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 noise


We have learnt in great detail about image filtering operations (box and Gaussian filtering). We have also seen that, in general, image averaging tends to blur our input image. Let us now stop and ponder why (and in what scenario) we would need to perform such averaging operations. What prompted the need to replace each pixel with an average (or a weighted average of its neighbors)? The answer to these questions lies in the concept of image noise.

Images are nothing but two-dimensional signals (mapping a pair of x and y coordinate values to corresponding pixel intensities) and just like any signal, they are susceptible to noise. When we say that an image is noisy, we mean that there is a small or large variation in the intensity values of the pixels from the ideal value that we would expect. Noise in an image creeps in due to defects in digital cameras or photographic film.

The following image demonstrates some examples of noisy photographs:

There are two different types of noise...