Instead of using some third party app, I'd like to write an app in Ruby that when invoked, will capture the full screen and save it in c:\screenshot\snap000001.png
The graphic package is readily there, but how can you capture a region from the full screen so as to save it?
This program is to be invoked by some hot-key, such as setting it to be running when CTRL-PrtScn is pressed, or CTRL-CTRL (both control on left and right), or ALT-ALT.