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Setting Up OpenCV for Use in an Ubuntu

Environment

Jeremy Martin

11/8/2013

Abstract OpenCV is an open source package to aid in image processing with real-time

computer vision. It contains plenty of functions including: motion tracking, gesture

recognition, segmentation, object identification, and many others. In order to get started

with the package, many other libraries are required for full use and compilation of

programs. This document will provide you with all steps leading up to your own

experimentation of coding with OpenCV

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Table of Contents

Abstract........................................................................................... 1

Useful Ubuntu Terminal Commands........................................... 3 Sudo............................................................................................................. 3

Apt-get ......................................................................................................... 3

Required Packages for OpenCV .................................................. 3 GCC............................................................................................................. 3

CMake ......................................................................................................... 5

Git ................................................................................................................ 6

GTK+........................................................................................................... 7

Pkg-config ................................................................................................... 8

Python & Numpy......................................................................................... 9

FFmpeg........................................................................................................ 9

Setting up OpenCV........................................................................ 9 Creating a Stable OpenCV Folder............................................................... 9

Building OpenCV...................................................................................... 10

Conclusion .................................................................................... 11

References ..................................................................................... 12

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Useful Ubuntu Terminal Commands

Sudo

In Ubuntu, the sudo command (substitute user do) is a command used for

privilege authorization. With the installation of many different packages, this command is

critical if authorization is an issue. Sudo allows for programs to be run with the priveleges

of a superuser. The only input required is a user password instead of the root password.

Apt-get

As with all computer science, installing packages should be clean and simple. The

apt-get (advanced packaging tool) command allows for clean and simple installations of

packages. Initially, users had to unzip and compile .tar.gz files manually to use a given

program. Because users wanted a faster approach to this method, apt was created. By

using apt-get install <package_name>, many packages can be easily installed and

monitored. With the simple commands apt-get update and apt-get upgrade, apt will make

sure your source list is up to date, and that all installed packages are at their latest stable

release.

Required Packages for OpenCV

GCC

The first package required for OpenCV is GCC. Luckily, GCC is included with

the build-essential package. Build-essential will install all packages needed to compile a

Debian package. All packages currently included within build-essential can be found in

the Debian Policy Manual (www.debian.org/doc/debian-policy/).

What is a Debian package? From the Debian GNU/Linux FAQ Chapter 7:

Packages generally contain all of the files necessary to implement a set of related

commands or features. There are two types of Debian packages:

• Binary packages, which contain executables, configuration files, man/info pages,

copyright information, and other documentation. These packages are distributed

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in a Debian-specific archive format (see What is the format of a Debian binary

package?, Section 7.2); they are usually distinguished by having a '.deb' file

extension. Binary packages can be unpacked using the Debian utility dpkg

(possibly via a frontend like aptitude); details are given in its manual page.

• Source packages, which consist of a .dsc file describing the source package

(including the names of the following files), a .orig.tar.gz file that contains

the original unmodified source in gzip-compressed tar format and usually a

.diff.gz file that contains the Debian-specific changes to the original source.

The utility dpkg-source packs and unpacks Debian source archives; details are

provided in its manual page. (The program apt-get can get used a frontend for

dpkg-source.)

Running the following line of code will install all essential packages for Debian

compilation, including GCC:

The package GCC is the GNU Compiler Collection. It is used to generate executables

that can be used on many different operating systems. Thanks to this package, the

software developed within OpenCV can be used cross-platform very easily.

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CMake

CMake (cross-platform make) will manage the building of software. Although we

will be using it specifically for Linux, the cross-platform compatibility makes it a very

versatile piece of software. Examples of the different makefiles and workspaces it

simulates are given in figure 1. With the ability to support programs made from many

directories and multiple libraries, this is a critical piece of OpenCV. With massive

libraries filled with plenty of different codes and programs, it can be very difficult to

manage without a dedicated builder. In order to incorporate CMake, a CMakeLists.txt file

must be created in each source directory and used when compiling programs. A

CMakeLists.txt file will have the following format:

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The above example was taken from a tutorial project within OpenCV. The DisplayImage

file is in C++ format, and OpenCV is required to use it. An executable is made after

running the following commands:

No matter the operating system, CMake will always give consistent executables. This is

the benefit of a cross-platform make program. Install CMake with the following line of

code from terminal:

After executing the command, your terminal will start unpacking data as shown in figure

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Figure 2. Installing CMake

Git

One of the most widely-accepted source code management (SCM) projects, Git is

an easy-to-use program allowing you to keep up-to-date with packages under

development. Users that are developing software often use a Git repository to manage

their code. To create a copy of the repository on our system, we can use the command:

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This will create an identical folder to the online repository. In the case of the OpenCV

repository, we would use the following commands taken from the OpenCV tutorial:

If you would like to learn more on building software packages with Git, more can be read

at: http://git-scm.com/docs/gittutorial. We have only covered copying a repository

because that is what is needed to use the cutting-edge version of OpenCV.

Git can be installed directly from terminal using:

GTK+

GTK+ (GIMP Toolkit) is a package used for developing graphic user interfaces

(GUIs). It is open source, and the cross-platform compatibility and makes its usefulness

on-par with CMake. Creating GUIs is another expansive topic, and will not be covered in

this document. GTK+ can be installed with the terminal using the command:

Once executed, terminal will start unpacking and installing as shown in figure 3.

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Figure 3. Installing GTK+

Pkg-config

Pkg-config aids in the insertion of compiler options on a command line. A .pc file

can be created that holds all the library data for a program being compiled. An example

of a .pc file for libpng taken from Wikipedia:

Then to use pkg-config on the command line during compilation:

To install pkg-config, use the following command in terminal:

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Python & Numpy

Python is a language that can be used with OpenCV. It is an easy-to-understand

programming language with a syntax much more simple in comparison to C and C++.

Numpy is an additional module for Python, creating a more MATLAB-type of

environment. Numpy documentation can be found at:

http://docs.scipy.org/doc/numpy/user/

To install both Python and Numpy, run the following commands in terminal:

FFmpeg

From the about page on http://www.ffmpeg.org:

“FFmpeg is the leading multimedia framework, able to decode, encode, transcode, mux,

demux, stream, filter and play pretty much anything that humans and machines have

created. It supports the most obscure ancient formats up to the cutting edge. No matter if

they were designed by some standards committee, the community or a corporation. It

contains libavcodec, libavutil, libavformat, libavfilter, libavdevice, libswscale and

libswresample which can be used by applications. As well as ffmpeg, ffserver, ffplay and

ffprobe which can be used by end users for transcoding, streaming and playing”

For OpenCV, this package is very useful for handling multimedia data such as

audio and video. To install FFmpeg, run the following command in terminal:

Afterwards, we are ready to move on to downloading and installing OpenCV.

Setting up OpenCV

Creating a Stable OpenCV Folder

As discussed in the Git section, creating your directory is as easy as running the

following line of code in terminal:

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This will get you the latest stable version of OpenCV, and it can be updated at any time

using simple Git commands. Cloning into the repository will look similar to figure 4

inside of the terminal.

Figure 4. Cloning the OpenCV Repository

Building OpenCV

Now that we have our OpenCV folder, we can build the entire directory for use.

Again from the OpenCV Linux tutorial, run the following commands in terminal:

Afterwards, the terminal will start running tests and look similar to figure 5. To continue

the installation, type the following lines of code in terminal:

Once this has completed, terminal should look similar to figure 6. At this point, the

building and installation of OpenCV is completed, and users are able to create their own

programs.

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Figure 5. Performing Tests with CMake

Figure 6. Final Step in Building OpenCV

Conclusion Now that OpenCV and the required packages are built and installed, it is up to the

user to continue to broaden their knowledge on the programs available to them. OpenCV

has almost endless possibilities and takes time to learn. Additional knowledge on CMake

and the building process will also be needed, available at www.cmake.org.

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References

About CMake:

http://www.cmake.org/cmake/project/about.html

How to use apt-get:

https://help.ubuntu.com/community/AptGet/Howto

Installing OpenCV on Linux:

http://docs.opencv.org/doc/tutorials/introduction/linux_install/linux_install.html