propagateVisitFlags.py

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# This file is part of pipe_tasks.
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__all__ = ["PropagateVisitFlagsConfig", "PropagateVisitFlagsTask"]
import numpy
from lsst.pex.config import Config, Field, DictField
from lsst.pipe.base import Task
import lsst.geom as geom
import lsst.afw.table as afwTable
import lsst.pex.exceptions as pexExceptions
from deprecated.sphinx import deprecated
 
 
class PropagateVisitFlagsConfig(Config):
    """Configuration for propagating flags to coadd."""
 
    flags = DictField(keytype=str, itemtype=float,
                      default={"calib_psf_candidate": 0.2, "calib_psf_used": 0.2, "calib_psf_reserved": 0.2,
                               "calib_astrometry_used": 0.2, "calib_photometry_used": 0.2,
                               "calib_photometry_reserved": 0.2, },
                      doc=("Source catalog flags to propagate, with the threshold of relative occurrence "
                           "(valid range: [0-1], default is 0.2).  Coadd object will have flag set if the "
                           "fraction of input visits in which it is flagged is greater than the threshold."))
    matchRadius = Field(dtype=float, default=0.2, doc="Source matching radius (arcsec)")
    ccdName = Field(dtype=str, default='ccd', doc="Name of ccd to give to butler")
 
 
@deprecated(reason="This task has been replaced with PropagateSourceFlagsTask",
            version="v24.0", category=FutureWarning)
class PropagateVisitFlagsTask(Task):
    """Task to propagate flags from single-frame measurements to coadd measurements.
 
    Parameters
    ----------
    schema : `lsst.afw.table.Schema`
        The input schema for the reference source catalog, used to initialize
        the output schema.
    **kwargs
        Additional keyword arguments.
 
    Notes
    -----
    We want to be able to set a flag for sources on the coadds using flags
    that were determined from the individual visits.  A common example is sources
    that were used for PSF determination, since we do not do any PSF determination
    on the coadd but use the individual visits.  This requires matching the coadd
    source catalog to each of the catalogs from the inputs (see
    PropagateVisitFlagsConfig.matchRadius), and thresholding on the number of
    times a source is flagged on the input catalog.
 
    An important consideration in this is that the flagging of sources in the
    individual visits can be somewhat stochastic, e.g., the same stars may not
    always be used for PSF determination because the field of view moves slightly
    between visits, or the seeing changed.  We there threshold on the relative
    occurrence of the flag in the visits (see PropagateVisitFlagsConfig.flags).
    Flagging a source that is always flagged in inputs corresponds to a threshold
    of 1, while flagging a source that is flagged in any of the input corresponds
    to a threshold of 0.  But neither of these extrema are really useful in
    practise.
 
    Setting the threshold too high means that sources that are not consistently
    flagged (e.g., due to chip gaps) will not have the flag propagated.  Setting
    that threshold too low means that random sources which are falsely flagged in
    the inputs will start to dominate.  If in doubt, we suggest making this
    threshold relatively low, but not zero (e.g., 0.1 to 0.2 or so).  The more
    confidence in the quality of the flagging, the lower the threshold can be.
    The relative occurrence accounts for the edge of the field-of-view of the
    camera, but does not include chip gaps, bad or saturated pixels, etc.
 
    Initialization
 
    Beyond the usual Task initialization, PropagateVisitFlagsTask also requires
    a schema for the catalog that is being constructed.
 
    The 'run' method (described below) is the entry-point for operations.  The
    'getCcdInputs' staticmethod is provided as a convenience for retrieving the
    'ccdInputs' (CCD inputs table) from an Exposure.
 
    .. code-block :: none
 
        # Requires:
        # * butler: data butler, for retrieving the CCD catalogs
        # * coaddCatalog: catalog of source measurements on the coadd (lsst.afw.table.SourceCatalog)
        # * coaddExposure: coadd (lsst.afw.image.Exposure)
        from lsst.pipe.tasks.propagateVisitFlags import PropagateVisitFlagsTask, PropagateVisitFlagsConfig
        config = PropagateVisitFlagsConfig()
        config.flags["calib_psf_used"] = 0.3 # Relative threshold for this flag
        config.matchRadius = 0.5 # Matching radius in arcsec
        task = PropagateVisitFlagsTask(coaddCatalog.schema, config=config)
        ccdInputs = task.getCcdInputs(coaddExposure)
        task.run(butler, coaddCatalog, ccdInputs, coaddExposure.getWcs())
    """
 
    ConfigClass = PropagateVisitFlagsConfig
 
    def __init__(self, schema, **kwargs):
        Task.__init__(self, **kwargs)
        self.schema = schema
        self._keys = dict((f, self.schema.addField(f, type="Flag", doc="Propagated from visits")) for
                          f in self.config.flags)
 
    @staticmethod
    def getCcdInputs(coaddExposure):
        """Convenience method to retrieve the CCD inputs table from a coadd exposure.
 
        Parameters
        ----------
        coaddExposure : `lsst.afw.image.Exposure`
            The exposure we need to retrieve the CCD inputs table from.
 
        Returns
        -------
        ccdInputs : ``
            CCD inputs table from a coadd exposure.
        """
        return coaddExposure.getInfo().getCoaddInputs().ccds
 
    def run(self, butler, coaddSources, ccdInputs, coaddWcs, visitCatalogs=None, wcsUpdates=None):
        """Propagate flags from individual visit measurements to coadd.
 
        This requires matching the coadd source catalog to each of the catalogs
        from the inputs, and thresholding on the number of times a source is
        flagged on the input catalog.  The threshold is made on the relative
        occurrence of the flag in each source.  Flagging a source that is always
        flagged in inputs corresponds to a threshold of 1, while flagging a
        source that is flagged in any of the input corresponds to a threshold of
        0.  But neither of these extrema are really useful in practise.
 
        Setting the threshold too high means that sources that are not consistently
        flagged (e.g., due to chip gaps) will not have the flag propagated.  Setting
        that threshold too low means that random sources which are falsely flagged in
        the inputs will start to dominate.  If in doubt, we suggest making this threshold
        relatively low, but not zero (e.g., 0.1 to 0.2 or so).  The more confidence in
        the quality of the flagging, the lower the threshold can be.
 
        The relative occurrence accounts for the edge of the field-of-view of
        the camera, but does not include chip gaps, bad or saturated pixels, etc.
 
        Parameters
        ----------
        butler : `Unknown`
            Data butler, for retrieving the input source catalogs.
        coaddSources : `lsst.afw.image.SourceCatalog`
            Source catalog from the coadd.
        ccdInputs : `lsst.afw.table.ExposureCatalog`
            Table of CCDs that contribute to the coadd.
        coaddWcs : `lsst.afw.geom.SkyWcs`
            Wcs for coadd.
        visitCatalogs : `list` of `lsst.afw.image.SourceCatalog`, optional
            List of loaded source catalogs for each input ccd in
            the coadd. If provided this is used instead of this
            method loading in the catalogs itself.
        wcsUpdates : `list` of `lsst.afw.geom.SkyWcs`, optional
            If visitCatalogs is a list of ccd catalogs, this
            should be a list of updated wcs to apply.
 
        Raises
        ------
        ValueError
            Raised if any of the following occur:
            - A list of wcs updates for each catalog is not supplied in the wcsUpdates parameter
            and ccdInputs is a list of src catalogs.
            - The visitCatalogs and ccdInput parameters are both `None`.
        """
        if len(self.config.flags) == 0:
            return
 
        flags = self._keys.keys()
        counts = dict((f, numpy.zeros(len(coaddSources), dtype=int)) for f in flags)
        indices = numpy.array([s.getId() for s in coaddSources])  # Allowing for non-contiguous data
        radius = self.config.matchRadius*geom.arcseconds
 
        def processCcd(ccdSources, wcsUpdate):
            for sourceRecord in ccdSources:
                sourceRecord.updateCoord(wcsUpdate)
            for flag in flags:
                # We assume that the flags will be relatively rare, so it is more efficient to match
                # against a subset of the input catalog for each flag than it is to match once against
                # the entire catalog.  It would be best to have built a kd-tree on coaddSources and
                # keep reusing that for the matching, but we don't have a suitable implementation.
                mc = afwTable.MatchControl()
                mc.findOnlyClosest = False
                matches = afwTable.matchRaDec(coaddSources, ccdSources[ccdSources.get(flag)], radius, mc)
                for m in matches:
                    index = (numpy.where(indices == m.first.getId()))[0][0]
                    counts[flag][index] += 1
 
        if visitCatalogs is not None:
            if wcsUpdates is None:
                raise pexExceptions.ValueError("If ccdInputs is a list of src catalogs, a list of wcs"
                                               " updates for each catalog must be supplied in the "
                                               "wcsUpdates parameter")
            for i, ccdSource in enumerate(visitCatalogs):
                processCcd(ccdSource, wcsUpdates[i])
        else:
            if ccdInputs is None:
                raise pexExceptions.ValueError("The visitCatalogs and ccdInput parameters can't both be None")
            visitKey = ccdInputs.schema.find("visit").key
            ccdKey = ccdInputs.schema.find("ccd").key
 
            self.log.info("Propagating flags %s from inputs", flags)
 
            # Accumulate counts of flags being set
            for ccdRecord in ccdInputs:
                v = ccdRecord.get(visitKey)
                c = ccdRecord.get(ccdKey)
                dataId = {"visit": int(v), self.config.ccdName: int(c)}
                ccdSources = butler.get("src", dataId=dataId, immediate=True)
                processCcd(ccdSources, ccdRecord.getWcs())
 
        # Apply threshold
        for f in flags:
            key = self._keys[f]
            for s, num in zip(coaddSources, counts[f]):
                numOverlaps = len(ccdInputs.subsetContaining(s.getCentroid(), coaddWcs, True))
                s.setFlag(key, bool(num > numOverlaps*self.config.flags[f]))
            self.log.info("Propagated %d sources with flag %s", sum(s.get(key) for s in coaddSources), f)