coadd.py

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# 
# LSST Data Management System
# Copyright 2008, 2009, 2010 LSST Corporation.
# 
# 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
# (at your option) any later version.
# 
# 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.
# 
# You should have received a copy of the LSST License Statement and 
# the GNU General Public License along with this program.  If not, 
# see <http://www.lsstcorp.org/LegalNotices/>.
#
import lsst.pex.logging as pexLog
import lsst.coadd.utils as coaddUtils
import chisquaredLib

__all__ = ["Coadd"]

class Coadd(coaddUtils.Coadd):
    def __init__(self, bbox, wcs, badMaskPlanes, logName="coadd.chisquared.Coadd"):
        """Create a chi-squared coadd
        
        Inputs:
        @param[in] bbox: bounding box of coadd Exposure with respect to parent (afwGeom.Box2I):
            coadd dimensions = bbox.getDimensions(); xy0 = bbox.getMin()
        @param[in] wcs: WCS of coadd exposure (lsst.afw.math.Wcs)
        @param[in] badMaskPlanes: mask planes to pay attention to when rejecting masked pixels.
            Specify as a collection of names.
            badMaskPlanes should always include "EDGE".
        @param[in] logName: name by which messages are logged
        """
        coaddUtils.Coadd.__init__(self,
            bbox = bbox,
            wcs = wcs,
            badMaskPlanes = badMaskPlanes,
            logName = logName,
        )

    def addExposure(self, exposure, weightFactor=1.0):
        """Add a an exposure to the coadd; it is assumed to have the same WCS as the coadd

        Inputs:
        @param[in] exposure: Exposure to add to coadd; this must be:
            - background-subtracted or background-matched to the other images being coadded
            - psf-matched to the desired PSF model (optional)
            - warped to match the coadd
        @param[in] weightFactor: weight with which to add exposure to coadd

        @return
        - overlapBBox: region of overlap between exposure and coadd in parent coordinates (afwGeom.Box2I)
        - weight: weight with which exposure was added to coadd; weight = weightFactor for this kind of coadd
        """
        self._log.log(pexLog.Log.INFO, "add exposure to coadd")

        # save filter info
        filter = exposure.getFilter()
        self._filterDict.setdefault(filter.getName(), filter)

        overlapBBox = chisquaredLib.addToCoadd(self._coadd.getMaskedImage(), self._weightMap,
            exposure.getMaskedImage(), self._badPixelMask, weightFactor)

        return overlapBBox, weightFactor