

What is this
============

This is a library and an exectuable that reimplement A. Torralba's
GIST image descriptor in C. The original Matlab implementation is
here:

http://people.csail.mit.edu/torralba/code/spatialenvelope/

How to compile
==============

The library depends on fftw3. It is available at: 

http://www.fftw.org/

or along with your Linux distribution. Versions 3.1.2 and 3.2.1 work.

If it is installed in a non-standard location, set the WFFTINC and
WFFTLIB accordingly in the Makefile.

The code compiles on linux 32 and 64 bit with gcc 4.2.1. It has not
been tested on other platforms.

How to test
===========

The library comes with a mini-executable that computes the GIST
descriptor of a PPM image. To test: 

./compute_gist ar.ppm 

Should display 960 float values that start with: 

0.0579 0.1926 0.0933 0.0662 .... 

and end with 

.... 0.0563 0.0575 0.0640

The code works on non-square images, but it is of little interest:
descriptors computed on images of different sizes are not comparable.

The library should compute the exact same descriptor as the Matlab
version. Be careful that encoding a small image in JPEG (even with the
maximum quality factor) changes the descriptor.

Quizz: where does the ar.ppm test image come from? 

Who made it
===========

The library was developed in 2009 in the Lear group at INRIA. It was
used in

@INPROCEEDINGS{JDSAS09,
  author = {Matthijs Douze and Herve Jegou and Harsimrat Singh and Laurent Amsaleg
	and Cordelia Schmid},
  title = {Evaluation of GIST descriptors for web-scale image search},
  booktitle = {civr},
  year = {2009},
}

Licence: GPL

Comments, complaints to: matthijs.douze@inria.fr

History
=======

jan 2009: Reimplementation of GIST added to Lear's internal image
processing library by Christophe Smekens.

jul 2009: Standalone version packaged by Matthijs Douze


