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# nonfree. Non-free functionality

The module contains algorithms that may be patented in some countries or have some other limitations on the use.

- Feature Detection and Description
  - SIFT
  - SIFT::SIFT
  - SIFT::operator ()
  - SURF
  - SURF::SURF
  - SURF::operator()
  - gpu::SURF_GPU
  - ocl::SURF_OCL

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