SubtractBackgroundTask

class lsst.meas.algorithms.SubtractBackgroundTask(config: Config | None = None, *, name: str | None = None, parentTask: Task | None = None, log: logging.Logger | lsst.utils.logging.LsstLogAdapter | None = None)

Bases: Task

Subtract the background from an exposure

Methods Summary

emptyMetadata()	Empty (clear) the metadata for this Task and all sub-Tasks.
fitBackground(maskedImage[, nx, ny, algorithm])	Estimate the background of a masked image
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(exposure[, background, stats, statsKeys])	Fit and subtract the background of an exposure.
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.

fitBackground(maskedImage, nx=0, ny=0, algorithm=None)

Estimate the background of a masked image

Parameters:

maskedImagelsst.afw.image.maskedImage

Masked image whose background is to be computed

nx‘int`

Number of x bands; if 0 compute from width and self.config.binSizeX

nyint

Number of y bands; if 0 compute from height and self.config.binSizeY

algorithmstr

Name of interpolation algorithm; if None use self.config.algorithm

Returns:

bglsst.afw.math.Background

A fit background

Raises:

RuntimeError

Raised if lsst.afw.math.makeBackground returns None, an indicator of failure.

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

getTaskDict() → dict[str, weakref.ReferenceType[lsst.pipe.base.task.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.

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")

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.

run(exposure, background=None, stats=True, statsKeys=None)

Fit and subtract the background of an exposure.

Parameters:

exposurelsst.afw.image.Exposure

Exposure whose background is to be subtracted.

backgroundlsst.afw.math.BackgroundList

Initial background model already subtracted. May be None if no background has been subtracted.

statsbool

If True then measure the mean and variance of the full background model and record the results in the exposure’s metadata.

statsKeystuple

Key names used to store the mean and variance of the background in the exposure’s metadata (another tuple); if None then use (“BGMEAN”, “BGVAR”); ignored if stats is false.

Returns:

backgroundlsst.afw.math.BackgroundLst

Full background model (initial model with changes), contained in an lsst.pipe.base.Struct.

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.

See also

lsst.utils.timer.logInfo

Examples

Creating a timer context:

with self.timer("someCodeToTime"):
    pass  # code to time