Hello Robert, On Sat, 14 Jul 2012 18:51:15 -0400 Robert Krawitz <rlk alum mit edu> wrote: > On Sun, 15 Jul 2012 01:19:52 +0400, Alexandre Prokoudine wrote: > > On Sat, Jul 14, 2012 at 12:35 PM, Martin Jambon wrote: > >> Hi, > >> > >> I am totally new here but I wrote a standalone program that does a > >> decent job of removing purple fringing from photos, and I would like to > >> be able to implement the same functionality for Gimp. > >> > >> Here are some examples of what it does: > >> > >> http://mjambon.com/purple-fringe/examples.html > >> > >> My algorithm needs to perform pixelwise operations (+, -, min, max > >> between two channels; scaling of one channel) but I also would prefer > >> something that is easy to install (for users) and easy to maintain (fo> >> > >> The OCaml source code is here; it should give an idea of what's needed: > >> > >> https://github.com/mjambon/purple-fringe/blob/master/src/unpurple.ml > >> > >> (see functions make_purple_blur and remove_purple_blur, lines 103-177) > >> > >> My questions are: > >> > >> 1. Is it possible to do that using a Gimp script? > >> > >> 2. If so, Scheme or Python? > >> > >> 3. If a plugin makes more sense, will average users be able to install > >> it for themselves or would I have to wait for the inclusion in some > >> standard precompiled distribution? > > > > Just in case, are you aware of http://kcd.sourceforge.net/fix-ca.php ? > > That fixes lateral chromatic aberration (the focal length, or image > magnification, is different for different wavelengths but the focal > plane is the same). Purple fringing is caused by longitudinal chromatic > aberration (the focal plane is different for different wavelengths). > It's a different lens defect and is much more difficult to fix (stopping > down reduces the problem, since it increases depth of field, but there > are often reasons why you don't want to do that). > > Lateral chromatic aberration will be zero at the center of the image and > will increase toward the edges; longitudinal chromatic aberration will > affect the entire image field (including the very center) more or less > equally. > > Martin's tool looks very impressive, particularly for those of us who > have the Canon 85 f/1.8 -- a truly great lens marred only by a fair bit > of purple fringing at large apertures. I second that, his work is impressive! Regards, -- wwp
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