Hi list,

I'm interested in noise reduction using GIMP. A little (skippable)
background first.

I recently bought a digital camera, a very nice Canon IXUS 40. One big
plus over traditional "chemical" photography is that you can change
sensitivity for poor light conditions. However, this increases noise
in the resulting image. Digital noise tends to be uglier than its
analog counterpart, I'm not sure why; maybe we will get used to it
eventually, or maybe not.

In the meantime, digital noise is quite annoying. Since the picture is
already in the computer, I tried to GIMP the noise off, but had no
luck. People seem to use "unsharp mask", but the results are frankly
quite poor. I have found several programs that seem to do the trick
more or less, but all of them proprietary and all of them for Mac / PC
(I'm on Linux). Of course, none work with GIMP.

So after many offroads (like improving on Remi's excellent FFT
plugin), and being of the geek persuasion, I tried to create my own
GIMP plugin. It has been a very interesting process, and results are
not bad even at this preliminary stage. I have used several algorithms
(stdev discrimination, linear regression); right now I'm trying out a
combination of median and interquartile range which is promising, but
still not perfect.

Now, let's go to the questions.

  - Is there a noise reduction technique / plugin for GIMP that I haven't found?
  - Where can I upload the result of my own efforts so that people can
try it out or even improve it?
  - Do you know any algorithms that work really well for noise
reduction? I came across this message:
  so if someone can point me to the paper mentioned or similar, I
would be most grateful.


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