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ThresholdImage_HSx

Header:	FIL.h
Namespace:	fil
Module:	FoundationLite

Transforms each pixel value to minimum or maximum depending on whether it belongs to specified region in the HSV, HSL or HSI color space.

Applications: Color analysis.

Syntax

void fil::ThresholdImage_HSx
(
	const fil::Image& inRgbImage,
	ftl::Optional<const fil::Region&> inRoi,
	fil::HSxColorModel::Type inColorModel,
	int inBeginHue,
	int inEndHue,
	ftl::Optional<int> inMinSaturation,
	ftl::Optional<int> inMaxSaturation,
	ftl::Optional<int> inMinBrightness,
	ftl::Optional<int> inMaxBrightness,
	float inFuzziness,
	fil::Image& outMonoImage,
	fil::Image& diagHSxImage
)

Parameters

Name	Type	Range	Default	Description
inRgbImage	const Image&			Input image in the RGB color space
inRoi	Optional<const Region&>		NIL	Region of interest
inColorModel	HSxColorModel::Type			Selected color model
inBeginHue	int	0 - 255	0	Lowest acceptable Hue; if higher than inEndHue, then range wrapping is used
inEndHue	int	0 - 255	255	Highest acceptable Hue, if lower than inBeginHue, then range wrapping is used
inMinSaturation	Optional<int>	0 - 255	128
inMaxSaturation	Optional<int>	0 - 255	NIL
inMinBrightness	Optional<int>	0 - 255	128	Minimum brightness; denotes V, L or I, depending on inColorModel
inMaxBrightness	Optional<int>	0 - 255	NIL	Maximum brightness; denotes V, L or I, depending on inColorModel
inFuzziness	float	0.0 -		Tolerance for value ranges that results in intermediate output values
outMonoImage	Image&
diagHSxImage	Image&			Image in HSx color space

Requirements

For input inRgbImage only pixel formats are supported: 3⨯uint8.

Read more about pixel formats in Image documentation.

Description

The operation transforms each pixel of three-channel inRgbImage to the maximum or minimum level thus creating binary image. The input image is considered to be encoded using RGB color representation. Each of the image pixel is internally converted to HSx (HSV, HSL or HSI) color representation and then examined.

Pixels meeting all of the following conditions are transformed to the maximum level:
- Value of the Hue parameter is in cyclic range (inBeginHue, inEndHue).
- Value of the Saturation parameter is in range (inMinSaturation, inMaxSaturation).
- Value of the Brightness parameter is in range (inMinBrightness, inMaxBrightness).
Other pixels are transformed to the minimum level.

If any of the parameters inMinSaturation, inMinBrightness is not set, it is assumed to be -infinity.

If any of the parameters inMaxSaturation, inMaxBrightness is not set, it is assumed to be infinity.

Parameter inFuzziness (set to 0 by default) allows to perform fuzzy thresholding which linearly interpolates those pixel values that differ by at most inFuzziness from the border parameter values; thus creating smooth transition between minimum and maximum values in the resulting image.

Hints

Choose inColorModel taking into account accuracy and execution speed (HSV is the fastest, HSI is usually the most accurate).
Define the range of HSV/HSL/HSI values that best separates the foreground and background pixels. Analyze the results on the outMonoImage output.
Use inFuzziness to add some smooth transitions between black and white pixels in the result.

Examples

ThresholdImage_HSx performed on the sample image with inColorModel = HSV, inBeginHue = 0.0, inEndHue = 10.0, inMinSaturation = 120.0, inMinBrightness = 70.0.

Hardware Acceleration

This operation supports automatic parallelization for multicore and multiprocessor systems.

Errors

List of possible exceptions:

Error type	Description
DomainError	Not a 3-channel and 8-bit image in ThresholdImage_HSx.
DomainError	Region exceeds an input image in ThresholdImage_HSx.
DomainError	Not supported inRgbImage pixel format in ThresholdImage_HSx. Supported formats: 3xUInt8.