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ThresholdToRegion

Header:	FIL.h
Namespace:	fil
Module:	FoundationBasic

Creates a region containing image pixels with values within the specified range.

Applications: Extraction of a region of objects that can be defined by a salient brightness.

Syntax

void fil::ThresholdToRegion
(
	const fil::Image& inImage,
	ftl::Optional<const fil::Region&> inRoi,
	ftl::Optional<float> inMinValue,
	ftl::Optional<float> inMaxValue,
	float inHysteresis,
	fil::Region& outRegion
)

Parameters

Name	Type	Range	Default	Description
inImage	const Image&			Input image
inRoi	Optional<const Region&>		NIL	Region of interest
inMinValue	Optional<float>		128.0f	Minimum value of a pixel that is considered foreground (Auto = -INF)
inMaxValue	Optional<float>		NIL	Maximum value of a pixel that is considered foreground (Auto = +INF)
inHysteresis	float	0.0 -	0.0f	Defines how much the threshold criteria are lowered for pixels neighboring with other foreground pixels
outRegion	Region&			Output region

Description

The operation is a cousin of ThresholdImage yet computes a region instead of an image. The resulting region contains those pixels of the input image that meet one of the following conditions:

Pixel value is in range [inMinValue, inMaxValue].
Pixel value is in range [inMinValue-inHysteresis, inMinValue) or in range (inMaxValue, inMaxValue+inHysteresis] and in the processed image there is a path of consecutive pixels of value in range [inMinValue-inHysteresis, inMaxValue+inHysteresis] that connects the pixel being considered and any pixel with value in range [inMinValue, inMaxValue].

If any of the parameters inMinValue, inMaxValue is not set, it is assumed to be, accordingly, -infinity or infinity.

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

Hints

Define inMinValue to extract bright objects (brighter than the specified value).
Define inMaxValue to extract dark objects (darker than the specified value).
Use inHysteresis to allow weaker threshold for pixels neighboring with already extracted ones.

Examples

ThresholdToRegion performed on the sample image with inMinValue = 80.0, inMaxValue = auto.

Hardware Acceleration

This operation is optimized for SSE2 technology for pixels of types: 1xUINT8, 3xUINT8, 1xINT16, 1xUINT16.

This operation is optimized for NEON technology for pixels of types: 1xUINT8, 3xUINT8, 1xINT16.

This operation supports automatic parallelization for multicore and multiprocessor systems.

Errors

List of possible exceptions:

Error type	Description
DomainError	Region exceeds an input image in ThresholdToRegion.