11.43. ITK Iso Contour Distance Image Filter

For a level-set (signed) image, estimates how far each grid pixel near the zero contour is from that contour.

Group (Subgroup)

ITKDistanceMap (DistanceMap)

Description

This is a specialized filter used in level-set methods. A level-set image is a signed image whose zero crossing (the iso-contour at value 0) implicitly represents a curve or surface — pixels inside the shape are negative and pixels outside are positive. As a level-set evolves, the values drift away from a true distance and must periodically be “reinitialized” back to a clean signed-distance field.

This filter performs the first step of that reinitialization: for the grid pixels lying immediately next to the iso-contour (those for which the contour crosses a segment to a direct neighbor), it computes an accurate estimate of the distance from the pixel to the interpolated contour. Pixels farther from the contour are left at a saturated “far” value. If a narrowband is supplied, only pixels within that band are processed.

This filter is for users implementing level-set / fast-marching workflows; for a general-purpose distance transform of a binary mask use one of the distance-map filters such as ITK Signed Maurer Distance Map Image Filter.

Parameter Guidance

  • Level Set Value — the iso-value whose contour is located, in the input image’s intensity units (default 0, the usual zero level set).

  • Far Value — the saturation distance assigned to pixels that are not adjacent to the contour. Pixels beyond the immediate neighborhood of the contour are clamped to this value (default 10), so it should be set larger than the band width you care about. (Units are the same length units as the computed distances.)

Required Input Sources

Operates on a signed scalar (level-set) image — typically the output of a prior level-set or distance-map filter.

Reference

K. Krissian and C.-F. Westin, “Fast and Accurate Redistancing for Level Set Methods,” EUROCAST NeuroImaging Workshop, Ninth International Conference on Computer Aided Systems Theory, pp. 48-51, Feb 2003.

Input Parameter(s)

Parameter Name

Parameter Type

Parameter Notes

Description

Level Set Value

Scalar Value

Float64

Set/Get the value of the level set to be located. The default value is 0.

Far Value

Scalar Value

Float64

The saturation distance assigned to pixels that are not adjacent to the iso-contour. Pixels beyond the immediate neighborhood of the contour are clamped to this value. The default value is 10.

Input Cell Data

Parameter Name

Parameter Type

Parameter Notes

Description

Image Geometry

Geometry Selection

Image

Select the Image Geometry Group from the DataStructure.

Input Cell Data

Array Selection

Allowed Types: int8, uint8, int16, uint16, int32, uint32, int64, uint64, float32, float64

The image data that will be processed by this filter.

Output Cell Data

Parameter Name

Parameter Type

Parameter Notes

Description

Output Image Data Array

DataObjectName

The result of the processing will be stored in this Data Array.

Example Pipelines

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