Theory of simple pattern recognition

Question

Pattern recognition

There is a task to recognize simple objects from the phone's camera. There are many analogues of such applications, many recognize faces, whole pictures and other complex shapes.
Where and how to build on real-time recognition of simple shapes? Maybe there are some freebies, docks, manuals?

Answer 1

Google for queries: OpenCV: Blob detection. shape recognition.
If the figures are quite primitive, you can select the contour, make an approximation (all this is easily done through OpenCV, literally in a couple of lines, + it seems like there is just such a thing in the examples) and look at the characteristics of the resulting figure.
Or through Blob Detection - so let's say markers are recognized, faces (although this is already more difficult, but again, there are plenty of examples)