From: Zach Dennis <zdennis@...>
Date: 2005-07-15T14:16:00+09:00
Subject: Re: Capturing window display of another program?

David Brady wrote:
> Is it possible to take a screenshot of another window in Ruby?  (On Win32)
> 
> I'd like to write a script to scrape the output of a graphics test 
> program (which I do not have source for) at regular intervals, and run 
> tests against them.  E.g., grab the display area & check to see if it's 
> generating a gradient fill (good), or a black display (bad) by testing 
> some of the pixels inside the display area.
> 
> What about sending clicks, drags and keypresses to that window?  At that 
> point, it would be a poor man's WinRunner, hrm....
> 

This has to be possible, because you can do this with GIMP. Perhaps 
looking into... Windows GDI and...

EnumWindows
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowfunctions/getwindow.asp

FindWindow
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowfunctions/getwindow.asp

GetWindow
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowfunctions/getwindow.asp

BitBlt - to perform the screenshot
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/bitmaps_0fzo.asp

GetWindowRect
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowfunctions/getwindow.asp

Good luck! Let us know when you get something working!

Zach