ImageDifferenceTask¶

Python API summary¶

from lsst.pipe.tasks.imageDifference import ImageDifferenceTask

classImageDifferenceTask(butler=None, **kwargs): Subtract an image from a template and measure the result...

attributeconfig: Access configuration fields and retargetable subtasks.

methodrun(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...

methodrunDataRef(sensorRef, templateIdList=None): Subtract an image from a template coadd and measure the result...

Retargetable subtasks¶

astrometer¶

Default: lsst.meas.astrom.astrometry.AstrometryTask
Field type: ConfigurableField

astrometry task; used to match sources to reference objects, but not to fit a WCS

decorrelate¶

Default: lsst.ip.diffim.imageDecorrelation.DecorrelateALKernelSpatialTask
Field type: ConfigurableField

Decorrelate effects of A&L kernel convolution on image difference, only if doSubtract is True. If this option is enabled, then detection.thresholdValue should be set to 5.0 (rather than the default of 5.5).

detection¶

Default: lsst.meas.algorithms.detection.SourceDetectionTask
Field type: ConfigurableField

Low-threshold detection for final measurement

evalLocCalib¶

Default: lsst.meas.base.evaluateLocalCalibration.EvaluateLocalCalibrationTask
Field type: ConfigurableField

Task to strip calibrations from an exposure and store their local values in the output DiaSource catalog.

forcedMeasurement¶

Default: lsst.meas.base.forcedMeasurement.ForcedMeasurementTask
Field type: ConfigurableField

Subtask to force photometer PVI at diaSource location.

getTemplate¶

Default: lsst.ip.diffim.getTemplate.GetCoaddAsTemplateTask
Field type: ConfigurableField

Subtask to retrieve template exposure and sources

measurement¶

Default: lsst.ip.diffim.dipoleFitTask.DipoleFitTask
Field type: ConfigurableField

Enable updated dipole fitting method

refObjLoader¶

Default: lsst.meas.algorithms.loadIndexedReferenceObjects.LoadIndexedReferenceObjectsTask
Field type: ConfigurableField

reference object loader

register¶

Default: lsst.pipe.tasks.registerImage.RegisterTask
Field type: ConfigurableField

Task to enable image-to-image image registration (warping)

scaleVariance¶

Default: lsst.pipe.tasks.scaleVariance.ScaleVarianceTask
Field type: ConfigurableField

Subtask to rescale the variance of the template to the statistically expected level

sourceSelector¶

Default: lsst.meas.algorithms.objectSizeStarSelector.ObjectSizeStarSelectorTask
Field type: ConfigurableField

Source selection algorithm

subtract¶

Default

'al'

Field type

Single-selection RegistryField

Choices

'al': lsst.ip.diffim.imagePsfMatch.ImagePsfMatchTask
'zogy': lsst.ip.diffim.zogy.ZogyImagePsfMatchTask

Subtraction Algorithm

Configuration fields¶

coaddName¶

Default: 'deep'
Field type: str Field

coadd name: typically one of deep, goodSeeing, or dcr

controlRandomSeed¶

Default: 10
Field type: int Field

Random seed for shuffing the control sample

controlStepSize¶

Default: 5
Field type: int Field

What step size (every Nth one) to select a control sample from the kernelSources

convolveTemplate¶

Default: True
Field type: bool Field

Which image gets convolved (default = template)

diaSourceMatchRadius¶

Default: 0.5
Field type: float Field

Match radius (in arcseconds) for DiaSource to Source association

doAddCalexpBackground¶

Default: False
Field type: bool Field

Add background to calexp before processing it. Useful as ipDiffim does background matching.

doAddMetrics¶

Default: True
Field type: bool Field

Add columns to the source table to hold analysis metrics?

doDebugRegister¶

Default: False
Field type: bool Field

Writing debugging data for doUseRegister

doDecorrelation¶

Default: False
Field type: bool Field

Perform diffim decorrelation to undo pixel correlation due to A&L kernel convolution? If True, also update the diffim PSF.

doDetection¶

Default: True
Field type: bool Field

Detect sources?

doDipoleFitting¶

Default: True
Field type: bool Field

Measure dipoles using new algorithm?

doEvalLocCalibration¶

Default: True
Field type: bool Field

Store calibration products (local wcs and photoCalib) in the output DiaSource catalog.

doForcedMeasurement¶

Default: True
Field type: bool Field

Force photometer diaSource locations on PVI?

doMatchSources¶

Default: True
Field type: bool Field

Match diaSources with input calexp sources and ref catalog sources

doMeasurement¶

Default: True
Field type: bool Field

Measure diaSources?

doMerge¶

Default: True
Field type: bool Field

Merge positive and negative diaSources with grow radius set by growFootprint

doPreConvolve¶

Default: True
Field type: bool Field

Convolve science image by its PSF before PSF-matching?

doScaleTemplateVariance¶

Default: False
Field type: bool Field

Scale variance of the template before PSF matching

doSelectDcrCatalog¶

Default: False
Field type: bool Field

Select stars of extreme color as part of the control sample

doSelectSources¶

Default: True
Field type: bool Field

Select stars to use for kernel fitting

doSelectVariableCatalog¶

Default: False
Field type: bool Field

Select stars that are variable to be part of the control sample

doSpatiallyVarying¶

Default: False
Field type: bool Field

If using Zogy or A&L decorrelation, perform these on a grid across the image in order to allow for spatial variations

doSubtract¶

Default: True
Field type: bool Field

Compute subtracted exposure?

doUseRegister¶

Default: True
Field type: bool Field

Use image-to-image registration to align template with science image

doWriteMatchedExp¶

Default: False
Field type: bool Field

Write warped and PSF-matched template coadd exposure?

doWriteSources¶

Default: True
Field type: bool Field

Write sources?

doWriteSubtractedExp¶

Default: True
Field type: bool Field

Write difference exposure?

growFootprint¶

Default: 2
Field type: int Field

Grow positive and negative footprints by this amount before merging

kernelSourcesFromRef¶

Default: False
Field type: bool Field

Select sources to measure kernel from reference catalog if True, template if false

templateSipOrder¶

Default: 2
Field type: int Field

Sip Order for fitting the Template Wcs (default is too high, overfitting)

useGaussianForPreConvolution¶

Default: True
Field type: bool Field

Use a simple gaussian PSF model for pre-convolution (else use fit PSF)? Ignored if doPreConvolve false.

Python API reference¶

lsst.pipe.tasks.imageDifference Module¶

Classes¶

`ImageDifferenceConfig`	Config for ImageDifferenceTask
`ImageDifferenceTask`([butler])	Subtract an image from a template and measure the result

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