Book Image

Learning OpenCV 4 Computer Vision with Python 3 - Third Edition

By : Joseph Howse, Joe Minichino
Book Image

Learning OpenCV 4 Computer Vision with Python 3 - Third Edition

By: Joseph Howse, Joe Minichino

Overview of this book

Computer vision is a rapidly evolving science, encompassing diverse applications and techniques. This book will not only help those who are getting started with computer vision but also experts in the domain. You’ll be able to put theory into practice by building apps with OpenCV 4 and Python 3. You’ll start by understanding OpenCV 4 and how to set it up with Python 3 on various platforms. Next, you’ll learn how to perform basic operations such as reading, writing, manipulating, and displaying still images, videos, and camera feeds. From taking you through image processing, video analysis, and depth estimation and segmentation, to helping you gain practice by building a GUI app, this book ensures you’ll have opportunities for hands-on activities. Next, you’ll tackle two popular challenges: face detection and face recognition. You’ll also learn about object classification and machine learning concepts, which will enable you to create and use object detectors and classifiers, and even track objects in movies or video camera feed. Later, you’ll develop your skills in 3D tracking and augmented reality. Finally, you’ll cover ANNs and DNNs, learning how to develop apps for recognizing handwritten digits and classifying a person's gender and age. By the end of this book, you’ll have the skills you need to execute real-world computer vision projects.
Table of Contents (13 chapters)

Detecting DoG features and extracting SIFT descriptors

The preceding technique, which uses cv2.cornerHarris, is great for detecting corners and has a distinct advantage because corners are corners; they are detected even if the image is rotated. However, if we scale an image to a smaller or larger size, some parts of the image may lose or even gain a corner quality.

For example, take a look at the following corner detections in an image of the F1 Italian Grand Prix track:

Here is the corner detection result with a smaller version of the same image:

You will notice how the corners are a lot more condensed; however, even though we gained some corners, we lost others! In particular, let's examine the Variante Ascari chicane, which looks like a squiggle at the end of the part of the track that runs straight from northwest to southeast. In the larger version of the image, both...