The SIFT algorithm provides the capability to identify key feature
points within arbitrary images. It further extracts highly distinct
information for each such point and allows to characterize the point
invariant to a number of modifications to the image. It is invariant
to contrast/brightness changes, to rotation, scaling and partially
invariant to other kinds of transformations. The algorithm can be
flexibly used to create input data for image matching, object
identification and other computer vision related algorithms.

autopano-sift-C is a C port of the C# software autopano-sift. It is
somewhat faster and doesn't require a C# runtime. Additionally,
autopano-sift-C has experimental modifications to perform feature
identification in conformal image space, this helps with wide angle or
fisheye Projection photographs.