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DM-15635: Approximate filter throughput for DcrCoadds #102

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Oct 26, 2018
Merged

DM-15635: Approximate filter throughput for DcrCoadds #102

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b5b14c2
Add option to approximate finite bandwidth of DcrModel subfilters.
isullivan Oct 19, 2018
b61b41e
Rename `useMidpoint` -> `splitSubfilters`
isullivan Oct 19, 2018
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64 changes: 48 additions & 16 deletions python/lsst/ip/diffim/dcrModel.py
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Expand Up @@ -289,7 +289,8 @@ def assign(self, dcrSubModel, bbox=None):
model.assign(subModel[bbox], bbox)

def buildMatchedTemplate(self, exposure=None, warpCtrl=None,
visitInfo=None, bbox=None, wcs=None, mask=None):
visitInfo=None, bbox=None, wcs=None, mask=None,
splitSubfilters=False):
"""Create a DCR-matched template image for an exposure.

Parameters
Expand All @@ -310,6 +311,9 @@ def buildMatchedTemplate(self, exposure=None, warpCtrl=None,
Ignored if ``exposure`` is set.
mask : `lsst.afw.image.Mask`, optional
reference mask to use for the template image.
splitSubfilters : `bool`, optional
Calculate DCR for two evenly-spaced wavelengths in each subfilter,
instead of at the midpoint. Default: False

Returns
-------
Expand All @@ -335,10 +339,10 @@ def buildMatchedTemplate(self, exposure=None, warpCtrl=None,
warpCtrl = afwMath.WarpingControl("lanczos3", "bilinear",
cacheSize=0, interpLength=max(bbox.getDimensions()))

dcrShift = calculateDcr(visitInfo, wcs, self.filter, len(self))
dcrShift = calculateDcr(visitInfo, wcs, self.filter, len(self), splitSubfilters=splitSubfilters)
templateImage = afwImage.MaskedImageF(bbox)
for subfilter, dcr in enumerate(dcrShift):
templateImage += applyDcr(self[subfilter][bbox], dcr, warpCtrl)
templateImage += applyDcr(self[subfilter][bbox], dcr, warpCtrl, splitSubfilters=splitSubfilters)
if mask is not None:
templateImage.setMask(mask[bbox])
return templateImage
Expand Down Expand Up @@ -533,7 +537,7 @@ def applyImageThresholds(self, maskedImage, highThreshold=None, lowThreshold=Non
image[lowPixels] = lowThreshold[lowPixels]


def applyDcr(maskedImage, dcr, warpCtrl, bbox=None, useInverse=False):
def applyDcr(maskedImage, dcr, warpCtrl, bbox=None, useInverse=False, splitSubfilters=False):
"""Shift a masked image.

Parameters
Expand All @@ -549,23 +553,38 @@ def applyDcr(maskedImage, dcr, warpCtrl, bbox=None, useInverse=False):
Shifts the entire image if None (Default).
useInverse : `bool`, optional
Use the reverse of ``dcr`` for the shift. Default: False
splitSubfilters : `bool`, optional
Calculate DCR for two evenly-spaced wavelengths in each subfilter,
instead of at the midpoint. Default: False

Returns
-------
`lsst.afw.image.maskedImageF`
shiftedImage : `lsst.afw.image.maskedImageF`
A masked image, with the pixels within the bounding box shifted.
"""
padValue = afwImage.pixel.SinglePixelF(0., maskedImage.mask.getPlaneBitMask("NO_DATA"), 0)
if bbox is None:
bbox = maskedImage.getBBox()
shiftedImage = afwImage.MaskedImageF(bbox)
transform = makeTransform(AffineTransform((-1.0 if useInverse else 1.0)*dcr))
afwMath.warpImage(shiftedImage, maskedImage[bbox],
transform, warpCtrl, padValue=padValue)
if splitSubfilters:
shiftedImage = afwImage.MaskedImageF(bbox)
transform0 = makeTransform(AffineTransform((-1.0 if useInverse else 1.0)*dcr[0]))
afwMath.warpImage(shiftedImage, maskedImage[bbox],
transform0, warpCtrl, padValue=padValue)
shiftedImage1 = afwImage.MaskedImageF(bbox)
transform1 = makeTransform(AffineTransform((-1.0 if useInverse else 1.0)*dcr[1]))
afwMath.warpImage(shiftedImage1, maskedImage[bbox],
transform1, warpCtrl, padValue=padValue)
shiftedImage += shiftedImage1
shiftedImage /= 2.
else:
shiftedImage = afwImage.MaskedImageF(bbox)
transform = makeTransform(AffineTransform((-1.0 if useInverse else 1.0)*dcr))
afwMath.warpImage(shiftedImage, maskedImage[bbox],
transform, warpCtrl, padValue=padValue)
return shiftedImage


def calculateDcr(visitInfo, wcs, filterInfo, dcrNumSubfilters):
def calculateDcr(visitInfo, wcs, filterInfo, dcrNumSubfilters, splitSubfilters=False):
"""Calculate the shift in pixels of an exposure due to DCR.

Parameters
Expand All @@ -578,14 +597,18 @@ def calculateDcr(visitInfo, wcs, filterInfo, dcrNumSubfilters):
The filter definition, set in the current instruments' obs package.
dcrNumSubfilters : `int`
Number of sub-filters used to model chromatic effects within a band.
splitSubfilters : `bool`, optional
Calculate DCR for two evenly-spaced wavelengths in each subfilter,
instead of at the midpoint. Default: False

Returns
-------
`lsst.afw.geom.Extent2I`
dcrShift : `lsst.afw.geom.Extent2I`
The 2D shift due to DCR, in pixels.
"""
rotation = calculateImageParallacticAngle(visitInfo, wcs)
dcrShift = []
weight = [0.75, 0.25]
lambdaEff = filterInfo.getFilterProperty().getLambdaEff()
for wl0, wl1 in wavelengthGenerator(filterInfo, dcrNumSubfilters):
# Note that diffRefractAmp can be negative, since it's relative to the midpoint of the full band
Expand All @@ -597,11 +620,20 @@ def calculateDcr(visitInfo, wcs, filterInfo, dcrNumSubfilters):
elevation=visitInfo.getBoresightAzAlt().getLatitude(),
observatory=visitInfo.getObservatory(),
weather=visitInfo.getWeather())
diffRefractAmp = (diffRefractAmp0 + diffRefractAmp1)/2.
diffRefractPix = diffRefractAmp.asArcseconds()/wcs.getPixelScale().asArcseconds()
shiftX = diffRefractPix*np.sin(rotation.asRadians())
shiftY = diffRefractPix*np.cos(rotation.asRadians())
dcrShift.append(afwGeom.Extent2D(shiftX, shiftY))
if splitSubfilters:
diffRefractPix0 = diffRefractAmp0.asArcseconds()/wcs.getPixelScale().asArcseconds()
diffRefractPix1 = diffRefractAmp1.asArcseconds()/wcs.getPixelScale().asArcseconds()
diffRefractArr = [diffRefractPix0*weight[0] + diffRefractPix1*weight[1],
diffRefractPix0*weight[1] + diffRefractPix1*weight[0]]
shiftX = [diffRefractPix*np.sin(rotation.asRadians()) for diffRefractPix in diffRefractArr]
shiftY = [diffRefractPix*np.cos(rotation.asRadians()) for diffRefractPix in diffRefractArr]
dcrShift.append((afwGeom.Extent2D(shiftX[0], shiftY[0]), afwGeom.Extent2D(shiftX[1], shiftY[1])))
else:
diffRefractAmp = (diffRefractAmp0 + diffRefractAmp1)/2.
diffRefractPix = diffRefractAmp.asArcseconds()/wcs.getPixelScale().asArcseconds()
shiftX = diffRefractPix*np.sin(rotation.asRadians())
shiftY = diffRefractPix*np.cos(rotation.asRadians())
dcrShift.append(afwGeom.Extent2D(shiftX, shiftY))
return dcrShift


Expand Down