Opencv in ubuntu14.04 step by step?

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The steps to follow are quite simple

// Clone the opencv repository in a folder
git clone https://github.com/Itseez/opencv.git opencv
cd opencv
// Select the proper branch you want to built
git checkout 2.4
//git checkout master
// Make a building folder and build the repo
mkdir build
cd build/
cmake -D CMAKE_BUILD_TYPE=DEBUG -D CMAKE_INSTALL_PREFIX=/usr/local ..
sudo make -j 10
sudo make install

Thats it! Then simply link your environment tot the installation.