lsst.meas.algorithms  22.0.1-19-g9283e855+9358885a19
psfSelectionFromMatchList.py
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1 # This file is part of meas_algorithms.
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5 # (https://www.lsst.org).
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21 
22 __all__ = ["selectPsfSources"]
23 
24 import numpy as np
25 import lsst.afw.math as afwMath
26 import lsst.meas.algorithms as measAlg
27 import lsst.afw.display as afwDisplay
28 
29 args = [None, "MatchList", None] # allow the user to probe for this signature
30 
31 
32 def selectPsfSources(exposure, matches, psfPolicy):
33  """Get a list of suitable stars to construct a PSF."""
34 
35  import lsstDebug
36  display = lsstDebug.Info(__name__).display
37  displayExposure = lsstDebug.Info(__name__).displayExposure # display the Exposure + spatialCells
38  #
39  # Unpack policy
40  #
41  kernelSize = psfPolicy.get("kernelSize")
42  borderWidth = psfPolicy.get("borderWidth")
43  sizePsfCellX = psfPolicy.get("sizeCellX")
44  sizePsfCellY = psfPolicy.get("sizeCellY")
45  #
46  mi = exposure.getMaskedImage()
47 
48  if display and displayExposure:
49  disp = afwDisplay.Display(frame=0)
50  disp.mtv(mi, title="PSF candidates")
51 
52  psfCellSet = afwMath.SpatialCellSet(mi.getBBox(), sizePsfCellX, sizePsfCellY)
53  psfStars = []
54 
55  for val in matches:
56  ref, source = val[0:2]
57  if not (ref.getFlagForDetection() & measAlg.Flags.STAR) or \
58  (source.getFlagForDetection() & measAlg.Flags.BAD):
59  continue
60 
61  try:
62  cand = measAlg.makePsfCandidate(source, mi)
63  #
64  # The setXXX methods are class static, but it's convenient to call them on
65  # an instance as we don't know Exposure's pixel type (and hence cand's exact type)
66  if cand.getWidth() == 0:
67  cand.setBorderWidth(borderWidth)
68  cand.setWidth(kernelSize + 2*borderWidth)
69  cand.setHeight(kernelSize + 2*borderWidth)
70 
71  im = cand.getMaskedImage().getImage()
72  max = afwMath.makeStatistics(im, afwMath.MAX).getValue()
73  if not np.isfinite(max):
74  continue
75 
76  psfCellSet.insertCandidate(cand)
77 
78  if display and displayExposure:
79  disp.dot("+", source.getXAstrom() - mi.getX0(), source.getYAstrom() - mi.getY0(),
80  size=4, ctype=afwDisplay.CYAN)
81  disp.dot("o", source.getXAstrom() - mi.getX0(), source.getYAstrom() - mi.getY0(),
82  size=4, ctype=afwDisplay.CYAN)
83  except Exception:
84  continue
85 
86  source.setFlagForDetection(source.getFlagForDetection() | measAlg.Flags.STAR)
87  psfStars += [source]
88 
89  return psfStars, psfCellSet
Fit spatial kernel using approximate fluxes for candidates, and solving a linear system of equations.
Definition: mainpage.dox:13