Re: [Gegl-developer] gaussian reduce operator, and GIMPGEGL operator
- From: <bootch nc rr com>
- To: Øyvind Kolås <pippin gimp org>
- Cc: gegl-developer-list gnome org
- Subject: Re: [Gegl-developer] gaussian reduce operator, and GIMPGEGL operator
- Date: Thu, 29 Mar 2012 15:10:37 -0400
---- "Øyvind Kolås" <pippin gimp org> wrote:
On Thu, Mar 29, 2012 at 4:12 PM, <bootch nc rr com> wrote:
This message has two subjects.
1. Is there a gaussian reduce operation in GEGL? Â Refer to the paper by Burt and Adelson, 1983, where it
is called REDUCE and apparently claims that it is faster than operation gaussian blur followed by
down-sample (scale by 1/2). Â Used in the production of a gaussian pyramid. Â It seems to me to be a
fundamental operation and should be in GEGL. Â A search shows that the operation mantiuk06 for GSOC might
have generated gaussian pyramids but AFAIK did not expose reduce() as a operation. Â There is also a
corresponding inverse operation EXPAND, which is useful in generating a Laplacian pyramid. Â I have a use
for a gaussian pyramid and might consider implementing gaussian reduce for GEGL (instead of the naive
approach of using gaussian blur followed by scale.) Â The gaussian and laplacian pyramids are used in
texture synthesis and image compression.
There is no such op at the moment, but it does sound like something
that would be a useful building block for other things.
!? Nevermind: I think the gegl:scale with filter=cubic might be the same as reduce. I will study more.
2. A few weeks ago I posted to GIMP-dev list about https://github.com/bootchk/pluginGEGLpluginGIMP a GEGL
operation that lets you used GEGL in GIMP plugins written in Python and using Pygegl binding. Â Its not in
the form of a proper patch to GEGL but I would make a patch if I thought it would help anyone to evaluate
whether it should be part of GEGL.
The proper migration of GIMP to GEGL has ramped up significantly the
last month, in GIMP-2.10 the tile based drawable API will be marked as
deprecated and the official way for plug-ins to interact with the GIMP
core will be through GeglBuffers, for a very simple example see this
file:
http://git.gnome.org/browse/gimp/tree/plug-ins/common/goat-exercise.c?h=goat-invasion
OK. It is not clear to me that the new API using GeglBuffers will let Python plugins use GEGL,
only C-language plugins, unless there are more changes to, for example, the GIMP PDB or to Pygimp.
But I understand it is not high priority, since few GIMP plugin developers, using Python and Scheme, need
direct access to GEGL?
I suppose the guiding principle is that fundamental filter operations should be GEGL plugins written in C.
But why should non-fundamental Python GIMP plugins need to go through the PDB to get to GEGL?
I suppose the architecture of GIMP plugins is of no concern to GEGL, and I am not an expert.
Anyway, I will defer until after 2.10.
/Øyvind K.
--
«The future is already here. It's just not very evenly distributed»
                         -- William Gibson
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