Re: [Gimp-developer] How to deal with pixel-per-pixel operations?

On Tue, Jun 11, 2013 at 1:32 AM, Alessandro Francesconi <
alessandrofrancesconi live it> wrote:

Hello, I'm starting to write a GIMP plugin and I'm facing the problem of
"pixel-per-pixel" algorithms and their speed.
Without going on details, my algorithm should take every pixel in the
image and for each one it must check its 24 neighbours, it does some simple
calcs and finally it set a new color for the pixel.

How to speed-up the execution? I tried with the easiest approach with a
classic "for-in-for" loop but the computation is really slow. Looking
around, I've seen some GIMP functions like:

gimppixelfetcher — Functions for operating on pixel regions.
gimppixelrgn — Functions for operating on pixel regions.
gimpregioniterator — Functions to traverse a pixel regions.

All of the above functions are considered deprecated; even when developing
a GIMP plug-in and not a GEGL operation you would be encouraged to use
GeglBuffer APIs (search for "gegl" in gimp's plug-in directories.). Though
for a filter plug-in like you describe, the most proper way to do it now
and for the future is to write a GeglOperation that derives from the
provided GeglOperationAreaFilter like for instance:

you'd probably want to fetch the entire neighborhood of the rectangular
region being processed though; rather than doing like that particular
plug-in which gegl_buffer_get's pixels one by one.


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