OpenCV comes with a trainer as well as a detector. In this section, we will demonstrate the detection (skip training a model) with the pre-trained classifiers for face, eyes, smile, and so on. OpenCV already contains many such models already trained; we are going to use them instead of training a classifier from scratch. These pre-trained classifiers are serialized as XML files and come with an OpenCV installation (this can be found in the opencv/data/haarcascades/ folder).
In order to detect a face from an input image, first we need to load the required XML classifiers, and then load the input image (in grayscale mode). The faces in the image can be ...
