1 | initial version |
Have a look at the car detector. As it seems your spot are well defined (you could have static bounding box for each car spot), you have to detect if a car is present or not.
The idea is to train a Cascade Classifier with HAAR or LBP, or a HOG Detector. You could find some nice tutorial online for that, as well as book. The training code is provided by OpenCV also here.