lsst.meas.deblender gc6308e37c7+d06ddb1514
Classes | Functions
lsst.meas.deblender.plugins Namespace Reference

Classes

class  DeblenderPlugin
 

Functions

def clipFootprintToNonzeroImpl (foot, image)
 
def fitPsfs (debResult, log, psfChisqCut1=1.5, psfChisqCut2=1.5, psfChisqCut2b=1.5, tinyFootprintSize=2)
 
def buildSymmetricTemplates (debResult, log, patchEdges=False, setOrigTemplate=True)
 
def rampFluxAtEdge (debResult, log, patchEdges=False)
 
def medianSmoothTemplates (debResult, log, medianFilterHalfsize=2)
 
def makeTemplatesMonotonic (debResult, log)
 
def clipFootprintsToNonzero (debResult, log)
 
def weightTemplates (debResult, log)
 
def reconstructTemplates (debResult, log, maxTempDotProd=0.5)
 
def apportionFlux (debResult, log, assignStrayFlux=True, strayFluxAssignment='r-to-peak', strayFluxToPointSources='necessary', clipStrayFluxFraction=0.001, getTemplateSum=False)
 

Function Documentation

◆ apportionFlux()

def lsst.meas.deblender.plugins.apportionFlux (   debResult,
  log,
  assignStrayFlux = True,
  strayFluxAssignment = 'r-to-peak',
  strayFluxToPointSources = 'necessary',
  clipStrayFluxFraction = 0.001,
  getTemplateSum = False 
)
Apportion flux to all of the peak templates in each filter

Divide the ``maskedImage`` flux amongst all of the templates based
on the fraction of flux assigned to each ``template``.
Leftover "stray flux" is assigned to peaks based on the other parameters.

Parameters
----------
debResult: `lsst.meas.deblender.baseline.DeblenderResult`
    Container for the final deblender results.
log: `log.Log`
    LSST logger for logging purposes.
assignStrayFlux: `bool`, optional
    If True then flux in the parent footprint that is not covered by any
    of the template footprints is assigned to templates based on
    their 1/(1+r^2) distance.
    How the flux is apportioned is determined by ``strayFluxAssignment``.
strayFluxAssignment: `string`, optional
    Determines how stray flux is apportioned.

    * ``trim``: Trim stray flux and do not include in any footprints
    * ``r-to-peak`` (default): Stray flux is assigned based on
      (1/(1+r^2) from the peaks
    * ``r-to-footprint``: Stray flux is distributed to the footprints
      based on 1/(1+r^2) of the minimum distance from the stray flux
      to footprint
    * ``nearest-footprint``: Stray flux is assigned to the footprint
      with lowest L-1 (Manhattan) distance to the stray flux

strayFluxToPointSources: `string`, optional
    Determines how stray flux is apportioned to point sources

    * ``never``: never apportion stray flux to point sources
    * ``necessary`` (default): point sources are included only if there
      are no extended sources nearby
    * ``always``: point sources are always included in
      the 1/(1+r^2) splitting

clipStrayFluxFraction: `float`, optional
    Minimum stray-flux portion.
    Any stray-flux portion less than ``clipStrayFluxFraction`` is
    clipped to zero.
getTemplateSum: `bool`, optional
    As part of the flux calculation, the sum of the templates is
    calculated. If ``getTemplateSum==True`` then the sum of the
    templates is stored in the result (a `DeblendedFootprint`).

Returns
-------
modified: `bool`
    Apportion flux always modifies the templates, so ``modified`` is
    always ``True``. However, this should likely be the final step and
    it is unlikely that any deblender plugins will be re-run.

Definition at line 1250 of file plugins.py.

◆ buildSymmetricTemplates()

def lsst.meas.deblender.plugins.buildSymmetricTemplates (   debResult,
  log,
  patchEdges = False,
  setOrigTemplate = True 
)
Build a symmetric template for each peak in each filter

Given ``maskedImageF``, ``footprint``, and a ``DebldendedPeak``, creates
a symmetric template (``templateImage`` and ``templateFootprint``) around
the peak for all peaks not flagged as ``skip`` or ``deblendedAsPsf``.

Parameters
----------
debResult: `lsst.meas.deblender.baseline.DeblenderResult`
    Container for the final deblender results.
log: `log.Log`
    LSST logger for logging purposes.
patchEdges: `bool`, optional
    If True and if the parent Footprint touches pixels with the
    ``EDGE`` bit set, then grow the parent Footprint to include
    all symmetric templates.

Returns
-------
modified: `bool`
    If any peaks are not skipped or marked as point sources,
    ``modified`` is ``True. Otherwise ``modified`` is ``False``.

Definition at line 708 of file plugins.py.

◆ clipFootprintsToNonzero()

def lsst.meas.deblender.plugins.clipFootprintsToNonzero (   debResult,
  log 
)
Clip non-zero spans in the template footprints for every peak in each filter.

Peak ``Footprint``\ s are clipped to the region in the image containing
non-zero values by dropping spans that are completely zero and moving
endpoints to non-zero pixels (but does not split spans that have
internal zeros).

Parameters
----------
debResult: `lsst.meas.deblender.baseline.DeblenderResult`
    Container for the final deblender results.
log: `log.Log`
    LSST logger for logging purposes.

Returns
-------
modified: `bool`
    Whether or not any templates were modified.
    This will be ``True`` as long as there is at least one source that
    is not flagged as a PSF.

Definition at line 1041 of file plugins.py.

◆ clipFootprintToNonzeroImpl()

def lsst.meas.deblender.plugins.clipFootprintToNonzeroImpl (   foot,
  image 
)
Clips the given *Footprint* to the region in the *Image*
containing non-zero values.

The clipping drops spans that are
totally zero, and moves endpoints to non-zero; it does not
split spans that have internal zeros.

Definition at line 38 of file plugins.py.

◆ fitPsfs()

def lsst.meas.deblender.plugins.fitPsfs (   debResult,
  log,
  psfChisqCut1 = 1.5,
  psfChisqCut2 = 1.5,
  psfChisqCut2b = 1.5,
  tinyFootprintSize = 2 
)
Fit a PSF + smooth background model (linear) to a small region
around each peak.

This function will iterate over all filters in deblender result but does
not compare results across filters.
DeblendedPeaks that pass the cuts have their templates modified to the
PSF + background model and their ``deblendedAsPsf`` property set
to ``True``.

This will likely be replaced in the future with a function that compares
the psf chi-squared cuts so that peaks flagged as point sources will be
considered point sources in all bands.

Parameters
----------
debResult: `lsst.meas.deblender.baseline.DeblenderResult`
    Container for the final deblender results.
log: `log.Log`
    LSST logger for logging purposes.
psfChisqCut*: `float`, optional
    ``psfChisqCut1`` is the maximum chi-squared-per-degree-of-freedom
    allowed for a peak to be considered a PSF match without recentering.
    A fit is also made that includes terms to recenter the PSF.
    ``psfChisqCut2`` is the same as ``psfChisqCut1`` except it
    determines the restriction on the fit that includes
    recentering terms.
    If the peak is a match for a re-centered PSF, the PSF is
    repositioned at the new center and
    the peak footprint is fit again, this time to the new PSF.
    If the resulting chi-squared-per-degree-of-freedom is less than
    ``psfChisqCut2b`` then it passes the re-centering algorithm.
    If the peak passes both the re-centered and fixed position cuts,
    the better of the two is accepted, but parameters for all three psf
    fits are stored in the ``DebldendedPeak``.
    The default for ``psfChisqCut1``, ``psfChisqCut2``, and
    ``psfChisqCut2b`` is ``1.5``.
tinyFootprintSize: `float`, optional
    The PSF model is shrunk to the size that contains the original
    footprint. If the bbox of the clipped PSF model for a peak is
    smaller than ``max(tinyFootprintSize,2)`` then ``tinyFootprint`` for
    the peak is set to ``True`` and the peak is not fit. The default is 2.

Returns
-------
modified: `bool`
    If any templates have been assigned to PSF point sources then
    ``modified`` is ``True``, otherwise it is ``False``.

Definition at line 164 of file plugins.py.

◆ makeTemplatesMonotonic()

def lsst.meas.deblender.plugins.makeTemplatesMonotonic (   debResult,
  log 
)
Make the templates monotonic.

The pixels in the templates are modified such that pixels further
from the peak will have values smaller than those closer to the peak.

Parameters
----------
debResult: `lsst.meas.deblender.baseline.DeblenderResult`
    Container for the final deblender results.
log: `log.Log`
    LSST logger for logging purposes.

Returns
-------
modified: `bool`
    Whether or not any templates were modified.
    This will be ``True`` as long as there is at least one source that
    is not flagged as a PSF.

Definition at line 1005 of file plugins.py.

◆ medianSmoothTemplates()

def lsst.meas.deblender.plugins.medianSmoothTemplates (   debResult,
  log,
  medianFilterHalfsize = 2 
)
Applying median smoothing filter to the template images for every
peak in every filter.

Parameters
----------
debResult: `lsst.meas.deblender.baseline.DeblenderResult`
    Container for the final deblender results.
log: `log.Log`
    LSST logger for logging purposes.
medianFilterHalfSize: `int`, optional
    Half the box size of the median filter, i.e. a
    ``medianFilterHalfSize`` of 50 means that each output pixel will
    be the median of  the pixels in a 101 x 101-pixel box in the input
    image. This parameter is only used when
    ``medianSmoothTemplate==True``, otherwise it is ignored.

Returns
-------
modified: `bool`
    Whether or not any templates were modified.
    This will be ``True`` as long as there is at least one source that
    is not flagged as a PSF.

Definition at line 956 of file plugins.py.

◆ rampFluxAtEdge()

def lsst.meas.deblender.plugins.rampFluxAtEdge (   debResult,
  log,
  patchEdges = False 
)
Adjust flux on the edges of the template footprints.

Using the PSF, a peak ``~afw.detection.Footprint`` with pixels on the edge
of ``footprint`` is grown by the ``psffwhm*1.5`` and filled in
with ramped pixels. The result is a new symmetric footprint
template for the peaks near the edge.

Parameters
----------
debResult: `lsst.meas.deblender.baseline.DeblenderResult`
    Container for the final deblender results.
log: `log.Log`
    LSST logger for logging purposes.
patchEdges: `bool`, optional
    If True and if the parent Footprint touches pixels with the
    ``EDGE`` bit set, then grow the parent Footprint to include
    all symmetric templates.

Returns
-------
modified: `bool`
    If any peaks have their templates modified to include flux at the
    edges, ``modified`` is ``True``.

Definition at line 770 of file plugins.py.

◆ reconstructTemplates()

def lsst.meas.deblender.plugins.reconstructTemplates (   debResult,
  log,
  maxTempDotProd = 0.5 
)
Remove "degenerate templates"

If galaxies have substructure, such as face-on spirals, the process of
identifying peaks can "shred" the galaxy into many pieces. The templates
of shredded galaxies are typically quite similar because they represent
the same galaxy, so we try to identify these "degenerate" peaks
by looking at the inner product (in pixel space) of pairs of templates.
If they are nearly parallel, we only keep one of the peaks and reject
the other. If only one of the peaks is a PSF template, the other template
is used, otherwise the one with the maximum template value is kept.

Parameters
----------
debResult: `lsst.meas.deblender.baseline.DeblenderResult`
    Container for the final deblender results.
log: `log.Log`
    LSST logger for logging purposes.
maxTempDotProd: `float`, optional
    All dot products between templates greater than ``maxTempDotProd``
    will result in one of the templates removed.

Returns
-------
modified: `bool`
    If any degenerate templates are found, ``modified`` is ``True``.

Definition at line 1149 of file plugins.py.

◆ weightTemplates()

def lsst.meas.deblender.plugins.weightTemplates (   debResult,
  log 
)
Weight the templates to best fit the observed image in each filter

This function re-weights the templates so that their linear combination
best represents the observed image in that filter.
In the future it may be useful to simultaneously weight all of the
filters together.

Parameters
----------
debResult: `lsst.meas.deblender.baseline.DeblenderResult`
    Container for the final deblender results.
log: `log.Log`
    LSST logger for logging purposes.

Returns
-------
modified: `bool`
    ``weightTemplates`` does not actually modify the ``Footprint``
    templates other than to add a weight to them, so ``modified``
    is always ``False``.

Definition at line 1077 of file plugins.py.