ImageDifferenceTask¶

class lsst.pipe.tasks.imageDifference.ImageDifferenceTask(butler=None, **kwargs)¶

Bases: lsst.pipe.base.PipelineTask

Subtract an image from a template and measure the result.

Parameters:	butler : `lsst.daf.butler.Butler` or `None`, optional Butler object to use in constructing reference object loaders. kwargs Additional keyword arguments. .. deprecated:: v24.0** This Task has been replaced with lsst.ip.diffim.subtractImages and lsst.ip.diffim.detectAndMeasure. Will be removed after v25.

Attributes Summary

canMultiprocess

Methods Summary

`checkTemplateIsSufficient`(templateExposure)	Raise NoWorkFound if template coverage < requiredTemplateFraction.
`emptyMetadata`()	Empty (clear) the metadata for this Task and all sub-Tasks.
`fitAstrometry`(templateSources, …)	Fit the relative astrometry between templateSources and selectSources
`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.
`getResourceConfig`()	Return resource configuration for this task.
`getTaskDict`()	Get a dictionary of all tasks as a shallow copy.
`makeField`(doc)	Make a `lsst.pex.config.ConfigurableField` for this task.
`makeIdFactory`(expId, expBits)	Create IdFactory instance for unique 64 bit diaSource id-s.
`makeSubtask`(name, **keyArgs)	Create a subtask as a new instance as the `name` attribute of this task.
`prepareCalibratedExposure`(exposure[, …])	Prepare a calibrated exposure and apply finalized psf if so configured.
`run`([exposure, selectSources, …])	PSF matches, subtract two images and perform detection on the difference image.
`runDebug`(exposure, subtractRes, …)	Make debug plots and displays.
`runQuantum`(butlerQC, inputRefs, outputRefs)	Method to do butler IO and or transforms to provide in memory objects for tasks run method
`timer`(name, logLevel)	Context manager to log performance data for an arbitrary block of code.

Attributes Documentation

canMultiprocess = True¶

Methods Documentation

checkTemplateIsSufficient(templateExposure)¶

Raise NoWorkFound if template coverage < requiredTemplateFraction.

Parameters:	templateExposure : `lsst.afw.image.ExposureF` The template exposure to check.
Raises:	NoWorkFound Raised if fraction of good pixels, defined as not having NO_DATA set, is less then the configured requiredTemplateFraction.

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

fitAstrometry(templateSources, templateExposure, selectSources)¶

Fit the relative astrometry between templateSources and selectSources

Notes

TODO: Remove this method. It originally fit a new WCS to the template before calling register.run because our TAN-SIP fitter behaved badly for points far from CRPIX, but that’s been fixed. It remains because a subtask overrides it.

getFullMetadata() → lsst.pipe.base._task_metadata.TaskMetadata¶

Get metadata for all tasks.

Returns:	metadata : `TaskMetadata` 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:	fullName : `str` 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:	taskName : `str` Name of the task.

See also

getFullName

getResourceConfig() → Optional[ResourceConfig]¶

Return resource configuration for this task.

Returns:	Object of type `ResourceConfig` or `None` if resource configuration is not defined for this task.

getTaskDict() → Dict[str, weakref.ReferenceType[lsst.pipe.base.task.Task]]¶

Get a dictionary of all tasks as a shallow copy.

Returns:	taskDict : `dict` Dictionary containing full task name: task object for the top-level task and all subtasks, sub-subtasks, etc.

classmethod makeField(doc: str) → lsst.pex.config.configurableField.ConfigurableField¶

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

Parameters:	doc : `str` Help text for the field.
Returns:	configurableField : `lsst.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")

static makeIdFactory(expId, expBits)¶

Create IdFactory instance for unique 64 bit diaSource id-s.

Parameters:	expId : `int` Exposure ID. expBits : `int` Number of used bits in `expId`.
Returns:	idFactory : `lsst.afw.table.IdFactory` Generator object to assign ids to detected sources in the difference image.

Notes

The diasource id-s consists of the expId stored fixed in the highest value expBits of the 64-bit integer plus (bitwise or) a generated sequence number in the low value end of the integer.

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

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

Parameters:	name : `str` 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.

prepareCalibratedExposure(exposure, finalizedPsfApCorrCatalog=None)¶

Prepare a calibrated exposure and apply finalized psf if so configured.

Parameters:	exposure : `lsst.afw.image.exposure.Exposure` Input exposure to adjust calibrations. finalizedPsfApCorrCatalog : `lsst.afw.table.ExposureCatalog`, optional Exposure catalog with finalized psf models and aperture correction maps to be applied if config.doApplyFinalizedPsf=True. Catalog uses the detector id for the catalog id, sorted on id for fast lookup.
Returns:	exposure : `lsst.afw.image.exposure.Exposure` Exposure with adjusted calibrations.

run(exposure=None, selectSources=None, templateExposure=None, templateSources=None, idFactory=None, calexpBackgroundExposure=None, subtractedExposure=None)¶

PSF matches, subtract two images and perform detection on the difference image.

Parameters:

exposure : lsst.afw.image.ExposureF, optional: The science exposure, the minuend in the image subtraction. Can be None only if config.doSubtract==False.
selectSources : lsst.afw.table.SourceCatalog, optional: Identified sources on the science exposure. This catalog is used to select sources in order to perform the AL PSF matching on stamp images around them. The selection steps depend on config options and whether templateSources and matchingSources specified.
templateExposure : lsst.afw.image.ExposureF, optional: The template to be subtracted from exposure in the image subtraction. templateExposure is modified in place if config.doScaleTemplateVariance==True. The template exposure should cover the same sky area as the science exposure. It is either a stich of patches of a coadd skymap image or a calexp of the same pointing as the science exposure. Can be None only if config.doSubtract==False and subtractedExposure is not None.
templateSources : lsst.afw.table.SourceCatalog, optional: Identified sources on the template exposure.
idFactory : lsst.afw.table.IdFactory: Generator object to assign ids to detected sources in the difference image.
calexpBackgroundExposure : lsst.afw.image.ExposureF, optional: Background exposure to be added back to the science exposure if config.doAddCalexpBackground==True.
subtractedExposure : lsst.afw.image.ExposureF, optional: If config.doSubtract==False and config.doDetection==True, performs the post subtraction source detection only on this exposure. Otherwise should be None.

Returns:

results : lsst.pipe.base.Struct

Results as a struct with attributes:

subtractedExposure: Difference image (lsst.afw.image.ExposureF).
scoreExposure: The zogy score exposure, if calculated (lsst.afw.image.ExposureF or None).
matchedExposure: The matched PSF exposure (lsst.afw.image.ExposureF).
subtractRes: The returned result structure of the ImagePsfMatchTask subtask (lsst.pipe.base.Struct).
diaSources: The catalog of detected sources (lsst.afw.table.SourceCatalog).
selectSources: The input source catalog with optionally added Qa information (lsst.afw.table.SourceCatalog).

Notes

The following major steps are included:

warp template coadd to match WCS of image
PSF match image to warped template
subtract image from PSF-matched, warped template
detect sources
measure sources

For details about the image subtraction configuration modes see lsst.ip.diffim.

runDebug(exposure, subtractRes, selectSources, kernelSources, diaSources)¶

Make debug plots and displays.

Parameters:	exposure : `lsst.afw.image.exposure.Exposure` Input exposure. subtractRes : `lsst.pipe.base.Struct` Returned result structure of the ImagePsfMatchTask subtask. selectSources : `lsst.afw.table.SourceCatalog` Input source catalog. kernelSources : `lsst.afw.table.SourceCatalog` unknown diaSources : `lsst.afw.table.SourceCatalog` The catalog of detected sources.

Notes

TODO: Test and update for current debug display and slot names.

runQuantum(butlerQC: lsst.pipe.base.butlerQuantumContext.ButlerQuantumContext, inputRefs: lsst.pipe.base.connections.InputQuantizedConnection, outputRefs: lsst.pipe.base.connections.OutputQuantizedConnection)¶

Method to do butler IO and or transforms to provide in memory objects for tasks run method

Parameters:

butlerQC : ButlerQuantumContext: A butler which is specialized to operate in the context of a lsst.daf.butler.Quantum.
inputRefs : InputQuantizedConnection: Datastructure whose attribute names are the names that identify connections defined in corresponding PipelineTaskConnections class. The values of these attributes are the lsst.daf.butler.DatasetRef objects associated with the defined input/prerequisite connections.
outputRefs : OutputQuantizedConnection: Datastructure whose attribute names are the names that identify connections defined in corresponding PipelineTaskConnections class. The values of these attributes are the lsst.daf.butler.DatasetRef objects associated with the defined output connections.

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

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

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

Navigation

ImageDifferenceTask¶