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ThresholdImage_Hysteresis

Header:	FIL.h
Namespace:	fil
Module:	FoundationBasic

Thresholds an image with a hysteresis, i.e. with a lower threshold for neighboring pixels.

Syntax

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

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 -	16.0f	Defines how much the threshold criteria are lowered for pixels neighboring with other foreground pixels
outMonoImage	Image&

Description

The operation transforms each pixel value to the maximum or minimum level thus creating binary image. The result of the transformation depends on the pixel intensity:

Pixel values in range [inMinValue, inMaxValue] are transformed to the maximum level.
Pixel values lower than inMinValue-inHysteresis or higher than inMaxValue+inHysteresis are transformed to the minimum level.
Pixel values in range [inMinValue-inHysteresis, inMinValue) or in range (inMaxValue, inMaxValue+inHysteresis] are transformed to the maximum if (and only if) 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].

In the multichannel images the operation uses an average of channel values in each pixel, thus the resulting image is always monochromatic.

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.