MPSImageGaussianBlur(3) MetalPerformanceShaders.framework MPSImageGaussianBlur(3)

MPSImageGaussianBlur

#import <MPSImageConvolution.h>

Inherits MPSUnaryImageKernel.


(nonnull instancetype) - initWithDevice:sigma:
(nullable instancetype) - initWithCoder:device:
(nonnull instancetype) - initWithDevice:


float sigma

The MPSImageGaussianBlur convolves an image with gaussian of given sigma in both x and y direction.



            The MPSImageGaussianBlur utilizes a very fast algorith that typically runs at approximately


            1/2 of copy speeds. Notably, it is faster than either the tent or box blur except perhaps


            for very large filter windows. Mathematically, it is an approximate gaussian. Some


            non-gaussian behavior may be detectable with advanced analytical methods such as FFT.  


            If a analytically clean gaussian filter is required, please use the MPSImageConvolution 


            filter instead with an appropriate set of weights. The MPSImageGaussianBlur is intended


            to be suitable for all common image processing needs demanding ~10 bits of precision or


            less.

- (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 MPSUnaryImageKernel.

- (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 MPSUnaryImageKernel.

- (nonnull instancetype) initWithDevice: (nonnull id< MTLDevice >) device(float) sigma

Initialize a gaussian blur filter for a particular sigma and device

Parameters:

device The device the filter will run on
sigma The standard deviation of gaussian blur filter. Gaussian weight, centered at 0, at integer grid i is given as w(i) = 1/sqrt(2*pi*sigma) * exp(-i^2/(2*sigma^2)) If we take cut off at 1% of w(0) (max weight) beyond which weights are considered 0, we have ceil (sqrt(-log(0.01)*2)*sigma) ~ ceil(3.7*sigma) as rough estimate of filter width

Returns:

A valid object or nil, if failure.

- sigma [read], [nonatomic], [assign]

Read-only sigma value with which filter was created

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Mon Jul 9 2018 Version MetalPerformanceShaders-119.3