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From: | Henning Müller |
Subject: | Re: [help-GIFT] Feature Extraction - Range breakdown |
Date: | Tue, 20 Dec 2011 11:42:30 +0100 |
User-agent: | Mozilla/5.0 (Macintosh; Intel Mac OS X 10.5; rv:8.0) Gecko/20111105 Thunderbird/8.0 |
Hi,GIFT does not do any feature selection. Many features are binary and thus either present or absent. The different number results from some images containing for example fewer colors than other images and from the fact that not all images have all direction/scale/strength combinations of the Gabor filter responses. For the Gabor filters that default configuration does not use the lowest energy band, meaning the images with many flat regions have fewer features. This is an option in the source code and can be changed.
There is a feature description file in the index directory that has the feature number and feature group (on of the four Gabor histogram, Gabor block, color histogram, color blocks). I do not remember the exact details but it should be described in the early papers on the system such as: http://publications.hevs.ch/index.php/publications/show/189
The Gabor blocks are indeed 16x16 blocks, where as the color blocks should be blocks at four scales, so first dividing the image into 4, then 16, 64, 256 blocks, so 340 blocks if I am not wrong.
Kind regards, Henning On 12/19/11 12:44 PM, Xavier Clements wrote:
Greetings, I have two questions, the first having two parts. 1. How does GIFT select features for extraction given that I read in one of these discussions that the range of features extracted for any one image is between 341 to 3686? Is this upper limit arbitrary in nature and able to be altered in the code? 2. Is the following breakdown of the ranges for each of the four extracted feature types correct (taken from a previous post)? "1. color blocks - 1st 256 times 16x16 color blocks, where each has 166 possible values (i.e. features 0..42 495, where 0..165 are from the first block etc.) - 2nd 64 32x32 blocks, (10 624 more feats, i.e.42 496 .. 53 119 <tel:42%20496%20..%2053%20119>) - 3rd 16 64x64 blocks, (2 656 more, i.e.53 120 .. 55 775 <tel:53%20120%20..%2055%20775>) - 4th 4 128x128 blocks (664 more, i.e. 55 776 .. 56 439) 2. color histogram 166 features (feats 56 440 .. 56 606) 3. gabor blocks - 256 times 16x16 blocks, each block containing 120 possible Gabor features (features 56 607 .. 87 325 so that in 56 607..56 726 are the Gabors calculated from the first block and in 56 726..56 845 <tel:56%20726..56%20845> are from the second etc.) 4. gabor histogram last 120 features ( 87 326 .. 87445 )" Forgive this newcomer for potentially asking questions that have been previously answered (I looked through a number of the forum's archives...honest). Thanks in advance, Xavier _______________________________________________ help-GIFT mailing list address@hidden https://lists.gnu.org/mailman/listinfo/help-gift
-- Henning Müller, PhD, Prof. HES-SO Valais TechnoArk 3, 3960 Sierre, Switzerland Tel. +41 27 606 9036 http://medgift.hevs.ch/
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