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SelectThresholdValue

Selects best threshold value using the image histogram.

Name	Type	Description
inImage	Image	Input image
inRoi	Region *	Range of pixels to be processed
inMethod	ThresholdSelectionMethod	Method used to select the best threshold
outThresholdValue	Real	Best threshold separating background pixels from foreground pixels
diagThresholdRatings	Real Array	Contains ratings gained if that threshold would be chosen
diagBackgroundPixelsFraction	Real Array	Fraction of pixels that are darker than the index value
diagForegroundPixelsFraction	Real Array	Fraction of pixels that are brighter than the index value

Requirements

For input inImage only pixel formats are supported: uint8.

Read more about pixel formats in Image documentation.

Applications

Usually used before a thresholding filter when the image brightness is variable. Use with care.

Description

The operation estimates an intensity threshold value that discriminates foreground pixels from background pixels in inImage.

Note that to provide meaningful results it is required that the image in fact consists of foreground and background components that strongly differ in brightness.

Hints

Choose inMethod that works best in your application. None of the methods is perfect, but ClusteringOtsu is the most universal one.

Examples

SelectThresholdValue performed on the sample image (on the left) with inMethod = ClusteringKittler yields outThresholdValue = 189.5. Pixels of the input image brighter than 189.5 are presented on the right.

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 SelectThresholdValue.
DomainError	Not supported inImage pixel format in SelectThresholdValue.

Complexity Level

This filter is available on Advanced Complexity Level.