public class WebsiteToImage
{
private Bitmap m_Bitmap;
private string m_Url;
private string m_FileName = string.Empty;

public WebsiteToImage(string url)
{
// Without file
m_Url = url;
}

public WebsiteToImage(string url, string fileName)
{
// With file
m_Url = url;
m_FileName = fileName;
}

public Bitmap Generate()
{
// Thread
var m_thread = new Thread(_Generate);
m_thread.SetApartmentState(ApartmentState.STA);
m_thread.Start();
m_thread.Join();
return m_Bitmap;
}

private void _Generate()
{
var browser = new WebBrowser { ScrollBarsEnabled = false };
browser.Navigate(m_Url);
browser.DocumentCompleted += WebBrowser_DocumentCompleted;

while (browser.ReadyState != WebBrowserReadyState.Complete)
{
Application.DoEvents();
}

browser.Dispose();
}

private void WebBrowser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
// Capture
var browser = (WebBrowser)sender;
browser.ClientSize = new Size(browser.Document.Body.ScrollRectangle.Width, browser.Document.Body.ScrollRectangle.Bottom);
browser.ScrollBarsEnabled = false;
m_Bitmap = new Bitmap(browser.Document.Body.ScrollRectangle.Width, browser.Document.Body.ScrollRectangle.Bottom);
browser.BringToFront();
browser.DrawToBitmap(m_Bitmap, browser.Bounds);

// Save as file?
if (m_FileName.Length > 0)
{
// Save
m_Bitmap.SaveJPG100(m_FileName);
}
}
}

public static class BitmapExtensions
{
public static void SaveJPG100(this Bitmap bmp, string filename)
{
var encoderParameters = new EncoderParameters(1);
encoderParameters.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L);
bmp.Save(filename, GetEncoder(ImageFormat.Jpeg), encoderParameters);
}

public static void SaveJPG100(this Bitmap bmp, Stream stream)
{
var encoderParameters = new EncoderParameters(1);
encoderParameters.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L);
bmp.Save(stream, GetEncoder(ImageFormat.Jpeg), encoderParameters);
}

public static ImageCodecInfo GetEncoder(ImageFormat format)
{
var codecs = ImageCodecInfo.GetImageDecoders();

foreach (var codec in codecs)
{
if (codec.FormatID == format.Guid)
{
return codec;
}
}

// Return
return null;
}
}