casa::ImageFFT Class Reference

FFT an image. More...

#include <ImageFFT.h>

Public Member Functions
	ImageFFT ()
	ImageFFT (const ImageFFT &other)
ImageFFT &	operator= (const ImageFFT &other)
	Assignment (reference semantics).
	~ImageFFT ()
void	fftsky (const ImageInterface< Float > &in)
	Do the FFT of the sky plane to the uv plane Masked pixels are set to zero before the FT.
void	fftsky (const ImageInterface< Complex > &in)
void	fft (const ImageInterface< Float > &in, const Vector< Bool > &axes)
	Do the FFT of the specified pixel axes (True to FT).
void	fft (const ImageInterface< Complex > &in, const Vector< Bool > &axes)
	Do the FFT of the specified pixel axes (True to FT).
void	getComplex (ImageInterface< Complex > &out) const
	Return the FFT (from the last call to fftsky or fft) in the desired form.
void	getReal (ImageInterface< Float > &out) const
void	getImaginary (ImageInterface< Float > &out) const
void	getAmplitude (ImageInterface< Float > &out) const
void	getPhase (ImageInterface< Float > &out) const
Private Member Functions
void	checkAxes (const CoordinateSystem &cSys, uInt ndim, const Vector< Bool > &axes)
	Check axes for multi-dim FFT.
void	copyMask (ImageInterface< Float > &out) const
	Copy the mask to the output.
void	copyMask (ImageInterface< Complex > &out) const
void	copyMask (ImageInterface< Float > &out, const ImageInterface< Float > &in) const
void	copyMask (ImageInterface< Float > &out, const ImageInterface< Complex > &in) const
void	copyMask (ImageInterface< Complex > &out, const ImageInterface< Float > &in) const
void	copyMask (ImageInterface< Complex > &out, const ImageInterface< Complex > &in) const
void	copyMiscellaneous (ImageInterface< Float > &out) const
	Copy MiscInfo, ImageInfo, Unit, logSInk to output.
void	copyMiscellaneous (ImageInterface< Complex > &out) const
void	_fftsky2 (ImageInterface< Complex > &out, const ImageInterface< Float > &in, const Vector< Int > &pixelAxes)
void	_fftsky2 (ImageInterface< Complex > &out, const ImageInterface< Complex > &in, const Vector< Int > &pixelAxes)
void	fft2 (ImageInterface< Complex > &out, const ImageInterface< Float > &in, const Vector< Bool > &axes)
	FFT (Float) given axes.
void	fft3 (ImageInterface< Complex > &out, const ImageInterface< Complex > &in, const Vector< Bool > &axes)
	FFT (Complex) given axes.
Bool	_findSky (Int &dC, Vector< Int > &pixelAxes, Vector< Int > &worldAxes, const CoordinateSystem &cSys, Bool throwIt)
	Find the sky axes in this CoordinateSystem.
void	_setSkyCoordinates (ImageInterface< Complex > &out, const CoordinateSystem &csys, const IPosition &shape, uInt dC)
	Overwrite the coordinate system with Fourier coordinates for sky axes only.
void	_setCoordinates (ImageInterface< Complex > &out, const CoordinateSystem &cSys, const Vector< Bool > &axes, const IPosition &shape)
	Overwrite the coordinate system with Fourier coordinates for all desginated axes.
Private Attributes
SPIIC	_tempImagePtr
SPIIF	_floatImage
SPIIC	_complexImage
Bool	_done

Detailed Description

FFT an image.

Intended use:

Public interface

Review Status

Date Reviewed:: yyyy/mm/dd

Prerequisite

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 (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
 
 IPosition shape(2, 10, 20);
 PagedImage<Float> im1(shape, CoordinateUtil::defaultCoords2D(), "im1");
 im1.set(1.0);
 
 // Create output images with masks if needed
 
 PagedImage<Float> r1(shape, CoordinateUtil::defaultCoords2D(), "real1");
 PagedImage<Float> i1(shape, CoordinateUtil::defaultCoords2D(), "imag1");
 if (im1.isMasked()) {
 LCPagedMask mask1 = LCPagedMask(RegionHandler::makeMask (r1, "mask0"));
 mask1.set(True);
 r1.defineRegion ("mask0", ImageRegion(mask1), RegionHandler::Masks);
 r1.setDefaultMask("mask0");
 LCPagedMask mask2 = LCPagedMask(RegionHandler::makeMask (i1, "mask0"));
 mask2.set(True);
 i1.defineRegion ("mask0", ImageRegion(mask1), 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 130 of file ImageFFT.h.

Constructor & Destructor Documentation

casa::ImageFFT::ImageFFT ( )

casa::ImageFFT::ImageFFT ( const ImageFFT & other )

casa::ImageFFT::~ImageFFT ( )

Member Function Documentation

void casa::ImageFFT::_fftsky2	(	ImageInterface< Complex > &	out,
		const ImageInterface< Complex > &	in,
		const Vector< Int > &	pixelAxes
	)			`[private]`

void casa::ImageFFT::_fftsky2	(	ImageInterface< Complex > &	out,
		const ImageInterface< Float > &	in,
		const Vector< Int > &	pixelAxes
	)			`[private]`

Bool casa::ImageFFT::_findSky	(	Int &	dC,
		Vector< Int > &	pixelAxes,
		Vector< Int > &	worldAxes,
		const CoordinateSystem &	cSys,
		Bool	throwIt
	)			`[private]`

Find the sky axes in this CoordinateSystem.

void casa::ImageFFT::_setCoordinates	(	ImageInterface< Complex > &	out,
		const CoordinateSystem &	cSys,
		const Vector< Bool > &	axes,
		const IPosition &	shape
	)			`[private]`

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

void casa::ImageFFT::_setSkyCoordinates	(	ImageInterface< Complex > &	out,
		const CoordinateSystem &	csys,
		const IPosition &	shape,
		uInt	dC
	)			`[private]`

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

void casa::ImageFFT::checkAxes	(	const CoordinateSystem &	cSys,
		uInt	ndim,
		const Vector< Bool > &	axes
	)			`[private]`

Check axes for multi-dim FFT.

void casa::ImageFFT::copyMask	(	ImageInterface< Complex > &	out,
		const ImageInterface< Complex > &	in
	)			const `[private]`

void casa::ImageFFT::copyMask	(	ImageInterface< Complex > &	out,
		const ImageInterface< Float > &	in
	)			const `[private]`

void casa::ImageFFT::copyMask	(	ImageInterface< Float > &	out,
		const ImageInterface< Complex > &	in
	)			const `[private]`

void casa::ImageFFT::copyMask	(	ImageInterface< Float > &	out,
		const ImageInterface< Float > &	in
	)			const `[private]`

void casa::ImageFFT::copyMask ( ImageInterface< Complex > & out ) const [private]

void casa::ImageFFT::copyMask ( ImageInterface< Float > & out ) const [private]

Copy the mask to the output.

void casa::ImageFFT::copyMiscellaneous ( ImageInterface< Complex > & out ) const [private]

void casa::ImageFFT::copyMiscellaneous ( ImageInterface< Float > & out ) const [private]

Copy MiscInfo, ImageInfo, Unit, logSInk to output.

void casa::ImageFFT::fft	(	const ImageInterface< Complex > &	in,
		const Vector< 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

void casa::ImageFFT::fft	(	const ImageInterface< Float > &	in,
		const Vector< 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

void casa::ImageFFT::fft2	(	ImageInterface< Complex > &	out,
		const ImageInterface< Float > &	in,
		const Vector< Bool > &	axes
	)			`[private]`

FFT (Float) given axes.

void casa::ImageFFT::fft3	(	ImageInterface< Complex > &	out,
		const ImageInterface< Complex > &	in,
		const Vector< Bool > &	axes
	)			`[private]`

FFT (Complex) given axes.

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

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

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

void casa::ImageFFT::getAmplitude ( ImageInterface< Float > & out ) const

void casa::ImageFFT::getComplex ( ImageInterface< Complex > & out ) const

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

The CoordinateSystem, MiscInfo, 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.

void casa::ImageFFT::getImaginary ( ImageInterface< Float > & out ) const