MPSCNNLocalContrastNormalization(3)

NAME

       MPSCNNLocalContrastNormalization

SYNOPSIS

       #import <MPSCNNNormalization.h>

       Inherits MPSCNNKernel.

   Instance Methods
       (nonnull instancetype) - initWithDevice:kernelWidth:kernelHeight:
       (nullable instancetype) - initWithCoder:device:
       (nonnull instancetype) - initWithDevice:

   Properties
       float alpha
       float beta
       float delta
       float p0
       float pm
       float ps
       NSUInteger kernelWidth
       NSUInteger kernelHeight

   Additional Inherited Members

Detailed Description

       This depends on Metal.framework  Specifies the local contrast
       normalization filter. The local contrast normalization is quite similar
       to spatial normalization (see MPSCNNSpatialNormalization) in that it
       applies the filter over local regions which extend spatially, but are
       in separate feature channels (i.e., they have shape 1 x kernelWidth x
       kernelHeight), but instead of dividing by the local 'energy' of the
       feature, the denominator uses the local variance of the feature -
       effectively the mean value of the feature is subtracted from the
       signal. For each feature channel, the function computes the variance
       VAR(i,j) and mean M(i,j) of X(i,j) inside each rectangle around the
       spatial point (i,j).

       Then the result is computed for each element of X as follows:

       Y(i,j) = pm + ps * ( X(i,j) - p0 * M(i,j)) / (delta + alpha * VAR(i,j))^beta,



       where kw and kh are the kernelWidth and the kernelHeight and pm, ps and
       p0 are parameters that can be used to offset and scale the result in
       various ways. For example setting pm=0, ps=1, p0=1, delta=0, alpha=1.0
       and beta=0.5 scales input data so that the result has unit variance and
       zero mean, provided that input variance is positive. It is the end-
       users responsibility to ensure that the combination of the parameters
       delta and alpha does not result in a situation where the denominator
       becomes zero - in such situations the resulting pixel-value is
       undefined. A good way to guard against tiny variances is to regulate
       the expression with a small value for delta, for example delta = 1/1024
       = 0.0009765625.

Method Documentation

   - (nullable instancetype) initWithCoder: (NSCoder *__nonnull)
       aDecoder(nonnull id< MTLDevice >) device
       NSSecureCoding compatability  While the standard
       NSSecureCoding/NSCoding method -initWithCoder: should work, since the
       file can't know which device your data is allocated on, we have to
       guess and may guess incorrectly. To avoid that problem, use
       initWithCoder:device instead.

       Parameters:
           aDecoder The NSCoder subclass with your serialized MPSKernel
           device The MTLDevice on which to make the MPSKernel

       Returns:
           A new MPSKernel object, or nil if failure.



       Reimplemented from MPSCNNKernel.

   - (nonnull instancetype) initWithDevice: (nonnull id< MTLDevice >) device
       Standard init with default properties per filter type

       Parameters:
           device The device that the filter will be used on. May not be NULL.

       Returns:
           A pointer to the newly initialized object. This will fail,
           returning nil if the device is not supported. Devices must be
           MTLFeatureSet_iOS_GPUFamily2_v1 or later.



       Reimplemented from MPSCNNKernel.

   - (nonnull instancetype) initWithDevice: (nonnull id< MTLDevice >)
       device(NSUInteger) kernelWidth(NSUInteger) kernelHeight
       Initialize a local contrast normalization filter

       Parameters:
           device The device the filter will run on
           kernelWidth The width of the kernel
           kernelHeight The height of the kernel

       Returns:
           A valid MPSCNNLocalContrastNormalization object or nil, if failure.

       NOTE: For now, kernelWidth must be equal to kernelHeight

Property Documentation

   - alpha [read],  [write],  [nonatomic],  [assign]
       The value of alpha. Default is 0.0  The default value 0.0 is not
       recommended and is preserved for backwards compatibility. With alpha 0,
       it performs a local mean subtraction. The
       MPSCNNLocalContrastNormalizationNode used with the MPSNNGraph uses 1.0
       as a default.

   - beta [read],  [write],  [nonatomic],  [assign]
       The value of beta. Default is 0.5

   - delta [read],  [write],  [nonatomic],  [assign]
       The value of delta. Default is 1/1024

   - kernelHeight [read],  [nonatomic],  [assign]
       The height of the filter window

   - kernelWidth [read],  [nonatomic],  [assign]
       The width of the filter window

   - p0 [read],  [write],  [nonatomic],  [assign]
       The value of p0. Default is 1.0

   - pm [read],  [write],  [nonatomic],  [assign]
       The value of pm. Default is 0.0

   - ps [read],  [write],  [nonatomic],  [assign]
       The value of ps. Default is 1.0

Author

       Generated automatically by Doxygen for
       MetalPerformanceShaders.framework from the source code.





Version MetalPerformanceShaders-Thu2Jul 13 MPSCNNLocalContrastNormalization(3)


Mac OS X 10.13.1 - Generated Mon Nov  6 18:12:21 CST 2017