Update: This project is essentially unmaintained at this point, since I don't have time to work on it, and my focus has moved on to other things. Note that this very code was long ago incorporated directly into OpenCV and, as far as I know, still serves as the basis of OpenCV's SIFT implementation. Thus, if you have any issues with this project, I encourage you to use OpenCV's SIFT implementation directly.
This is a collection of code I've put together to detect SIFT features in images and to use SIFT (or other) features to compute image transforms with RANSAC. It includes a SIFT function library as well as some executables to detect, match, and display keypoints. For more information on SIFT, refer to the paper by Lowe:
Lowe, D. Distinctive image features from scale-invariant keypoints. International Journal of Computer Vision, 60, 2 (2004), pp.91--110.
Or see Lowe's website: http://www.cs.ubc.ca/~lowe/keypoints/
Some of the code also works with affine-invariant features from the code by the VGG at oxford: http://www.robots.ox.ac.uk:5000/~vgg/research/affine/index.html
Check out match.c for an example of how to use the RANSAC function. Try
match beaver.png beaver_xform.png to see it work.
Documentation is included in the docs/ directory. If it is not there,
use make docs to build it (you need Doxygen).
Help is available for executables using the '-h' command line option.
All code in this package requires the OpenCV library (known working version is 2.3): http://sourceforge.net/projects/opencvlibrary/
Some functions require GDK/GTK+2 (known working version is 2.18.4): http://www.gtk.org/
To build everything, use make:
make
This should produce a few executables in bin/, a static library lib/libopensift.a, and some HTML documentation in docs/. You can use the -h argument to get help with any of the executables. libopensift.a can be compiled into your own code using the standard method:
gcc -I/path/to/opensift/include/ -L/path/to/opensift/lib/ yourcode.c -o yourexecutable -lopensift
The documentation in docs/ describes all of the functions available in libopensift.a as well as #defines, etc. Use the documentation to determine what header files from include/ to include in your code.
You can also individually build any of the executables or libopensift.a, e.g.
make libopensift.a
See the file LICENSE for more information on the legal terms of the use of this package.