DM-30993: Implement reference catalog culling for astrometry in SFM

[laurenam]

No description provided.

[isullivan]

I have a concern about how coordinates are handled in the new CullFromMaskedRegion. I have a few different suggestions in the comments, depending on the desired behavior.

[isullivan]

I think this will break if the bbox has a non-zero XY0.

Possible alternative:

xRefList = catalog[self.xColName]
yRefList = catalog[self.yColName]
bbox = exposure.getBBox()
badMaskNames = []
maskPlaneDict = exposure.getMask().getMaskPlaneDict()
for badName in self.badMaskNames:
    if badName in maskPlaneDict:
        badMaskNames.append(badName)
bitmask = exposure.mask.getPlaneBitMask(badMaskNames)
selected = np.array([(exposure.mask[xv, yv] & bitmask) == 0 for xv, yv in zip(xRefList, yRefList)])

[isullivan]

On the other hand, the above will break if any of the catalog sources are outside the image. That is easy to fix with an extra isInBbox = bbox.contains(xRefList, yRefList) and using that to throw out sources.

[isullivan]

Alternately, to keep the current behavior where off-image sources are moved to the edge of the image for the check, I would suggest:

x0, y0 = exposure.getXY0()
xMax, yMax = exposure.getDimensions()
xRefList = [int(min(max(0, xRef - x0), xMax)) for xRef in xRefList]
yRefList = [int(min(max(0, yRef - y0), yMax)) for yRef in yRefList]

[laurenam]

UPDATED: my first version was wrong. This is what I have now and I've added what I think works as a test of a non (0, 0) XY0 exposure in the unittest.

Another nice catch, thanks! I do want to keep the current (battle-tested) behavior, so I'm going with this one, but it has to slightly modify it to:

x0, y0 = exposure.getXY0()
xMax, yMax = exposure.getDimensions()
xRefList = [int(min(max(0, xRef - x0), xMax - 1)) for xRef in xRefList]
yRefList = [int(min(max(0, yRef - y0), yMax - 1)) for yRef in yRefList]

Let me know if this looks wrong to you...