Class FastLineDetector

Class implementing the FLD (Fast Line Detector) algorithm described in @cite Lee14.

Inheritance
System.Object
DisposableObject
DisposableCvObject
Algorithm
FastLineDetector
Implements
Inherited Members
Namespace: OpenCvSharp.XImgProc
Assembly: OpenCvSharp.dll
Syntax
public class FastLineDetector : Algorithm, ICvPtrHolder

Constructors

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FastLineDetector(IntPtr)

Creates instance by raw pointer

Declaration
protected FastLineDetector(IntPtr p)
Parameters
Type Name Description
IntPtr p

Methods

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Create(Int32, Single, Double, Double, Int32, Boolean)

Creates a smart pointer to a FastLineDetector object and initializes it

Declaration
public static FastLineDetector Create(int lengthThreshold = 10, float distanceThreshold = 1.41421354F, double cannyTh1 = 50, double cannyTh2 = 50, int cannyApertureSize = 3, bool doMerge = false)
Parameters
Type Name Description
System.Int32 lengthThreshold

Segment shorter than this will be discarded
System.Single distanceThreshold

A point placed from a hypothesis line segment farther than this will be regarded as an outlier
System.Double cannyTh1

First threshold for hysteresis procedure in Canny()
System.Double cannyTh2

Second threshold for hysteresis procedure in Canny()
System.Int32 cannyApertureSize

Aperturesize for the sobel operator in Canny()
System.Boolean doMerge

If true, incremental merging of segments will be perfomred
Returns
Type Description
FastLineDetector
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Detect(InputArray)

Finds lines in the input image. This is the output of the default parameters of the algorithm on the above shown image.

Declaration
public virtual Vec4f[] Detect(InputArray image)
Parameters
Type Name Description
InputArray image

A grayscale (CV_8UC1) input image. If only a roi needs to be selected, use: fld_ptr-\>detect(image(roi), lines, ...); lines += Scalar(roi.x, roi.y, roi.x, roi.y);
Returns
Type Description
Vec4f[]

A vector of Vec4f elements specifying the beginning and ending point of a line. Where Vec4f is (x1, y1, x2, y2), point 1 is the start, point 2 - end.Returned lines are directed so that the brighter side is on their left.
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Detect(InputArray, OutputArray)

Finds lines in the input image. This is the output of the default parameters of the algorithm on the above shown image.

Declaration
public virtual void Detect(InputArray image, OutputArray lines)
Parameters
Type Name Description
InputArray image

A grayscale (CV_8UC1) input image. If only a roi needs to be selected, use: fld_ptr-\>detect(image(roi), lines, ...); lines += Scalar(roi.x, roi.y, roi.x, roi.y);
OutputArray lines

A vector of Vec4f elements specifying the beginning and ending point of a line. Where Vec4f is (x1, y1, x2, y2), point 1 is the start, point 2 - end.Returned lines are directed so that the brighter side is on their left.
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DisposeManaged()

Releases managed resources

Declaration
protected override void DisposeManaged()
Overrides
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DisposeUnmanaged()

Declaration
protected override void DisposeUnmanaged()
Overrides
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DrawSegments(InputOutputArray, IEnumerable<Vec4f>, Boolean)

Draws the line segments on a given image.

Declaration
public virtual void DrawSegments(InputOutputArray image, IEnumerable<Vec4f> lines, bool drawArrow = false)
Parameters
Type Name Description
InputOutputArray image

The image, where the lines will be drawn. Should be bigger or equal to the image, where the lines were found.
IEnumerable<Vec4f> lines

A vector of the lines that needed to be drawn.
System.Boolean drawArrow

If true, arrow heads will be drawn.
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DrawSegments(InputOutputArray, InputArray, Boolean)

Draws the line segments on a given image.

Declaration
public virtual void DrawSegments(InputOutputArray image, InputArray lines, bool drawArrow = false)
Parameters
Type Name Description
InputOutputArray image

The image, where the lines will be drawn. Should be bigger or equal to the image, where the lines were found.
InputArray lines

A vector of the lines that needed to be drawn.
System.Boolean drawArrow

If true, arrow heads will be drawn.
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Get()

Declaration
public override IntPtr Get()
Returns
Type Description
IntPtr

Implements