OpenCV is an open source C++ library for image processing and computer vision application originally developed by Intel.It is free for  both commercial and  non-commercial usage. computer vision defers from  image processing,in computer vision image and  its characteristics treated as a signal.  based on the signal different activity can be computed in computer programs.More than 500 different algorithms have been implemented in OpenCV and exposed as c/c++ API. Usage ranges from     interactive art, to mines inspection, stitching maps ,etc.

what is opencv

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Building and installing OpenCV for Linux

$ wget http://sourceforge.net/projects/opencvlibrary/files/opencv-unix/2.4.7/opencv-2.4.7.tar.gz/download$ tar -xzvf opencv-2.4.7.tar.gz$ cd opencv-2.4.7

# mkdir build# cd build# cmake -D WITH_TBB=ON -D INSTALL_C_EXAMPLES=ON# make# make install

In build directory you can run example code , the best way to learn opencv by example code.