30 """Generate a list of Footprints of sky objects
32 Sky objects don't overlap with other objects. This is determined
33 through the provided `mask` (in which objects are typically flagged
36 The algorithm for determining sky objects is random trial and error:
37 we try up to `nTrialSkySources` random positions to find `nSources`
42 mask : `lsst.afw.image.Mask`
43 Input mask plane, which identifies pixels to avoid for the sky
46 Random number generator seed.
47 config : `SkyObjectsConfig`
48 Configuration for finding sky objects.
52 skyFootprints : `list` of `lsst.afw.detection.Footprint`
53 Footprints of sky objects. Each will have a peak at the center
56 if config.nSources <= 0:
59 skySourceRadius = config.sourceRadius
60 nSkySources = config.nSources
61 nTrialSkySources = config.nTrialSources
62 if nTrialSkySources
is None:
63 nTrialSkySources = config.nTrialSourcesMultiplier*nSkySources
66 box.grow(-(int(skySourceRadius) + 1))
67 xMin, yMin = box.getMin()
68 xMax, yMax = box.getMax()
71 if config.growMask > 0:
72 avoid = avoid.dilated(config.growMask)
77 for _
in range(nTrialSkySources):
78 if len(skyFootprints) == nSkySources:
81 x = int(rng.flat(xMin, xMax))
82 y = int(rng.flat(yMin, yMax))
84 if spans.overlaps(avoid):
89 skyFootprints.append(fp)