lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask Class Reference

Inheritance diagram for lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask:

Public Member Functions
def	__init__ (self, config, *display=None, **kwargs)
def	run (self, exp, *donutDiameter=None, doDisplay=False)

Static Public Member Functions
def	detectObjectsInExp (exp, nSigma, nPixMin, grow=0)
def	checkResult (exp, centroid, srcNum, percentile)

Public Attributes
	display
	centroidName
	shapeName
	schema
	control
	centroider
	sdssShape
	shaper
	apFluxControl
	apFluxer
	table
	plateScale

Static Public Attributes
	ConfigClass = QuickFrameMeasurementTaskConfig

Detailed Description

WARNING: An experimental new task with changable API! Do not rely on yet!

This task finds the centroid of the brightest source in a given CCD-image
and returns its centroid and a rough estimate of the seeing/PSF.

It is designed for speed, such that it can be used in observing scripts
to provide pointing offsets, allowing subsequent pointings to place
a source at an exact pixel position.

The approach taken here is deliberately sub-optimal in the detection and
measurement sense, with all optimisation being done for speed and robustness
of the result.

A small set of unit tests exist for this task, which run automatically
if afwdata is setup. These, however, are stricky unit tests, and will not
catch algorithmic regressions. TODO: DM-29038 exists to merge a regression
real test which runs against 1,000 LATISS images, but is therefore slow
and requires access to the data.

Parameters
----------
config : `lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTaskConfig`
    Configuration class for the QuickFrameMeasurementTask.
display : `lsst.afw.display.Display`, optional
    The display to use for showing the images, detections and centroids.

Returns
-------
result : `lsst.pipe.base.Struct`
    Return strucure containing whether the task was successful, the main
    source's centroid, its the aperture fluxes, the ixx and iyy of the
    source, and the median ixx, iyy of the detections in the exposure.
    See run() method for further details.

Raises
------
This task should *never* raise, as the run() method is enclosed in an
except Exception block, so that it will never fail during observing.
Failure modes should be limited to returning a return Struct() with the same
structure as the success case, with all value set to np.nan but with
result.success=False.

Definition at line 96 of file quickFrameMeasurement.py.

Constructor & Destructor Documentation

__init__()

def lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.__init__	(		self,
			config,
		*	display = None,
		**	kwargs
	)

Definition at line 142 of file quickFrameMeasurement.py.

    def __init__(self, config, *, display=None, **kwargs):
        super().__init__(config=config, **kwargs)
        self.makeSubtask("installPsf")
 
        self.display = None
        if display:
            self.display = display
 
        self.centroidName = "base_SdssCentroid"
        self.shapeName = "base_SdssShape"
        self.schema = afwTable.SourceTable.makeMinimalSchema()
        self.schema.getAliasMap().set("slot_Centroid", self.centroidName)
        self.schema.getAliasMap().set("slot_Shape", self.shapeName)
        self.control = measBase.SdssCentroidControl()
        self.centroider = measBase.SdssCentroidAlgorithm(self.control, self.centroidName, self.schema)
        self.sdssShape = measBase.SdssShapeControl()
        self.shaper = measBase.SdssShapeAlgorithm(self.sdssShape, self.shapeName, self.schema)
        self.apFluxControl = measBase.ApertureFluxControl()
        md = dafBase.PropertySet()
        self.apFluxer = measBase.CircularApertureFluxAlgorithm(self.apFluxControl, "aperFlux",
                                                               self.schema, md)
 
        self.table = afwTable.SourceTable.make(self.schema)  # make sure to call this last!
 

Member Function Documentation

checkResult()

def lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.checkResult (   exp,   centroid,   srcNum,   percentile  )

static

Perform a final check that centroid location is actually bright.

Parameters
----------
exp : `lsst.afw.image.Exposure`
    The exposure on which to operate
centroid : `tuple` of `float`
    Location of the centroid in pixel coordinates
scrNum : `int`
    Number of the source in the source catalog. Only used if the check
    is failed, for debug purposes.
percentile : `float`
    Image's percentile above which the pixel containing the centroid
    must be in order to pass the check.

Raises
------
ValueError
    Raised if the centroid's pixel is not above the percentile threshold

Definition at line 195 of file quickFrameMeasurement.py.

    def checkResult(exp, centroid, srcNum, percentile):
        """Perform a final check that centroid location is actually bright.
 
        Parameters
        ----------
        exp : `lsst.afw.image.Exposure`
            The exposure on which to operate
        centroid : `tuple` of `float`
            Location of the centroid in pixel coordinates
        scrNum : `int`
            Number of the source in the source catalog. Only used if the check
            is failed, for debug purposes.
        percentile : `float`
            Image's percentile above which the pixel containing the centroid
            must be in order to pass the check.
 
        Raises
        ------
        ValueError
            Raised if the centroid's pixel is not above the percentile threshold
        """
        threshold = np.percentile(exp.image.array, percentile)
        pixelValue = exp.image[centroid]
        if pixelValue < threshold:
            msg = (f"Final centroid pixel value check failed: srcNum {srcNum} at {centroid}"
                   f" has central pixel = {pixelValue:3f} <"
                   f" {percentile} percentile of image = {threshold:3f}")
            raise ValueError(msg)
        return
 

detectObjectsInExp()

def lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.detectObjectsInExp (   exp,   nSigma,   nPixMin,   grow = 0  )

static

Run a very basic but fast threshold-based object detection on an exposure
Return the footPrintSet for the objects in a postISR exposure.

Parameters
----------
exp : `lsst.afw.image.Exposure`
    Image in which to detect objects.
nSigma : `float`
    nSigma above image's stddev at which to set the detection threshold.
nPixMin : `int`
    Minimum number of pixels for detection.
grow : `int`
    Grow the detected footprint by this many pixels.

Returns
-------
footPrintSet : `lsst.afw.detection.FootprintSet`
    FootprintSet containing the detections.

Definition at line 167 of file quickFrameMeasurement.py.

    def detectObjectsInExp(exp, nSigma, nPixMin, grow=0):
        """Run a very basic but fast threshold-based object detection on an exposure
        Return the footPrintSet for the objects in a postISR exposure.
 
        Parameters
        ----------
        exp : `lsst.afw.image.Exposure`
            Image in which to detect objects.
        nSigma : `float`
            nSigma above image's stddev at which to set the detection threshold.
        nPixMin : `int`
            Minimum number of pixels for detection.
        grow : `int`
            Grow the detected footprint by this many pixels.
 
        Returns
        -------
        footPrintSet : `lsst.afw.detection.FootprintSet`
            FootprintSet containing the detections.
        """
        threshold = afwDetect.Threshold(nSigma, afwDetect.Threshold.STDEV)
        footPrintSet = afwDetect.FootprintSet(exp.getMaskedImage(), threshold, "DETECTED", nPixMin)
        if grow > 0:
            isotropic = True
            footPrintSet = afwDetect.FootprintSet(footPrintSet, grow, isotropic)
        return footPrintSet
 

run()

def lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.run	(		self,
			exp,
		*	donutDiameter = None,
			doDisplay = False
	)

Calculate position, flux and shape of the brightest star in an image.

Given an an assembled (and at least minimally ISRed exposure),
quickly and robustly calculate the centroid of the
brightest star in the image.

Parameters
----------
exp : `lsst.afw.image.Exposure`
    The exposure in which to find and measure the brightest star.
donutDiameter : `int` or `float`, optional
    The expected diameter of donuts in pixels for use in the centre of
    mass centroid measurement. If None is provided, the config option
    is used.
doDisplay : `bool`
    Display the image and found sources. A diplay object must have
    been passed to the task constructor.

Returns
-------
result : `lsst.pipe.base.Struct`
    Struct containing:
        Whether the task ran successfully and found the object (bool)
        The object's centroid (float, float)
        The object's ixx, iyy (float, float)
        The object's 70 pixel aperture flux (float)
        The object's 25 pixel aperture flux (float)
        The images's median ixx, iyy (float, float)
    If unsuccessful, the success field is False and all other results
    are np.nan of the expected shape.

Notes
-----
Because of this task's involvement in observing scripts, the run method
should *never* raise. Failure modes are noted by returning a Struct with
the same structure as the success case, with all value set to np.nan and
result.success=False.

Definition at line 448 of file quickFrameMeasurement.py.

    def run(self, exp, *, donutDiameter=None, doDisplay=False):
        """Calculate position, flux and shape of the brightest star in an image.
 
        Given an an assembled (and at least minimally ISRed exposure),
        quickly and robustly calculate the centroid of the
        brightest star in the image.
 
        Parameters
        ----------
        exp : `lsst.afw.image.Exposure`
            The exposure in which to find and measure the brightest star.
        donutDiameter : `int` or `float`, optional
            The expected diameter of donuts in pixels for use in the centre of
            mass centroid measurement. If None is provided, the config option
            is used.
        doDisplay : `bool`
            Display the image and found sources. A diplay object must have
            been passed to the task constructor.
 
        Returns
        -------
        result : `lsst.pipe.base.Struct`
            Struct containing:
                Whether the task ran successfully and found the object (bool)
                The object's centroid (float, float)
                The object's ixx, iyy (float, float)
                The object's 70 pixel aperture flux (float)
                The object's 25 pixel aperture flux (float)
                The images's median ixx, iyy (float, float)
            If unsuccessful, the success field is False and all other results
            are np.nan of the expected shape.
 
        Notes
        -----
        Because of this task's involvement in observing scripts, the run method
        should *never* raise. Failure modes are noted by returning a Struct with
        the same structure as the success case, with all value set to np.nan and
        result.success=False.
        """
        try:
            result = self._run(exp=exp, donutDiameter=donutDiameter, doDisplay=doDisplay)
            return result
        except Exception as e:
            self.log.warning("Failed to find main source centroid %s", e)
            result = self._makeEmptyReturnStruct()
            return result
 

Member Data Documentation

apFluxControl

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.apFluxControl

Definition at line 159 of file quickFrameMeasurement.py.

apFluxer

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.apFluxer

Definition at line 161 of file quickFrameMeasurement.py.

centroider

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.centroider

Definition at line 156 of file quickFrameMeasurement.py.

centroidName

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.centroidName

Definition at line 150 of file quickFrameMeasurement.py.

ConfigClass

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.ConfigClass = QuickFrameMeasurementTaskConfig

static

Definition at line 139 of file quickFrameMeasurement.py.

control

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.control

Definition at line 155 of file quickFrameMeasurement.py.

display

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.display

Definition at line 146 of file quickFrameMeasurement.py.

plateScale

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.plateScale

Definition at line 503 of file quickFrameMeasurement.py.

schema

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.schema

Definition at line 152 of file quickFrameMeasurement.py.

sdssShape

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.sdssShape

Definition at line 157 of file quickFrameMeasurement.py.

shapeName

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.shapeName

Definition at line 151 of file quickFrameMeasurement.py.

shaper

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.shaper

Definition at line 158 of file quickFrameMeasurement.py.

table

lsst.pipe.tasks.quickFrameMeasurement.QuickFrameMeasurementTask.table

Definition at line 164 of file quickFrameMeasurement.py.

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

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/pipe_tasks/21.0.0-172-gfb10e10a+18fedfabac/python/lsst/pipe/tasks/quickFrameMeasurement.py