C#生成网页缩略图的方法，我们需要采用WebBrower控件

废话少说，看代码

原理其实是在请求页面加载完毕后触发缩略图生成事件，生成显示回来的数据

private void OnDocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
       WebBrowser browser = (sender as WebBrowser);
       
       if (browser != null)
       {
         mshtml.IHTMLDocument2 document = (browser.Document.DomDocument as mshtml.IHTMLDocument2);
         if (document != null)
         {
           mshtml.IHTMLElement element = (document.body as mshtml.IHTMLElement);
           if (element != null)
           {
             IHTMLElementRender render = (element as IHTMLElementRender);
             if (render != null)
             {
               using (Graphics graphics = this.CreateGraphics())
               {
                 IntPtr hdcDestination = graphics.GetHdc();
                 render.DrawToDC(hdcDestination);
                 IntPtr hdcMemory = GDI32.CreateCompatibleDC(hdcDestination);
                 IntPtr bitmap = GDI32.CreateCompatibleBitmap(
                   hdcDestination,
                   browser.ClientRectangle.Width,
                   browser.ClientRectangle.Height
                   );
                 
                 if (bitmap != IntPtr.Zero)
                 {
                   IntPtr hOld = (IntPtr)GDI32.SelectObject(hdcMemory, bitmap);
                   GDI32.BitBlt(
                     hdcMemory,
                     0, 0,
                     browser.ClientRectangle.Width, browser.ClientRectangle.Height,
                     hdcDestination,
                     0, 0,
                     TernaryRasterOperations.SRCCOPY
                     );
                   GDI32.SelectObject(hdcMemory, hOld);
                   GDI32.DeleteDC(hdcMemory);
                   graphics.ReleaseHdc(hdcDestination);
                   
                   SaveThumbnail(Image.FromHbitmap(bitmap));
                 }
               }
             }
           }
         }
       }
} 

从这里获取了内容的话，我们就很容易生成缩略图了，代码如下

//by crazycoder.cn
private void SaveThumbnail(Image image)
{
       if (image != null)
       {//创建一个位图图像
         Bitmap thumbnail = new Bitmap(160, 120, PixelFormat.Format24bppRgb);
         thumbnail.SetResolution(image.HorizontalResolution, image.VerticalResolution);
         
         using (Graphics resize = Graphics.FromImage(thumbnail))
         {
           resize.InterpolationMode = InterpolationMode.HighQualityBicubic;
           resize.DrawImage(image,
             new Rectangle(0, 0, 160, 120),
             new Rectangle(0, 0, _webBrowser.ClientRectangle.Width, _webBrowser.ClientRectangle.Height),
             GraphicsUnit.Pixel);
         }
         thumbnail.Save(_file.FullName, ImageFormat.Png);
       }
} 

下载整个项目代码  CrazyCoder_WebPageToImage.zip