lsst::meas::base::BaseTransform Class Reference

Abstract base class for all C++ measurement transformations. More...

#include <Transform.h>

Inheritance diagram for lsst::meas::base::BaseTransform:

Public Member Functions
	BaseTransform (std::string const &name)
virtual	~BaseTransform ()
virtual void	operator() (afw::table::SourceCatalog const &inputCatalog, afw::table::BaseCatalog &outputCatalog, afw::geom::SkyWcs const &wcs, afw::image::PhotoCalib const &photoCalib) const =0

Protected Member Functions
void	checkCatalogSize (afw::table::BaseCatalog const &cat1, afw::table::BaseCatalog const &cat2) const
	Ensure that catalogs have the same size. More...

Protected Attributes
std::string	_name

Detailed Description

Abstract base class for all C++ measurement transformations.

Measurement plugins return results in raw, uncalibrated units (eg fluxes or positions in pixels). The transformation system provides a mechanism for post-processing those results into a calibrated form (magnitudes, celestial coordinates, etc).

A measurement transformation should derive from BaseTransform. It should implement a constructor which takes three arguments:

• A Control object describing the configuration of the measurement plugin.
• The name of the measurement plugin whose outputs are to be transformed (std::string);
• An lsst::afw::table::SchemaMapper which links the input and output catalogs;

The constructor should use the SchemaMapper to map fields from the input to output schemas and add additional keys to the output as required. For example:

class SillyTransform :
    public lsst::meas::base::BaseTransform
{
public:
    typedef SillyCentroidControl Control;

    SillyTransform(Control const & ctrl, std::string const & name, lsst::afw::table::SchemaMapper & mapper)
                   : BaseTransform(name), _ctrl(ctrl) {
        // Map these fields from the input to the output
        lsst::afw::table::Key<double> xkey = mapper.getInputSchema()[name + "_x"];
        lsst::afw::table::Key<double> ykey = mapper.getInputSchema()[name + "_y"];
        mapper.addMapping(xkey);
        mapper.addMapping(ykey);

        // Add these fields to the output schema to fill in later; the keys
        // are stored as members of this class
        _key_revX = mapper.editOutputSchema().addField<double>(name + "_reverse_x", "reversed X");
        _key_revY = mapper.editOutputSchema().addField<double>(name + "_reverse_y", "reversed Y");
    }

Derived classes should also implement operator() following the interface below. This will be called with a catalog containing the results of the measurement plugin and a catalog to be populated with transformed quantities, as well as WCS and calibration information. For example:

    virtual void operator()(lsst::afw::table::SourceCatalog const& inputCatalog,
                            lsst::afw::table::BaseCatalog& outputCatalog, lsst::afw::geom::SkyWcs const& wcs,
                            lsst::afw::image::PhotoCalib const& photoCalib) const {
        checkCatalogSize(inputCatalog, outputCatalog);
        lsst::afw::table::Key<double> xkey = inputCatalog.getSchema()[_name + "_x"];
        lsst::afw::table::Key<double> ykey = inputCatalog.getSchema()[_name + "_y"];
        lsst::afw::table::SourceCatalog::const_iterator inSrc = inputCatalog.begin();
        lsst::afw::table::BaseCatalog::iterator outSrc = outputCatalog.begin();
        for (; inSrc < inputCatalog.end() && outSrc < outputCatalog.end(); ++inSrc, ++outSrc) {
            // Store the "reversed" versions of the x and y positions in the
            // output catalog.
            outSrc->set(_key_revX, -1.0 * inSrc->get(xkey));
            outSrc->set(_key_revY, -1.0 * inSrc->get(ykey));
        }
    }  // operator()

Note that it is safe to assume that both catalogs passed to operator() are contiguous in memory. It is good practice to ensure that they are equal in size: this may be conveniently achieved by calling BaseTransform::checkCatalogSize().

operator() may throw LengthError if the transformation is impossible to complete. In this case, the contents of outputCatalog is not guaranteed.

Definition at line 86 of file Transform.h.

Constructor & Destructor Documentation

BaseTransform()

lsst::meas::base::BaseTransform::BaseTransform ( std::string const &  name )

inlineexplicit

Definition at line 88 of file Transform.h.

: _name(name) {}

~BaseTransform()

virtual lsst::meas::base::BaseTransform::~BaseTransform ( )

inlinevirtual

Definition at line 89 of file Transform.h.

{}

Member Function Documentation

checkCatalogSize()

void lsst::meas::base::BaseTransform::checkCatalogSize ( afw::table::BaseCatalog const &  cat1, afw::table::BaseCatalog const &  cat2  ) const

inlineprotected

Ensure that catalogs have the same size.

Parameters

[in]	cat1	Catalog for comparison
[in]	cat2	Catalog for comparison

Exceptions

LengthError

Catalog sizes do not match

Definition at line 102 of file Transform.h.

                                                                                                  {
        if (cat1.size() != cat2.size()) {
            throw LSST_EXCEPT(pex::exceptions::LengthError, "Catalog size mismatch");
        }
    }

operator()()

virtual void lsst::meas::base::BaseTransform::operator() ( afw::table::SourceCatalog const &  inputCatalog, afw::table::BaseCatalog &  outputCatalog, afw::geom::SkyWcs const &  wcs, afw::image::PhotoCalib const &  photoCalib  ) const

pure virtual

Implemented in lsst::meas::base::SdssShapeTransform, lsst::meas::base::ApertureFluxTransform, lsst::meas::base::FluxTransform, and lsst::meas::base::CentroidTransform.

Member Data Documentation

_name

std::string lsst::meas::base::BaseTransform::_name

protected

Definition at line 107 of file Transform.h.

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

• /j/snowflake/release/lsstsw/stack/Linux64/meas_base/17.0.1-7-g35889ee+1/include/lsst/meas/base/Transform.h