Gaussian Filter¶

Filters an image using a Gaussian filter.

Description

This function applies a Gaussian filter to the source image with the specified kernel radius. Algorithm parameters shall be set through the gaussian_spec class. The values of border pixels are assigned in accordance with the border type. The formulae below describe the algorithm to compute kernel.

where

K is kernel size, K/2 is kernel radius
sigma - standard deviation of gaussian distribution
G_i,j are gaussian kernel values

Headers

oneapi/ipl/filter/gaussian.hpp

Syntax

template<typename ComputeT = float, formats Format, typename DataT, typename SrcAllocatorT, typename DstAllocatorT> sycl::event oneapi::ipl::gaussian(sycl::queue &queue, image<Format, DataT, SrcAllocatorT> &src, image<Format, DataT, DstAllocatorT> &dst, const gaussian_spec_t<Format, DataT, ComputeT> &spec, const std::vector<sycl::event> &dependencies = {})¶

Gaussian filter.

Template Parameters

ComputeT – type to perform calculations
Format – source/destination image format
DataT – source/destination image data type
SrcAllocatorT – source image allocator
DstAllocatorT – destination image allocator

Parameters

queue – SYCL queue
src – source image
dst – destination image
spec – algorithmic spec
dependencies – dependencies

Returns

SYCL event

Supported values for ComputeT:

float	double	half
v	v	x

Supported combinations for DataT/Formats:

DataT/Formats	plane	rgb/bgr	rgba/bgra	rgbp
std::uint8_t	v	v	v	x
std::int8_t	v	v	v	x
std::uint16_t	v	v	v	x
std::int16_t	v	v	v	x
std::uint32_t	v	v	v	x
std::int32_t	v	v	v	x
float	v	v	v	x
double	v	v	v	x

Supported values for subsampled Format (only for DataT = std::uint8_t):

nv12	i420
x	x

Parameters

border type support

Type of border. Possible values are:

const_val - Values of all border pixels are set to constant.

repl - Border is replicated from the edge pixels.

mirror - Border is mirrored from the edge pixels.

template<int NumChannels = 1, typename DataT = std::uint8_t, typename ComputeT = float> class oneapi::ipl::gaussian_spec : public oneapi::ipl::border_spec_base<1, std::uint8_t>¶

Gaussian filter parameters.

Template Parameters

NumChannels – the number of channels in border value vector
DataT – the type for constant border value component
ComputeT – the type for computations

Public Types

using border_spec_base_t = border_spec_base<NumChannels, DataT>¶: Type alias for base class of spec with border parameters.

using native_pixel_t = sycl::vec<std::uint8_t, NumChannels>¶: Type alias for pixel type.

Public Functions

template<int OtherNumChannels, typename OtherDataT, typename OtherComputeT> gaussian_spec(const gaussian_spec<OtherNumChannels, OtherDataT, OtherComputeT> &other)¶

Conversion constructor for gaussian specification.

Template Parameters

OtherNumChannels – other number of channels
OtherDataT – other data type
OtherComputeT – the other type for computations

Parameters

other – the other gaussian specification

explicit gaussian_spec(std::size_t radius, border_types border = border_types::repl, crop_types crop = crop_types::on)¶

Construct gaussian spec by OpenCV formula and given border type and crop flag.

Parameters

radius – kernel radius
border – border type
crop – crop flag

template<int OtherNumChannels, typename OtherDataT> explicit gaussian_spec(std::size_t radius, const sycl::vec<OtherDataT, OtherNumChannels> &border_val, crop_types crop = crop_types::on)¶

Construct gaussian spec by OpenCV formula and given value for constant border and crop flag.

Template Parameters

OtherNumChannels – other number of channels
OtherDataT – other data type

Parameters

radius – kernel radius
border_val – value for constant border
crop – crop flag

template<typename OtherComputeT> explicit gaussian_spec(std::size_t radius, OtherComputeT sigma, border_types border = border_types::repl, crop_types crop = crop_types::on)¶

Construct gaussian spec with given radius, sigma, border type and crop flag.

Template Parameters

OtherComputeT – other type for computations

Parameters

radius – kernel radius
sigma – sigma parameter of gaussian
border – border type
crop – crop flag

template<int OtherNumChannels, typename OtherDataT, typename OtherComputeT> explicit gaussian_spec(std::size_t radius, OtherComputeT sigma, const sycl::vec<OtherDataT, OtherNumChannels> &border_val, crop_types crop = crop_types::on)¶

Construct gaussian spec with given radius, sigma, value for constant border and crop flag.

Template Parameters

OtherNumChannels – other number of channels
OtherDataT – other data type
OtherComputeT – other type for computations

Parameters

radius – kernel radius
sigma – sigma parameter of gaussian
border_val – value for constant border
crop – crop flag

std::size_t get_radius() const noexcept¶

Returns the radius of gaussian filter.

Returns: the radius of gaussian filter

ComputeT get_sigma() const noexcept¶

Returns the sigma of gaussian filter.

Returns: the sigma of gaussian filter

crop_types get_crop() const noexcept¶

Returns the crop type.

Returns: crop type

border_types get_border() const noexcept¶

Returns the border type.

Returns: border type

auto get_border_val() const noexcept -> const native_pixel_t&¶

Returns the border value.

Returns: border value

auto get_border_val_ptr() const -> const std::uint8_t*¶

Returns the border value pointer.

Returns: border value pointer

Errors

compile-time format check	Indicates an error when image format is not supported.
compile-time data type check	Indicates an error when image data type is not supported.
compile-time compute data type check	Indicates an error when compute data type is not supported.
`invalid_argument`	Indicates an error when ROI sizes of the source image and the destination image are not equal.
`invalid_argument` exception	Indicates an error when one of the pitch values is not divisible by size of component data type in bytes.
`unimplemented` exception	Indicates an error when border type is not supported.

The code example below demonstrates how to use the oneapi::ipl::gaussian:

// Create queue
sycl::queue queue{};

image<formats::rgba, std::uint8_t> src_image{ src_data_pointer, size };
image<formats::rgba, std::uint8_t> dst_image{ size };

// Create a gaussian arguments (kernel radius = 2, sigma is caluculated)
const gaussian_spec spec{ 2 };

(void)gaussian(queue, src_image, dst_image, spec);

oneIPL Specification documentation

Gaussian Filter¶