createMatchMetadata.py

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from __future__ import absolute_import, division, print_function

from lsst.daf.base import PropertyList
from lsst.afw.geom import Box2D
from lsst.afw.image.utils import getDistortedWcs

__all__ = ["MatchMetadata", "createMatchMetadata"]


class MatchMetadata(PropertyList):
    """Metadata required for unpersisting a match list"""

    def __init__(self, ctrCoord, radius, filterName):
        """!Ctor

        @param[in] ctrCoord: Coordinates of center (lsst.afw.coord.IcrsCoord)
        @param[in] radius: Minimum radius for selecting sources (lsst.afw.geom.Angle)
        @param[in] filterName: Name of filter (str) or None
        """
        PropertyList.__init__(self)
        ctrCoord = ctrCoord.toIcrs()
        self.add('RA', ctrCoord.getRa().asDegrees(), 'field center in degrees')
        self.add('DEC', ctrCoord.getDec().asDegrees(), 'field center in degrees')
        self.add('RADIUS', radius.asDegrees(), 'field radius in degrees, minimum')
        self.add('SMATCHV', 1, 'SourceMatchVector version number')
        self.add('FILTER', filterName or "UNKNOWN", 'filter name for photometric data')


def createMatchMetadata(exposure, border=0):
    """Create metadata required for unpersisting a match list

    @param[in] exposure  exposure for which to create metadata
    @param[in] border    number of pixels by which to grow the bbox in all directions

    @return metadata about the field (a daf_base PropertyList)
    """
    bboxd = Box2D(exposure.getBBox())
    bboxd.grow(border)
    wcs = getDistortedWcs(exposure.getInfo())
    ctrCoord = wcs.pixelToSky(bboxd.getCenter()).toIcrs()
    approxRadius = max(ctrCoord.angularSeparation(wcs.pixelToSky(pp).toIcrs()) for pp in bboxd.getCorners())
    return MatchMetadata(ctrCoord, approxRadius, exposure.getFilter().getName())