Class SURF

Class for extracting Speeded Up Robust Features from an image.

Inheritance
System.Object
DisposableObject
DisposableCvObject
Algorithm
Feature2D
SURF
Implements
Inherited Members
Namespace: OpenCvSharp.XFeatures2D
Assembly: OpenCvSharp.dll
Syntax
public class SURF : Feature2D, ICvPtrHolder

Constructors

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SURF(IntPtr)

Creates instance by raw pointer cv::SURF*

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

Properties

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Extended

false means that the basic descriptors (64 elements each) shall be computed. true means that the extended descriptors (128 elements each) shall be computed

Declaration
public bool Extended { get; set; }
Property Value
Type Description
System.Boolean
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HessianThreshold

Threshold for the keypoint detector. Only features, whose hessian is larger than hessianThreshold are retained by the detector. Therefore, the larger the value, the less keypoints you will get. A good default value could be from 300 to 500, depending from the image contrast.

Declaration
public double HessianThreshold { get; set; }
Property Value
Type Description
System.Double
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NOctaveLayers

The number of images within each octave of a gaussian pyramid. It is set to 2 by default.

Declaration
public int NOctaveLayers { get; set; }
Property Value
Type Description
System.Int32
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NOctaves

The number of a gaussian pyramid octaves that the detector uses. It is set to 4 by default. If you want to get very large features, use the larger value. If you want just small features, decrease it.

Declaration
public int NOctaves { get; set; }
Property Value
Type Description
System.Int32
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Upright

false means that detector computes orientation of each feature. true means that the orientation is not computed (which is much, much faster). For example, if you match images from a stereo pair, or do image stitching, the matched features likely have very similar angles, and you can speed up feature extraction by setting upright=true.

Declaration
public bool Upright { get; set; }
Property Value
Type Description
System.Boolean

Methods

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

The SURF constructor.

Declaration
public static SURF Create(double hessianThreshold, int nOctaves = 4, int nOctaveLayers = 2, bool extended = true, bool upright = false)
Parameters
Type Name Description
System.Double hessianThreshold

Only features with keypoint.hessian larger than that are extracted.
System.Int32 nOctaves

The number of a gaussian pyramid octaves that the detector uses. It is set to 4 by default. If you want to get very large features, use the larger value. If you want just small features, decrease it.
System.Int32 nOctaveLayers

The number of images within each octave of a gaussian pyramid. It is set to 2 by default.
System.Boolean extended

false means basic descriptors (64 elements each), true means extended descriptors (128 elements each)
System.Boolean upright

false means that detector computes orientation of each feature. true means that the orientation is not computed (which is much, much faster).
Returns
Type Description
SURF
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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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Get()

Declaration
public override IntPtr Get()
Returns
Type Description
IntPtr

Implements