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

Image derivatives


Those of you who may have taken up a basic calculus course in your high school will know the definition of a derivative as it applies to functions. For the sake of others, we repeat the same here, albeit very briefly. Mathematically, a derivative is represented as follows:

Note

Note that we are not trying to be mathematically fastidious, our only intention here is to give you an intuition into the concept of a derivative and how it applies to images. So, this chapter won't go into the intricacies behind the mathematics that is involved. Rather, our focus will be on how the principles of derivatives of functions are transferred to the domain of images.

What the preceding formula essentially tells you is that the derivative of a function f(x) at any point is the ratio of the change in the output to the input, as the input is varied by an infinitesimal amount in and around that point. Imagine that you have a 2D plot of the graph of the function f(x). You sample the function...