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CannyEdgeDetector Class

Canny edge detector.
Inheritance Hierarchy
SystemObject
  Accord.Imaging.FiltersBaseUsingCopyPartialFilter
    Accord.Imaging.FiltersCannyEdgeDetector

Namespace:  Accord.Imaging.Filters
Assembly:  Accord.Imaging (in Accord.Imaging.dll) Version: 3.7.0
Syntax
public class CannyEdgeDetector : BaseUsingCopyPartialFilter
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The CannyEdgeDetector type exposes the following members.

Constructors
  NameDescription
Public methodCannyEdgeDetector
Initializes a new instance of the CannyEdgeDetector class.
Public methodCannyEdgeDetector(Byte, Byte)
Initializes a new instance of the CannyEdgeDetector class.
Public methodCannyEdgeDetector(Byte, Byte, Double)
Initializes a new instance of the CannyEdgeDetector class.
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Properties
  NameDescription
Public propertyFormatTranslations
Format translations dictionary.
(Overrides BaseUsingCopyPartialFilterFormatTranslations.)
Public propertyGaussianSigma
Gaussian sigma.
Public propertyGaussianSize
Gaussian size.
Public propertyHighThreshold
High threshold.
Public propertyLowThreshold
Low threshold.
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Methods
  NameDescription
Public methodApply(Bitmap)
Apply filter to an image.
(Inherited from BaseUsingCopyPartialFilter.)
Public methodApply(BitmapData)
Apply filter to an image.
(Inherited from BaseUsingCopyPartialFilter.)
Public methodApply(UnmanagedImage)
Apply filter to an image in unmanaged memory.
(Inherited from BaseUsingCopyPartialFilter.)
Public methodApply(UnmanagedImage, UnmanagedImage)
Apply filter to an image in unmanaged memory.
(Inherited from BaseUsingCopyPartialFilter.)
Public methodApplyInPlace(Bitmap)
Apply filter to an image.
(Inherited from BaseUsingCopyPartialFilter.)
Public methodApplyInPlace(BitmapData)
Apply filter to an image.
(Inherited from BaseUsingCopyPartialFilter.)
Public methodApplyInPlace(UnmanagedImage)
Apply filter to an unmanaged image.
(Inherited from BaseUsingCopyPartialFilter.)
Public methodApplyInPlace(Bitmap, Rectangle)
Apply filter to an image or its part.
(Inherited from BaseUsingCopyPartialFilter.)
Public methodApplyInPlace(BitmapData, Rectangle)
Apply filter to an image or its part.
(Inherited from BaseUsingCopyPartialFilter.)
Public methodApplyInPlace(UnmanagedImage, Rectangle)
Apply filter to an unmanaged image or its part.
(Inherited from BaseUsingCopyPartialFilter.)
Public methodEquals
Determines whether the specified object is equal to the current object.
(Inherited from Object.)
Protected methodFinalize
Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.
(Inherited from Object.)
Public methodGetHashCode
Serves as the default hash function.
(Inherited from Object.)
Public methodGetType
Gets the Type of the current instance.
(Inherited from Object.)
Protected methodMemberwiseClone
Creates a shallow copy of the current Object.
(Inherited from Object.)
Protected methodProcessFilter
Process the filter on the specified image.
(Overrides BaseUsingCopyPartialFilterProcessFilter(UnmanagedImage, UnmanagedImage, Rectangle).)
Public methodToString
Returns a string that represents the current object.
(Inherited from Object.)
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Extension Methods
  NameDescription
Public Extension MethodHasMethod
Checks whether an object implements a method with the given name.
(Defined by ExtensionMethods.)
Public Extension MethodIsEqual
Compares two objects for equality, performing an elementwise comparison if the elements are vectors or matrices.
(Defined by Matrix.)
Public Extension MethodToT
Converts an object into another type, irrespective of whether the conversion can be done at compile time or not. This can be used to convert generic types to numeric types during runtime.
(Defined by ExtensionMethods.)
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Remarks

The filter searches for objects' edges by applying Canny edge detector. The implementation follows Bill Green's Canny edge detection tutorial.

Note Note
The implemented canny edge detector has one difference with the above linked algorithm. The difference is in hysteresis step, which is a bit simplified (getting faster as a result). On the hysteresis step each pixel is compared with two threshold values: HighThreshold and LowThreshold. If pixel's value is greater or equal to HighThreshold, then it is kept as edge pixel. If pixel's value is greater or equal to LowThreshold, then it is kept as edge pixel only if there is at least one neighbouring pixel (8 neighbours are checked) which has value greater or equal to HighThreshold; otherwise it is none edge pixel. In the case if pixel's value is less than LowThreshold, then it is marked as none edge immediately.

The filter accepts 8 bpp grayscale images for processing.

Sample usage:

// create filter
CannyEdgeDetector filter = new CannyEdgeDetector( );
// apply the filter
filter.ApplyInPlace( image );

Initial image:

Result image:

See Also