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

Color histograms in OpenCV


In this chapter so far, we have been working with grayscale images. Let's take a moment to understand the concept of histograms when applied to multichannel color images. For all demonstration purposes in this section, we will be working with the color version of Lena's picture as our input image:

While talking about the transition from grayscale to color images, we have always visualized color images as being composed of three channels of red, green, and blue. We have maintained that all three channels can be treated independently as grayscale images themselves. And this is exactly what we will do in the case of color histograms as well.

In the last few sections, we have seen how to compute as well as plot histograms for single-channel grayscale images. Now imagine performing the same operation across all the three channels of a color image to obtain three separate histograms. Since each individual channel is exactly the same as a grayscale image (all pixel intensities...