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Re: [help-GIFT] GIFT Features

From: Wolfgang Müller
Subject: Re: [help-GIFT] GIFT Features
Date: Wed, 21 May 2003 13:14:36 +0200
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> More questions
> 3.What is the purpose of ,if histogram
> intersection is the method that is empoyed?

OK. As Henning made clear, histogram intersection is not the only method 
employed. The general idea of the normalizers is that there are some query 
wighting methods that divide the score by some measure of the total document 
length --> we need to apply that operation in the end of the scoring. The 
other point is that one of the requirements at the time of writing Viper was 
that the the score of the query applied on itself be equal to one. As the 
query can be comprised of many images, we need to apply the actual query 
derived of a couple of images on itself, then memorize the result and use 
that for normalization of the score. is for 
normalizing the query if you want to normalize by the square of its L2 

> 4.If I have to write a plugin say for providing the option of using
> different distance measures under a “Distance Measure” Plugin. How should I
> go about it, if I would like the user to be able to select different
> distance measure from a list of options.

I do not quite fully understand. Do you want to use the Viper engine and add 
some measures? Then you inherit from weighting function and maybe from the 
QueryNormalizers, and add your new stuff to the CWeighterFactory in the file . If you want to do everything differently, then you might 
want to write a new plugin. A student of mine is in the process of writing a 
howto for that. I will send her your address, if you'd like to get her howto 
and to improve it.

> 5. Or suppose I’d like to change the colour space used to Luv/Lab and use
> Euclidean distance measure, which are the files I could modify/ redo?

Look at everything looking like *hsv* in the FeatureExtraction directory. The 
code is not mine (it's David's) and I rarely touch it, but an easy fashion to 
see what happens when you change the colorspace would be to make 
drop-in-replacements for the rgb_to_hsv functions that must be in there 
(under some other name).

Oh, yes, you want:
void rgb2hsv(double R, double G, double B, double *H, double *S, double *V)
from the rgb2hsv_utils.c file, I guess.


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