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_x, sigma_y - standard deviations of gaussian distribution by X, Y directions
G_i,j are gaussian kernel values

Headers

oneapi/ipl/filter/gaussian.hpp

Syntax

template<typename ComputeT = float, typename SrcImageT, typename DstImageT> sycl::event oneapi::ipl::gaussian(sycl::queue &queue, SrcImageT &src, DstImageT &dst, const gaussian_spec_t<SrcImageT::layout_v, typename SrcImageT::data_t, ComputeT> &spec, const std::vector<sycl::event> &dependencies = {})#

Gaussian filter.

Template Parameters

ComputeT – type to perform calculations
SrcImageT – Source image type
DstImageT – Destination image type

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/Layouts:

DataT/Layouts	plane	channel3	channel4	plane3
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 layout (only for std::uint8_t data type):

sub420	sub420i
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 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<DataT, 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 (same for both X and Y directions), border type and crop flag.

Template Parameters

OtherComputeT – other type for computations

Parameters

radius – kernel radius
sigma – sigma parameter of Gaussian filter
border – border type
crop – crop flag

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

Construct Gaussian spec with given radius, 2-component sigma, border type, and crop flag.

Template Parameters

OtherComputeT – other type for computations

Parameters

radius – kernel radius
sigma – 2-component sigma parameter of Gaussian filter
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 (same for both X and Y directions), 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 filter
border_val – value for constant border
crop – crop flag

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

Construct Gaussian spec with given radius, 2-component 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 – 2-component sigma parameter of Gaussian filter
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

const sigma_t<ComputeT> &get_sigma() const noexcept#

Returns 2-component sigma of Gaussian filter.

Returns: the 2-component 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 DataT*#

Returns the border value pointer.

Returns: border value pointer

Errors

compile-time memory layout check	Indicates an error when image memory layout 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 shall be called oneapi::ipl::gaussian:

using namespace oneapi;

sycl::queue                 queue;
ipl::shared_usm_allocator_t allocator{ queue };
const sycl::range<2>        image_size{ height, width };

// Source 4-channel image data
ipl::image<ipl::layouts::channel4, std::uint8_t> src_image{ queue, p_image_data, image_size, allocator };
// Destination 4-channel image data
ipl::image<ipl::layouts::channel4, std::uint8_t> dst_image{ image_size, allocator };

const ipl::gaussian_spec spec{ 2 };

// Gaussian filter with kernel radius = 2 and sigma calculated
auto event = ipl::gaussian(queue, src_image, dst_image, spec);

oneIPL Specification documentation

Gaussian Filter

Gaussian Filter#