OpenCV 2.4.9 on Ubuntu 14.04

OpenCV 2.4.9 was released on April 2014. See more here.

This is another post in a series of walkthroughs that will hopefully make your life easier to configure, compile, install and test it out.

The dependencies are divided into categories. I have only tested it with GTK.

If you don't need the latest OpenCV then you can easily install version 2.4 using apt:

sudo apt-get install libopencv-dev

If you wanna use the latest version, then follow the steps above:

Install Dependencies

Essentials
These are libraries and tools required by OpenCV.

sudo apt-get install build-essential checkinstall cmake pkg-config yasm

Image I/O

Libraries for reading and writing various image types. If you do not install then the versions supplied by OpenCV will be used.

sudo apt-get install libtiff4-dev libjpeg-dev libjasper-dev

Video I/O
You need some or all of these packages to add video capturing/encoding/decoding capabilities to the highgui module.

sudo apt-get install libavcodec-dev libavformat-dev libswscale-dev libdc1394-22-dev libxine-dev libgstreamer0.10-dev libgstreamer-plugins-base0.10-dev libv4l-dev

Python
Packages needed to build the Python wrappers.

sudo apt-get install python-dev python-numpy

Other third-party libraries
Install Intel TBB to enable parallel code in OpenCV.

sudo apt-get install libtbb-dev

GUI
The default back-end for highgui in Linux is GTK. You can optionally install QT instead of GTK and later enable it in the configuration (see next section) but I haven't tested it with QT on Ubuntu 14.04 yet. 

sudo apt-get install libqt4-dev libgtk2.0-dev

Download Compile & Install

Get a copy of the source code here, extract and create a build directory:

unzip opencv-2.4.9.zip
cd opencv-2.4.9/
mkdir build
cd build

Configure using CMake. You have a lot of options in this step. This is what I use:

cmake -D WITH_XINE=ON -D WITH_OPENGL=ON -D WITH_TBB=ON -D BUILD_EXAMPLES=ON ..

If you add -D WITH_QT=ON, the highgui module will use QT instead of GTK. For more information on the options, look at the CMakeLists.txt file. When you are happy with the configuration you have, you can start compiling:

make

If compilation finishes without errors, you can install by saying:

sudo make install

Finally, make sure that your programs can link to the OpenCV library in run-time by adding the following line at the end of your /etc/ld.so.conf:

/usr/local/lib

And then configure dynamic linker run-time bindings:

sudo ldconfig

Testing

An easy way to test that the compilation went well is to use the OpenCV tests and samples. For example, go to opencv-2.4.9/build/bin and run:

./cpp-example-opencv_version

You should get the correct version.

If you run other tests notice that some failures come from missing image files. To correctly run these tests or samples you should move the corresponding image files from opencv-2.4.9/samples to OpenCV-2.4.9/build/bin.

For testing that you can compile your own programs and link against the installed OpenCV libraries I have packaged the face detection sample with all the necessary files and a simple Makefile. Download it here, extract and type:

make

This should compile and run with a test image, so you should see something like this:

Command line tips

The intention of this post is to collect a list of my favorite command line tips. Feel free to leave yours in the comment section.

• Instead of using clear you can just press ctrl-r.
• The command units can be used for any unit conversion you can imagine. See man page.
• You can use multitail to monitor multiple log files on a terminal.

Sources:

Give me that one command you wish you knew years ago

Mark Stosberg's bash tips
TechBar: Linux shell tips and tricks

Extract decimals from text using grep

Let's say you have a log file that looks like this:

I/Profiling: TimeInterval1:  3271.72 ms
I/Profiling: TimeInterval1:  3379.15 ms
I/Profiling: TimeInterval1:  3645.32 ms
...

and you want to extract all decimal numbers so that you can get the average, or plot them. Here's how you would use grep to do this:

grep -o ' [0-9]\+\.[0-9]\+' mylogfile.log

The -o option is for just printing the matching text and not the whole line.

Simple HTTP Server in Python

A very easy way to setup a simple HTTP server is by using this built-in Python capability. This will turn any directory into a web server directory. The only thing you have to do is run:

python -m SimpleHTTPServer

on the directory you want to host the files from and that's it. You can drop an index.html file in there, for example, and hit

http://127.0.0.1:8000

in your browser and voila!

Ogre3D Object Placement Utility

I wrote an open source object placement utility that allows for placing objects (trees) on a terrain using the mouse.

It consists of a terrain and a water surface (pond). The user can select from 3 different models of trees and place them on the terrain. You enter edit mode by pressing space and a toolbar with all available models appears on the left side of the screen. The toolbar can easily be extended with more models.

I hope people will find it useful for object placement in scenes or using it as a base for terrain editors and such.

The build system is currently for Linux only (cmake and make) but it should be easy to compile in Windows or MacOS. The code is not perfect so any comments and suggestions are welcome.


Here is a demo:

Links
Souce code on GitHub
Object Placement Utility at Ogre3D Forums

Icon Action Sheet for iOS 6

One of the new features of iOS 6 is the replacement of the button based action sheet with the new icon  action sheet. If you tap the options for a library photo for example you get icons for emailing the photo, posting it on Facebook, tweeting it, etc. But how can you integrate this feature on your app?

Github user jgrana recently posted an open source reusable class that does exactly this; it allows you to easily reproduce this control in your app.

Links: IconActionSheet on GitHub

OpenCV 2.4 on Ubuntu 12.04

Edit (August 2013): Just used these steps to install OpenCV 2.4.6.1 on Ubuntu 12.10 without problems.

OpenCV 2.4.0 was released on May 2012 providing, a lot of improvements and bug fixes. For a complete change log see here.

This post will hopefully make your life easier to configure, compile, install and test it out.

This time I tried to categorize and explain the dependencies, so that it is easier to configure it for your needs. As always, comments and suggestions are welcome.

Ubuntu 12.04 provides a package of OpenCV 2.3.1 that you can easily install by typing:

sudo apt-get install libopencv-dev

If you do not care about having the latest version you could skip the rest of the post.

Install Dependencies

Essentials
These are libraries and tools required by OpenCV.

sudo apt-get install build-essential checkinstall cmake pkg-config yasm

Image I/O

Libraries for reading and writing various image types. If you do not install then the versions supplied by OpenCV will be used.

sudo apt-get install libtiff4-dev libjpeg-dev libjasper-dev

Video I/O
You need some or all of these packages to add video capturing/encoding/decoding capabilities to the highgui module.

sudo apt-get install libavcodec-dev libavformat-dev libswscale-dev libdc1394-22-dev libxine-dev libgstreamer0.10-dev libgstreamer-plugins-base0.10-dev libv4l-dev

Python
Packages needed to build the Python wrappers.

sudo apt-get install python-dev python-numpy

Other third-party libraries
Install Intel TBB to enable parallel code in OpenCV.

sudo apt-get install libtbb-dev

GUI
The default back-end for highgui in Linux is GTK. You can optionally install QT instead of GTK and later enable it in the configuration (see next section). 

sudo apt-get install libqt4-dev libgtk2.0-dev

Compile and Install

Get a copy of the source code here, extract and create a build directory:

tar -xvf OpenCV-2.4.0.tar.bz2
cd OpenCV-2.4.0/
mkdir build
cd build

Configure using CMake. You have a lot of options in this step. This is what I use:

cmake -D WITH_QT=ON -D WITH_XINE=ON -D WITH_OPENGL=ON -D WITH_TBB=ON -D BUILD_EXAMPLES=ON ..

Notice, that by adding the -D WITH_QT=ON, the highgui module will use QT instead of GTK. If you want to go with GTK just remove this. For more information on the options, look at the CMakeLists.txt file. When you are happy with the configuration you have, you can start compiling:

make

If compilation finishes without errors, you can install by saying:

sudo make install

Finally, make sure that your programs can link to the OpenCV library in run-time by adding the following line at the end of your /etc/ld.so.conf:

/usr/local/lib

And then configure dynamic linker run-time bindings:

sudo ldconfig

Testing

An easy way to test that the compilation went well is to use the OpenCV test utilities. For example, to test the core module go to OpenCV-2.4.0/build/bin and run:

 ./opencv_test_core

You should see something like that:

Note that some failures when testing other modules may come from missing image files. To correctly run these tests or samples you should move the corresponding image files from OpenCV-2.4.0/samples to OpenCV-2.4.0/build/bin.

For testing that you can compile your own programs and link against the installed OpenCV libraries I have packaged the face detection sample with all the necessary files and a simple Makefile. Download it here, extract and type:

make

This should compile and run with a test image, so you should see something like this:

Elapsed Time for Shell Scripts

A lot of times you want to calculate the time it takes for a part of a shell script to run. Here is one of the ways you can do this:

T1=$(date +%s)
# Do something here
T2=$(date +%s)
diffsec="$(expr $T2 - $T1)"
echo | awk -v D=$diffsec '{printf "Elapsed time: %02d:%02d:%02d\n",D/(60*60),D%(60*60)/60,D%60}'

This will tell you the elapsed time between setting T1 and setting T2. The output is formatted as HH:MM:SS and printed to the console. You can easily redirect to a file for logging.

Using FFMPEG

FFMPEG is a complete, cross-platform solution to record, convert and stream audio and video. It includes libavcodec; the leading audio/video codec library. FFMPEG is a free software project and it is published under the GNU Lesser General Public License 2.1+ or GNU General Public License 2+ (depending on which options are enabled).

To install FFMPEG in Ubuntu just type:

sudo apt-get install ffmpeg

This post contains a collection of useful examples of using FFMPEG from the command line.

Video Information
Get information on the video (codec, frame rate, etc.).

ffmpeg -i myvideo.avi

Video Encoding
To encode the video using a different codec we specify it using the -vcodec option.

ffmpeg -i myvideo.avi -vcodec mpg4 video_out.avi

Now let's say we want a better quality compression and a different frame rate from the original. We specify 1Mb/s bitrate using the -b option (default is 200kb/s) and we change the frame rate to 12 fps using the -r option.

ffmpeg -i myvideo.avi -vcodec mpg4 -b 1M -r 12 video_out.avi

Other values for the -vcodec option include:

copy:	Copy raw codec data as is (do not reencode)
rawvideo:	Raw video (uncompressed)
xvid:	XviD (MPEG-4 Part2)
wmv2:	Windows Video Media

Extracting Video Frames
The following example extracts the frames from the video and saves them as frame_001.png, frame_002.png,...

ffmpeg -i myvideo.avi -f image2 frame_%03d.png

Cropping a video to a specific time interval
The following example extracts a scene from the input video that start at 1 minute 45 seconds and has a duration of 30 seconds.

ffmpeg -i myvideo.avi -ss 00:01:45 -t 00:00:45 myscene.avi

Slow down or speed up a video
Let's say we need to slow down a video now. Unfortunately, decreasing the frame rate with the -r option will not do, since ffmpeg will drop frames to keep the duration of the video the same. We need to use mjpegtools to do that. To install mjpegtools type:

sudo apt-get install mjpegtools

For this example the original video has a frame rate of 30fps and we want to make it play at 1/3 of the speed. So we have to trick ffmpeg to believe that the original video had a 10fps frame rate. The yuvfps tool does exactly that. Make sure that the input frame rate (-s option) and the output frame rate (-r option) are the same.

ffmpeg -i myVideo.avi -f yuv4mpegpipe - | yuvfps -s 10:1 -r 10:1 | ffmpeg -f yuv4mpegpipe -i - -vcodec mpeg4 -b 12M  mySlowVideo.avi

Note that this will not work unless your video has one of the yuv pixel formats. If your pixel format is not compatible (rgba for example) you would have to convert it like this:

ffmpeg -i myVideo.avi -pix_fmt yuv420p myVideo2.avi

OpenCV 2.3.1 on Ubuntu 10.10 or later

*Update: For OpenCV 2.4 on Ubuntu 12.04 see my latest post.

This post will guide you on how to compile and run OpenCV 2.3.1 on Ubuntu 10.10 or later.

First, install all prerequisites:

sudo apt-get install build-essential checkinstall git cmake ffmpeg libfaac-dev libjack-jackd2-dev libmp3lame-dev libopencore-amrnb-dev libopencore-amrwb-dev libsdl1.2-dev libtheora-dev libva-dev libvdpau-dev libvorbis-dev libx11-dev libxfixes-dev libxvidcore-dev texi2html yasm zlib1g-dev libtbb-dev libv4l-dev libopenexr-dev libunicap2-dev libavformat-dev libswscale-dev libdc1394-22-dev libgstreamer0.10-0 libgstreamer0.10-dev gstreamer0.10-tools gstreamer0.10-plugins-base libgstreamer-plugins-base0.10-dev gstreamer0.10-plugins-good gstreamer0.10-plugins-ugly gstreamer0.10-plugins-bad gstreamer0.10-ffmpeg python-numpy

This is not a minimal set of libraries, but it's a collection that will give you most of the functionality. For example, if you are sure that you will never need to use a firewire camera, you can ignore libdc1394-22-dev. But if you actually need to use this feature you will have to recompile OpenCV. Also, if you need CUDA support, follow the instructions in this post before continuing here.

Download OpenCV:

wget downloads.sourceforge.net/project/opencvlibrary/opencv-unix/2.3.1/OpenCV-2.3.1a.tar.bz2

Extract and create a build directory:

tar -xvf OpenCV-2.3.1a.tar.bz2
cd OpenCV-2.3.1/
mkdir build
cd build

Now run cmake:

cmake -D WITH_TBB=ON -D BUILD_NEW_PYTHON_SUPPORT=ON -D WITH_V4L=OFF -D INSTALL_C_EXAMPLES=ON -D INSTALL_PYTHON_EXAMPLES=ON -D BUILD_EXAMPLES=ON ..

At this point check the output of cmake to make sure that all the features you are going to need are supported. If not you will have to install the corresponding libraries and run cmake again. Compile:

make

If everything went well you can go ahead and install:

sudo make install

Finally, add the following lines in your .bashrc:

# OpenCV stuff
PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig

To test that everything works, let's run the face detection demo. Go to the bin directory:

cd bin

And run:

./facedetect --cascade="../../data/haarcascades/haarcascade_frontalface_alt.xml" --nested-cascade="../../data/haarcascades/haarcascade_eye.xml" --scale=1.3 ../../samples/c/lena.jpg

You should see something like this:

How to install CUDA 4.0 on Ubuntu 10.10 or later

First, you need to install the NVIDIA development drivers. Download the current version (270.41.19) here.

To install the dev drivers, reboot and go into recovery mode. Select the "Drop to root shell prompt" option. Now type:

sudo telinit 3

Login again using your username, then cd to the directory where you downloaded the drivers (e.g. ~/Downloads):

cd ~/Downloads
chmod u+x devdriver_4.0_linux_64_270.41.19.run
sudo ./devdriver_4.0_linux_64_270.41.19.run

Follow the instructions on the screen. Make sure you write to your xorg.conf file. When done reboot:

sudo reboot

Download the CUDA Toolkit from this page (Linux -> CUDA Toolkit for Ubuntu Linux 10.10).

cd ~/Downloads
chmod u+x cudatoolkit_4.0.17_linux_64_ubuntu10.10.run
sudo ./cudatoolkit_4.0.17_linux_64_ubuntu10.10.run

Finally, download the GPU Computing SDK from the above website.

cd ~/Downloads
chmod u+x gpucomputingsdk_4.0.17_linux
./gpucomputingsdk_4.0.17_linux

Add the these lines at the end of your ~/.profile (if your OS is 32-bit, remove the lib64 entry):

#CUDA stuff
export PATH=/usr/local/cuda/bin:$PATH
export LD_LIBRARY_PATH=/usr/local/cuda/lib:/usr/local/cuda/lib64:$LD_LIBRARY_PATH

Now you just need to compile the samples. Assuming you installed the SDK in your home directory:

cd ~/NVIDIA_GPU_Computing_SDK
make

You can now run one of the demos, e.g. the particle demo

~/NVIDIA_GPU_Computing_SDK/C/bin/linux/release/particles

and you should see something like this:

How to add users on Ubuntu

First, add the new user:

sudo useradd -c “John Smith” -m -s “/bin/bash” jsmith

and then create a password for the new user:

sudo passwd jsmith

The -c options lets you give a full name for the user, -m option creates a home folder, -s specifies the default shell.

Install Ubuntu Tweak on Ubuntu 10.10

Open a terminal and type:

sudo add-apt-repository ppa:tualatrix/ppa
sudo apt-get update
sudo apt-get install ubuntu-tweak

Install and Configure Tomcat6 on Ubuntu Linux

Apache Tomcat is an open source software implementation of the Java Servlet and JavaServer Pages technologies.

The Java Servlet and JavaServer Pages specifications are developed under the Java Community Process.

Part 1
First, install tomcat6:

sudo apt-get install tomcat6 tomcat6-docs tomcat6-examples tomcat6-admin

Then configure a user to be manager and admin by adding the following lines

  <role rolename="admin"/>
  <role rolename="manager"/>
  <user username="YOURUSERNAME" password="YOURPASSWORD" roles="admin,manager"/>

in your /var/lib/tomcat6/conf/tomcat-users.xml. Make sure you put it between the <tomcat-users> and </tomcat-users> tags and don't forget to replace YOURUSERNAME with your actual username.
Now go to a browser and hit:

http://localhost:8080/

and you should see the welcome page.

Part 2
To restart tomcat you just need to say:

sudo /etc/init.d/tomcat6 restart

or if you want to start/stop/get status you just replace restart with start/stop/status.
To make this easier go to a terminal and type:

gedit tomcat

then add the following lines of text:

#!/bin/bash

/etc/init.d/tomcat6 $1

then save and close and type:

chmod u+x tomcat
sudo mv tomcat /usr/local/bin

so if you want to stop tomcat you can now say:

sudo tomcat stop

Let's add auto-completion to our new command now. Open a terminal and type:

gedit tomcat

then copy paste the following

_tomcat() 
{
    local cur prev opts
    COMPREPLY=()
    cur="${COMP_WORDS[COMP_CWORD]}"
    prev="${COMP_WORDS[COMP_CWORD-1]}"
    opts="start stop restart status"

    if [[ ${cur} == * ]] ; then
        COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) )
        return 0
    fi
}
complete -F _tomcat tomcat

save and close gedit. Now type:

sudo mv tomcat /etc/bash_completion.d

You need to restart for this to take effect, but if you want to test it right away type:

. /etc/bash_completion.d/tomcat

Then as an example, type:

sudo tomcat re

and hit tab a couple of times. It should complete the word restart for you since it's the only valid option that begins with "re".

Install Sun Java JDK in Ubuntu 10.10

To install Sun's Java 6 JDK on Ubuntu 10.10, add the Sun Java6 Community PPA and install:

sudo add-apt-repository ppa:sun-java-community-team/sun-java6
sudo apt-get update
sudo apt-get install sun-java6-jdk sun-java6-plugin
sudo update-java-alternatives -s java-6-sun

GRUB 2 Splash Images on Ubuntu

Here is how you can get a nice background image for GRUB boot menu.
First, install the "grub2-splashimages" package:

sudo apt-get install grub2-splashimages

Then edit /etc/default/grub and add the following line

GRUB_BACKGROUND=/usr/share/images/grub/yourImage.png

Also, make sure that GRUB is loaded in the same resolution as the image

GRUB_GFXMODE=1680x1050

...and that's it. Update GRUB

sudo update-grub

and restart to see the results.

How to delete all .svn directories

If you are using subversion, at some point you probably tried to take some folders from one repository and try to commit then to another. Since each folder has a hidden .svn folder, subversion will complain that "they are already under version control". Here is how to recursively delete all .svn folders:

find . -name ".svn" -type d -exec rm -rf {} \; -prune -print

Copy Paste between Emacs and other applications

If you are using GNU Emacs in an X-windows environment like Gnome, you would have noticed that sometimes copy-pasting from Emacs to other applications or vice versa does not work.
To fix this, edit your .emacs file (located in your home folder) and add the following lines:

;; Send primary selection to clipboard so copy-paste works with other X-applications
(global-set-key "\C-w" 'clipboard-kill-region)
(global-set-key "\M-w" 'clipboard-kill-ring-save)
(global-set-key "\C-y" 'clipboard-yank)

OpenCV 2.2 on Ubuntu 10.10

*Update: For OpenCV 2.4 on Ubuntu 12.04 see my latest post.

OpenCV (Open Source Computer Vision) is a library of programming functions for real time computer vision. It is released under a BSD license, it is free for both academic and commercial use. It has C++, C, Python and soon Java interfaces running on Windows, Linux, Android and Mac.

This is how to build and install OpenCV 2.2 on Ubuntu 10.10.

First, install the dependencies from the repositories:

sudo apt-get install build-essential libgtk2.0-dev libavcodec-dev libavformat-dev libjpeg62-dev libtiff4-dev cmake libswscale-dev libjasper-dev

Download the source code:

wget http://sourceforge.net/projects/opencvlibrary/files/opencv-unix/2.2/OpenCV-2.2.0.tar.bz2

Extract, create the build directory:

tar xfv OpenCV-2.2.0.tar.bz2
rm OpenCV-2.2.0.tar.bz2
cd OpenCV-2.2.0
mkdir opencv.build
cd opencv.build

Configure, make and install:

cmake ..
make
sudo make install

To configure the library, edit the following file (might be empty):

sudo gedit /etc/ld.so.conf.d/opencv.conf

and add the line

/usr/local/lib

Then run:

sudo ldconfig

Finally, edit the file:

sudo gedit /etc/bash.bashrc

and add the following lines at the end:

PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig
export PKG_CONFIG_PATH

Most of the above was find here.

Older versions? Take a look at the following links:

OpenCV 2.1 on Ubuntu 10.04 (pretty much the same as above, but with TBB)
OpenCV 2.0 on Ubuntu 9.10

For OpenCV 2.3.1 see this post.

Completely Disable Touchpad in Ubuntu

To temporarily disable the touchpad while typing just go to
System > Preferences > Touchpad
and check
Disable touchpad while typing
but if you want to completely disable it, you can do the following
In a terminal type:

xinput list | grep -i touchpad

to determine the device ID (in my case, 14). Then disable by typing:

xinput set-prop 14 "Device Enabled" 0

To enable it, type:

xinput set-prop 14 "Device Enabled" 1

From the Ubuntu Documentation: Synaptics Touchpad