what library is able to extract SIFT features in Python?

Question

In python which library is able to extract SIFT visual descriptors? I know opencv has an implementation but it is not free to use and skimage does not include SIFT particularly.

Answer 1

I would like to suggest VLFeat, another open source vision library. It also has a python wrapper. The implementation of SIFT in VLFeat is modified from the original algorithm, but I think the performance is good.

Answer 2

OpenCV is free to use.

But SIFT itself as algorithm is patented, so if you would make your own implementation of SIFT, not based on Lowe`s code, you still could not use it in commercial application. So, unless you have got a license for SIFT, no library with it, is free.

But you can consult with patent guys - some countries like Russia does not allow to patent algorithms - so you can you SIFT inside such country.