A new Era: The first Python version can be found under the files section. The working test system runs XUbuntu 16.04 and uses Python 2.7, OpenCV 2.4.9., python-opencv and Numpy.
I am using Spyder as Python IDE
The default video input source is the first camera (device index 0). This can be changed by uncommenting and editing line 52 or the -i / --input_source command line option. The latter allows video files as input as well.
The program will open three windows for the raw video, the output (Schlieren!) and the background pattern. The background window is black until you choose 1 (chequerboard) or 2 (stripes). All three windows can be resized. There is no video recording option (yet!).
c use current frame as reference frame
q quit program
1 use chequerboard background pattern
2 use striped background pattern
=+ increase pattern size
-_ decrase pattern size