The fastest possible way to catch the screen? Any Language - language-agnostic

Question

I need to take print-screens of a Windows application very very fast to make a video out of it... I have been using C# all the way, but I'm open to any language in which this process may be faster.
I have used many techniques:
.net functions: Bitmap.CopyFromScreen()
GDI
Direct3d/DirectX
The fastest I've got was using GDI and still I get less than 10 fotograms per second. I would need a bit more than that, at least 20 or 30...
It seems very strange to me that such a simple operation is so demanding. And it looks as if using a faster cpu doesn't change the situation.
What can I do? Is it possible to directly capture the drawing of an application using gdi or something? Or maybe even lower-level functions to catch the info being thrown to the graphics card?
Any light on this issue would be pretty much appreciated.
Thanks a lot

Answer 1

A lot of programs use a driver and allows your application to hook into the lower level display routines. I'm not exactly sure how this is done, but it is possible.
Here is a starting point on writing Windows driver. http://msdn.microsoft.com/en-us/library/ms809956.aspx
Here is something I just found via Google:
http://www.hmelyoff.com/index.php?section=17

Answer 2

You probably want to use something like Camtasia. Depends on why you're making the video.
I use a rewritten version of Jeff's User-Friendly Exception Handling, and he uses BitBlt from GDI to capture screenshots. Seems fast enough to me, but I haven't benchmarked it, and we just use it for one-at-a-time shots when there's an unhandled exception thrown.
#region Win32 API screenshot calls
// Win32 API calls necessary to support screen capture
[DllImport("gdi32", EntryPoint = "BitBlt", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
private static extern int BitBlt(int hDestDC, int x, int y, int nWidth, int nHeight, int hSrcDC, int xSrc,
int ySrc, int dwRop);
[DllImport("user32", EntryPoint = "GetDC", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
private static extern int GetDC(int hwnd);
[DllImport("user32", EntryPoint = "ReleaseDC", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
private static extern int ReleaseDC(int hwnd, int hdc);
#endregion
private static ImageFormat screenshotImageFormat = ImageFormat.Png;
/// <summary>
/// Takes a screenshot of the desktop and saves to filename and format specified
/// </summary>
/// <param name="fileName"></param>
private static void TakeScreenshotPrivate(string fileName)
{
Rectangle r = Screen.PrimaryScreen.Bounds;
using (Bitmap bitmap = new Bitmap(r.Right, r.Bottom))
{
const int SRCCOPY = 13369376;
using (Graphics g = Graphics.FromImage(bitmap))
{
// Get a device context to the windows desktop and our destination bitmaps
int hdcSrc = GetDC(0);
IntPtr hdcDest = g.GetHdc();
// Copy what is on the desktop to the bitmap
BitBlt(hdcDest.ToInt32(), 0, 0, r.Right, r.Bottom, hdcSrc, 0, 0, SRCCOPY);
// Release device contexts
g.ReleaseHdc(hdcDest);
ReleaseDC(0, hdcSrc);
string formatExtension = screenshotImageFormat.ToString().ToLower();
string expectedExtension = string.Format(".{0}", formatExtension);
if (Path.GetExtension(fileName) != expectedExtension)
{
fileName += expectedExtension;
}
switch (formatExtension)
{
case "jpeg":
BitmapToJPEG(bitmap, fileName, 80);
break;
default:
bitmap.Save(fileName, screenshotImageFormat);
break;
}
// Save the complete path/filename of the screenshot for possible later use
ScreenshotFullPath = fileName;
}
}
}
/// <summary>
/// Save bitmap object to JPEG of specified quality level
/// </summary>
/// <param name="bitmap"></param>
/// <param name="fileName"></param>
/// <param name="compression"></param>
private static void BitmapToJPEG(Image bitmap, string fileName, long compression)
{
EncoderParameters encoderParameters = new EncoderParameters(1);
ImageCodecInfo codecInfo = GetEncoderInfo("image/jpeg");
encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality, compression);
bitmap.Save(fileName, codecInfo, encoderParameters);
}