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

Rotating faces


Let us start with image rotation. As mentioned a while back, the aim of rotating faces is to ensure that all the images have faces that are approximately straight (not tilted to the left or right). If you look at the sample images, you will notice that the face of George W. Bush is tilted slightly to the (the viewer's) left.

On the other hand, Tom Cruise's face has a tilt in the opposite direction-to the right:

We would ideally want all faces to be absolutely straight-as is the case with Kalpana Chawla:

How do we go about doing that? Keep in mind; we need a system that should accomplish the following:

  1. If the face is tilted, rotate it so that the tilt is nullified.

  2. For faces that are already straight, the system should leave that as it is.

Since our aim is to reach a state where the face has zero-tilt, let's try to emulate some properties that such a face possesses so that, given any facial image, we can devise a procedure to reach there. The mechanism that we propose goes...