What is Face Detection?
Face detection is an AI-based computer technology that can identify and locate the presence of human faces in digital photos and videos. It can be regarded as a special case of object-class detection, where the task is to find the locations and specify the sizes of all the objects that belong to a given class – in this case, faces – within a specific image or images.
Due to the advancements in face detection technology, it is now possible to detect faces in an image or video, regardless of head pose, lighting conditions, and skin color.
How does Face Detection work?
Face detection applications use algorithms that determine whether images are positive images (i.e. images with a face) or negative images (i.e. images without a face). To be able to do this accurately, the algorithms must be trained on huge datasets containing hundreds of thousands of face images and non-face images.
Once trained, the algorithms are able to answer two questions in response to
input in the form of an image:
Are there any faces in this image?
If yes, where are they?
If a face or faces are present in an image, the algorithms will answer these questions by placing a bounding box around the detected face(s), as illustrated below:
In the past, these algorithms were machine-learning based, and were heavily affected by factors such as extreme head poses (where the head is rotated far to one side or tilted far up or far down, for example) and varying lighting conditions. Today, however, we can use deep learning methods to carry out accurate face detection in a wide range of scenarios.
Why is Face Detection important?
Face detection is the first step in various other applications, including face tracking, face analysis and face recognition.
In the context of face analysis, face detection tells the face analysis algorithms which parts of an image (or video) to focus on when identifying age, recognizing gender, and analyzing emotions based on facial expressions.
And when it comes to facial recognition, face detection is necessary for the algorithms to know which parts of an image (or video) to use to generate the faceprints that are compared with previously stored faceprints to establish whether or not there is a match.
How can you use Face Detection?
Aside from using face detection in conjunction with the technologies described above, you can use face detection to:
Count the number of people entering a retail store or looking at a digital display
Identify which areas of an image to blur to ensure privacy (see Face Blur)