noise

Clean CCD Noise

gfxcoder — Mon, 06 Jul 2009 01:28:05 +0200

This script helps fix noise found in digital camera pictures.

Important:

G'MIC must be installed! When this script calls up the G'MIC plug-in, select Bilateral Filter with default settings.

There seems to be some confusion as to what all this script does... So here's a short description of the procedure:

Duplicates the active layer
Calls G'MIC plug-in (requiring user to select the Bilateral Filter with default settings, then OK'ing)
This layer is duplicated (saved for later)...
The layer is subtracted from a copy of the original layer and ran through curves-spline to increase the contrast at the lowest end
Finally, this layer acts as a alpha mask for the original copied layer (from above)

The subtracted mask tempers dark spots found in browns (wood, some skin, etc). This is found with red / green highlights in the brown to begin with.... I believe.

Version 1.1 (2009 July 06)

Tempered darkening noise found in browns (wood)

Feedback welcome!

The script is located in "<Image> / Script-Fu / Enhance / Clean CCD Noise"

G'MIC plug-in

dtschump — Tue, 13 Jan 2009 14:16:31 +0100

The G'MIC plug-in for GIMP defines a set of various filters, including artistic filters, image denoising and enhancement, 3D renderers, etc.. It is a quite large plug-in, integrating a lot of different effects to apply.

This plug-in is able to update his list of filter definitions from the Internet (so it improves itself over time), as well as allows any user to add its own custom filters in it.
It has been written by the author of the GREYCstoration algorithm (used for image denoising). It is actually intended to replace it in a near future.

Download G'MIC for Windows 32 bits

Here is one screenshot of the plug-in in action, as well as a result of filter application :

Noise Generator 0.2.5 Windows 32 binary

Francois_C — Mon, 12 Jan 2009 12:14:08 +0100

A Windows 32 version of noise-generator-0.2.5, another great plugin by Marcor.
Without console window (compiled with LDFLAGS=-mwindows).

DustCleaner

solotim — Mon, 05 Jan 2009 08:10:42 +0100

DustCleaner is a GIMP plug-in to automatically detect and remove the dust spots in digital images. It was registered under the menu of filter->noise.
Up-to-date version can be found here (SVN):
https://sourceforge.net/projects/dustcleaner/
Demo can be found here:
http://picasaweb.google.com/franktao.cn/DustCleanerBeta#
Enjoy~ :-)

Noise generator

marcor — Mon, 22 Dec 2008 19:13:22 +0100

This filter generates noise in an image. Available noise types are

Poisson noise
Gaussian noise
Uniform noise
Laplace noise
Lorentz noise

It is possible to generate (YCbCr) luminance noise only and to apply a gamma correction.

General description

for Poisson noise: the amount of photons per pixel value.
for Gaussian noise: the standard deviation of the noise distribution.
for uniform noise: the width of the uniform distribution.
for Laplace noise: the scale parameter.
for Lorentz noise: the half width half maximum (HWHM).

For all noise types together you can select whether a gamma correction should be applied on the image such that noise is applied to linear image data. After noise application the image is retransformed to sRGB. You can also select whether or not you want to have luminance noise only and for that the image is transformed to the YCbCr colour space before adding noise.

Noise types

Here the different noise types are described. The histogram of each noise type is a real application of the filter on a neutal gray image (128).

Poisson noise

A source for Poisson noise is photon counting. When taking a picture in the real world photons (light particles) arrive at a certain rate. However photons are not correlated and thus the time between photons is not always the same. Therefore given the shutter time of your camera and a photon rate you may collect more or less photons in subsequent pictures. The number of photons you actually collect is Poisson distributed.

Calculating poisson distributed random numbers takes a lot of time, especially for bright pixels and many photons. You can decrease computation time by selecting "Approximate" which approximates the Poisson distribution with a Gaussian distribution with the correct variance. As you can see in the histogram, Poisson noise closely resebles Gaussian noise. However, there is an important difference in for dark image values!

You can see the difference to Gaussian noise in the stepwedge below.

Gaussian noise

In nature nearly everything is normally distributed. Normally distributed noise is Gaussian noise. It appears in image from thermal noise in the amplifier and other effects. An important aspect of Gaussian noise is that its variance does not depend on the intensity of the image.

Uniform noise

Uniform noise rarely occurs in nature but when digitizing a signal errors take place that are uniformly distributed. Like Gaussian noise the noise variance is independent of the image intensity.

Laplace noise

Laplace noise has a double exponential distribution. The scale parameter determines the width of the distribution.

Lorentz noise

Lorentz noise has Cauchy-Lorentz distribution which describes resonances and decays very slowly. This is a so called fat-tail distribution and causes here salt-and-pepper noise.

Comparison between noise types

In the images below the noise variance is the same for all noise types at a brightness of neutral gray (128) except for Lorentz noise where the variance is not defined.

Film Grain

manutd101 — Sun, 26 Oct 2008 18:56:35 +0100

This script adds a realistic film grain effect to a black and white or toned image. To install, copy the attached file to GIMP/share/gimp/2.0/scripts. The larger the file you are running it on, the larger the value you should have for Strength. The value for Sharpness depends on your preferences, but I usually start at 1 and go from there. The lower the value, the sharper the noise.

Wavelet denoise

marcor — Sun, 04 May 2008 11:28:25 +0200

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.

Features

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.

Details

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.

Example

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.

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.

License

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

Layer Effects

JonStipe — Thu, 24 Jan 2008 22:43:37 +0100

This is a series of scripts that implement various layer effects:

Drop Shadow
Inner Shadow
Outer Glow
Inner Glow
Bevel and Emboss
Satin
Color Overlay
Gradient Overlay
Pattern Overlay
Stroke

Some effects can have contours (a.k.a. curves) and noise added to them. Effects can either be applied on a separate layer, or be merged into the active layer (which in some cases gives better results).

Tested with GIMP 2.4.2.

Updated 6/9/2009:

Stroke now supports gradients and patterns! (Python version only)
Better undo handling in the Python version.
Various bugfixes.

Updated 11/15/2008:

The Python version now has live previewing! With the "Preview" checkbox active, the preview now updates automatically every time you change a setting!
New "Reapply Effects" function: Reapplies all effects that have been applied to the current layer. If you change anything on the layer, use this to update all the effects in one go! (Mind you, this only works for effects that were not applied using the "Merge with layer" option.)
Various bugfixes.

Updated 09/02/2008:

Bugfix in Script-Fu version.

Updated 07/19/2008:

You can now scale patterns in pattern overlays. (Python version only.)

Updated 07/08/2008:
This script has now been rewritten as a Python plugin! This adds several new features that weren't possible in Script-Fu!

You can now preview effects! Click the "Preview" button to see what it will look like with the currently selected settings.
The plugin now records the settings used to make an effect, so now you can reapply it! Run the same effect plugin on the same layer again, and it recovers the previous settings for that layer and shows them in the dialog box. You can then change the settings and apply the effect again, and it will replace the original effect layer! (Note: This will only work if you don't select "Merge with layer". Once an effect has been merged into the layer, it can't be removed or changed.)

Updated 04/21/2008:

Bugfix

Updated 03/02/2008:

Added grayscale support
Bugfixes

How to install (Script-Fu version):

Right-click on the link below that says "layerfx.scm". A pop-up menu should appear. Click "Save Target As..." or "Save Link As..." or whatever the equivalent option in your browser is.
Save the file "layerfx.scm" in your scripts folder. If you're not sure where your scripts folder is, you can check by opening GIMP and going to <Toolbox>/File/Preferences -> Folders -> Scripts. If more than one folder is shown, then any one of them will work.
Once you have saved the file in your scripts folder, if you are already running GIMP, either click <Toolbox>/Xtns/Script-Fu/Refresh Scripts, or just close and reopen GIMP.
If you have done this correctly, the scripts will appear in the menu under <Image>/Script-Fu/Layer Effects. If this menu is not there, try clicking <Toolbox>/Xtns/Script-Fu/Refresh Scripts. If it's still not there, make sure the file is in your scripts folder and that the filename ends with ".scm", not ".txt" or ".scm.txt" or something.

How to install (Python version):

Right-click on the link below that says "layerfx.py". A pop-up menu should appear. Click "Save Target As..." or "Save Link As..." or whatever the equivalent option in your browser is.
Save the file "layerfx.py" in your plug-ins folder. If you're not sure where your plug-ins folder is, you can check by opening GIMP and going to <Toolbox>/File/Preferences -> Folders -> Plug-Ins. If more than one folder is shown, then any one of them will work.
If you're on a UNIX system, make sure layerfx.py is executable by typing this in the shell:
chmod +x layerfx.py
On other operating systems, you might have to do something else to make it executable.
Once you have saved the file in your plug-ins folder, if you are already running GIMP, close and reopen it.
If you have done this correctly, the scripts will appear in the menu under <Image>/Layer/Layer Effects, and <Layers>/Layer Effects. If these menus are not there, close and reopen GIMP. If they're still not there, make sure the file is in your plug-ins folder, that it is executable, that you have Python support installed, and that the filename ends with ".py", not ".txt" or ".py.txt" or something.

ISO noise reduction

eg — Mon, 07 Jan 2008 13:51:14 +0100

Implements an ISO noise reduction as described in the tutorial below, also this script uses different methods (masking the edges and then blurring the individual color channels or the luminance channel only)

Tutorial: http://www.gimpguru.org/Tutorials/ReducingCCDNoise/

PS - Using a plugin like Wavelet denoise from http://registry.gimp.org/node/4235/ or greycstoration from http://www.greyc.ensicaen.fr/~dtschump/greycstoration/ might actually give you better results and more options for fine tuning.

Add Film Grain

eg — Mon, 07 Jan 2008 13:44:27 +0100

Add adding realistic film grain to BW images

Description for PS: http://www.outbackphoto.com/workflow/wf_95/essay.html