Bag-of-colors for improved image search


[Paper](https://hal.inria.fr/inria-00614523/document)

This package contains the bag-of-colors signature extracted published in 

| Christian Wengert, Matthijs Douze and Hervé Jégou,
| Bag of colors for improved image search
| Proc. ACM Multimedia'11, November, 2011. 


It also provides an evaluation framework to evaluate the global signature 
extraction. 

There are several paramaters (number of colors, normalization type's, distance
type, etc) that can be changed. The default is for a codebook comprising 256 
colors and with almost optimal parameters with respect to the search accuracy. 


CONTENT
-------

The purpose of the files in the bag_of_colors_package/ root directory
is as follows:


config_boc.m             The configuration file, that contains both the library
                         paths and parameters for the descriptor generation. 

compute_main_colors.m    Extract the main colors using the procedure detailled
                         in the paper. Note that this step is costly. Therefore
                         the output of this stage (performed on the Flickr60K
                         dataset) is already provided and stored in the matlab 
                         file 'maincolors.mat'

learn_color.m            Learn the color codebook using the maincolors

compute_color_histo.m    Function that compute the histogram of colors from an 
                         input image

boc_from_histo.m         Convert an histogram of color into the descriptor

launch_compute_boc.m     compute the set of BOC for a given dataset

evaluate_boc.m           Compute the retrieval score 


make_ppmsmall.sh         This script was used to reduce the size of the images. 
                         Since we provide the images from Holidays already 
                         resized, you should not need it. 
                         It is required only if you want to consider a new 
                         dataset. 


The subdirectories contain the following:

utils/      contains some basic functions, evaluation functions,
            and configuration files for the dataset.
            Changing the paths in the config_* files if needed.

flickr60k/  In this directory, we provide some data extracted from our Flickr60K
            dataset. It is used for the learning stage only.
            We provide pre-computed dominant colors, color palettes. 
            The images are not provided itself, due to copyright reasons,
            but any large enough dataset of images from Flickr could do the job. 

holidays/   This directory contains the ground-truth used to compute the score. 
            It will also contain the re-sized images downloaded in the additional 
            package.


PRE-REQUISITES
--------------

The yael library, more precisely with a working Matlab interface, is required 
to have a working and efficient execution of this package

Install a recent yael library. 
The last version can be obtained (with open-source license) at 

https://gforge.inria.fr/projects/yael/


If you want to do all steps yourself, the INRIA holidays dataset is required.  
You can download the set at

http://pascal.inrialpes.fr/data/holidays/jpg1.tar.gz
and
http://pascal.inrialpes.fr/data/holidays/jpg2.tar.gz

Use the make_ppmsmall.sh script to resize and preprocess the images.
   

INSTALLATION AND EXECUTION
--------------------------

First, you have to download and install Yael. Once you get a working 
yael, you should adapt the config_boc.m M-file to adapt the paths to your 
configuration, and to the desired parameters. 

The package must be used with some data that are provided in a separate archive. 
Download it from our website:

  wget http://www.kooaba.com/docs/holidays_16384pix.zip

and extract it in the root directory of the package. This additional package 
contains the re-sized and normalized images (created with make_ppmsmall.sh). 


Then, you should be able to execute the following matlab commands to 
produce and evaluate global BOC descriptors. 

> learn_color          % Learn a color codebook
                       % This stage is not mandatory, as we already give
                       % some pre-computed codebooks


> launch_compute_boc   % Compute the histogram of colors and BOC vectors

> evaluate_boc         % Compute the mAP value (by default, on Holidays)