Screen capture during testing

Question

This is an application for reviewing performance tests. Simple in concept, tricky to describe. Picture:

1) Recording interactions with a WPF program so the inputs can be played back.

2) Playing the inputs back while doing a continuous screen capture.

3) Capturing wall time as well as continuous CPU percentages during playback.

4) Repeating steps (2) and (3) lots of times.

5) Writing the relevant stuff out to files/db.

6) Reading it and putting it all in a fancy UI for easy review/analysis.

The killer for me is (2). I could use some guidance on a good, possibly commercial, screen capture SDK. I would also welcome the news that my whole problem already has a solution. And of course any thoughts on the overall idea would also be great.

Thanks.

Ed

Answer 1

If you are going to do development for this, you can setup Cucumber / SpecFlow using Windows Automation... and here's a sample in WPF of taking a screenshot of the App under test.

        /// <summary>
        /// Take screen shot
        /// </summary>
        /// <param name="left">left</param>
        /// <param name="top">top</param>
        /// <param name="width">width</param>
        /// <param name="height">height</param>
        /// <returns>screen shot in bytes</returns>
        public static byte[] TakeScreenShot(int left, int top, int width, int height)
        {
            // Set the bitmap object to the size of the screen
            var bmpScreenshot = new Bitmap(width, height,
                                                  PixelFormat.Format32bppArgb);

            // Create a graphics object from the bitmap
            var gfxScreenshot = Graphics.FromImage(bmpScreenshot);

            // Take the screenshot from the upper left corner to the right bottom corner
            gfxScreenshot.CopyFromScreen(left, top, 0, 0,
                                             new Size(width, height), CopyPixelOperation.SourceCopy);

            var buffer = new byte[bmpScreenshot.Size.Height * bmpScreenshot.Size.Width * 4];

            var stream = new MemoryStream(buffer);

            bmpScreenshot.Save(stream, ImageFormat.Png);

            return stream.ToArray();
        }

Answer 2

You can do the screen capture in your own application using DirectShow.

See Video Capture for general details on how to do video capture using DirectShow and links to example code. To capture specifically from the screen you'll need the "Screen Capture filter" filter found in wmpsrcwp.dll, which is found in newer versions of Windows and can also be downloaded as part as the Windows Media Encoder.

Although UI Automation can be used to play back events, it cannot record. If you need to record system events, I recommend you use Windows Hooks for both recording and playback.

DirectShow is easiest to do in C++/CLR instead of C# because you can easily include C++ header files and make unmanaged calls, and Windows Hooks should only be done in native code.