ImageDifferenceTask¶

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

Bases: lsst.pipe.base.CmdLineTask

Subtract an image from a template and measure the result

Attributes Summary

canMultiprocess

Methods Summary

`applyOverrides`(config)	A hook to allow a task to change the values of its config after the camera-specific overrides are loaded but before any command-line overrides are applied.
`emptyMetadata`()	Empty (clear) the metadata for this Task and all sub-Tasks.
`fitAstrometry`(templateSources, …)	Fit the relative astrometry between templateSources and selectSources
`getAllSchemaCatalogs`()	Get schema catalogs for all tasks in the hierarchy, combining the results into a single dict.
`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.
`getSchemaCatalogs`()	Return a dict of empty catalogs for each catalog dataset produced by 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.
`parseAndRun`([args, config, log, doReturnResults])	Parse an argument list and run the command.
`run`([exposure, selectSources, …])	PSF matches, subtract two images and perform detection on the difference image.
`runDataRef`(sensorRef[, templateIdList])	Subtract an image from a template coadd and measure the result.
`runDebug`(exposure, subtractRes, …)	Make debug plots and displays.
`timer`(name[, logLevel])	Context manager to log performance data for an arbitrary block of code.
`writeConfig`(butler[, clobber, doBackup])	Write the configuration used for processing the data, or check that an existing one is equal to the new one if present.
`writeMetadata`(dataRef)	Write the metadata produced from processing the data.
`writePackageVersions`(butler[, clobber, …])	Compare and write package versions.
`writeSchemas`(butler[, clobber, doBackup])	Write the schemas returned by `lsst.pipe.base.Task.getAllSchemaCatalogs`.

Attributes Documentation

canMultiprocess = True¶

Methods Documentation

classmethod applyOverrides(config)¶

A hook to allow a task to change the values of its config after the camera-specific overrides are loaded but before any command-line overrides are applied.

Parameters:	config : instance of task’s `ConfigClass` Task configuration.

Notes

This is necessary in some cases because the camera-specific overrides may retarget subtasks, wiping out changes made in ConfigClass.setDefaults. See LSST Trac ticket #2282 for more discussion.

Warning

This is called by CmdLineTask.parseAndRun; other ways of constructing a config will not apply these overrides.

emptyMetadata()¶: Empty (clear) the metadata for this Task and all sub-Tasks.

fitAstrometry(templateSources, templateExposure, selectSources)¶: Fit the relative astrometry between templateSources and selectSources

getAllSchemaCatalogs()¶

Get schema catalogs for all tasks in the hierarchy, combining the results into a single dict.

Returns:	schemacatalogs : `dict` Keys are butler dataset type, values are a empty catalog (an instance of the appropriate lsst.afw.table Catalog type) for all tasks in the hierarchy, from the top-level task down through all subtasks.

Notes

This method may be called on any task in the hierarchy; it will return the same answer, regardless.

The default implementation should always suffice. If your subtask uses schemas the override Task.getSchemaCatalogs, not this method.

getFullMetadata()¶

Get metadata for all tasks.

Returns:	metadata : `lsst.daf.base.PropertySet` The `PropertySet` 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()¶

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()¶

Get the name of the task.

Returns:	taskName : `str` Name of the task.

See also

getFullName

getSchemaCatalogs()¶: Return a dict of empty catalogs for each catalog dataset produced by this task.

getTaskDict()¶

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)¶

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("a brief description of what this task does")

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`

makeSubtask(name, **keyArgs)¶

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 pex_config ConfigurableField or RegistryField.

classmethod parseAndRun(args=None, config=None, log=None, doReturnResults=False)¶

Parse an argument list and run the command.

Parameters:

args : list, optional: List of command-line arguments; if None use sys.argv.
config : lsst.pex.config.Config-type, optional: Config for task. If None use Task.ConfigClass.
log : lsst.log.Log-type, optional: Log. If None use the default log.
doReturnResults : bool, optional: If True, return the results of this task. Default is False. This is only intended for unit tests and similar use. It can easily exhaust memory (if the task returns enough data and you call it enough times) and it will fail when using multiprocessing if the returned data cannot be pickled.

Returns:

struct : lsst.pipe.base.Struct

Fields are:

argumentParser: the argument parser (lsst.pipe.base.ArgumentParser).
parsedCmd: the parsed command returned by the argument parser’s parse_args method (argparse.Namespace).
taskRunner: the task runner used to run the task (an instance of Task.RunnerClass).
resultList: results returned by the task runner’s run method, one entry per invocation (list). This will typically be a list of Struct, each containing at least an exitStatus integer (0 or 1); see Task.RunnerClass (TaskRunner by default) for more details.

Notes

Calling this method with no arguments specified is the standard way to run a command-line task from the command-line. For an example see pipe_tasks bin/makeSkyMap.py or almost any other file in that directory.

If one or more of the dataIds fails then this routine will exit (with a status giving the number of failed dataIds) rather than returning this struct; this behaviour can be overridden by specifying the --noExit command-line option.

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. 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

subtractedExposure : lsst.afw.image.ExposureF: Difference image.
matchedExposure : lsst.afw.image.ExposureF: The matched PSF exposure.
subtractRes : lsst.pipe.base.Struct: The returned result structure of the ImagePsfMatchTask subtask.
diaSources : lsst.afw.table.SourceCatalog: The catalog of detected sources.
selectSources : lsst.afw.table.SourceCatalog: The input source catalog with optionally added Qa information.

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.

runDataRef(sensorRef, templateIdList=None)¶

Subtract an image from a template coadd and measure the result.

Data I/O wrapper around run using the butler in Gen2.

Parameters:

sensorRef : lsst.daf.persistence.ButlerDataRef

Sensor-level butler data reference, used for the following data products:

Input only: - calexp - psf - ccdExposureId - ccdExposureId_bits - self.config.coaddName + “Coadd_skyMap” - self.config.coaddName + “Coadd” Input or output, depending on config: - self.config.coaddName + “Diff_subtractedExp” Output, depending on config: - self.config.coaddName + “Diff_matchedExp” - self.config.coaddName + “Diff_src”

Returns:

results : lsst.pipe.base.Struct: Returns the Struct by run.

runDebug(exposure, subtractRes, selectSources, kernelSources, diaSources)¶: Make debug plots and displays.

timer(name, logLevel=10000)¶

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 `lsst.log` level constant.

Navigation

ImageDifferenceTask¶