Nicolas Modrzyk [Nicolas Modrzyk] - Java Image Processing Recipes: With OpenCV and JVM

A few years ago, while on a trip to Shanghai, a very good friend of mine bought me a massive book on OpenCV. It had tons of photography manipulation, realtime video analysis samples, and in-depth explanations that were very appealing, and I just could not wait to get things up and running on my local environment.

OpenCV, as you may know, stands for Open Source Computer Vision ; it is an open source library that gives you ready-to-use implementations of advanced imaging algorithms, going from simple-to-use but advanced image manipulations to shape recognition and real-time video analysis spy powers.

The very core of OpenCV is a multidimensional matrix object named Mat. Mat is going to be our best friend all along this book. Input objects are Mat, operations are run on Mat, and the output of our work is also going to be Mat.

Mat , even though it is going to be our best friend, is a C++ object, and as such, is not the easiest of friends to bring and show around. You have to recompile, install, and be very gentle about the new environment almost anywhere you take him.

But Mat can be packaged.

Mat, even though he is a native (i.e., runs natively), can be dressed to run on the Java Virtual Machine almost without anyone noticing.

This first chapter wants to get you introduced to work with OpenCV with some of the main languages of the Java Virtual Machine, namely Java of course, but also the easier-to-read Scala and the Google-hyped Kotlin.

To run all these different languages in a similar fashion, you will first get (re-?)introduced to a Java build tool named leiningen and then you will move on to use simple OpenCV functions with it.

The road of this first chapter will take you to the door of the similarly JVM-based language Clojure, which will give your OpenCV code instant visual feedback for great creativity. That will be for Chapter .

You remember the write-once-run-everywhere quote, and you would like to compile Java code and run the Java program in an easy and portable manner across different machines. Obviously, you can always revert to using the plain javac command to compile Java code, and pure Java on the command line to run your compiled code , but we are in the 21st century, and hey, you are looking for something more.

Whatever the programming language, setting up your working environment by hand is quite a task, and when you are done, it is hard to share with other people.

Using a build tool, you can define in simple ways what is required to work on your project, and get other users to get started quickly.

You would like to get started with an easy-to-work-with build tool.

Leiningen is a build tool targeting (mostly) the JavaVM. It is similar in that sense to other famous ones like (Remember? The) Ant, (Oh My God) Maven, and (it used to work) Gradle.

Once the leiningen command is installed, you can use it to create new JavaVM projects based on templates, and run them without the usual headaches.

This recipe shows how to install Leiningen quickly and run your first Java program with it.

You will start by simply installing Leiningen where you need it, and then creating a blank Java project with it.