OpenCV is an open source computer vision and machine learning software library. It is a BSD-licence product thus free for both business and academic purposes.The Library provides more than 2500 algorithms that include machine learning tools for classification and clustering, image processing and vision algorithm, basic algorithms and drawing functions, GUI and I/O functions for images and videos. Some applications of these algorithms include face detection, object recognition, extracting 3D models, image processing, camera calibration, motion analysis etc.
OpenCV is written natively in C/C++. It has C++, C, Python and Java interfaces and supports Windows, Linux, Mac OS, iOS, and Android. OpenCV was designed for computational efficiency and targeted for real-time applications. Written in optimized C/C++, the library can take advantage of multi-core processing.
Face detection is a technique that identifies or locates human faces in digital images. A typical example of face detection occurs when we take photographs through our smartphones, and it instantly detects faces in the picture. Face detection is different from Face recognition. Face detection detects merely the presence of faces in an image while facial recognition involves identifying whose face it is.
Face detection is performed by using classifiers. A classifier is essentially an algorithm that decides whether a given image is positive(face) or negative(not a face). A classifier needs to be trained on thousands of images with and without faces. Fortunately, OpenCV already has two pre-trained face detection classifiers, which can readily be used in a program. The two classifiers are: Haar Classifier and Local Binary Pattern(LBP) classifier.
- 'Haar features' extraction
- 'Integral Images' concept
- Using 'Cascade of Classifiers' Face Detection with OpenCV-Python