More Windows Secrets for Visual Basic

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Capturing the Screen, Quick and Easy

When it comes to showing people how to capture the screen, most VB.NET authors I've seen tend to revert to the old-school method of working: using the API. There is, however, a better way.

The following function is called GetScreenCapture and returns an Image object. It captures the screen by running a series of "Print Screen" key presses, which puts a screen grab on the Clipboard, ready for my nifty little function to devour and return. My function accepts a FullScreen argument, too: Pass True to capture the whole screen, or False to capture just the active window.

Here's the code:

Public Function GetScreenCapture( _
   Optional ByVal FullScreen As Boolean = False) As Image
   ' Captures the current screen and returns as an Image
   ' object
   Dim objSK As SendKeys
   Dim imgCapture As Image
   If FullScreen = True Then
       ' Print Screen pressed twice here as some systems
       ' grab active window "accidentally" on first run
       objSK.SendWait("{PRTSC 2}")
   Else
       objSK.SendWait("%{PRTSC}")
   End If
   Dim objData As IDataObject = Clipboard.GetDataObject()
   Return objData.GetData(DataFormats.Bitmap)
End Function

And here are a couple of examples demonstrating how to use that Image object—firstly, saving it as a file; and secondly, using it to set the Image property of a PictureBox control:

GetScreenCapture(True).Save("c:\screengrab.bmp")
PictureBox1.Image = GetScreenCapture()

My sample application, capturing the active window (again and again)

Next Time

Coming up in part three of Windows Secrets, check out:

• How to 'Reset' a Form
• The Facts on Visual Inheritance
• Secrets of Working with the System Tray
• Best of All Worlds: Creating an Ultra-Thin Client

See you next time!

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