Is it possible to save certain parts of a screenshot I'd like to reduce the time necessary to create screenshots. I want to skip reopening and cutting and saving. Instead I'd like to use a python script to determine the size of the part of the screen and crop the screenshot accordingly.

So, there's three (four) questions in one: 


Is it possible to take a screenshot with python?
Can I edit the screenshot with python?
Can I determine the size of an element in the user interface to crop accordingly?
Is there already a solution out there?
This answer is given with assumption that you would like to save different windows screen shot only.

Here are the steps to take screenshots of specific windows in Blender e.g 3dView, UV Windows, Properties.


Hover your mouse over required window.
Press Ctrl + F3.
Before saving screen shot, Uncheck Full Screen box to save only specific windows shot. It is available in Save Screenshot Properties Box.