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 in two dimensions


Now that we are comfortable with the theory behind image derivatives in one dimension, we will see how the concept can be scaled to two dimensions. After all, when we start our OpenCV implementation from the next section onward, we will deal with images: two-dimensional data.

From what we have gathered in this chapter until now, derivatives essentially measure how our function changes. When we are dealing with one-dimensional data, there is only one possible direction along which this change can take place. When we talk about two-dimensional functions, we have two variables that we can vary independently, typically x and y. So, changing one of them (while keeping the other constant) allows us to measure the change in our function value (the thing we call derivative) along two directions as opposed to one. Therefore, it is prudent to assume that for two-dimensional functions (such as images), two different derivatives are computed. One derivative measures...