> Could you perhaps say a little more?  After 5 years of GIMP experience,
> I've never heard of this filter or have any idea what it does, and your
> page doesn't yet help.

Ok.  So a short explanation for the younger folks... ,-)

The User Filter plug-in  was a work-alike to the Filter Factory (I'll write FF 
now for this) of Adobe's Photoshop (PS from now on).
It was able to load filter descriptions for this tool in different text file 
formats (.afs is a FF source, .txt a source from a 3rd-party tool and .ffl a 
filter conllection).   FF also "compiled" these filters into stand-alone .8bf  
plug-ins for PS (which could be used using Tor Lillquist's pspi plug-in, by 
the way) which also could be used with User Filter.

The general idea behind the whole thing is to provide a means to be able to 
write filters without the need of going through the whole process of studying 
the SDK (Glib, Gtk+, libgimp in our case), compiling, and installing.
Instead, the plug-in offers an editor with which filters can be implemented by 
writing a formula for each color channel that manipulates the pixel data of 
the image.

It is possible to implement almost any kind of filter with this tool - alas, 
since the code is interpreted byte-code, it'll not be as fast as a 
hand-written plug-in.  Yet, if the formulas are not too complex, it is still 
quite fast.  There will also be a tool to translate the formulas into C code, 
so there is another speed gain possible (although, again, this won't be as 
efficient as a hand-written plug-in).

Think of it as some kind of interpreter extension for The Gimp - but unlike 
script-fu or python-fu which are mainly used to combine effects, this is used 
to create effects.

This version of the User Filter plug-in is derived from the last (v0.8) 
version that was available back in 2003 (and which was just a compile-fix for 
the new Glib and Gtk+).   A couple of bugs that were in the old version have 
been fixed, code that used deprecated functions was replaced, and the 
functionality of the plug-in was extended a little.

To get an idea what a filter description might look like, you can go to
where you can find a few samples.

By default, these filter descriptions should be installed in
But that's run-time configurable (you can change the search path from within 
the plug-in to any place where you would like to store filter descriptions).
The plug-in will recursively search those paths for filters on start-up.

I will try to get some more information (and more important: documentation) on 
the project webpage during the weekend (though I can't promise anything).

Now some information for the old and grey who might still remember the 
original version of the plug-in...

You will certainly notice a couple of changes (besides a slightly different 
look).  The most important is, that you cannot take any FF filter and place 
it in the userfilter data directory any more - you will have to import the 
filter through the editor and save it in the new .guf file format.
This might sound inconvenient at first, but I have done this on purpose:
The new data handling makes extension of filter functionality easy and also 
offers a means to include locale data (for filter controls etc).

hth for starters


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