DecorrelateALKernelSpatialTask¶

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

Bases: lsst.pipe.base.Task

Decorrelate the effect of convolution by Alard-Lupton matching kernel in image difference

Notes

Pipe-task that removes the neighboring-pixel covariance in an image difference that are added when the template image is convolved with the Alard-Lupton PSF matching kernel.

This task is a simple wrapper around @ref DecorrelateALKernelTask, which takes a spatiallyVarying parameter in its run method. If it is False, then it simply calls the run method of @ref DecorrelateALKernelTask. If it is True, then it uses the @ref ImageMapReduceTask framework to break the exposures into subExposures on a grid, and performs the run method of @ref DecorrelateALKernelTask on each subExposure. This enables it to account for spatially-varying PSFs and noise in the exposures when performing the decorrelation.

This task has no standalone example, however it is applied as a subtask of pipe.tasks.imageDifference.ImageDifferenceTask. There is also an example of its use in tests/testImageDecorrelation.py.

Methods Summary

`computeVarianceMean`(exposure)	Compute the mean of the variance plane of `exposure`.
`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.
`getTaskDict`()	Get a dictionary of all tasks as a shallow copy.
`makeField`(doc)	Make a `lsst.pex.config.ConfigurableField` for this task.
`makeSubtask`(name, **keyArgs)	Create a subtask as a new instance as the `name` attribute of this task.
`run`(scienceExposure, templateExposure, …)	Perform decorrelation of an image difference exposure.
`timer`(name, logLevel)	Context manager to log performance data for an arbitrary block of code.

Methods Documentation

computeVarianceMean(exposure)¶: Compute the mean of the variance plane of exposure.

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

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

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")

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.

run(scienceExposure, templateExposure, subtractedExposure, psfMatchingKernel, spatiallyVarying=True, preConvKernel=None, templateMatched=True, preConvMode=False)¶

Perform decorrelation of an image difference exposure.

Decorrelates the diffim due to the convolution of the templateExposure with the A&L psfMatchingKernel. If spatiallyVarying is True, it utilizes the spatially varying matching kernel via the imageMapReduce framework to perform spatially-varying decorrelation on a grid of subExposures.

Parameters:

scienceExposure : lsst.afw.image.Exposure: the science Exposure used for PSF matching
templateExposure : lsst.afw.image.Exposure: the template Exposure used for PSF matching
subtractedExposure : lsst.afw.image.Exposure: the subtracted Exposure produced by ip_diffim.ImagePsfMatchTask.subtractExposures()
psfMatchingKernel : an (optionally spatially-varying) PSF matching kernel produced: by ip_diffim.ImagePsfMatchTask.subtractExposures()
spatiallyVarying : bool: if True, perform the spatially-varying operation
preConvKernel : lsst.meas.algorithms.Psf: if not none, the scienceExposure has been pre-filtered with this kernel. (Currently this option is experimental.)
templateMatched : bool, optional: If True, the template exposure was matched (convolved) to the science exposure.
preConvMode : bool, optional: If True, subtractedExposure is assumed to be a likelihood difference image and will be noise corrected as a likelihood image.

Returns:

results : lsst.pipe.base.Struct: a structure containing: - correctedExposure : the decorrelated diffim

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.

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DecorrelateALKernelSpatialTask¶