lsst::meas::base::SdssCentroidAlgorithm Class Reference

The Sdss Centroid Algorithm. More...

#include <SdssCentroid.h>

Inheritance diagram for lsst::meas::base::SdssCentroidAlgorithm:

Public Types
typedef SdssCentroidControl	Control
	A typedef to the Control object for this algorithm, defined above.

Public Member Functions
	SdssCentroidAlgorithm (Control const &ctrl, std::string const &name, afw::table::Schema &schema)
virtual void	measure (afw::table::SourceRecord &measRecord, afw::image::Exposure< float > const &exposure) const
	Called to measure a single child source in an image.
virtual void	fail (afw::table::SourceRecord &measRecord, MeasurementError *error=nullptr) const
	Handle an exception thrown by the current algorithm by setting flags in the given record.
void	measureForced (afw::table::SourceRecord &measRecord, afw::image::Exposure< float > const &exposure, afw::table::SourceRecord const &refRecord, afw::geom::SkyWcs const &refWcs) const override
	Called to measure a single child source in an image.
void	measureNForced (afw::table::SourceCatalog const &measCat, afw::image::Exposure< float > const &exposure, afw::table::SourceCatalog const &refRecord, afw::geom::SkyWcs const &refWcs) const override
	Called to simultaneously measure all children in a deblend family, in a single image.
virtual void	measureN (afw::table::SourceCatalog const &measCat, afw::image::Exposure< float > const &exposure) const
	Called to simultaneously measure all children in a deblend family, in a single image.
std::string	getLogName () const

Static Public Member Functions
static FlagDefinitionList const &	getFlagDefinitions ()

Static Public Attributes
static FlagDefinition const	FAILURE = flagDefinitions.addFailureFlag()
static FlagDefinition const	EDGE
static FlagDefinition const	NO_SECOND_DERIVATIVE
static FlagDefinition const	ALMOST_NO_SECOND_DERIVATIVE
static FlagDefinition const	NOT_AT_MAXIMUM
static FlagDefinition const	NEAR_EDGE

Protected Attributes
std::string	_logName

Detailed Description

The Sdss Centroid Algorithm.

Definition at line 71 of file SdssCentroid.h.

Member Typedef Documentation

Control

typedef SdssCentroidControl lsst::meas::base::SdssCentroidAlgorithm::Control

A typedef to the Control object for this algorithm, defined above.

The control object contains the configuration parameters for this algorithm.

Definition at line 84 of file SdssCentroid.h.

Constructor & Destructor Documentation

SdssCentroidAlgorithm()

lsst::meas::base::SdssCentroidAlgorithm::SdssCentroidAlgorithm	(	Control const &	ctrl,
		std::string const &	name,
		afw::table::Schema &	schema )

Definition at line 286 of file SdssCentroid.cc.

        : _ctrl(ctrl),
          _centroidKey(CentroidResultKey::addFields(schema, name, "centroid from Sdss Centroid algorithm",
                                                    SIGMA_ONLY)),
          _flagHandler(FlagHandler::addFields(schema, name, getFlagDefinitions())),
          _centroidExtractor(schema, name, true),
          _centroidChecker(schema, name, ctrl.doFootprintCheck, ctrl.maxDistToPeak) {}

Member Function Documentation

fail()

void lsst::meas::base::SdssCentroidAlgorithm::fail ( afw::table::SourceRecord & measRecord, MeasurementError * error = nullptr ) const

virtual

Handle an exception thrown by the current algorithm by setting flags in the given record.

fail() is called by the measurement framework when an exception is allowed to propagate out of one the algorithm's measure() methods. It should generally set both a general failure flag for the algorithm as well as a specific flag indicating the error condition, if possible. To aid in this, if the exception was an instance of MeasurementError, it will be passed in, carrying information about what flag to set.

An algorithm can also to chose to set flags within its own measure() methods, and then just return, rather than throw an exception. However, fail() should be implemented even when all known failure modes do not throw exceptions, to ensure that unexpected exceptions thrown in lower-level code are properly handled.

Implements lsst::meas::base::BaseAlgorithm.

Definition at line 417 of file SdssCentroid.cc.

                                                                                                {
    _flagHandler.handleFailure(measRecord, error);
}

getFlagDefinitions()

FlagDefinitionList const & lsst::meas::base::SdssCentroidAlgorithm::getFlagDefinitions ( )

static

Definition at line 55 of file SdssCentroid.cc.

{ return flagDefinitions; }

getLogName()

std::string lsst::meas::base::BaseAlgorithm::getLogName ( ) const

inlineinherited

Definition at line 66 of file Algorithm.h.

{ return _logName; }

measure()

void lsst::meas::base::SdssCentroidAlgorithm::measure ( afw::table::SourceRecord & measRecord, afw::image::Exposure< float > const & exposure ) const

virtual

Called to measure a single child source in an image.

Before this method is called, all neighbors will be replaced with noise, using the outputs of the deblender. Outputs should be saved in the given SourceRecord, which can also be used to obtain centroid (see SafeCentroidExtractor) and shape (see SafeShapeExtractor) information.

Implements lsst::meas::base::SingleFrameAlgorithm.

Definition at line 294 of file SdssCentroid.cc.

                                                                                   {
    // get our current best guess about the centroid: either a centroider measurement or peak.
    geom::Point2D center = _centroidExtractor(measRecord, _flagHandler);
    CentroidResult result;
    result.x = center.getX();
    result.y = center.getY();
    measRecord.set(_centroidKey, result);  // better than NaN
 
    typedef afw::image::Exposure<float>::MaskedImageT MaskedImageT;
    typedef MaskedImageT::Image ImageT;
    typedef MaskedImageT::Variance VarianceT;
    bool negative = false;
    try {
        negative = measRecord.get(measRecord.getSchema().find<afw::table::Flag>("is_negative").key);
    } catch (pexExcept::Exception &e) {
    }
 
    MaskedImageT const &mimage = exposure.getMaskedImage();
    ImageT const &image = *mimage.getImage();
    std::shared_ptr<afw::detection::Psf const> psf = exposure.getPsf();
 
    int const x = image.positionToIndex(center.getX(), afw::image::X).first;
    int const y = image.positionToIndex(center.getY(), afw::image::Y).first;
 
    if (!image.getBBox().contains(geom::Extent2I(x, y) + image.getXY0())) {
        _flagHandler.setValue(measRecord, EDGE.number, true);
        _flagHandler.setValue(measRecord, SdssCentroidAlgorithm::FAILURE.number, true);
        return;
    }
 
    // Algorithm uses a least-squares fit (implemented via a convolution) to a symmetrized PSF model.
    // If you don't have a Psf, you need to use another centroider, such as GaussianCentroider.
    if (!psf) {
        throw LSST_EXCEPT(FatalAlgorithmError, "SdssCentroid algorithm requires a Psf with every exposure");
    }
 
    int binX = 1;
    int binY = 1;
    double xc = 0., yc = 0., dxc = 0., dyc = 0.;  // estimated centre and error therein
    bool stopBinning = false;
    for (int binsize = 1; binsize <= _ctrl.binmax; binsize *= 2) {
        std::tuple<MaskedImageT, double, int> smoothResult =
            smoothAndBinImage(psf, x, y, mimage, binX, binY, _flagHandler);
        int errorFlag = std::get<2>(smoothResult);
        if (errorFlag == static_cast<int>(EDGE.number)) {
            psf = std::make_shared<afw::detection::GaussianPsf>(5, 5, 0.5);
            smoothResult = smoothAndBinImage(psf, x, y, mimage, binX, binY, _flagHandler);
            stopBinning = true;
            errorFlag = std::get<2>(smoothResult);
            if (errorFlag == 0) {
                errorFlag = NEAR_EDGE.number;
            }
        }
        if (errorFlag > 0) {
            _flagHandler.setValue(measRecord, errorFlag, true);
            _flagHandler.setValue(measRecord, SdssCentroidAlgorithm::FAILURE.number, true);
            // if NEAR_EDGE is not a fatal error we continue otherwise return
            if (errorFlag != static_cast<int>(NEAR_EDGE.number)) {
                return;
            }
        }
        MaskedImageT const smoothedImage = std::get<0>(smoothResult);
        double const smoothingSigma = std::get<1>(smoothResult);
 
        MaskedImageT::xy_locator mim =
                smoothedImage.xy_at(smoothedImage.getWidth() / 2, smoothedImage.getHeight() / 2);
 
        double sizeX2, sizeY2;  // object widths^2 in x and y directions
        double peakVal;         // peak intensity in image
 
        errorFlag = doMeasureCentroidImpl(&xc, &dxc, &yc, &dyc, &sizeX2, &sizeY2, &peakVal, mim, smoothingSigma, negative,
                                          _flagHandler);
        if (errorFlag > 0) {
            _flagHandler.setValue(measRecord, errorFlag, true);
            _flagHandler.setValue(measRecord, SdssCentroidAlgorithm::FAILURE.number, true);
            return;
        }
 
        if (binsize > 1) {
            // dilate from the lower left corner of central pixel
            xc = (xc + 0.5) * binX - 0.5;
            dxc *= binX;
            sizeX2 *= binX * binX;
 
            yc = (yc + 0.5) * binY - 0.5;
            dyc *= binY;
            sizeY2 *= binY * binY;
        }
 
        xc += x;  // xc, yc are measured relative to pixel (x, y)
        yc += y;
 
        if (stopBinning) {
            break;
        }
 
        double const fac = _ctrl.wfac * (1 + smoothingSigma * smoothingSigma);
        double const facX2 = fac * binX * binX;
        double const facY2 = fac * binY * binY;
 
        if (sizeX2 < facX2 && ::pow(xc - x, 2) < facX2 && sizeY2 < facY2 && ::pow(yc - y, 2) < facY2) {
            if (binsize > 1 || _ctrl.peakMin < 0.0 || peakVal > _ctrl.peakMin) {
                break;
            }
        }
 
        if (sizeX2 >= facX2 || ::pow(xc - x, 2) >= facX2) {
            binX *= 2;
        }
        if (sizeY2 >= facY2 || ::pow(yc - y, 2) >= facY2) {
            binY *= 2;
        }
    }
    result.x = afw::image::indexToPosition(xc + image.getX0());
    result.y = afw::image::indexToPosition(yc + image.getY0());
 
    result.xErr = sqrt(dxc * dxc);
    result.yErr = sqrt(dyc * dyc);
    measRecord.set(_centroidKey, result);
    _centroidChecker(measRecord);
}

measureForced()

void lsst::meas::base::SimpleAlgorithm::measureForced ( afw::table::SourceRecord & measRecord, afw::image::Exposure< float > const & exposure, afw::table::SourceRecord const & refRecord, afw::geom::SkyWcs const & refWcs ) const

inlineoverridevirtualinherited

Called to measure a single child source in an image.

Before this method is called, all neighbors will be replaced with noise, using the outputs of the deblender. Outputs should be saved in the given SourceRecord, which can also be used to obtain centroid (see SafeCentroidExtractor) and shape (see SafeShapeExtractor) information.

Implements lsst::meas::base::ForcedAlgorithm.

Reimplemented in lsst::meas::extensions::photometryKron::KronFluxAlgorithm.

Definition at line 172 of file Algorithm.h.

                                                                           {
        measure(measRecord, exposure);
    }

measureN()

void lsst::meas::base::SingleFrameAlgorithm::measureN ( afw::table::SourceCatalog const & measCat, afw::image::Exposure< float > const & exposure ) const

virtualinherited

Called to simultaneously measure all children in a deblend family, in a single image.

Outputs should be saved in the given SourceCatalog, which can also be used to obtain centroid (see SafeCentroidExtractor) and shape (see SafeShapeExtractor) information.

The default implementation simply throws an exception, indicating that simultaneous measurement is not supported.

Definition at line 31 of file Algorithm.cc.

                                                                                   {
    throw LSST_EXCEPT(pex::exceptions::LogicError, "measureN not implemented for this algorithm");
}

measureNForced()

void lsst::meas::base::SimpleAlgorithm::measureNForced ( afw::table::SourceCatalog const & measCat, afw::image::Exposure< float > const & exposure, afw::table::SourceCatalog const & refRecord, afw::geom::SkyWcs const & refWcs ) const

inlineoverridevirtualinherited

Called to simultaneously measure all children in a deblend family, in a single image.

Outputs should be saved in the given SourceCatalog, which can also be used to obtain centroid (see SafeCentroidExtractor) and shape (see SafeShapeExtractor) information.

The default implementation simply throws an exception, indicating that simultaneous measurement is not supported.

Reimplemented from lsst::meas::base::ForcedAlgorithm.

Definition at line 179 of file Algorithm.h.

                                                                            {
        measureN(measCat, exposure);
    }

Member Data Documentation

_logName

std::string lsst::meas::base::BaseAlgorithm::_logName

protectedinherited

Definition at line 69 of file Algorithm.h.

ALMOST_NO_SECOND_DERIVATIVE

FlagDefinition const lsst::meas::base::SdssCentroidAlgorithm::ALMOST_NO_SECOND_DERIVATIVE

static

Initial value:

=
        flagDefinitions.add("flag_almostNoSecondDerivative", "Almost vanishing second derivative")

Definition at line 78 of file SdssCentroid.h.

EDGE

FlagDefinition const lsst::meas::base::SdssCentroidAlgorithm::EDGE

static

Initial value:

=
        flagDefinitions.add("flag_edge", "Object too close to edge; peak used.")

Definition at line 76 of file SdssCentroid.h.

FAILURE

FlagDefinition const lsst::meas::base::SdssCentroidAlgorithm::FAILURE = flagDefinitions.addFailureFlag()

static

Definition at line 75 of file SdssCentroid.h.

NEAR_EDGE

FlagDefinition const lsst::meas::base::SdssCentroidAlgorithm::NEAR_EDGE

static

Initial value:

=
        flagDefinitions.add("flag_near_edge", "Object close to edge; fallback kernel used.")

Definition at line 80 of file SdssCentroid.h.

NO_SECOND_DERIVATIVE

FlagDefinition const lsst::meas::base::SdssCentroidAlgorithm::NO_SECOND_DERIVATIVE

static

Initial value:

=
        flagDefinitions.add("flag_noSecondDerivative", "Vanishing second derivative")

Definition at line 77 of file SdssCentroid.h.

NOT_AT_MAXIMUM

FlagDefinition const lsst::meas::base::SdssCentroidAlgorithm::NOT_AT_MAXIMUM

static

Initial value:

=
        flagDefinitions.add("flag_notAtMaximum", "Object is not at a maximum")

Definition at line 79 of file SdssCentroid.h.

---

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

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-10.0.0/Linux64/meas_base/g3fc7d4f5b9+a4d3a2d8bb/include/lsst/meas/base/SdssCentroid.h
• /j/snowflake/release/lsstsw/stack/lsst-scipipe-10.0.0/Linux64/meas_base/g3fc7d4f5b9+a4d3a2d8bb/src/SdssCentroid.cc