OpenCV (Open Source Computer Vision Library) is the leading open-source library for computer vision and image processing. For developers who build systems that see, understand, and act on images and video, it provides a fast, dependable foundation for everything from edge detection to deep learning. This book is a practical guide to computer vision with OpenCV 4. It covers image and video fundamentals, core image processing, feature detection and matching, object detection, face analysis, motion analysis and tracking, camera calibration and 3D vision, machine learning integration, and video analysis. It also covers performance optimisation, OpenCV tools and utilities, and project development, so you can take working code through to production. Each chapter includes runnable Python and C++ examples you can reuse in your own projects, with an emphasis on clean code, accuracy, and OpenCV 4's deep learning engine.