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OtsuThreshold Class

Otsu thresholding.
Inheritance Hierarchy
SystemObject
  Accord.Imaging.FiltersBaseInPlacePartialFilter
    Accord.Imaging.FiltersOtsuThreshold

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

Constructors
  NameDescription
Public methodOtsuThreshold
Initializes a new instance of the OtsuThreshold class.
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Properties
Methods
  NameDescription
Public methodApply(Bitmap)
Apply filter to an image.
(Inherited from BaseInPlacePartialFilter.)
Public methodApply(BitmapData)
Apply filter to an image.
(Inherited from BaseInPlacePartialFilter.)
Public methodApply(UnmanagedImage)
Apply filter to an image in unmanaged memory.
(Inherited from BaseInPlacePartialFilter.)
Public methodApply(UnmanagedImage, UnmanagedImage)
Apply filter to an image in unmanaged memory.
(Inherited from BaseInPlacePartialFilter.)
Public methodApplyInPlace(Bitmap)
Apply filter to an image.
(Inherited from BaseInPlacePartialFilter.)
Public methodApplyInPlace(BitmapData)
Apply filter to an image.
(Inherited from BaseInPlacePartialFilter.)
Public methodApplyInPlace(UnmanagedImage)
Apply filter to an unmanaged image.
(Inherited from BaseInPlacePartialFilter.)
Public methodApplyInPlace(Bitmap, Rectangle)
Apply filter to an image or its part.
(Inherited from BaseInPlacePartialFilter.)
Public methodApplyInPlace(BitmapData, Rectangle)
Apply filter to an image or its part.
(Inherited from BaseInPlacePartialFilter.)
Public methodApplyInPlace(UnmanagedImage, Rectangle)
Apply filter to an unmanaged image or its part.
(Inherited from BaseInPlacePartialFilter.)
Public methodCalculateThreshold(Bitmap, Rectangle)
Calculate binarization threshold for the given image.
Public methodCalculateThreshold(BitmapData, Rectangle)
Calculate binarization threshold for the given image.
Public methodCalculateThreshold(UnmanagedImage, Rectangle)
Calculate binarization threshold for the given image.
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 BaseInPlacePartialFilterProcessFilter(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 class implements Otsu thresholding, which is described in N. Otsu, "A threshold selection method from gray-level histograms", IEEE Trans. Systems, Man and Cybernetics 9(1), pp. 62–66, 1979.

This implementation instead of minimizing the weighted within-class variance does maximization of between-class variance, what gives the same result. The approach is described in this presentation.

The filter accepts 8 bpp grayscale images for processing.

Sample usage:

// create filter
OtsuThreshold filter = new OtsuThreshold( );
// apply the filter
filter.ApplyInPlace( image );
// check threshold value
byte t = filter.ThresholdValue;
// ...

Initial image:

Result image (calculated threshold is 97):

See Also