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

Face detection in OpenCV


After a lot of theory, we finally arrive at a point where we are now ready to do face detection using OpenCV. As always, we will straightaway dive into code.

First, we include the required header files. Here, you'll note the appearance of a new header--objdetect.hpp. This file contains all the function declarations that we'll use for our face detection:

#include <iostream> 
#include <opencv2/core/core.hpp> 
#include <opencv2/highgui/highgui.hpp> 
#include <opencv2/objdetect/objdetect.hpp> 
#include <opencv2/imgproc/imgproc.hpp> 
 
using namespace std; 
using namespace cv; 

Here, we declare the path to what we call the cascade classifier. Let us take a moment to understand what this file contains and why we need it in our code. During our explanation of the Viola-Jones framework, we saw that given some Haar features computed from within the sub-window, a classifier (arranged within a cascade) must...