The book assumes that readers have a firm grasp of programming concepts and software engineering skills, building and running software from scratch in C++. The book also features code in JavaScript, Python, Java, and Swift. Engineers looking to dive deeper into those sections will benefit from programming language knowledge beyond C++.

Readers of this book should be able to obtain an installation of OpenCV in its various flavors. Some chapters will require a Python, others an Android, installation. Obtaining these and installing them is discussed thoroughly in the accompanying code and in the text.

You can download the example code files for this book from your account at www.packt.com. If you purchased this book elsewhere, you can visit www.packt.com/support and register to have the files emailed directly to you.

You can download the code files by following these steps:

1. Log in or register at www.packt.com.
2. Select the SUPPORT tab.
3. Click on Code Downloads & Errata.
4. Enter the name of the book in the Search box and follow the onscreen instructions.

Once the file is downloaded, please make sure that you unzip or extract the folder using the latest version of:

• WinRAR/7-Zip for Windows
• Zipeg/iZip/UnRarX for Mac
• 7-Zip/PeaZip for Linux

The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/Mastering-OpenCV-4-Third-Edition. In case there's an update to the code, it will be updated on the existing GitHub repository.

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!

We also provide a PDF file that has color images of the screenshots/diagrams used in this book. You can download it here: http://www.packtpub.com/sites/default/files/downloads/9781789533576_ColorImages.pdf.

There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "To see the remaining space on your SD card, run df -h | head -2."

A block of code is set as follows:

Mat bigImg; 
 resize(smallImg, bigImg, size, 0,0, INTER_LINEAR); 
 dst.setTo(0); 
 bigImg.copyTo(dst, mask);

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

Mat bigImg; 
 resize(smallImg, bigImg, size, 0,0, INTER_LINEAR); 
 dst.setTo(0); 
 bigImg.copyTo(dst, mask);

Any command-line input or output is written as follows:

sudo apt-get purge -y wolfram-engine

Bold: Indicates a new term, an important word, or words that you see on screen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "Navigate to Media | Open Network Stream."