Book Image

Computer Vision with OpenCV 3 and Qt5

By : Amin Ahmadi Tazehkandi
4 (1)
Book Image

Computer Vision with OpenCV 3 and Qt5

4 (1)
By: Amin Ahmadi Tazehkandi

Overview of this book

Developers have been using OpenCV library to develop computer vision applications for a long time. However, they now need a more effective tool to get the job done and in a much better and modern way. Qt is one of the major frameworks available for this task at the moment. This book will teach you to develop applications with the combination of OpenCV 3 and Qt5, and how to create cross-platform computer vision applications. We’ll begin by introducing Qt, its IDE, and its SDK. Next you’ll learn how to use the OpenCV API to integrate both tools, and see how to configure Qt to use OpenCV. You’ll go on to build a full-fledged computer vision application throughout the book. Later, you’ll create a stunning UI application using the Qt widgets technology, where you’ll display the images after they are processed in an efficient way. At the end of the book, you’ll learn how to convert OpenCV Mat to Qt QImage. You’ll also see how to efficiently process images to filter them, transform them, detect or track objects as well as analyze video. You’ll become better at developing OpenCV applications.
Table of Contents (19 chapters)
Title Page
Dedication
Packt Upsell
Foreword
Contributors
Preface

Low-level multithreading using QThread


In this section, we will learn how to use QThread and its classes to create multithreaded applications. We will go through this by creating an example project, which processes and displays the input and output from a video source using a separate thread. This helps leave the GUI thread (main thread) free and responsive while more intensive processes are handled with the second thread. As it was mentioned earlier, we will focus mostly on the use cases common to computer vision and GUI development; however, the same (or a very similar) approach can be applied to any multithreading problem.

We will use this example project to implement multithreading using two different approaches available in Qt for working with QThread classes. First, subclassing and overriding the run method, and second, using the moveToThread function available in all Qt objects, or, in other words, QObject subclasses.

Subclassing QThread

Let's start by creating an example Qt Widgets...