根据html代码利用WebBrowser控件生成图片功能。 可以利用此代码完成长微博的发布。

gistfile1.cs

namespace Utils
{
    /*
    Bitmap bitmap = Utils.Html2Image.GenerateImage("<h1>标题一</h1><h2>标题二</h2><font color=\"red\">红色普通</font><br /><img src=\"https://www.google.com/images/srpr/logo4w.png\" />", 440);
    //MemoryStream ms = new MemoryStream();
    //bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Png);//JPG、GIF、PNG等均可
    bitmap.Save(Server.MapPath("img.png"), System.Drawing.Imaging.ImageFormat.Png);
    */
    using System;
    using System.Drawing;
    using System.Threading;
    using System.Windows.Forms;
    public class Html2Image
    {
        Bitmap _Bitmap;
        string _txtHtml;
        int _BrowserWidth, _BrowserHeight, _ThumbnailWidth, _ThumbnailHeight;
        public Html2Image(string txtHtml, int maxWidth)
        {
            _txtHtml = txtHtml;
            _ThumbnailWidth = maxWidth;
        }
        public static Bitmap GenerateImage(string txtHtml, int maxWidth)
        {
            Html2Image thumbnailGenerator = new Html2Image(txtHtml, maxWidth);
            return thumbnailGenerator.CreateThumbnailImage();
        }
        public Bitmap CreateThumbnailImage()
        {
            Thread thd = new Thread(new ThreadStart(_GenerateThumbnailImage));
            thd.SetApartmentState(ApartmentState.STA);
            thd.Start();
            thd.Join();
            return _Bitmap;
        }
        private void _GenerateThumbnailImage()
        {
            WebBrowser Browser = new WebBrowser();
            Browser.ScrollBarsEnabled = false;
            Browser.DocumentText = _txtHtml;
            Browser.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(WebBrowser_DocumentCompleted);
            while (Browser.ReadyState != WebBrowserReadyState.Complete)
            {
                Application.DoEvents();
            }
            Browser.Dispose();
        }
        private void WebBrowser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
        {
            WebBrowser Browser = (WebBrowser)sender;
            HtmlDocument hd = Browser.Document;
            int height = Convert.ToInt32(hd.Body.GetAttribute("scrollHeight")) + 10;
            int width = Convert.ToInt32(hd.Body.GetAttribute("scrollWidth")) + 10;
            this._BrowserHeight = height;
            this._BrowserWidth = width;

            //如果html的内容区域大于设定的图片大小，则缩略
            if (width <= _ThumbnailWidth) { _ThumbnailWidth = width; }
            _ThumbnailHeight = height * _ThumbnailWidth / width;

            Browser.ClientSize = new Size(this._BrowserWidth, this._BrowserHeight);
            Browser.ScrollBarsEnabled = false;
            _Bitmap = new Bitmap(_ThumbnailWidth, _ThumbnailHeight);
            Graphics g = Graphics.FromImage(_Bitmap);
            g.Clear(Color.White);
            Browser.BringToFront();
            Browser.DrawToBitmap(_Bitmap, Browser.Bounds);
            _Bitmap = (Bitmap)_Bitmap.GetThumbnailImage(_ThumbnailWidth, _ThumbnailHeight, null, IntPtr.Zero);
        }
    }
}