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# 

# LSST Data Management System 

# Copyright 2008-2016 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/>. 

# 

 

__all__ = ["SnapPsfMatchConfigDF", "SnapPsfMatchConfigAL", "SnapPsfMatchConfig", "SnapPsfMatchTask"] 

 

import lsst.pex.config as pexConfig 

from .psfMatch import PsfMatchConfigDF, PsfMatchConfigAL 

from .imagePsfMatch import ImagePsfMatchTask, ImagePsfMatchConfig 

 

 

class SnapPsfMatchConfigDF(PsfMatchConfigDF): 

"""Delta-function Psf-matching config optimized for snap subtraction""" 

 

def setDefaults(self): 

PsfMatchConfigDF.setDefaults(self) 

 

# No regularization 

self.useRegularization = False 

 

# Pca 

self.usePcaForSpatialKernel = True 

self.subtractMeanForPca = True 

self.numPrincipalComponents = 5 

 

 

class SnapPsfMatchConfigAL(PsfMatchConfigAL): 

"""Sum-of-Gaussian (Alard-Lupton) Psf-matching config optimized for snap subtraction""" 

 

def setDefaults(self): 

PsfMatchConfigAL.setDefaults(self) 

 

# Simple basis set 

self.alardNGauss = 2 

self.alardDegGauss = (4, 2) 

self.alardSigGauss = (1.0, 2.5) 

 

 

class SnapPsfMatchConfig(ImagePsfMatchConfig): 

kernel = pexConfig.ConfigChoiceField( 

doc="kernel type", 

typemap=dict( 

AL=SnapPsfMatchConfigAL, 

DF=SnapPsfMatchConfigDF 

), 

default="AL", 

) 

 

doWarping = pexConfig.Field( 

dtype=bool, 

doc="Warp the snaps?", 

default=False 

) 

 

def setDefaults(self): 

ImagePsfMatchConfig.setDefaults(self) 

 

# No spatial variation in model 

self.kernel.active.spatialKernelOrder = 0 

 

# Don't fit for differential background 

self.kernel.active.fitForBackground = False 

 

# Small kernel size 

self.kernel.active.kernelSize = 7 

 

# With zero spatial order don't worry about spatial clipping 

self.kernel.active.spatialKernelClipping = False 

 

## @addtogroup LSST_task_documentation 

## @{ 

## @page SnapPsfMatchTask 

## @ref SnapPsfMatchTask_ "SnapPsfMatchTask" 

## @copybrief SnapPsfMatchTask 

## @} 

 

 

class SnapPsfMatchTask(ImagePsfMatchTask): 

"""! 

@anchor SnapPsfMatchTask_ 

 

@brief Image-based Psf-matching of two subsequent snaps from the same visit 

 

@section ip_diffim_snappsfmatch_Contents Contents 

 

- @ref ip_diffim_snappsfmatch_Purpose 

- @ref ip_diffim_snappsfmatch_Initialize 

- @ref ip_diffim_snappsfmatch_IO 

- @ref ip_diffim_snappsfmatch_Config 

- @ref ip_diffim_snappsfmatch_Metadata 

- @ref ip_diffim_snappsfmatch_Debug 

- @ref ip_diffim_snappsfmatch_Example 

 

#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 

 

@section ip_diffim_snappsfmatch_Purpose Description 

 

@copybrief SnapPsfMatchTask 

 

This Task differs from ImagePsfMatchTask in that it matches two Exposures assuming that the images have 

been acquired very closely in time. Under this assumption, the astrometric misalignments and/or 

relative distortions should be within a pixel, and the Psf-shapes should be very similar. As a 

consequence, the default configurations for this class assume a very simple solution. 

 

. The spatial variation in the kernel (SnapPsfMatchConfig.spatialKernelOrder) is assumed to be zero 

 

. With no spatial variation, we turn of the spatial clipping loops (SnapPsfMatchConfig.spatialKernelClipping) 

 

. The differential background is _not_ fit for (SnapPsfMatchConfig.fitForBackground) 

 

. The kernel is expected to be appx. a delta function, and has a small size (SnapPsfMatchConfig.kernelSize) 

 

The sub-configurations for the Alard-Lupton (SnapPsfMatchConfigAL) and delta-function (SnapPsfMatchConfigDF) 

bases also are designed to generate a small, simple kernel. 

 

#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 

 

@section ip_diffim_snappsfmatch_Initialize Task initialization 

 

Initialization is the same as base class ImagePsfMatch.__init__, with the difference being that the Task's 

ConfigClass is SnapPsfMatchConfig. 

 

#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 

 

@section ip_diffim_snappsfmatch_IO Invoking the Task 

 

The Task is only configured to have a subtractExposures method, which in turn calls 

ImagePsfMatchTask.subtractExposures. 

 

#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 

 

@section ip_diffim_snappsfmatch_Config Configuration parameters 

 

See @ref SnapPsfMatchConfig, which uses either @ref SnapPsfMatchConfigDF and @ref SnapPsfMatchConfigAL 

as its active configuration. 

 

#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 

 

@section ip_diffim_snappsfmatch_Metadata Quantities set in Metadata 

 

See @ref ip_diffim_psfmatch_Metadata "PsfMatchTask" 

 

#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 

 

@section ip_diffim_snappsfmatch_Debug Debug variables 

 

The @link lsst.pipe.base.cmdLineTask.CmdLineTask command line task@endlink interface supports a 

flag @c -d/--debug to import @b debug.py from your @c PYTHONPATH. The relevant contents of debug.py 

for this Task include: 

 

@code{.py} 

import sys 

import lsstDebug 

def DebugInfo(name): 

di = lsstDebug.getInfo(name) 

if name == "lsst.ip.diffim.psfMatch": 

di.display = True # enable debug output 

di.maskTransparency = 80 # ds9 mask transparency 

di.displayCandidates = True # show all the candidates and residuals 

di.displayKernelBasis = False # show kernel basis functions 

di.displayKernelMosaic = True # show kernel realized across the image 

di.plotKernelSpatialModel = False # show coefficients of spatial model 

di.showBadCandidates = True # show the bad candidates (red) along with good (green) 

elif name == "lsst.ip.diffim.imagePsfMatch": 

di.display = True # enable debug output 

di.maskTransparency = 30 # ds9 mask transparency 

di.displayTemplate = True # show full (remapped) template 

di.displaySciIm = True # show science image to match to 

di.displaySpatialCells = True # show spatial cells 

di.displayDiffIm = True # show difference image 

di.showBadCandidates = True # show the bad candidates (red) along with good (green) 

elif name == "lsst.ip.diffim.diaCatalogSourceSelector": 

di.display = False # enable debug output 

di.maskTransparency = 30 # ds9 mask transparency 

di.displayExposure = True # show exposure with candidates indicated 

di.pauseAtEnd = False # pause when done 

return di 

lsstDebug.Info = DebugInfo 

lsstDebug.frame = 1 

@endcode 

 

Note that if you want addional logging info, you may add to your scripts: 

@code{.py} 

import lsst.log.utils as logUtils 

logUtils.traceSetAt("ip.diffim", 4) 

@endcode 

 

#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 

 

@section ip_diffim_snappsfmatch_Example A complete example of using SnapPsfMatchTask 

 

This code is snapPsfMatchTask.py in the examples directory, and can be run as @em e.g. 

@code 

examples/snapPsfMatchTask.py 

examples/snapPsfMatchTask.py --debug 

examples/snapPsfMatchTask.py --debug --template /path/to/templateExp.fits --science /path/to/scienceExp.fits 

@endcode 

 

@dontinclude snapPsfMatchTask.py 

First, create a subclass of SnapPsfMatchTask that accepts two exposures. Ideally these exposures would have 

been taken back-to-back, such that the pointing/background/Psf does not vary substantially between the two: 

@skip MySnapPsfMatchTask 

@until return 

 

And allow the user the freedom to either run the script in default mode, or point to their own images on disk. 

Note that these images must be readable as an lsst.afw.image.Exposure: 

@skip main 

@until parse_args 

 

We have enabled some minor display debugging in this script via the --debug option. However, if you 

have an lsstDebug debug.py in your PYTHONPATH you will get additional debugging displays. The following 

block checks for this script: 

@skip args.debug 

@until sys.stderr 

 

 

@dontinclude snapPsfMatchTask.py 

Finally, we call a run method that we define below. First set up a Config and choose the basis set to use: 

@skip run(args) 

@until AL 

 

Make sure the images (if any) that were sent to the script exist on disk and are readable. If no images 

are sent, make some fake data up for the sake of this example script (have a look at the code if you want 

more details on generateFakeImages; as a detail of how the fake images were made, you do have to fit for a 

differential background): 

@skip requested 

@until sizeCellY 

 

Display the two images if --debug: 

@skip args.debug 

@until Science 

 

Create and run the Task: 

@skip Create 

@until result 

 

And finally provide optional debugging display of the Psf-matched (via the Psf models) science image: 

@skip args.debug 

@until result.subtractedExposure 

 

#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 

""" 

ConfigClass = SnapPsfMatchConfig 

 

# Override ImagePsfMatchTask.subtractExposures to set doWarping on config.doWarping 

def subtractExposures(self, templateExposure, scienceExposure, 

templateFwhmPix=None, scienceFwhmPix=None, 

candidateList=None): 

return ImagePsfMatchTask.subtractExposures(self, 

templateExposure=templateExposure, 

scienceExposure=scienceExposure, 

templateFwhmPix=templateFwhmPix, 

scienceFwhmPix=scienceFwhmPix, 

candidateList=candidateList, 

doWarping=self.config.doWarping, 

)