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Wavelet denoise

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The wavelet denoise plugin is a tool to reduce noise in each channel of an image separately. The default colour space to do denoising is YCbCr which has the advantage that chroma noise can be reduced without affecting image details. Denoising in CIELAB (L*a*b*) or RGB is available as an option. The user interface allows colour mode and preview channel selection. The denoising threshold can be set for each colour channel independently.


  • User interface with preview is available.
  • Amount of denoising for each channel is selectable.
  • Possibility to denoise YCbCr or CIELAB channels instead of RGB exists.
  • Noise profiling is done.
  • Conversion from RGB to YCbCr and RGB to CIELAB is lossless.
  • Preview is capable of displaying one single channel only if desired.
  • Processing time is reasonably fast (around 20 seconds for a 10 Megapixel image) and independent from the amount of denoising applied.
  • User interface in multiple languages is available.


The wavelet denoise plugin for The GIMP reduces noise in an image using the algorithm copied and altered from the UFRaw program [Udi Fuchs] (which inherited the algorithm from dcraw [Dave Coffin]). Instead of denoising all RGB channels at once, the plugin implementation allows to denoise the RGB channels in dividually 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. Because the algorithm implements a wavelet filtering it runs quite fast.


This is part of a picture taken with the Nikon D80 DSLR camera at ISO 1600 in
RAW format. The face is lit by two candles and a colour temperature setting of
2500 K was used. The file was opened with the UFRaw plugin.

The goal is not to reduce all noise. The unpleasant part is the chroma noise
which appears only when shooting the camera in RAW mode at a high ISO speed. As
you can see the colour (chroma) noise is almost completely gone in the second picture and the luminance noise is slightly reduced. If you look closely at the face you will notice that the image details have not been altered much, the sharpness is almost the same.

Note that this is just the result of a uniform application of the filter on the unprocessed image. Masking the filter effect with a selection is possible which could improve the result even more.


This plug-in runs on multiple platforms:

  • Linux

    The plugin can easily be compiled from sources but be aware that some Linux distributions provide packages:

    • Ubuntu: Install the package 'gimp-plugin-registry'.
    • ArchLinux: Install the package 'gimp-plugin-wavelet-denoise'.
    • Debian: Install the package 'gimp-plugin-registry'.
  • Windows

    There exists a pre compiled binary for the plugin here. (Thank you Francois C.!)

  • Mac OS X

    'Gimp on OS X' provides a complete Gimp distribution which includes the plugin. You can download it here. (Thanks, Simone!)

What's new in version 0.3

The most significant changes are the introduction of noise profiling and internationalization.

  • Noise profiling is done.
  • Internationalization is possible now, several translations exist.
  • New slider "Softness" (which replaces the old "Detail" slider, but is completely different from it) to control the thresholding mechanism.
  • Introduction of the CIELAB (L*a*b*) colour space.
  • Reorganisation of source files and new installation routine via Makefiles.

What's new in version 0.2

There are several changes that have been made to improve the plugin.

  • The denoising is done on linear data now. The sRGB gamma of approximately 2.
    2 is compensated.
  • The interface has been reorganized
  • A 'Detail' slider has been added which affects the thresholds dependency on
    noise frequency.
  • Tool-tips have been added.
  • The single channel preview can now be displayed in colour.
  • There is a 'Reset' button which resets the currently selected channel tempor
    arily (during the time the button is pressed).
  • Normal reset buttons have been added.
  • The size of the dialog is saved now after it is closed.
  • The default thresholds are all zero now.
  • The progress bar was fixed and tweaked.

Apart from that minor other changes have been made.


The plugin is distributed under the General Public License (GPL).

GIMP Version: 
Code License: 


Thanks to JamesH a binary for Windows is now available. Please comment if you are experiencing problems with it.

Please add in the install instructions information on how to install "gimptool" because many users probably try to use synaptic, but they will notfind gimptool there. --- One needs to install libgimp2.0-dev (plus several dozens more libraries via dependencies). EDIT: Installation worked flawless; and I am impressed with the tool. Thanks for providing it!

Thank you for pointing this out. I was not aware that there are distributions where gimptool-2.0 did not come with the GIMP package. Using google I found that there is a package "gimp-plugin-registry" for Debian and one for Ubuntu with the same name, that includes my plugin (however, I believe it's still the beta version). To get gimptool-2.0 going to compile it yourself, please refer to the GIMP manuals.

Finally the new version of wavelet denoise has been released!

There is one or two important difference between the final release and the beta version: the plugin now operates on linear image data (as opposed to gamma corrected data) and the processing speed has been increased.

Here's the complete list of changes from version 0.1.1:

  • Operates on linear data now (not gamma corrected).
  • Increased processing speed.
  • Interface reorganized.
  • Added 'Detail' slider which affects the thresholds dependency on frequency.
  • Added tool-tips in the user interface.
  • Colour previev of single channels added.
  • Button 'Reset temporarily' added for preview.
  • Reset buttons added.
  • The size of the dialog is saved now.
  • Changed default thresholds.
  • Progress bar bugfix done.
  • Minor fixes.


I can test on xp the binary provided by jamesH , i suppose are still for the beta version and not updated to this release.. Correct? i'm happy to help with some testing in windows if needed and i may check also "if the license, install, readme files are included in the archive." and if not fix that details in a new package I'm not good in building in windows but once the bigger part of the job is done and the binary is ready... ...well , ...then add a folder with "the license, how install, read me files" and even a link to the source code and zip all for me is not a problem , i will happy to do at soon i get a reply

I had build the windows binary and mail to marco on Aug 1 2008

Thank JamesH to find the time to build Marcor you may post a link to download (even by PM if should be added yet license and source code link ) PS i just finish testing the previous win version seems working fine but i must find more meaningful sample, i do not trace much "noisy photos" adapt for a test have you some for a confront?

The beta version of the plugin wavelet denoise 0.2 has been released. There are many changes - suggestions are welcome.


  • Interface reorganized.
  • Added 'Detail' slider which affects the thresholds dependency on frequency.
  • Added tool-tips in the user interface.
  • Colour preview of single channels added.
  • Button 'Reset temporarily' added for preview.
  • Reset buttons added.
  • The size of the dialog is saved now.
  • Changed default thresholds.
  • Minor fixes.

I think it would be a great addition.

You surely know that there is denoising in UFRaw. That's where I took the algorithm for this denoising plugin from. In UFRaw the denoising is done on linear data before bayer interpolation and therefore colour model conversions cannot be made. It could be done after the interpolation though.

However, I share the belief that software is not perfect when there is nothing left to add but when there is nothing left to leave away. I talked to the author of UFRaw and I think he will not change it. (I did not request it, you know.) Note that there is no 100% magnification of the preview image available in UFRaw at the moment and that would be necessary for decent denoising.

What's wrong with using a plugin for the job? Let's not make UFRaw complicated!


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