A transform that maps intermediate world coordinates to pixel coordinates according to the SIP convention. More...

#include <SipTransform.h>

Inheritance diagram for lsst::meas::astrom::SipReverseTransform:

Public Member Functions
	SipReverseTransform (geom::Point2D const &pixelOrigin, geom::LinearTransform const &cdMatrix, PolynomialTransform const &reverseSipPoly)
	Construct a SipReverseTransform from its components. More...

	SipReverseTransform (SipReverseTransform const &other)=default

	SipReverseTransform (SipReverseTransform &&other)=default

SipReverseTransform &	operator= (SipReverseTransform const &other)=default

SipReverseTransform &	operator= (SipReverseTransform &&other)=default

void	swap (SipReverseTransform &other)

geom::AffineTransform	linearize (geom::Point2D const &in) const
	Return an approximate affine transform at the given point. More...

geom::Point2D	operator() (geom::Point2D const &xy) const
	Apply the transform to a point. More...

SipReverseTransform	transformPixels (geom::AffineTransform const &s) const
	Return a new reverse SIP transform that includes a transformation of the pixel coordinate system by the given affine transform. More...

geom::Point2D const &	getPixelOrigin () const
	Return the pixel origin (CRPIX, but zero-indexed) of the transform. More...

geom::LinearTransform const &	getCdMatrix () const
	Return the CD matrix of the transform. More...

PolynomialTransform const &	getPoly () const
	Return the polynomial component of the transform (A,B) or (AP,BP). More...

Static Public Member Functions
static SipReverseTransform	convert (PolynomialTransform const &poly, geom::Point2D const &pixelOrigin, geom::LinearTransform const &cdMatrix)
	Convert a PolynomialTransform to an equivalent SipReverseTransform. More...

static SipReverseTransform	convert (ScaledPolynomialTransform const &scaled, geom::Point2D const &pixelOrigin, geom::LinearTransform const &cdMatrix)
	Convert a ScaledPolynomialTransform to an equivalent SipReverseTransform. More...

static SipReverseTransform	convert (ScaledPolynomialTransform const &scaled)
	Convert a ScaledPolynomialTransform to an equivalent SipReverseTransform. More...

Protected Member Functions
void	swap (SipTransformBase &other)

void	transformPixelsInPlace (geom::AffineTransform const &s)

Protected Attributes
geom::Point2D	_pixelOrigin

geom::LinearTransform	_cdMatrix

PolynomialTransform	_poly

Friends
class	PolynomialTransform

class	ScaledPolynomialTransform

Detailed Description

A transform that maps intermediate world coordinates to pixel coordinates according to the SIP convention.

The SIP reverse transform is defined as

\[ \left[\begin{array}{ c } u \\ v \end{array}\right] = \left[\begin{array}{ c } u_0 + U + {\displaystyle\sum_{p,q}^{0 \le p + q \le N}} \mathrm{AP}_{p,q} U^p V^q \\ v_0 + V + {\displaystyle\sum_{p,q}^{0 \le p + q \le N}} \mathrm{BP}_{p,q} U^p V^q \\ \end{array}\right] \]

with

\[ \left[\begin{array}{ c } U \\ V \end{array}\right] = \mathbf{Z}^{-1} \left[\begin{array}{ c } x \\ y \end{array}\right] \]

and

\((u,v)\) are pixel coordinates.
\((x,y)\) are "intermediate world coordinates" – the result of applying the gnomonic (TAN) projection at sky origin CRVAL to sky coordinates).
\(\mathbf{Z}\) is the \(2 \times 2\) linear transform ( \(\mathrm{CD}\)) matrix.
\((u_0,v_0)\) is the pixel origin \(\mathrm{CRPIX}\) (but zero-indexed; the FITS standard is 1-indexed).
\(\mathrm{AP}\), \(\mathrm{BP}\) are the polynomial coefficients of the reverse transform.

SipForwardTransform instances should be confined to a single thread.

Definition at line 246 of file SipTransform.h.

Constructor & Destructor Documentation

◆ SipReverseTransform() [1/3]

lsst::meas::astrom::SipReverseTransform::SipReverseTransform	(	geom::Point2D const &	pixelOrigin,
		geom::LinearTransform const &	cdMatrix,
		PolynomialTransform const &	reverseSipPoly
	)

inline

Construct a SipReverseTransform from its components.

Parameters

[in]	pixelOrigin	CRPIX \((u_0,v_0)\) (zero-indexed)
[in]	cdMatrix	CD matrix \(Z\)
[in]	reverseSipPoly	Polynomial transform \((AP,BP)\)

Definition at line 285 of file SipTransform.h.

287 : SipTransformBase(pixelOrigin, cdMatrix, reverseSipPoly), _cdInverse(cdMatrix.inverted()) {}

lsst::meas::astrom::SipTransformBase::SipTransformBase

SipTransformBase(geom::Point2D const &pixelOrigin, geom::LinearTransform const &cdMatrix, PolynomialTransform const &poly)

Construct a SipTransformBase from its components.

Definition: SipTransform.h:76

◆ SipReverseTransform() [2/3]

lsst::meas::astrom::SipReverseTransform::SipReverseTransform ( SipReverseTransform const & other )

default

◆ SipReverseTransform() [3/3]

lsst::meas::astrom::SipReverseTransform::SipReverseTransform ( SipReverseTransform && other )

default

Member Function Documentation

◆ convert() [1/3]

SipReverseTransform lsst::meas::astrom::SipReverseTransform::convert	(	PolynomialTransform const &	poly,
		geom::Point2D const &	pixelOrigin,
		geom::LinearTransform const &	cdMatrix
	)

static

Convert a PolynomialTransform to an equivalent SipReverseTransform.

Parameters

[in]	poly	PolynomialTransform to convert.
[in]	pixelOrigin	CRPIX \((u_0,v_0)\) (zero-indexed)
[in]	cdMatrix	CD matrix \(Z\)

Definition at line 101 of file SipTransform.cc.

                                                                                       {
     auto reverseSipPoly = compose(geom::AffineTransform(-geom::Extent2D(pixelOrigin)),
                                   compose(poly, geom::AffineTransform(cdMatrix)));
     // Account for the terms outside the sum in the definition (see comment
     // earlier in the file for more explanation).
     reverseSipPoly._xCoeffs(1, 0) -= 1;
     reverseSipPoly._yCoeffs(0, 1) -= 1;
     return SipReverseTransform(pixelOrigin, cdMatrix, reverseSipPoly);
 }

◆ convert() [2/3]

SipReverseTransform lsst::meas::astrom::SipReverseTransform::convert ( ScaledPolynomialTransform const & scaled )

static

Convert a ScaledPolynomialTransform to an equivalent SipReverseTransform.

The pixel origin CRPIX and CD matrix are defined to reproduce the translation and linear transformation in the ScaledPolynomialTransforms output and input scalings (respectively).

Definition at line 126 of file SipTransform.cc.

                                                                                         {
     return convert(scaled, geom::Point2D(scaled.getOutputScalingInverse().getTranslation()),
                    scaled.getInputScaling().getLinear());
 }

◆ convert() [3/3]

SipReverseTransform lsst::meas::astrom::SipReverseTransform::convert	(	ScaledPolynomialTransform const &	scaled,
		geom::Point2D const &	pixelOrigin,
		geom::LinearTransform const &	cdMatrix
	)

static

Convert a ScaledPolynomialTransform to an equivalent SipReverseTransform.

Parameters

[in]	scaled	ScaledPolynomialTransform to convert.
[in]	pixelOrigin	CRPIX \((u_0,v_0)\) (zero-indexed)
[in]	cdMatrix	CD matrix \(Z\)

Definition at line 113 of file SipTransform.cc.

                                                                                       {
     auto reverseSipPoly =
             compose(geom::AffineTransform(-geom::Extent2D(pixelOrigin)) * scaled.getOutputScalingInverse(),
                     compose(scaled.getPoly(), scaled.getInputScaling() * geom::AffineTransform(cdMatrix)));
     // Account for the terms outside the sum in the definition (see comment
     // earlier in the file for more explanation).
     reverseSipPoly._xCoeffs(1, 0) -= 1;
     reverseSipPoly._yCoeffs(0, 1) -= 1;
     return SipReverseTransform(pixelOrigin, cdMatrix, reverseSipPoly);
 }

◆ getCdMatrix()

geom::LinearTransform const& lsst::meas::astrom::SipTransformBase::getCdMatrix ( ) const

inlineinherited

Return the CD matrix of the transform.

Definition at line 56 of file SipTransform.h.

56 { return _cdMatrix; }

lsst::meas::astrom::SipTransformBase::_cdMatrix

geom::LinearTransform _cdMatrix

Definition: SipTransform.h:94

◆ getPixelOrigin()

geom::Point2D const& lsst::meas::astrom::SipTransformBase::getPixelOrigin ( ) const

inlineinherited

Return the pixel origin (CRPIX, but zero-indexed) of the transform.

Definition at line 51 of file SipTransform.h.

51 { return _pixelOrigin; }

lsst::meas::astrom::SipTransformBase::_pixelOrigin

geom::Point2D _pixelOrigin

Definition: SipTransform.h:93

◆ getPoly()

PolynomialTransform const& lsst::meas::astrom::SipTransformBase::getPoly ( ) const

inlineinherited

Return the polynomial component of the transform (A,B) or (AP,BP).

Definition at line 61 of file SipTransform.h.

61 { return _poly; }

lsst::meas::astrom::SipTransformBase::_poly

PolynomialTransform _poly

Definition: SipTransform.h:95

◆ linearize()

geom::AffineTransform lsst::meas::astrom::SipReverseTransform::linearize ( geom::Point2D const & in ) const

Return an approximate affine transform at the given point.

Definition at line 138 of file SipTransform.cc.

                                                                               {
     return geom::AffineTransform(geom::Extent2D(getPixelOrigin())) *
            (geom::AffineTransform() + _poly.linearize(_cdInverse(in))) * _cdInverse;
 }

◆ operator()()

geom::Point2D lsst::meas::astrom::SipReverseTransform::operator() ( geom::Point2D const & xy ) const

Apply the transform to a point.

Definition at line 143 of file SipTransform.cc.

                                                                        {
     geom::Point2D UV = _cdInverse(xy);
     return geom::Extent2D(UV) + geom::Extent2D(getPixelOrigin()) + getPoly()(UV);
 }

◆ operator=() [1/2]

SipReverseTransform& lsst::meas::astrom::SipReverseTransform::operator= ( SipReverseTransform && other )

default

◆ operator=() [2/2]

SipReverseTransform& lsst::meas::astrom::SipReverseTransform::operator= ( SipReverseTransform const & other )

default

◆ swap() [1/2]

void lsst::meas::astrom::SipReverseTransform::swap ( SipReverseTransform & other )

inline

Definition at line 297 of file SipTransform.h.

                                           {
         SipTransformBase::swap(other);
         std::swap(_cdInverse, other._cdInverse);
     }

◆ swap() [2/2]

void lsst::meas::astrom::SipTransformBase::swap ( SipTransformBase & other )

inlineprotectedinherited

Definition at line 85 of file SipTransform.h.

                                        {
         std::swap(_pixelOrigin, other._pixelOrigin);
         std::swap(_cdMatrix, other._cdMatrix);
         _poly.swap(other._poly);
     }

◆ transformPixels()

SipReverseTransform lsst::meas::astrom::SipReverseTransform::transformPixels ( geom::AffineTransform const & s ) const

Return a new reverse SIP transform that includes a transformation of the pixel coordinate system by the given affine transform.

Definition at line 131 of file SipTransform.cc.

                                                                                            {
     SipReverseTransform result(*this);
     result.transformPixelsInPlace(s);
     result._cdInverse = result._cdMatrix.inverted();
     return result;
 }

◆ transformPixelsInPlace()

void lsst::meas::astrom::SipTransformBase::transformPixelsInPlace ( geom::AffineTransform const & s )

protectedinherited

Definition at line 40 of file SipTransform.cc.

                                                                           {
     // The implementation for transformPixels is identical for
     // SipForwardTransform and SipReverseTransform.  That's pretty obvious for
     // the pixel origin and CD matrix, which are the same in both cases, but
     // it wasn't obvious to me until I did the math that the polynomial
     // transforms are composed with the affine transform the same way.
     auto sInv = s.inverted();
     _pixelOrigin = s.getLinear()(_pixelOrigin - sInv.getTranslation());
     _cdMatrix = _cdMatrix * sInv.getLinear();
     _poly = compose(s.getLinear(), compose(getPoly(), sInv.getLinear()));
 }

Friends And Related Function Documentation

◆ PolynomialTransform

friend class PolynomialTransform

friend

Definition at line 319 of file SipTransform.h.

◆ ScaledPolynomialTransform

friend class ScaledPolynomialTransform

friend

Definition at line 320 of file SipTransform.h.

Member Data Documentation

◆ _cdMatrix

geom::LinearTransform lsst::meas::astrom::SipTransformBase::_cdMatrix

protectedinherited

Definition at line 94 of file SipTransform.h.

◆ _pixelOrigin

geom::Point2D lsst::meas::astrom::SipTransformBase::_pixelOrigin

protectedinherited

Definition at line 93 of file SipTransform.h.

◆ _poly

PolynomialTransform lsst::meas::astrom::SipTransformBase::_poly

protectedinherited

Definition at line 95 of file SipTransform.h.

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

/j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/meas_astrom/22.0.1-12-g44dc1dc+2a20fdde0d/include/lsst/meas/astrom/SipTransform.h
/j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/meas_astrom/22.0.1-12-g44dc1dc+2a20fdde0d/src/SipTransform.cc

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Friends

Detailed Description

Constructor & Destructor Documentation

◆ SipReverseTransform() [1/3]

◆ SipReverseTransform() [2/3]

◆ SipReverseTransform() [3/3]

Member Function Documentation

◆ convert() [1/3]

◆ convert() [2/3]

◆ convert() [3/3]

◆ getCdMatrix()

◆ getPixelOrigin()

◆ getPoly()

◆ linearize()

◆ operator()()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ swap() [1/2]

◆ swap() [2/2]

◆ transformPixels()

◆ transformPixelsInPlace()

Friends And Related Function Documentation

◆ PolynomialTransform

◆ ScaledPolynomialTransform

Member Data Documentation

◆ _cdMatrix

◆ _pixelOrigin

◆ _poly