In the preceding section, by detecting faces with a cascade classifier provided by OpenCV we know which regions are faces in an image. But with only rectangular regions, we don't know many details about the faces: where are the eyes, eyebrows, and nose on the faces? In face recognition technology, we call these details facial landmarks. In this section, we will try to find a way to detect these facial landmarks.
Unfortunately, the OpenCV core modules don't provide an algorithm to detect facial landmarks, so we should resort to the face module, which is an extra OpenCV module.
Before using the face extra module, we must ensure that the module is installed on our computer. In Chapter 2, Editing Images Like a Pro, in the Building and installing OpenCV from the source section, we built and installed OpenCV v4.0.0 from a source without the extra...
