lsst.pipe.tasks.diffractionSpikeMask Namespace Reference

Classes
class	DiffractionSpikeMaskConfig
class	DiffractionSpikeMaskTask

Functions
	getRegion (exposure, margin=None)
	boxSeparation (bbox, x, y)

Function Documentation

boxSeparation()

lsst.pipe.tasks.diffractionSpikeMask.boxSeparation	(		bbox,
			x,
			y )

Return the minimum horizontal or vertical distance from a point to the
outside edge of a bounding box.

Parameters
----------
bbox : `lsst.geom.Box2I`
    The bounding box to check.
x, y : `float`
    Coordinates of the point.

Returns
-------
distance : `float`
    The distance in pixels by which the point is outside the box, or 0 if
    it is inside.

Definition at line 468 of file diffractionSpikeMask.py.

def boxSeparation(bbox, x, y):
    """Return the minimum horizontal or vertical distance from a point to the
    outside edge of a bounding box.
 
    Parameters
    ----------
    bbox : `lsst.geom.Box2I`
        The bounding box to check.
    x, y : `float`
        Coordinates of the point.
 
    Returns
    -------
    distance : `float`
        The distance in pixels by which the point is outside the box, or 0 if
        it is inside.
    """
 
    x0, y0 = bbox.getBegin()
    x1, y1 = bbox.getEnd()
    dx = 0 if x0 <= x <= x1 else min(abs(x0 - x), abs(x - x1))
    dy = 0 if y0 <= y <= y1 else min(abs(y0 - y), abs(y - y1))
    return max(dx, dy)

getRegion()

lsst.pipe.tasks.diffractionSpikeMask.getRegion	(		exposure,
			margin = None )

Calculate an enveloping region for an exposure.

Parameters
----------
exposure : `lsst.afw.image.Exposure`
    Exposure object with calibrated WCS.
margin : `lsst.sphgeom.Angle`, optional
    Grow the surrounding region of the exposure by this amount, in order to
    mask the diffraction spikes of stars off the image.

Returns
-------
region : `lsst.sphgeom.Region`
    Region enveloping an exposure.

Definition at line 433 of file diffractionSpikeMask.py.

def getRegion(exposure, margin=None):
    """Calculate an enveloping region for an exposure.
 
    Parameters
    ----------
    exposure : `lsst.afw.image.Exposure`
        Exposure object with calibrated WCS.
    margin : `lsst.sphgeom.Angle`, optional
        Grow the surrounding region of the exposure by this amount, in order to
        mask the diffraction spikes of stars off the image.
 
    Returns
    -------
    region : `lsst.sphgeom.Region`
        Region enveloping an exposure.
    """
    # Bounding box needs to be a `Box2D` not a `Box2I` for `wcs.pixelToSky()`
    bbox = lsst.geom.Box2D(exposure.getBBox())
    wcs = exposure.getWcs()
 
    region = lsst.sphgeom.ConvexPolygon([pp.getVector() for pp in wcs.pixelToSky(bbox.getCorners())])
    if margin is not None:
        # This is an ad-hoc, approximate implementation. It should be good
        # enough for catalog loading, but is not a general-purpose solution.
        center = lsst.geom.SpherePoint(region.getCentroid())
        corners = [lsst.geom.SpherePoint(c) for c in region.getVertices()]
        # Approximate the region as a Euclidian square
        # geom.Angle(sphgeom.Angle) converter not pybind-wrapped???
        diagonal_margin = lsst.geom.Angle(margin.asRadians() * math.sqrt(2.0))
        padded = [c.offset(center.bearingTo(c), diagonal_margin) for c in corners]
        return lsst.sphgeom.ConvexPolygon.convexHull([c.getVector() for c in padded])
 
    return region