makeCoaddApCorrMap.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
# the Free Software Foundation, either version 3 of the License, or
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# This program is distributed in the hope that it will be useful,
# 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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# see <https://www.lsstcorp.org/LegalNotices/>.
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__all__ = ["makeCoaddApCorrMap", ]
 
from lsst.afw.image import ApCorrMap
from ._algorithmsLib import CoaddBoundedField, CoaddBoundedFieldElement
 
 
def makeCoaddApCorrMap(catalog, coaddBox, coaddWcs, weightFieldName="weight"):
    """Construct an ApCorrMap for a coadd
 
    Parameters
    ----------
    catalog: `lsst.afw.table.ExposureCatalog`
        A table of coadd inputs
    coaddBox : `lsst.geom.Box2I`
        Bounding box for coadd
    coaddWcs : `lsst.afw.geom.SkyWcs`
        Wcs for coadd
    weightFieldName : `str`
        Name of the weight field in the catalog
 
    Returns
    -------
    apCorrMap : `lsst.afw.image.ApCorrMap`
        Aperture corrections
    """
 
    # Assemble the BoundedFields for each type
    everything = {}  # name --> list of CoaddBoundedFieldElement
    weightKey = catalog.schema[weightFieldName].asKey()
    for row in catalog:
        apCorrMap = row.getApCorrMap()
        if not apCorrMap:
            continue
        weight = row.get(weightKey)
        wcs = row.getWcs()
        validPolygon = row.getValidPolygon()
        for name, bf in apCorrMap.items():
            if name not in everything:
                everything[name] = []
            everything[name].append(CoaddBoundedFieldElement(bf, wcs, validPolygon, weight))
 
    # Construct a CoaddBoundedField for each type
    apCorrMap = ApCorrMap()
    for name, elements in everything.items():
        apCorrMap.set(name, CoaddBoundedField(coaddBox, coaddWcs, elements))
 
    return apCorrMap