ZogyImagePsfMatchTask¶

class lsst.ip.diffim.ZogyImagePsfMatchTask(*args, **kwargs)¶

Bases: ImagePsfMatchTask

Task to perform Zogy PSF matching and image subtraction.

This class inherits from ImagePsfMatchTask to contain the _warper subtask and related methods.

Methods Summary

`emptyMetadata`()	Empty (clear) the metadata for this Task and all sub-Tasks.
`getFullMetadata`()	Get metadata for all tasks.
`getFullName`()	Get the task name as a hierarchical name including parent task names.
`getName`()	Get the name of the task.
`getSelectSources`(exposure[, sigma, ...])	Get sources to use for Psf-matching.
`getTaskDict`()	Get a dictionary of all tasks as a shallow copy.
`makeCandidateList`(templateExposure, ...[, ...])	Make a list of acceptable KernelCandidates.
`makeField`(doc)	Make a `lsst.pex.config.ConfigurableField` for this task.
`makeKernelBasisList`([targetFwhmPix, ...])	Wrapper to set log messages for `lsst.ip.diffim.makeKernelBasisList`.
`makeSubtask`(name, **keyArgs)	Create a subtask as a new instance as the `name` attribute of this task.
`matchExposures`(templateExposure, scienceExposure)	Warp and PSF-match an exposure to the reference.
`matchMaskedImages`(templateMaskedImage, ...)	PSF-match a MaskedImage (templateMaskedImage) to a reference MaskedImage (scienceMaskedImage).
`run`(scienceExposure, templateExposure[, ...])	Register, PSF-match, and subtract two Exposures, `scienceExposure - templateExposure` using the ZOGY algorithm.
`subtractExposures`(templateExposure, ...)	Register, Psf-match and subtract two Exposures.
`subtractMaskedImages`(templateExposure, ...)	Psf-match and subtract two MaskedImages.
`timer`(name[, logLevel])	Context manager to log performance data for an arbitrary block of code.

Methods Documentation

emptyMetadata() → None¶: Empty (clear) the metadata for this Task and all sub-Tasks.

getFullMetadata() → TaskMetadata¶

Get metadata for all tasks.

Returns:

metadataTaskMetadata: The keys are the full task name. Values are metadata for the top-level task and all subtasks, sub-subtasks, etc.

Notes

The returned metadata includes timing information (if @timer.timeMethod is used) and any metadata set by the task. The name of each item consists of the full task name with . replaced by :, followed by . and the name of the item, e.g.:

topLevelTaskName:subtaskName:subsubtaskName.itemName

using : in the full task name disambiguates the rare situation that a task has a subtask and a metadata item with the same name.

getFullName() → str¶

Get the task name as a hierarchical name including parent task names.

Returns:

fullNamestr

The full name consists of the name of the parent task and each subtask separated by periods. For example:

The full name of top-level task “top” is simply “top”.
The full name of subtask “sub” of top-level task “top” is “top.sub”.
The full name of subtask “sub2” of subtask “sub” of top-level task “top” is “top.sub.sub2”.

getName() → str¶

Get the name of the task.

Returns:

taskNamestr: Name of the task.

See also

getFullName

getSelectSources(exposure, sigma=None, doSmooth=True, idFactory=None)¶

Get sources to use for Psf-matching.

This method runs detection and measurement on an exposure. The returned set of sources will be used as candidates for Psf-matching.

Parameters:

exposurelsst.afw.image.Exposure: Exposure on which to run detection/measurement
sigmafloat: Detection threshold
doSmoothbool: Whether or not to smooth the Exposure with Psf before detection
idFactory: Factory for the generation of Source ids

Returns:

selectSources: source catalog containing candidates for the Psf-matching

getTaskDict() → Dict[str, ReferenceType[Task]]¶

Get a dictionary of all tasks as a shallow copy.

Returns:

taskDictdict: Dictionary containing full task name: task object for the top-level task and all subtasks, sub-subtasks, etc.

makeCandidateList(templateExposure, scienceExposure, kernelSize, candidateList=None)¶

Make a list of acceptable KernelCandidates.

Accept or generate a list of candidate sources for Psf-matching, and examine the Mask planes in both of the images for indications of bad pixels

Parameters:

templateExposurelsst.afw.image.Exposure: Exposure that will be convolved
scienceExposurelsst.afw.image.Exposure: Exposure that will be matched-to
kernelSizefloat: Dimensions of the Psf-matching Kernel, used to grow detection footprints
candidateListlist, optional: List of Sources to examine. Elements must be of type afw.table.Source or a type that wraps a Source and has a getSource() method, such as meas.algorithms.PsfCandidateF.

Returns:

candidateListlist of dict: A list of dicts having a “source” and “footprint” field for the Sources deemed to be appropriate for Psf matching

classmethod makeField(doc: str) → ConfigurableField¶

Make a lsst.pex.config.ConfigurableField for this task.

Parameters:

docstr: Help text for the field.

Returns:

configurableFieldlsst.pex.config.ConfigurableField: A ConfigurableField for this task.

Examples

Provides a convenient way to specify this task is a subtask of another task.

Here is an example of use:

class OtherTaskConfig(lsst.pex.config.Config):
    aSubtask = ATaskClass.makeField("brief description of task")

makeKernelBasisList(targetFwhmPix=None, referenceFwhmPix=None, basisDegGauss=None, basisSigmaGauss=None, metadata=None)¶

Wrapper to set log messages for lsst.ip.diffim.makeKernelBasisList.

Parameters:

targetFwhmPixfloat, optional: Passed on to lsst.ip.diffim.generateAlardLuptonBasisList. Not used for delta function basis sets.
referenceFwhmPixfloat, optional: Passed on to lsst.ip.diffim.generateAlardLuptonBasisList. Not used for delta function basis sets.
basisDegGausslist of int, optional: Passed on to lsst.ip.diffim.generateAlardLuptonBasisList. Not used for delta function basis sets.
basisSigmaGausslist of int, optional: Passed on to lsst.ip.diffim.generateAlardLuptonBasisList. Not used for delta function basis sets.
metadatalsst.daf.base.PropertySet, optional: Passed on to lsst.ip.diffim.generateAlardLuptonBasisList. Not used for delta function basis sets.

Returns:

basisList: list of lsst.afw.math.kernel.FixedKernel: List of basis kernels.

makeSubtask(name: str, **keyArgs: Any) → None¶

Create a subtask as a new instance as the name attribute of this task.

Parameters:

namestr

Brief name of the subtask.

keyArgs

Extra keyword arguments used to construct the task. The following arguments are automatically provided and cannot be overridden:

“config”.
“parentTask”.

Notes

The subtask must be defined by Task.config.name, an instance of ConfigurableField or RegistryField.

matchExposures(templateExposure, scienceExposure, templateFwhmPix=None, scienceFwhmPix=None, candidateList=None, doWarping=True, convolveTemplate=True)¶

Warp and PSF-match an exposure to the reference.

Do the following, in order:

Warp templateExposure to match scienceExposure,
if doWarping True and their WCSs do not already match
Determine a PSF matching kernel and differential background model
that matches templateExposure to scienceExposure
Convolve templateExposure by PSF matching kernel

Parameters:

templateExposurelsst.afw.image.Exposure

Exposure to warp and PSF-match to the reference masked image

scienceExposurelsst.afw.image.Exposure

Exposure whose WCS and PSF are to be matched to

templateFwhmPix :`float`

FWHM (in pixels) of the Psf in the template image (image to convolve)

scienceFwhmPixfloat

FWHM (in pixels) of the Psf in the science image

candidateListlist, optional

a list of footprints/maskedImages for kernel candidates; if None then source detection is run.

Currently supported: list of Footprints or measAlg.PsfCandidateF

doWarpingbool

what to do if templateExposure and scienceExposure WCSs do not match:

if True then warp templateExposure to match scienceExposure
if False then raise an Exception

convolveTemplatebool

Whether to convolve the template image or the science image:

if True, templateExposure is warped if doWarping, templateExposure is convolved
if False, templateExposure is warped if doWarping, scienceExposure is convolved

Returns:

resultslsst.pipe.base.Struct

An lsst.pipe.base.Struct containing these fields:

matchedImagethe PSF-matched exposure =
Warped templateExposure convolved by psfMatchingKernel. This has:
- the same parent bbox, Wcs and PhotoCalib as scienceExposure
- the same filter as templateExposure
- no Psf (because the PSF-matching process does not compute one)
psfMatchingKernel : the PSF matching kernel
backgroundModel : differential background model
kernelCellSet : SpatialCellSet used to solve for the PSF matching kernel

Raises:

RuntimeError: Raised if doWarping is False and templateExposure and scienceExposure WCSs do not match

matchMaskedImages(templateMaskedImage, scienceMaskedImage, candidateList, templateFwhmPix=None, scienceFwhmPix=None)¶

PSF-match a MaskedImage (templateMaskedImage) to a reference MaskedImage (scienceMaskedImage).

Do the following, in order:

Determine a PSF matching kernel and differential background model
that matches templateMaskedImage to scienceMaskedImage
Convolve templateMaskedImage by the PSF matching kernel

Parameters:

templateMaskedImagelsst.afw.image.MaskedImage

masked image to PSF-match to the reference masked image; must be warped to match the reference masked image

scienceMaskedImagelsst.afw.image.MaskedImage

maskedImage whose PSF is to be matched to

templateFwhmPixfloat

FWHM (in pixels) of the Psf in the template image (image to convolve)

scienceFwhmPixfloat

FWHM (in pixels) of the Psf in the science image

candidateListlist, optional

A list of footprints/maskedImages for kernel candidates; if None then source detection is run.

Currently supported: list of Footprints or measAlg.PsfCandidateF

Returns:

resultcallable
An lsst.pipe.base.Struct containing these fields:

psfMatchedMaskedImage: the PSF-matched masked image =
templateMaskedImage convolved with psfMatchingKernel. This has the same xy0, dimensions and wcs as scienceMaskedImage.
psfMatchingKernel: the PSF matching kernel
backgroundModel: differential background model
kernelCellSet: SpatialCellSet used to solve for the PSF matching kernel

Raises:

RuntimeError: Raised if input images have different dimensions

run(scienceExposure, templateExposure, doWarping=True)¶

Register, PSF-match, and subtract two Exposures, scienceExposure - templateExposure using the ZOGY algorithm.

Parameters:

templateExposurelsst.afw.image.Exposure: exposure to be warped to scienceExposure.
scienceExposurelsst.afw.image.Exposure: reference Exposure.
doWarpingbool: what to do if templateExposure’s and scienceExposure’s WCSs do not match: - if True then warp templateExposure to match scienceExposure - if False then raise an Exception

Returns:

resultslsst.pipe.base.Struct containing these fields:

subtractedExposure: lsst.afw.image.Exposure
The subtraction result.
warpedExposure: lsst.afw.image.Exposure or None
templateExposure after warping to match scienceExposure

Notes

Do the following, in order:

Warp templateExposure to match scienceExposure, if their WCSs do not already match
Compute subtracted exposure ZOGY image subtraction algorithm on the two exposures

This is the new entry point of the task as of DM-25115.

subtractExposures(templateExposure, scienceExposure, *args)¶

Register, Psf-match and subtract two Exposures.

Do the following, in order:

Warp templateExposure to match scienceExposure, if their WCSs do not already match
Determine a PSF matching kernel and differential background model
that matches templateExposure to scienceExposure
PSF-match templateExposure to scienceExposure
Compute subtracted exposure (see return values for equation).

Parameters:

templateExposurelsst.afw.image.ExposureF

Exposure to PSF-match to scienceExposure

scienceExposurelsst.afw.image.ExposureF

Reference Exposure

templateFwhmPixfloat

FWHM (in pixels) of the Psf in the template image (image to convolve)

scienceFwhmPixfloat

FWHM (in pixels) of the Psf in the science image

candidateListlist, optional

A list of footprints/maskedImages for kernel candidates; if None then source detection is run.

Currently supported: list of Footprints or measAlg.PsfCandidateF

doWarpingbool

What to do if templateExposure` and scienceExposure WCSs do not match:

if True then warp templateExposure to match scienceExposure
if False then raise an Exception

convolveTemplatebool

Convolve the template image or the science image

if True, templateExposure is warped if doWarping, templateExposure is convolved
if False, templateExposure is warped if doWarping, scienceExposure is convolved

Returns:

resultlsst.pipe.base.Struct

An lsst.pipe.base.Struct containing these fields:

subtractedExposuresubtracted Exposure
scienceExposure - (matchedImage + backgroundModel)
matchedImagetemplateExposure after warping to match
templateExposure (if doWarping true), and convolving with psfMatchingKernel
psfMatchingKernel : PSF matching kernel
backgroundModel : differential background model
kernelCellSet : SpatialCellSet used to determine PSF matching kernel

subtractMaskedImages(templateExposure, scienceExposure, *args)¶

Psf-match and subtract two MaskedImages.

Do the following, in order:

PSF-match templateMaskedImage to scienceMaskedImage
Determine the differential background
Return the difference: scienceMaskedImage
((warped templateMaskedImage convolved with psfMatchingKernel) + backgroundModel)

Parameters:

templateMaskedImagelsst.afw.image.MaskedImage

MaskedImage to PSF-match to scienceMaskedImage

scienceMaskedImagelsst.afw.image.MaskedImage

Reference MaskedImage

templateFwhmPixfloat

FWHM (in pixels) of the Psf in the template image (image to convolve)

scienceFwhmPixfloat

FWHM (in pixels) of the Psf in the science image

candidateListlist, optional

A list of footprints/maskedImages for kernel candidates; if None then source detection is run.

Currently supported: list of Footprints or measAlg.PsfCandidateF

Returns:

resultslsst.pipe.base.Struct

An lsst.pipe.base.Struct containing these fields:

subtractedMaskedImage : scienceMaskedImage - (matchedImage + backgroundModel)
matchedImage : templateMaskedImage convolved with psfMatchingKernel
psfMatchingKernel` : PSF matching kernel
backgroundModel : differential background model
kernelCellSet : SpatialCellSet used to determine PSF matching kernel

timer(name: str, logLevel: int = 10) → Iterator[None]¶

Context manager to log performance data for an arbitrary block of code.

Parameters:

namestr: Name of code being timed; data will be logged using item name: Start and End.
logLevel: A logging level constant.

Navigation

ZogyImagePsfMatchTask¶