I have many years of work on image processing. Also, I have used openCV in my work. So I think I can help. However, I would require some more information on the details of your project: In particular, is it a training-based system (in the sense that we have some pictures of the parking lot at design time) or it should work in an unsupervised manner? Also, does it have to use for many parking lots, or just the one we are interested. Can you, please, provide me with more details? In any case, I think I can help you prepare a high-quality project.