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SegmentImage_Color

Header:	AVL.h
Namespace:	avl
Module:	FoundationPro

Segments an image basing on distance to model colors.

Applications: Detection of objects of undefined shape, but characterized by uniform color and good contrast to the background.

Syntax

void avl::SegmentImage_Color
(
	const avl::Image& inImage,
	atl::Optional<const avl::Region&> inRoi,
	const atl::Array<avl::Pixel>& inReferenceColors,
	const float inMaxDifference,
	atl::Optional<const atl::Array<float>&> inDifferenceMultipliers,
	float inChromaAmount,
	bool inForceDisjointRegions,
	atl::Array<avl::Region>& outRegions
)

Parameters

Name	Type	Range	Default	Description
inImage	const Image&			Input image
inRoi	Optional<const Region&>		NIL	Range of pixels to be processed
inReferenceColors	const Array<Pixel>&			Colors to compare pixels to
inMaxDifference	const float	0.0 -	5.0f	Maximal difference between pixel and reference color to be accepted
inDifferenceMultipliers	Optional<const Array<float>&>		NIL	Scales for maximum differences for each color
inChromaAmount	float	0.0 - 1.0	0.7f	Proportion of chromatic information in distance computation
inForceDisjointRegions	bool			Force output regions to be disjoint
outRegions	Array<Region>&			Regions of pixels closest to colors

Description

The operation finds regions of similar colors in RGB color space within inImage.

First, for each pixel of the input image its distance to each color in inReferenceColors is computed (see ColorDistanceImage function).

Then, for each reference color c, the function computes region of pixels that are closer to c than its corresponding threshold. In case inDifferenceMultipliers is Nil, threshold is equal to inMaxDifference. If inDifferenceMultipliers is not Nil, corresponding threshold is the product of inMaxDifference and the element of inDifferenceMultipliers that corresponds to c.

If flag inForceDisjointRegions is set to True, the regions are forced to be disjoint. In case a pixel has distance less than threshold for more than one color, distances are divided by thresholds and the minimum of ratios is taken. In particular, if the function works in one-threshold mode, the operation described above becomes simply minimum of distances.

Examples

SegmentImage_Color run with colors taken from three points with inChromaAmount = 0.7 and inMaxDifference = 15

Hardware Acceleration

This operation supports automatic parallelization for multicore and multiprocessor systems.

Errors

List of possible exceptions:

Error type	Description
DomainError	Inconsistent array sizes in SegmentImage_Color.
DomainError	Reference color array size too big in SegmentImage_Color.