Building Computer Vision Projects with OpenCV 4 and C++

Eye detection

Eye detection can be very useful for face preprocessing, because for frontal faces, you can always assume a person's eyes should be horizontal and on opposite sides of the face, and should have a fairly standard position and size within a face, despite changes in facial expressions, lighting conditions, camera properties, distance to camera, and so on.

It is also useful to discard false positives, when the face detector says it has detected a face and it is actually something else. It is rare that the face detector and two eye detectors will all be fooled at the same time, so if you only process images with a detected face and two detected eyes, then it will not have many false positives (but will also give fewer faces for processing, ...