Windows – How to screenshot part of the screen under windows

Very easy to do. Hit Command + Shift + 3. You will notice the screenshot image appearing on your desktop. Note you didn't have to click anything!

Now open it up in Preview and crop to the specific window you want.

Just tested with import and a window extended beyond / bigger than the screen size; and it seems import will capture an image of the same size as the big window size -- unfortunately all pixels beyond the screen size, and all pixels covered by other windows, will be black.

So maybe the only way is to use xrandr to enlarge screen size (as in 'screen pannning') - or to use something else that will provide larger screen size: for instance, "How can I take browser screenshots at a higher resolution than my browser supports? - Super User" notes:

Use Xephyr to create a nested X session

(Xephyr is apparently in sudo apt-get install xserver-xephyr in Ubuntu)

Hope this helps,
Cheers!

Edit: yup, xrandr works with the usual printscreen for me (also with import, just needs enough space for a terminal to fit, so it doesn't overlap the target window), just note the Virtual size in xorg.conf (see "xrandr: screen cannot be larger than" ...)