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DetectSegments

Finds segments in an image using Hough Transform.

Syntax

C++
C#

void avl::DetectSegments
(
const avl::Image& inImage,
atl::Optional<const avl::Region&> inRoi,
float inAngleResolution,
float inMinAngleDelta,
float inMinDistance,
float inMinLength,
float inMinScore,
float inEdgeThreshold,
atl::Array<avl::Segment2D>& outSegments,
avl::Image& diagScoreImage
)


Parameters

Name Type Range Default Description
inImage const Image& Input image
inRoi Optional<const Region&> NIL Input region of interest
inAngleResolution float 0.1 - 180.0 1.0f Resolution of segments' orientation
inMinAngleDelta float 0.0 - 20.0f Minimum angle between two segments
inMinDistance float 0.0 - 20.0f Minimum distance between two segments
inMinLength float 0.0 - 20.0f Minimum segment length
inMinScore float 0.0 - 20.0f Minimum matching score
inEdgeThreshold float 10.0f Minimum accepted edge magnitude
outSegments Array<Segment2D>& Output segments
diagScoreImage Image& Calculated score for each pixel of an input image

Description

The operation detects straight edges in the inImage using the Hough Transform approach and treats them as segments by tracing gradients along lines. The output array is ordered from best matching to worst matching results.

The parameter inAngleResolution specifies the precision of detected lines' orientations. Value of n means the filter will be able to reliably distinguish lines in n-degree increments.

Parameters inMinAngleDelta and inMinDistance are used for neighbouring results suppression. inMinAngleDelta specifies the minimum angle between two lines while inMinDistance specifies the minimum distance between two parallel lines. Parameter inMinLength limits the length of segments (in pixels), suppressing too short segments.

The orientations of the resulting segments are always between 0 and 180 degrees.

Examples

DetectSegments performed on the sample image with inMinScore = 0.5, inMinLength = 25.

Remarks

Low values of inAngleResolution (under 0.5) may cause high memory consumption and decrease in performance.