This is the setup chapter. There are no particular software prerequisites at the outset; we will set up everything as we go along.

Basic instructions for running Python code are covered in Appendix C, Running with Snakes (or, First Steps with Python). After we set up a Python environment with OpenCV, you may want to refer to this appendix so that you know how to minimally test the environment.

We can develop our OpenCV applications on a desktop, a notebook, or even the humble Raspberry Pi (covered later, in the Setting up a Raspberry Pi section). Most of our apps have a memory footprint of less than 128 MB, so they can still run (albeit slowly) on old or low-powered machines. To save time, develop on your fastest machine first and test on slower machines later.

This book assumes that you have one of the following operating systems on your development machine:

• Windows 7 SP 1, or a later version.
• Mac OS 10.7 (Lion), or a later version.
• Debian Jessie, a later version, or a derivative such as the following:
  • Raspbian 2015-09-25, or a later version
  • Ubuntu 14.04, or a later version
  • Linux Mint 17, or a later version
• Fedora 28, a later version, or a derivative such as the following:
  • RHEL 8, or a later version
  • CentOS 8, or a later version...

Android Studio is Google's official integrated development environment (IDE) for Android app development. Since its first stable release in 2014, Android Studio has grown in popularity and has replaced Eclipse as the IDE of choice for Android developers. Although some of the OpenCV documentation still contains outdated tutorials on Android development in Eclipse, nowadays, the OpenCV Android library and Android sample projects are primarily intended for use with Android Studio, instead.

Google provides a good cross-platform tutorial on Android Studio installation at https://developer.android.com/studio/install. Follow the part of the tutorial that is relevant to your operating system.

Download the latest version of the OpenCV Android pack from https://opencv.org/releases.html. Unzip it to any destination, which we will refer to as &lt...

Unity (https://unity3d.com) is a three-dimensional game engine that supports development on 64-bit Windows or Mac, and deployment to many platforms, including Windows, Mac, Linux, iOS, Android, WebGL, and several game consoles. For one of our projects, we will use Unity along with a plugin called OpenCV for Unity, which is developed by Enox Software (http://enoxsoftware.com/.) The main programming language for Unity projects is C#, and OpenCV for Unity provides a C# API that is modeled on the OpenCV Java API for Android.

Unity has three license plans, Personal, Plus, and Pro, which all support the plugin that we want to use. The different editions are for different sizes of companies, as described in the licensing information at https://store.unity.com. The Personal license is free. The Plus and Pro licenses have subscription costs. If you are not...

Raspberry Pi is a single-board computer (SBC) with a low cost and low power consumption. It can be used as a desktop, a server, or an embedded system that controls other electronics. The Pi comes in several models. Currently, the flagship is Model 3 B+, which costs about $35. Compared to other models, it offers a faster CPU, more memory, and a faster Ethernet port, so it is a good candidate for computer vision experiments that rely on either local computing resources or the cloud. However, other models are also usable for computer vision projects.

Several operating systems are available for Raspberry Pi. We will use Raspbian, which is a port of Debian Stretch (a major Linux distribution) to ARM.

Download the latest Raspbian disk image from http://downloads.raspberrypi.org/raspbian_latest. You do not need to unzip the downloaded file. At the time of writing...

OpenCV's documentation is online, at https://docs.opencv.org/master/. The documentation includes a combined API reference for the latest OpenCV C++ API and its latest Python API (which is based on the C++ API). The latest Java API documentation is online, at http://docs.opencv.org/master/javadoc/.

If the documentation seems to leave your questions unanswered, try reaching out to the OpenCV community instead. The following sites are good venues for questions, answers, and shared experience:

• The official OpenCV forum, at http://answers.opencv.org/questions/
• The PyImageSearch site, where Adrian Rosebrock teaches computer vision and machine learning, at https://www.pyimagesearch.com/
• The support site for my OpenCV books, at http://nummist.com/opencv/

Finally, if you are an advanced user who wants to try new features, bug-fixes...

Besides Raspberry Pi, many other low-cost SBCs are suitable for running a desktop Linux distribution and OpenCV applications. The Raspberry Pi 3 models offer a quad-core ARMv8 processor and 1 GB RAM. However, some of the competing SBCs offer octa-core ARM processors and 2 GB RAM and can run more complex computer vision algorithms in real time. Moreover, unlike any current model of Pi, some of the competitors offer a USB 3 interface, which supports a wide range of high-resolution or high-speed cameras. These advantages tend to come with a higher price tag and higher power consumption. Here are some examples:

• Odroid XU4 (https://www.hardkernel.com/shop/odroid-xu4-special-price/): An octa-core SBC with 2 GB RAM and a USB 3 interface. It can run Ubuntu and other Linux distributions. At the time of writing, it is available from Odroid at a promotional...

This was all a setup! I hear you gasp. Yes, but we did it for good reason. Now, we have a diverse set of development tools that will enable us to explore OpenCV in many contexts. Besides, it never hurts to learn some things about a lot of application frameworks and to have them all set up, in case someone asks us to do a project in a hurry.

Remember, James Bond has encyclopedic knowledge. In a highly symbolic conversation about rare and deadly fish, he goes toe-to-toe with Karl Stromberg, the diabolical oceanographer (The Spy Who Loved Me, 1977). Although we never see Bond studying the fish books, he must do it as bedtime reading after the camera cuts out.

The moral is, be prepared. Next, we will use OpenCV, along with several of the Python libraries and tools that we have installed, to build a GUI application that finds and classifies images on the web.