23/B45AC41D-06EF-4D15-856C-3EEAE5A86D88.html