lsst.meas.base.tests.BlendContext Class Reference

Public Member Functions
	__init__ (self, owner)
	__enter__ (self)
	addChild (self, instFlux, centroid, shape=None)
	__exit__ (self, type_, value, tb)

Public Attributes
	owner
	parentRecord
	parentImage
	children

Detailed Description

Context manager which adds multiple overlapping sources and a parent.

Notes
-----
This is used as the return value for `TestDataset.addBlend`, and this is
the only way it should be used.

Definition at line 44 of file tests.py.

Constructor & Destructor Documentation

__init__()

lsst.meas.base.tests.BlendContext.__init__	(		self,
			owner )

Definition at line 53 of file tests.py.

    def __init__(self, owner):
        self.owner = owner
        self.parentRecord = self.owner.catalog.addNew()
        self.parentImage = lsst.afw.image.ImageF(self.owner.exposure.getBBox())
        self.children = []
 

Member Function Documentation

__enter__()

lsst.meas.base.tests.BlendContext.__enter__

(

self

)

Definition at line 59 of file tests.py.

    def __enter__(self):
        # BlendContext is its own context manager, so we just return self.
        return self
 

__exit__()

lsst.meas.base.tests.BlendContext.__exit__	(		self,
			type_,
			value,
			tb )

Definition at line 80 of file tests.py.

    def __exit__(self, type_, value, tb):
        # We're not using the context manager for any kind of exception safety
        # or guarantees; we just want the nice "with" statement syntax.
 
        if type_ is not None:
            # exception was raised; just skip all this and let it propagate
            return
 
        # On exit, compute and set the truth values for the parent object.
        self.parentRecord.set(self.owner.keys["nChild"], len(self.children))
        # Compute instFlux from sum of component fluxes
        instFlux = 0.0
        for record, image in self.children:
            instFlux += record.get(self.owner.keys["instFlux"])
        self.parentRecord.set(self.owner.keys["instFlux"], instFlux)
        # Compute centroid from instFlux-weighted mean of component centroids
        x = 0.0
        y = 0.0
        for record, image in self.children:
            w = record.get(self.owner.keys["instFlux"])/instFlux
            x += record.get(self.owner.keys["centroid"].getX())*w
            y += record.get(self.owner.keys["centroid"].getY())*w
        self.parentRecord.set(self.owner.keys["centroid"], lsst.geom.Point2D(x, y))
        # Compute shape from instFlux-weighted mean of offset component shapes
        xx = 0.0
        yy = 0.0
        xy = 0.0
        for record, image in self.children:
            w = record.get(self.owner.keys["instFlux"])/instFlux
            dx = record.get(self.owner.keys["centroid"].getX()) - x
            dy = record.get(self.owner.keys["centroid"].getY()) - y
            xx += (record.get(self.owner.keys["shape"].getIxx()) + dx**2)*w
            yy += (record.get(self.owner.keys["shape"].getIyy()) + dy**2)*w
            xy += (record.get(self.owner.keys["shape"].getIxy()) + dx*dy)*w
        self.parentRecord.set(self.owner.keys["shape"], lsst.afw.geom.Quadrupole(xx, yy, xy))
        # Run detection on the parent image to get the parent Footprint.
        self.owner._installFootprint(self.parentRecord, self.parentImage)
        # Create perfect HeavyFootprints for all children; these will need to
        # be modified later to account for the noise we'll add to the image.
        deblend = lsst.afw.image.MaskedImageF(self.owner.exposure.maskedImage, True)
        for record, image in self.children:
            deblend.image.array[:, :] = image.array
            heavyFootprint = lsst.afw.detection.HeavyFootprintF(self.parentRecord.getFootprint(), deblend)
            record.setFootprint(heavyFootprint)
 
 

addChild()

lsst.meas.base.tests.BlendContext.addChild	(		self,
			instFlux,
			centroid,
			shape = None )

Add a child to the blend; return corresponding truth catalog record.

instFlux : `float`
    Total instFlux of the source to be added.
centroid : `lsst.geom.Point2D`
    Position of the source to be added.
shape : `lsst.afw.geom.Quadrupole`
    Second moments of the source before PSF convolution.  Note that
    the truth catalog records post-convolution moments)

Definition at line 63 of file tests.py.

    def addChild(self, instFlux, centroid, shape=None):
        """Add a child to the blend; return corresponding truth catalog record.
 
        instFlux : `float`
            Total instFlux of the source to be added.
        centroid : `lsst.geom.Point2D`
            Position of the source to be added.
        shape : `lsst.afw.geom.Quadrupole`
            Second moments of the source before PSF convolution.  Note that
            the truth catalog records post-convolution moments)
        """
        record, image = self.owner.addSource(instFlux, centroid, shape)
        record.set(self.owner.keys["parent"], self.parentRecord.getId())
        self.parentImage += image
        self.children.append((record, image))
        return record
 

Member Data Documentation

children

lsst.meas.base.tests.BlendContext.children

Definition at line 57 of file tests.py.

owner

lsst.meas.base.tests.BlendContext.owner

Definition at line 54 of file tests.py.

parentImage

lsst.meas.base.tests.BlendContext.parentImage

Definition at line 56 of file tests.py.

parentRecord

lsst.meas.base.tests.BlendContext.parentRecord

Definition at line 55 of file tests.py.

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The documentation for this class was generated from the following file:

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-8.0.0/Linux64/meas_base/g212a7c68fe+04a9158687/python/lsst/meas/base/tests.py