OpenCV (Open Source Computer Vision) is a library of programming functions for real time computer vision.
The library has >500 optimized algorithms (see figure below). It is used around the world, has >2M downloads and >40K people in the user group. Uses range from interactive art, to mine inspection, stitching maps on the web on through advanced robotics.
The OpenCV book is Learning OpenCV: Computer Vision with the OpenCV Library
For the latest code, see the Install Guide.
Send your question to the OpenCV User Group.
The OpenCV Wiki is the OpenCV community's wiki.