Matrices in OpenCV's Python interface are presented with NumPy arrays. NumPy provides powerful yet clear tools to deal with multi-dimensional matrices, which are also called tensors. And, of course, NumPy supports plain 2-dimensional matrices. That's why we need to import its module. And this is the reason why we're using a lot of np's functions in this recipe.
Here it's necessary to say a few words about matrix dimensions and types. Matrices have two independent characteristics—shape type and element type. Firstly, let's talk about shape. Shape describes all dimensions of the matrix. A matrix usually has three spatial dimensions: width (also called number of columns), height (also called number of rows), and number of channels. ...
