Original wavelet denoise plugin from registry.gimp.org with compile fixes.
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The wavelet denoise plugin for The GIMP is an algorithm copied and slightly
altered from the UFRaw program (which inherited the algorithm from dcraw).
Instead of denoising all RGB channels at once the plugin implementation allows
to denoise the RGB channels individually and - even more useful - to denoise
the YCbCr or CIELAB channels individually. The colour model conversions are
nearly lossless as the internal calculations are done in floating point numbers
and rounding errors are avoided.


Copyright (C) 2008 by Marco Rossini. Distributed under the General Public
License. See the file COPYING which contains the license.


See the file INSTALL for instructions how to install the plugins.


Once the plugin is installed successfully, the plugin can be found in The GIMP
using the menu "Filters->Enhance->Wavelet denoise". It works for both Grayscale
and RGB (full colour) images, including alpha channels. The plugin dialog
allows to adjust several parameters.

1. First, the choice has to be made over what colour model is to be used. There
   are three possibilities (maybe there will be more in the future):

   a) RGB     (red-green-blue)

   b) YCbCr   (luminance-blueness-redness)

   c) CIELAB  (lightness-chroma)

   YCbCr and CIELAB allow separate reduction of luminance and chroma (colour)

2. The preview mode can be selected. Either all channels can be selected or
   the current active channel which is then displayed in grayscale or colour.

3. Select the channel you want to denoise.

4. The sliders adjust the the threshold for denoising. The softness controls
   the softness of the thresholding. The greater the softness, the more noise
   remains in the image.

For camera pictures I advise to use YCbCr mode (which is nearly lossless) and
to at least denoise the Cb and Cr channels to reduce the chroma (colour) noise.
Cameras shooting in JPEG mode normally have chroma noise already reduced. If
desired, the luminance noise can be reduced. This channel usually contains
most of the fine structures in the image and should mostly be left alone.