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EqualizeImageHistogram

Header:	FIL.h
Namespace:	fil
Module:	FoundationLite

Maps image pixels to new values to achieve uniform distribution of intensities in the range (0, 255).

Syntax

void fil::EqualizeImageHistogram
(
	const fil::Image& inImage,
	ftl::Optional<const fil::Region&> inRoi,
	float inSaturateBrightestFraction,
	float inSaturateDarkestFraction,
	fil::Image& outImage
)

Parameters

Name	Type	Range	Default	Description
inImage	const Image&			Input image
inRoi	Optional<const Region&>		NIL	Range of pixels to be processed
inSaturateBrightestFraction	float	0.0 - 1.0	0.0f	Fraction of the brightest pixels skipped during normalization
inSaturateDarkestFraction	float	0.0 - 1.0	0.0f	Fraction of the darkest pixels skipped during normalization
outImage	Image&			Output image

Requirements

For input inImage only pixel formats are supported: 1⨯uint8.

Read more about pixel formats in Image documentation.

In-place Processing

This function supports in-place data processing - you can pass the same reference to inImage and outImage

Description

The filter applies non-linear mapping to image pixel values so that pixel intensities of the resulting image are evenly distributed in range from 0 to 255.

The operation computes the cumulative histogram \(C\) of inImage and the image size \(N\). Then the result is computed as follows:

\[ \begin{aligned} outImage[i,j] &= C[ inImage[i,j] ] \times \frac{255}{N} \end{aligned} \]

Examples

EqualizeImageHistogram run on example image.

Hardware Acceleration

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 EqualizeImageHistogram.
DomainError	The sum of inSaturateBrightestFraction and inSaturateDarkestFraction can't be greater than 1 in EqualizeImageHistogram.
DomainError	Not supported inImage pixel format in EqualizeImageHistogram. Supported formats: 1xUInt8.