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DM-52586: Add check for unmasked pixels before setting HIGH_VARIANCE mask plane #434

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Merged
isullivan merged 1 commit into from
Sep 23, 2025
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DM-52586: Add check for unmasked pixels before setting HIGH_VARIANCE mask plane #434

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27 changes: 20 additions & 7 deletions python/lsst/ip/diffim/getTemplate.py
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Original file line number Diff line number Diff line change
Expand Up @@ -114,6 +114,12 @@ class GetTemplateConfig(
doc="Set the HIGH_VARIANCE mask plane for regions with variance"
" greater than the median by this factor.",
)
highVarianceMaskFraction = pexConfig.Field(
dtype=float,
default=0.1,
doc="Minimum fraction of unmasked pixels needed to set the"
" HIGH_VARIANCE mask plane.",
)

def setDefaults(self):
# Use a smaller cache: per SeparableKernel.computeCache, this should
Expand Down Expand Up @@ -398,13 +404,20 @@ def checkHighVariance(self, template):
The warped template exposure, which will be modified in place.
"""
highVarianceMaskPlaneBit = template.mask.addMaskPlane("HIGH_VARIANCE")
template.mask.getPlaneBitMask("HIGH_VARIANCE")
varianceExposure = template.clone()
varianceExposure.image.array = varianceExposure.variance.array
varianceBackground = self.varianceBackground.run(varianceExposure).background.getImage().array
threshold = self.config.highVarianceThreshold*np.nanmedian(varianceBackground)
highVariancePix = varianceBackground > threshold
template.mask.array[highVariancePix] |= 2**highVarianceMaskPlaneBit
ignoredPixelBits = template.mask.getPlaneBitMask(self.varianceBackground.config.ignoredPixelMask)
goodMask = (template.mask.array & ignoredPixelBits) == 0
goodFraction = np.count_nonzero(goodMask)/template.mask.array.size
if goodFraction < self.config.highVarianceMaskFraction:
self.log.info("Not setting HIGH_VARIANCE mask plane, only %2.1f%% of"
" pixels were unmasked for background estimation, but"
" %2.1f%% are required", 100*goodFraction, 100*self.config.highVarianceMaskFraction)
else:
varianceExposure = template.clone()
varianceExposure.image.array = varianceExposure.variance.array
varianceBackground = self.varianceBackground.run(varianceExposure).background.getImage().array
threshold = self.config.highVarianceThreshold*np.nanmedian(varianceBackground)
highVariancePix = varianceBackground > threshold
template.mask.array[highVariancePix] |= 2**highVarianceMaskPlaneBit

@staticmethod
def _checkInputs(dataIds, coaddExposures):
Expand Down