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Manipulating the Pixels

In order to build computer vision applications, you need to be able to access the image content and, eventually, modify or create images. This chapter will teach you how to manipulate the picture elements (also known as pixels). You will learn how to scan an image and process each of its pixels. You will also learn how to do this efficiently, since even images of modest dimensions can contain hundreds of thousands of pixels.

Fundamentally, an image is a matrix of numerical values. This is why, as we learned in Chapter 1, Playing with Images, OpenCV 4 manipulates them using the cv::Mat data structure. Each element of the matrix represents one pixel. For a gray-level image (a black-and-white image), pixels are unsigned 8-bit values where 0 corresponds to black and 255 corresponds to white. In the case of color images, three primary color values are required...

Key benefits

Explore the latest features and APIs in OpenCV 4 and build computer vision algorithms

Develop effective, robust, and fail-safe vision for your applications

Build computer vision algorithms with machine learning capabilities

Description

OpenCV is an image and video processing library used for all types of image and video analysis. Throughout the book, you'll work with recipes to implement a variety of tasks. With 70 self-contained tutorials, this book examines common pain points and best practices for computer vision (CV) developers. Each recipe addresses a specific problem and offers a proven, best-practice solution with insights into how it works, so that you can copy the code and configuration files and modify them to suit your needs. This book begins by guiding you through setting up OpenCV, and explaining how to manipulate pixels. You'll understand how you can process images with classes and count pixels with histograms. You'll also learn detecting, describing, and matching interest points. As you advance through the chapters, you'll get to grips with estimating projective relations in images, reconstructing 3D scenes, processing video sequences, and tracking visual motion. In the final chapters, you'll cover deep learning concepts such as face and object detection. By the end of this book, you'll have the skills you need to confidently implement a range of computer vision algorithms to meet the technical requirements of your complex CV projects.

What you will learn

Install and create a program using the OpenCV library

Segment images into homogenous regions and extract meaningful objects

Apply image filters to enhance image content

Exploit image geometry to relay different views of a pictured scene

Calibrate the camera from different image observations

Detect people and objects in images using machine learning techniques

Reconstruct a 3D scene from images

Explore face detection using deep learning

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