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Author tritical
Version v0.9.1
Download TIsophotev091.zip
Category Anti-aliasing
License GPLv2


[edit] Description

TIsophote is a level-set (isophote) smoothing filter. It does simple unconstrained level-set smoothing. Basically, it can smooth jagged edges in an image. If over used it will remove jagged edges as well as object features and eventually completely eliminate all level curves. For a more in-depth explanation see the technical info towards the bottom of the help file. Or for more info (includes information besides simple unconstrained smoothing): LSImageReconstruction.pdf.

[edit] Requirements

[edit] Syntax and Parameters

TIsophote (clip, int "iterations", float "tStep", int "type", bool "chroma")

clip  c =
Input clip to be processed.

int  iterations = 4
Sets the number of iterations used. More iterations will take more processing time. Increasing the number of iterations while holding tStep constant will result in more and more shortening of the level curves. Total 'time' of the filter is equal to - iterations*tStep. iterations must be set to at least 1.

float  tStep = 0.2
Sets the update per iteration. At 1.0, each iteration is a full cycle of the flow equation. At 0, the original image is always returned. Generally, lower values produce more "stable" flow but require more iterations. Recommended values are between 0.1 and 0.5, though setting this to 1.0 is usually ok and simply results in an extra overall smoothing. While this value can be anything, it really only makes sense when it is 0.0 <= tStep <= 1.0, other values will generally result in garbage output. This setting could be seen as a strength of smoothing per iteration setting (1.0 being strongest, 0.0 being nothing). Note: technically for long run numerical stability this value must be less then 0.25!

int  type = 2
Sets how the needed derivatives are calculated.
  • type 0 - simplest possible estimate of both first and second derivatives (fastest, probably best for clean video).
  • type 1 - sobel operator for first derivatives, simple estimate for second (in-between 0 and 2 speed wise and noise wise).
  • type 2 - sobel operator for first and similar inherent denoising operator for second (slowest, probably best for noisy video).

bool  chroma = false
If set to true the chroma planes are processed. If set to false the chroma planes from the source are simply copied to the output frame.

[edit] Examples

TIsophote with default settings:

TIsophote(iterations=2, tStep=0.2, type=2, chroma=false)

[edit] Changelog

Version      Date            Changes
v0.9.1 07/24/2004 - Changed default values for iterations, type, and chroma parameters - Fixed incorrect clipping for values below 0. Pixel values were clipped to 0-255 range but values below 0 were getting clipped to abs(pixel) instead of 0 which would lead to artifacts.
v0.9 06/25/2004 - Initial release

[edit] External Links

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