Book Image

Learning OpenCV 3 Application Development

By : Samyak Datta
Book Image

Learning OpenCV 3 Application Development

By: Samyak Datta

Overview of this book

Computer vision and machine learning concepts are frequently used in practical computer vision based projects. If you’re a novice, this book provides the steps to build and deploy an end-to-end application in the domain of computer vision using OpenCV/C++. At the outset, we explain how to install OpenCV and demonstrate how to run some simple programs. You will start with images (the building blocks of image processing applications), and see how they are stored and processed by OpenCV. You’ll get comfortable with OpenCV-specific jargon (Mat Point, Scalar, and more), and get to know how to traverse images and perform basic pixel-wise operations. Building upon this, we introduce slightly more advanced image processing concepts such as filtering, thresholding, and edge detection. In the latter parts, the book touches upon more complex and ubiquitous concepts such as face detection (using Haar cascade classifiers), interest point detection algorithms, and feature descriptors. You will now begin to appreciate the true power of the library in how it reduces mathematically non-trivial algorithms to a single line of code! The concluding sections touch upon OpenCV’s Machine Learning module. You will witness not only how OpenCV helps you pre-process and extract features from images that are relevant to the problems you are trying to solve, but also how to use Machine Learning algorithms that work on these features to make intelligent predictions from visual data!
Table of Contents (16 chapters)
Learning OpenCV 3 Application Development
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface

Chapter 8. Feature Descriptors in OpenCV

We have spent a good amount of time working with faces. Over the course of the last couple of chapters, we have learnt how to detect faces in a given image and how to align a set of faces so that they are of the same size and none of the faces have a head-tilt either to the right or to the left. We also mentioned that such a pre-processing step is necessary to enhance the performance of machine learning algorithms. We did a very brief discourse on image classification systems when we were discussing face detectors in Chapter 6, Face Detection Using OpenCV. We introduced the notion of features (specifically, Haar features). This chapter, along with the next, is going to be an in-depth analysis of these concepts.

When we introduced the concept of digital images right at the beginning of the very first chapter, we said that an image is represented by its set of pixel values. During the formative chapters, we played around with these pixel values to perform...