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Re: [help-GIFT] gift extension howto


From: Wolfgang Müller
Subject: Re: [help-GIFT] gift extension howto
Date: Mon, 7 Mar 2005 08:40:37 +0100
User-agent: KMail/1.7.2

Hi,

Sorry for the delay, I was on a conference.

> Wolfgang worked a little bit on including retrieval by image regions
> into MRML and this is detailed in one of the papers on MRML.

This concerned only additions to MRML, there was never any code doing it.

> The features will need to be added in the FeatureExtraction directory in
> the main gift tree.

Oh, there are a couple of things to do. There is first feature extraction, as 
you say. 

Then there is creating an extended/changed query engine.

There is a PluginMaker directory. I used it last 2 years ago, and I think I 
was the only user. I would be glad if someone tried it out again. The 
PluginMaker will create for you valid but empty GIFT plugins that can be 
filled with your code.

> In general, gift works on all image formats that are supported by
> imageMagick. You can simply add the extension svg to the
> gift-add-collection script to the other formats and it should work for
> the feature extraction.

True.

> I think that you might be better off using the php interface instead of
> charmer as charmer uses fairly old Java. 

...and the PHP interface uses fairly old PHP, right?

I have no trouble making Charmer work. AFAI recall, the last problems reported 
about Charmer were due to bad JAVA installations (wrongly set JAVA_HOME --> 
you do not see images, because the default security properties are badly 
set). However, Charmer could use some work, and it is not very beautiful 
code.

The advantages you would gain when using Charmer is that you could easily use 
Batik as a client side SVG interpreter (I do not know the license, but I 
think it is free software).

> PHP is lighter to use and there 
> are several packages available. If you are interested, I can send you
> one of those.

I think the coolest one is at gift.monosock.org. I would be interested in 
hearing of other ones.

> Handling the mrml using image regions will be a bit harder I think as
> this will include modification on several parts of gift.

Yes, it would involve creating your own plugin or doing tricky modifications 
of the query engine. 

One possible and relatively simple one would be excluding the transparent 
parts of the query from query processing. This could be done using the 
feature descriptions of the block features. Blocks that do not intersect with 
non-transparent parts of the SVG query image are discarded.

CAcIFFileSystem::URLToFeatureList(string inURL)const

in libGIFTAcInvertedFile might be a useful place to look at for adding the 
extraction of SVG images. Of course, another place to add it would be the 
query plugin. Probably this would be more useful in your case, as you want to 
look at transparency and stuff.

Cheers,
Wolfgang

-- 
Dr. Wolfgang Müller
LS Medieninformatik
Universität Bamberg




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