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ThresholdToRegion_Dynamic

Module:	FoundationBasic

Thresholds an image relatively to the average pixel value in a local rectangular neighborhood.

Applications

Useful in case of uneven illumination.

Name	Type	Range	Description
inImage	Image		Input image
inRoi	Region *		Region in which pixels are written
inSourceRoi	Region *		Region from which pixels are read
inRadiusX	Integer	0 - 65535	Horizontal radius of internal mean blur
inRadiusY	Integer *	0 - 65535	Vertical radius of internal mean blur (Auto = inRadiusX)
inMinRelativeValue	Real *		Minimum relative value of a pixel that is considered foreground (Auto = -INF)
inMaxRelativeValue	Real *		Maximum relative value of a pixel that is considered foreground (Auto = +INF)
inHysteresis	Real	0.0 -	Defines how much the threshold criteria are lowered for pixels neighboring with other foreground pixels
outRegion	Region		Output region
diagBaseImage	Image		Diagnostic blurred image.

Description

The operation is a cousin of ThresholdImage_Dynamic yet computes a region instead of an image. The resulting region contains only those pixels of the input image, which are brighter at least by inMinRelativeValue and at most by inMaxRelativeValue than the local average. If any of the parameters inMinRelativeValue, inMaxRelativeValue is not set, it is assumed to be, accordingly, -infinity or infinity.

Pixel neighbourhood used to compute the local average is a rectangle of dimensions $(2 \cdot \text{\textbf{inRadiusX} }+1) \times (2 \cdot \text{\textbf{inRadiusY} }+1)$ centered at the pixel being processed.

In the multichannel images the operation uses an average of channel values in each pixel.

Hints

Define inMinRelativeValue to extract objects which are brighter than the neighborhood.
Define inMaxRelativeValue to extract objects which are darker than the neighborhood.
Increase inRadiusX (and optionally inRadiusY) to define a bigger neighborhood.

Examples

Description of usage of this filter can be found in examples and tutorial: Capsules, Preparing an OCR model.

ThresholdToRegion_Dynamic performed on the sample image with inMinRelativeValue = 5.0, inMaxRelativeValue = auto.

Errors

This filter can throw an exception to report error. Read how to deal with errors in Error Handling.

List of possible exceptions:

Error type	Description
DomainError	Region exceeds an input image in ThresholdToRegion_Dynamic.
DomainError	Roi exceeds image dimensions in ThresholdToRegion_Dynamic.
DomainError	Source roi exceeds image dimensions in ThresholdToRegion_Dynamic.

Complexity Level

This filter is available on Basic Complexity Level.

Filter Group

This filter is member of ThresholdToRegion filter group.