Book Image

OpenCV 4 Computer Vision Application Programming Cookbook - Fourth Edition

By : David Millán Escrivá, Robert Laganiere
Book Image

OpenCV 4 Computer Vision Application Programming Cookbook - Fourth Edition

By: David Millán Escrivá, Robert Laganiere

Overview of this book

OpenCV is an image and video processing library used for all types of image and video analysis. Throughout the book, you'll work with recipes to implement a variety of tasks. With 70 self-contained tutorials, this book examines common pain points and best practices for computer vision (CV) developers. Each recipe addresses a specific problem and offers a proven, best-practice solution with insights into how it works, so that you can copy the code and configuration files and modify them to suit your needs. This book begins by guiding you through setting up OpenCV, and explaining how to manipulate pixels. You'll understand how you can process images with classes and count pixels with histograms. You'll also learn detecting, describing, and matching interest points. As you advance through the chapters, you'll get to grips with estimating projective relations in images, reconstructing 3D scenes, processing video sequences, and tracking visual motion. In the final chapters, you'll cover deep learning concepts such as face and object detection. By the end of this book, you'll have the skills you need to confidently implement a range of computer vision algorithms to meet the technical requirements of your complex CV projects.
Table of Contents (17 chapters)

Object detection with YOLOv3

In this recipe, we are going to use the YOLOv3 DNN algorithm, which performs object detection. Object detection in an image is a common task in computer vision; with deep learning techniques, we can achieve highly accurate detections. YOLOv3 reaches a 60.6 mAP in the COCO dataset (80 classes and more than 300,000 images), which has a very good precision with 20 fps or 33 mAP with 220 fps.

How to do it...

In this recipe, we are going to use the same functions and classes to load the model, convert the images, and predict, but we are going to introduce one more important function non-maximum suppression and a few util functions to draw the predictions with their labels:

  1. Create...