face_cascade.detectMultiScale

The face_cascade.detectMultiScale() is a function in OpenCV library that is used to detect faces in an image. It takes an image as an input and returns the coordinates of the bounding boxes around the detected faces. The function uses the Haar cascade classifier to detect the faces. It works by applying a sliding window technique to the image and evaluating a set of classifiers at each scale and location of the window. The classifiers are trained to detect specific features of the face like eyes, nose, and mouth. If enough of these features are detected, the window is classified as a face. The function can be tuned by adjusting the scale factor, minimum and maximum window sizes, and the number of neighbors required to classify a window as a face.