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Accord.NET (logo) BilateralSmoothing Class
Bilateral filter implementation - edge preserving smoothing and noise reduction that uses chromatic and spatial factors.
Inheritance Hierarchy
SystemObject
  Accord.Imaging.FiltersBaseUsingCopyPartialFilter
    Accord.Imaging.FiltersBilateralSmoothing

Namespace:  Accord.Imaging.Filters
Assembly:  Accord.Imaging (in Accord.Imaging.dll) Version: 3.4.0
Syntax
public class BilateralSmoothing : BaseUsingCopyPartialFilter
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The BilateralSmoothing type exposes the following members.

Constructors
  NameDescription
Public methodBilateralSmoothing
Initializes a new instance of the BilateralSmoothing class.
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Properties
  NameDescription
Public propertyColorFactor
Determines the variance of color for a color domain, >= 1.
Public propertyColorPower
Exponent power, used in Color function calculation, >= 1.
Public propertyEnableParallelProcessing
Enable or not parallel processing on multi-core CPUs.
Public propertyFormatTranslations
Format translations dictionary.
(Overrides BaseUsingCopyPartialFilterFormatTranslations.)
Public propertyKernelSize
Size of a square for limiting surrounding pixels that take part in calculations, [3, 255].
Public propertyLimitKernelSize
Specifies if exception must be thrown in the case a large kernel size is used which may lead to significant performance issues.
Public propertySpatialFactor
Determines smoothing power within a color domain (neighbor pixels of similar color), >= 1.
Public propertySpatialPower
Exponent power, used in Spatial function calculation, >= 1.
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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 MethodToTOverloaded.
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.)
Public Extension MethodToTOverloaded.
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 Matrix.)
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Remarks

Bilateral filter conducts "selective" Gaussian smoothing of areas of same color (domains) which removes noise and contrast artifacts while preserving sharp edges.

Two major parameters SpatialFactor and ColorFactor define the result of the filter. By changing these parameters you may achieve either only noise reduction with little change to the image or get nice looking effect to the entire image.

Although the filter can use parallel processing large KernelSize values (greater than 25) on high resolution images may decrease speed of processing. Also on high resolution images small KernelSize values (less than 9) may not provide noticeable results.

More details on the algorithm can be found by following this link.

The filter accepts 8 bpp grayscale images and 24/32 bpp color images for processing.

Sample usage:

// create filter
BilateralSmoothing filter = new BilateralSmoothing( );
filter.KernelSize    = 7;
filter.SpatialFactor = 10;
filter.ColorFactor   = 60;
filter.ColorPower    = 0.5;
// apply the filter
filter.ApplyInPlace( image );

Initial image:

Result image:

See Also