flaggedSourceSelector.py

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#
# LSST Data Management System
#
# Copyright 2008-2017  AURA/LSST.
#
# This product includes software developed by the
# LSST Project (http://www.lsst.org/).
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
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"""Select sources that have an existing flag field set."""
import lsst.pex.config
import lsst.afw.table
import lsst.pipe.base as pipeBase

from .sourceSelector import BaseSourceSelectorTask, sourceSelectorRegistry

__all__ = ["FlaggedSourceSelectorConfig", "FlaggedSourceSelectorTask"]


class FlaggedSourceSelectorConfig(BaseSourceSelectorTask.ConfigClass):
    field = lsst.pex.config.Field(
        dtype=str, default="calib_psf_used",
        doc="Name of a flag field that is True for Sources that should be used.",
    )


@lsst.pex.config.registerConfigurable("flagged", sourceSelectorRegistry)
class FlaggedSourceSelectorTask(BaseSourceSelectorTask):
    """
    A trivial SourceSelector that simply uses an existing flag field to filter
    a SourceCatalog.

    This is most frequently used in steps that occur after the a PSF model has
    been built, to allow other procedures that need Sources to use the set of
    Sources used to determine the PSF.

    Attributes
    ----------
    usesMatches : `bool`
        A boolean variable specify if the inherited source selector uses
        matches.
    """

    ConfigClass = FlaggedSourceSelectorConfig
    _DefaultName = "flagged"

    def selectSources(self, sourceCat, matches=None, exposure=None):
        """Return a bool array representing which sources to select from
        sourceCat.

        The input catalog must be contiguous in memory.

        Parameters
        ----------
        sourceCat : `lsst.afw.table.SourceCatalog`
            Catalog of sources to select from.
        matches : `list` of `lsst.afw.table.ReferenceMatch` or None
            Ignored in this SourceSelector.
        exposure : `lsst.afw.image.Exposure` or None
            The exposure the catalog was built from; used for debug display.

        Return
        ------
        struct : `lsst.pipe.base.Struct`
            The struct contains the following data:

            - selected : `array` of `bool`
                Boolean array of sources that were selected, same length as
                ``sourceCat``.
        """
        key = sourceCat.schema.find(self.config.field).key
        return pipeBase.Struct(selected=sourceCat.get(key))