Image::NISTImageResampler Class Reference

Image resampler for DPI-change operations, including upsampling and downsampling using NIST-compliant resampling algorithm provided by NFIR library. More...

#include <Image.h>

Collaboration diagram for Image::NISTImageResampler:

Public Types
enum class	InterpolationMethod : uint8_t { BICUBIC , BILINEAR }
	Enum defines possible types of interpolation methods to apply during image resampling. More...
enum class	FilterType : uint8_t { GAUSSIAN , IDEAL }
	Enum defines possible types of filtering methods to apply before image resampling. More...

Public Member Functions
	NISTImageResampler (ImageDpi targetDpi)
	Constructs a NIST-compliant image resampler for a target DPI.
	NISTImageResampler (ImageDpi targetDpi, InterpolationMethod interpolationMethod, FilterType filterType)
	Constructs a NIST-compliant image resampler for a target DPI using a custom interpolation method and filter.
std::shared_ptr< Image >	Resample (const inno::Image &image) const final
	Resample image to a target DPI using NIST resamling algorithm.

Protected Member Functions
ImageDpi	GetDpi () const
	Retrieves target DPI of the resampler.

Detailed Description

Image resampler for DPI-change operations, including upsampling and downsampling using NIST-compliant resampling algorithm provided by NFIR library.

Member Enumeration Documentation

FilterType

enum class FilterType : uint8_t

strong

Enum defines possible types of filtering methods to apply before image resampling.

Enumerator
GAUSSIAN	Apply a Gaussian filter for smoothing.
IDEAL	Apply an ideal filter for sharpness.

InterpolationMethod

enum class InterpolationMethod : uint8_t

strong

Enum defines possible types of interpolation methods to apply during image resampling.

Enumerator
BICUBIC	Apply bicubic interpolation.
BILINEAR	Apply bilinear interpolation.

Constructor & Destructor Documentation

NISTImageResampler() [1/2]

NISTImageResampler ( ImageDpi targetDpi )

inlineexplicit

Constructs a NIST-compliant image resampler for a target DPI.

This constructor initializes the image resampler to resample an image to the specified DPI using a NIST-compliant resampling algorithm with default interpolation and filtering settings.

Note

It is recommended to explicitly specify the interpolation method and filter type by using the constructor NISTImageResampler(ImageDpi targetDpi, InterpolationMethod interpolationMethod, FilterType filterType) rather than relying on the default settings. The best settings for your use case are likely to be determined through trial and error.

Parameters

targetDpi

The DPI (dots per inch) of the new image.

Exceptions

EnrollmentInvalidArgumentException

when targetDpi is 0

References Image::ImageResampler::ImageResampler().

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NISTImageResampler() [2/2]

NISTImageResampler ( ImageDpi targetDpi, InterpolationMethod interpolationMethod, FilterType filterType )

inline

Constructs a NIST-compliant image resampler for a target DPI using a custom interpolation method and filter.

This constructor initializes the image resampler to resample an image to the specified DPI using a NIST-compliant resampling algorithm and the provided interpolation and filtering methods.

Depending on the resize factor, the optimal configuration of the filter type and interpolation method for achieving the best extraction accuracy was experimentally determined, as shown in the table below:

Source DPI	Interpolation Method	Filter Type
600	Bicubic	Ideal
1000	Bilinear	Ideal
1200	Bilinear	Gaussian
Other	Bicubic	Ideal

This is also the default behavior of a resampler constructed using NISTImageResampler(ImageDpi targetDpi).

Note

It is recommended to explicitly specify the interpolation method and downsampling filter mask rather than relying on the default settings. The best settings for your use case are likely to be determined through trial and error.

Parameters

targetDpi	The DPI (dots per inch) of the new image.
interpolationMethod	The interpolation method to be applied during resampling.
filterType	The type of filtering to be applied before resampling.

Exceptions

EnrollmentInvalidArgumentException

when targetDpi is 0

References BICUBIC, BILINEAR, GAUSSIAN, IDEAL, and Image::ImageResampler::ImageResampler().

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Member Function Documentation

GetDpi()

ImageDpi GetDpi ( ) const

inlinenodiscardprotectedinherited

Retrieves target DPI of the resampler.

Returns

The target DPI (dots per inch) of the resampler

Referenced by Image::AreaImageResampler::Resample(), Image::BicubicImageResampler::Resample(), and Image::NISTImageResampler::Resample().

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Resample()

std::shared_ptr< Image > Resample ( const inno::Image & image ) const

inlinenodiscardfinalvirtual

Resample image to a target DPI using NIST resamling algorithm.

It creates new image as result of resampling with factor target DPI/original DPI.

Parameters

image

Image to resize.

Returns

image with given DPI

Exceptions

ImageException	when there is an processing error
EnrollmentInvalidArgumentException	when the image is not single-channel grayscale

Implements Image::ImageResampler.

References Image::ImageResampler::GetDpi().

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The documentation for this class was generated from the following file:

• Image/Image.h