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Old 6th March 2007, 21:08   #1  |  Link
AMSS0815
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Join Date: Aug 2006
Posts: 29
New smoothing plugin: Curvature Flow Approximation

Hi everybody,

recently I created a new smoothing plugin. This is the abstract from the help file:
Curvature flow equations smoothen images by smoothing their level lines. In contrast to linear smoothing filters, they do not only conserve sharp edges, but also have some remarkable properties like contrast invariance, or affine invariance. This filter resembles some recently discovered approximation schemes that (more or less) inherit many of those properties.
Common smoothing algorithms are often approximations of the heat equation applied to an image — in most cases realized by convolution with some smartly choosen kernel. This kind of smoothing removes (or "smears out") noise, but originally sharp edges become unlocatable. Moreover there are kinds of noise like impulse noise (also called Salt'n'Pepper noise) where the heat equation fails. Nonlinear filters like the well-known Median filter usually give better results. Sharp edges are untouched, but even nasty impuls noise can be removed satisfyingly. The Median filter is an approximation of the mean curvature flow — a mathematical object which smoothes the level lines of an image.
This filter collection provides several approximations of curvature flow filters, including the Median. These filters are realized by combining discrete erosions and dilations (operators that replace pixels with neighbor pixels that are darker or brighter, resp.) with several (nonlinear convolution) kernels, and resemble not only the mean curvature flow, but also the affine curvature flow, which gives usually even better results. The user may choose between a pure morphological approach, where no new color values are created, and an "almost-morphological" approach where the average value of erosions and dilations will be returned.
To put it in a nutshell, this plugin is a little collection of morphological smoothing filters. Morphological filters (especially the median) have been implemented quite often, so now I put myself in the list of morphological developers. I still hope this filter might have some nice applications, especially the erosion-/dilation-only-modes.

I recommend you to have Shubin's NoiseGenerator plugin (find it in WarpEnterprises' Filter Collection) installed if you want to try the Demo.avs script (a home made low-entropy noise generator will be used otherwise).
The filter is attached to this thread (as zip-file), I hope this works out...
Go ahead and try it - if you have some comments on this plugin, please don't hesitate and post them here - every comment is wellcome!

Regards,
AMSS

Edit: Added version 2008.02.23 as announced here. AMSS
Attached Files
File Type: zip AVSCurveFlow-2007.03.06.zip (73.1 KB, 294 views)
File Type: zip AVSCurveFlow-2008.02.23.zip (52.5 KB, 4243 views)

Last edited by AMSS0815; 23rd February 2008 at 15:49. Reason: added version 2008.02.23
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