lsst::meas::algorithms::PsfAttributes Class Reference

#include <PSF.h>

Public Types
enum	Method {   ADAPTIVE_MOMENT, FIRST_MOMENT, SECOND_MOMENT, NOISE_EQUIVALENT,   BICKERTON }

Public Member Functions
	PsfAttributes (boost::shared_ptr< lsst::afw::detection::Psf const > psf, int const iX, int const iY)
	Constructor for PsfAttributes. More...
	PsfAttributes (boost::shared_ptr< lsst::afw::detection::Psf const > psf, lsst::afw::geom::Point2I const &cen)
	Constructor for PsfAttributes. More...
double	computeGaussianWidth (Method how=ADAPTIVE_MOMENT) const
	Compute the 'sigma' value for an equivalent gaussian psf. More...
double	computeEffectiveArea () const
	Compute the effective area of the psf ( sum(I)^2/sum(I^2) ) More...

Private Attributes
boost::shared_ptr < lsst::afw::image::Image < double > >	_psfImage

Detailed Description

A class to contain various attributes of the Psf

• most notably, a width (1-D RMS size) to be used to make a single gaussian psf for fast convolution.

Deprecated:

This class is deprecated in favour of virtual methods on Psf

An example of the new API is:

* afwGeom::ellipses::Quadrupole shape = psf->computeShape();
* double const smoothingSigma = shape.getDeterminantRadius();
* 

Definition at line 66 of file PSF.h.

Member Enumeration Documentation

enum lsst::meas::algorithms::PsfAttributes::Method

Enumerator
ADAPTIVE_MOMENT	Calculate width using adaptive Gaussian weights.
FIRST_MOMENT	Calculate width using <r>
SECOND_MOMENT	Calculate width using <r^2>
NOISE_EQUIVALENT	Calculate width as sqrt(n_eff/(4 pi))
BICKERTON	Weight <r^2> by I^2 to avoid negative fluxes.

Definition at line 68 of file PSF.h.

                { ADAPTIVE_MOMENT,      
                  FIRST_MOMENT,         
                  SECOND_MOMENT,        
                  NOISE_EQUIVALENT,     
                  BICKERTON             
    };

Constructor & Destructor Documentation

lsst::meas::algorithms::PsfAttributes::PsfAttributes	(	boost::shared_ptr< lsst::afw::detection::Psf const >	psf,
		int const	iX,
		int const	iY
	)

Constructor for PsfAttributes.

Parameters

psf	The psf whose attributes we want
iX	the x position in the frame we want the attributes at
iY	the y position in the frame we want the attributes at

Definition at line 57 of file PsfAttributes.cc.

{
    // N.b. (iX, iY) are ints so that we know this image is centered in the central pixel of _psfImage
    _psfImage = psf->computeImage(afwGeom::PointD(iX, iY));
}

lsst::meas::algorithms::PsfAttributes::PsfAttributes	(	boost::shared_ptr< lsst::afw::detection::Psf const >	psf,
		lsst::afw::geom::Point2I const &	cen
	)

Constructor for PsfAttributes.

Parameters

psf	The psf whose attributes we want
cen	the position in the frame we want the attributes at

Definition at line 70 of file PsfAttributes.cc.

                              :
    // N.b. cen is a PointI so that we know this image is centered in the central pixel of _psfImage
    _psfImage(psf->computeImage(afwGeom::PointD(cen)))
{
}

Member Function Documentation

double lsst::meas::algorithms::PsfAttributes::computeEffectiveArea

(

)

const

Compute the effective area of the psf ( sum(I)^2/sum(I^2) )

Definition at line 360 of file PsfAttributes.cc.

                                                 {
    
    double sum = 0.0;
    double sumsqr = 0.0;
    for (int iY = 0; iY != _psfImage->getHeight(); ++iY) {
        afwImage::Image<double>::x_iterator end = _psfImage->row_end(iY);
        for (afwImage::Image<double>::x_iterator ptr = _psfImage->row_begin(iY); ptr != end; ++ptr) {
            sum += *ptr;
            sumsqr += (*ptr)*(*ptr);
        }
    }
    return sum*sum/sumsqr;
}

double lsst::meas::algorithms::PsfAttributes::computeGaussianWidth

(

PsfAttributes::Method

how = ADAPTIVE_MOMENT

)

const

Compute the 'sigma' value for an equivalent gaussian psf.

Definition at line 297 of file PsfAttributes.cc.

                                                                        {
    /*
     * Estimate the PSF's center.  This *really* needs to be rewritten to avoid using MeasureSources;
     * we shouldn't need to instantiate source objects just to measure an adaptive centroid!
     */
    afwImage::MaskedImage<double> mi = afwImage::MaskedImage<double>(_psfImage);
    typedef afwImage::Exposure<double> Exposure;
    Exposure::Ptr exposure = makeExposure(mi);

    afwDetection::Footprint::Ptr foot = boost::make_shared<afwDetection::Footprint>(exposure->getBBox(
        afwImage::LOCAL));

    GaussianCentroidControl ctrl;
    afwGeom::Point2D center(_psfImage->getX0() + _psfImage->getWidth()/2, 
                            _psfImage->getY0() + _psfImage->getHeight()/2);
    afw::table::Schema schema = afw::table::SourceTable::makeMinimalSchema();
    MeasureSources ms = MeasureSourcesBuilder().addAlgorithm(ctrl).build(schema);
    PTR(afw::table::SourceTable) table = afw::table::SourceTable::make(schema);
    PTR(afw::table::SourceRecord) source = table->makeRecord();
    source->setFootprint(foot);
    ms.apply(*source, *exposure, center);
    afw::table::Centroid::MeasKey key = table->getSchema()[ctrl.name];
    afw::table::Centroid::MeasValue centroid = source->get(key);
    float const xCen = centroid.getX() - _psfImage->getX0();
    float const yCen = centroid.getY() - _psfImage->getY0();

    switch (how) {
      case ADAPTIVE_MOMENT:
        return ::sqrt(0.5*computeSecondMomentAdaptive(_psfImage, xCen, yCen));
      case FIRST_MOMENT:
          return ::sqrt(2.0/afwGeom::PI)*computeFirstMoment(_psfImage, xCen, yCen);
      case SECOND_MOMENT:
        return ::sqrt(0.5*computeSecondMoment(_psfImage, xCen, yCen));
      case NOISE_EQUIVALENT:
        return ::sqrt(computeEffectiveArea()/(4*afwGeom::PI));
      case BICKERTON:
        {
            double sum = 0.0;
            double norm = 0.0;
            for (int iY = 0; iY != _psfImage->getHeight(); ++iY) {
                int iX = 0;
                for (afwImage::Image<double>::x_iterator ptr = _psfImage->row_begin(iY),
                                                         end = _psfImage->row_end(iY); ptr != end;
                     ++ptr, ++iX) {
                    double const x = iX - xCen;
                    double const y = iY - yCen;
                    double const r = std::sqrt( x*x + y*y );
                    double const m = (*ptr)*r;
                    norm += (*ptr)*(*ptr);
                    sum += m*m;
                }
            }
            return sqrt(sum/norm);
        }
      default:
        abort();
    }
}

Member Data Documentation

boost::shared_ptr< lsst::afw::image::Image<double> > lsst::meas::algorithms::PsfAttributes::_psfImage

private

Definition at line 82 of file PSF.h.

---

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

• /lsst/home/lsstsw/stack/Linux64/meas_algorithms/master-g7bce1f4e06+57/include/lsst/meas/algorithms/PSF.h
• /lsst/home/lsstsw/stack/Linux64/meas_algorithms/master-g7bce1f4e06+57/src/PsfAttributes.cc