Resize with Lanczos Interpolation

Changes an image size using interpolation with the Lanczos filter.

Description

This function changes an image size using interpolation with the Lanczos filter. The image size may be either reduced or increased in each direction, depending on the destination image size. This method is based on the 3-lobed Lanczos window function as an interpolation function. Algorithm parameters must be set through the resize_lanczos_spec class. The border pixels are processed in accordance with the border type. This function can operate with ROI (see Image Regions of Interest).

Headers

oneapi/ipl/transform/resize_lanczos.hpp

Syntax

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

Resize with the Lanczos interpolation method.

Template Parameters

• ComputeT – type to perform calculations

• SrcImageT – Source image type

• DstImageT – Destination image type

Parameters

• queue – [in] SYCL queue

• src – [in] source image

• dst – [out] destination image

• spec – [in] algorithm parameters

• dependencies – [in] other events dependencies

Returns

SYCL event, that represents algorithm completion

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
v	v

Parameters

border type support

Type of border. Possible values are: repl - Border is replicated from the edge pixels.

class resize_lanczos_spec : public oneapi::ipl::border_spec_base<>

Resize Lanczos parameters.

Public Types

using native_pixel_t = sycl::vec<DataT, NumChannels>

Type alias for pixel type.

Public Functions

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 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::resize_lanczos:

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 with x2 size
ipl::image<ipl::layouts::channel4, std::uint8_t> dst_image{ image_size * 2, allocator };

auto event = ipl::resize_lanczos(queue, src_image, dst_image);