FFT an image. More...

#include <ImageFFT.h>

Public Types
using	ComplexType = std::complex< typename casacore::NumericTraits< T >::BaseType >

using	RealType = typename casacore::NumericTraits< T >::BaseType

Public Member Functions
	ImageFFT ()

	ImageFFT (const ImageFFT &other)

ImageFFT &	operator= (const ImageFFT &other)
	Assignment (reference semantics) More...

	~ImageFFT ()

void	fftsky (const casacore::ImageInterface< T > &in)
	Do the FFT of the sky plane to the uv plane Masked pixels are set to zero before the FT. More...

void	fft (const casacore::ImageInterface< T > &in, const casacore::Vector< casacore::Bool > &axes)
	Do the FFT of the specified pixel axes (true to FT). More...

void	getComplex (casacore::ImageInterface< ComplexType > &out) const
	Return the FFT (from the last call to fftsky or fft) in the desired form. More...

void	getReal (casacore::ImageInterface< RealType > &out) const

void	getImaginary (casacore::ImageInterface< RealType > &out) const

void	getAmplitude (casacore::ImageInterface< RealType > &out) const

void	getPhase (casacore::ImageInterface< RealType > &out) const

Private Member Functions
void	checkAxes (const casacore::CoordinateSystem &cSys, casacore::uInt ndim, const casacore::Vector< casacore::Bool > &axes)
	Check axes for multi-dim FFT. More...

template<class U >
void	_copyMiscellaneous (casacore::ImageInterface< U > &out) const
	Copy MiscInfo, casacore::ImageInfo, casacore::Unit, logSInk to output. More...

template<class U >
void	_copyMost (casacore::ImageInterface< U > &out) const
	common image copy stuff More...

void	_setCoordinates (casacore::ImageInterface< ComplexType > &out, const casacore::CoordinateSystem &cSys, const casacore::Vector< casacore::Bool > &axes, const casacore::IPosition &shape)
	Overwrite the coordinate system with Fourier coordinates for all designated axes. More...

Static Private Member Functions
template<class U >
static void	_copyMask (casacore::ImageInterface< U > &out, const casacore::ImageInterface< T > &in)
	Copy the mask to the output. More...

template<class U >
static void	_fftsky (casacore::ImageInterface< U > &out, const casacore::ImageInterface< T > &in, const casacore::Vector< casacore::Int > &pixelAxes)
	U must be a complex type (Complex, DComplex) More...

template<class U >
static void	_fft (casacore::ImageInterface< U > &out, const casacore::ImageInterface< T > &in, const casacore::Vector< casacore::Bool > &axes)
	U must be a complex type (Complex, DComplex) More...

static casacore::Bool	_findSky (casacore::Int &dC, casacore::Vector< casacore::Int > &pixelAxes, casacore::Vector< casacore::Int > &worldAxes, const casacore::CoordinateSystem &cSys, casacore::Bool throwIt)
	Find the sky axes in this CoordinateSystem. More...

static void	_setSkyCoordinates (casacore::ImageInterface< ComplexType > &out, const casacore::CoordinateSystem &csys, const casacore::IPosition &shape, casacore::uInt dC)
	Overwrite the coordinate system with Fourier coordinates for sky axes only. More...

Private Attributes
SPIICT	_tempImagePtr

SPIIT	_image

casacore::Bool	_done

Detailed Description

template<class T>
class casa::ImageFFT< T >

FFT an image.

Intended use:

Public interface

Review Status

Date Reviewed:: yyyy/mm/dd

Prerequisite

LatticeFFT
ImageInterface
TempImage

Etymology

Take the fast Fourier Transform of an image.

Synopsis

This class takes the FFT of an image. It can take the FFT of just the sky plane(s) of an image or the specified axes.

When you specify axes, if any of them are a sky axis (casacore::DirectionCoordinate) you must give both sky axes.

Masked pixels are given the value 0.0 before the FFT is taken and the mask is copied to the output. Note that it is the callers responsibility to give the output a mask if the input is masked. Otherwise the mask will not be copied to the output

This class holds the FourierTransform internally in a TempImage object. This is in memory or on disk depending upon its size and the amount of memory in your computer. The algorithm used is that in TempLattice.

In generating the Fourier Coordinates, it is currently assumed that there is no coordinate rotation. This needs to be dealt with.

Example

// Make a constant image
casacore::IPosition shape(2, 10, 20);
casacore::PagedImage<casacore::Float> im1(shape, casacore::CoordinateUtil::defaultCoords2D(), "im1");
im1.set(1.0);
// Create output images with masks if needed
casacore::PagedImage<casacore::Float> r1(shape, casacore::CoordinateUtil::defaultCoords2D(), "real1");
casacore::PagedImage<casacore::Float> i1(shape, casacore::CoordinateUtil::defaultCoords2D(), "imag1");
if (im1.isMasked()) {
casacore::LCPagedMask mask1 = casacore::LCPagedMask(casacore::RegionHandler::makeMask (r1, "mask0"));
mask1.set(true);
r1.defineRegion ("mask0", casacore::ImageRegion(mask1), casacore::RegionHandler::Masks);
r1.setDefaultMask("mask0");
casacore::LCPagedMask mask2 = casacore::LCPagedMask(casacore::RegionHandler::makeMask (i1, "mask0"));
mask2.set(true);
i1.defineRegion ("mask0", casacore::ImageRegion(mask1), casacore::RegionHandler::Masks);
i1.setDefaultMask("mask0");
}
//
// FFT
ImageFFT fft;
fft.fftsky(im1);
// The coordinates and mask will be updated
fft.getReal(r1);
fft.getImag(i1);

Motivation

Taking the Fourier Transform of an image is a basic part of image analysis

To Do

reverse transformations

Definition at line 134 of file ImageFFT.h.

Member Typedef Documentation

template<class T>

using casa::ImageFFT< T >::ComplexType = std::complex<typename casacore::NumericTraits<T>::BaseType>

Definition at line 138 of file ImageFFT.h.

template<class T>

using casa::ImageFFT< T >::RealType = typename casacore::NumericTraits<T>::BaseType

Definition at line 140 of file ImageFFT.h.

Constructor & Destructor Documentation

template<class T>

casa::ImageFFT< T >::ImageFFT ( )

template<class T>

casa::ImageFFT< T >::ImageFFT ( const ImageFFT< T > & other )

template<class T>

casa::ImageFFT< T >::~ImageFFT ( )

Member Function Documentation

template<class T>

template<class U >

static void casa::ImageFFT< T >::_copyMask	(	casacore::ImageInterface< U > &	out,
		const casacore::ImageInterface< T > &	in
	)

staticprivate

Copy the mask to the output.

template<class T>

template<class U >

void casa::ImageFFT< T >::_copyMiscellaneous ( casacore::ImageInterface< U > & out ) const

private

Copy MiscInfo, casacore::ImageInfo, casacore::Unit, logSInk to output.

template<class T>

template<class U >

void casa::ImageFFT< T >::_copyMost ( casacore::ImageInterface< U > & out ) const

private

common image copy stuff

template<class T>

template<class U >

static void casa::ImageFFT< T >::_fft	(	casacore::ImageInterface< U > &	out,
		const casacore::ImageInterface< T > &	in,
		const casacore::Vector< casacore::Bool > &	axes
	)

staticprivate

U must be a complex type (Complex, DComplex)

template<class T>

template<class U >

static void casa::ImageFFT< T >::_fftsky	(	casacore::ImageInterface< U > &	out,
		const casacore::ImageInterface< T > &	in,
		const casacore::Vector< casacore::Int > &	pixelAxes
	)

staticprivate

U must be a complex type (Complex, DComplex)

template<class T>

static casacore::Bool casa::ImageFFT< T >::_findSky	(	casacore::Int &	dC,
		casacore::Vector< casacore::Int > &	pixelAxes,
		casacore::Vector< casacore::Int > &	worldAxes,
		const casacore::CoordinateSystem &	cSys,
		casacore::Bool	throwIt
	)

staticprivate

Find the sky axes in this CoordinateSystem.

template<class T>

void casa::ImageFFT< T >::_setCoordinates	(	casacore::ImageInterface< ComplexType > &	out,
		const casacore::CoordinateSystem &	cSys,
		const casacore::Vector< casacore::Bool > &	axes,
		const casacore::IPosition &	shape
	)

private

Overwrite the coordinate system with Fourier coordinates for all designated axes.

template<class T>

static void casa::ImageFFT< T >::_setSkyCoordinates	(	casacore::ImageInterface< ComplexType > &	out,
		const casacore::CoordinateSystem &	csys,
		const casacore::IPosition &	shape,
		casacore::uInt	dC
	)

staticprivate

Overwrite the coordinate system with Fourier coordinates for sky axes only.

template<class T>

void casa::ImageFFT< T >::checkAxes	(	const casacore::CoordinateSystem &	cSys,
		casacore::uInt	ndim,
		const casacore::Vector< casacore::Bool > &	axes
	)

private

Check axes for multi-dim FFT.

template<class T>

void casa::ImageFFT< T >::fft	(	const casacore::ImageInterface< T > &	in,
		const casacore::Vector< casacore::Bool > &	axes
	)

Do the FFT of the specified pixel axes (true to FT).

The rest are iterated over. Masked pixels are set to zero before the FT

template<class T>

void casa::ImageFFT< T >::fftsky ( const casacore::ImageInterface< T > & in )

Do the FFT of the sky plane to the uv plane Masked pixels are set to zero before the FT.

template<class T>

void casa::ImageFFT< T >::getAmplitude ( casacore::ImageInterface< RealType > & out ) const

template<class T>

void casa::ImageFFT< T >::getComplex ( casacore::ImageInterface< ComplexType > & out ) const

Return the FFT (from the last call to fftsky or fft) in the desired form.

The casacore::CoordinateSystem, MiscInfo, casacore::ImageInfo,

history and units are copied/updated in the output image from the image that was FFTd. If the input image is masked, and the output image has a writable mask, the mask will be transferred. Any output mask should be initialized to true before calling these functions.

template<class T>

void casa::ImageFFT< T >::getImaginary ( casacore::ImageInterface< RealType > & out ) const

template<class T>

void casa::ImageFFT< T >::getPhase ( casacore::ImageInterface< RealType > & out ) const

template<class T>

void casa::ImageFFT< T >::getReal ( casacore::ImageInterface< RealType > & out ) const

template<class T>

ImageFFT& casa::ImageFFT< T >::operator= ( const ImageFFT< T > & other )

Assignment (reference semantics)

Member Data Documentation

template<class T>

casacore::Bool casa::ImageFFT< T >::_done

private

Definition at line 185 of file ImageFFT.h.

template<class T>

SPIIT casa::ImageFFT< T >::_image

private

Definition at line 184 of file ImageFFT.h.

template<class T>

SPIICT casa::ImageFFT< T >::_tempImagePtr

private

Definition at line 183 of file ImageFFT.h.

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

casa/code/imageanalysis/ImageAnalysis/ImageFFT.h

Public Types

Public Member Functions

Private Member Functions

Static Private Member Functions

Private Attributes

Detailed Description

template<class T> class casa::ImageFFT< T >

Intended use:

Review Status

Prerequisite

Etymology

Synopsis

Example

Motivation

To Do

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation

template<class T>
class casa::ImageFFT< T >