This cookbook is based on the C++ API of the OpenCV library. It is therefore assumed that you have some experience with the C++ language. In order to run the examples presented in the recipes and experiment with them, you need a good C++ development environment. Microsoft Visual Studio and Qt are two popular choices.

You can download the example code files for this book from your account at www.packtpub.com.If you purchased this book elsewhere, you can visit www.packtpub.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.packtpub.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/OpenCV-4-Computer-Vision-Application-Programming-Cookbook-Fourth-Edition. 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: https://www.packtpub.com/sites/default/files/downloads/9781789340723_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: "The cv::Mat variable's image refers to the input image, while result refers to the binary output image."

A block of code is set as follows:

// compute distance from target color 
if (getDistanceToTargetColor(*it)<=maxDist) { 
        *itout= 255; 

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 scores = outs[i].row(j).colRange(5, outs[i].cols);
Point classIdPoint;  
double confidence;  // Get the value and location of the maximum score

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

cd llvm_root

Bold: Indicates a new term, an important word, or words that you see onscreen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "You then click on Build Solution in Visual Studio."