lsst.afw.image.exposure.exposureUtils Namespace Reference

Functions
	bbox_to_convex_polygon (bbox, wcs, padding=10)
	bbox_contains_sky_coords (bbox, wcs, ra, dec, padding=10)

Function Documentation

bbox_contains_sky_coords()

lsst.afw.image.exposure.exposureUtils.bbox_contains_sky_coords	(		bbox,
			wcs,
			ra,
			dec,
			padding = 10 )

Check if a set of sky positions are in the bounding box.

This uses a two-step process: first check that the coordinates are
inside a padded version of the bbox projected on the sky, and then
project the remaining points onto the bbox, to avoid inverting
the WCS outside of the valid region. The default padding
size was chosen to be sufficient for the most warped detectors at
the edges of the HyperSuprimeCam focal plane.

Parameters
----------
bbox : `lsst.geom.Box2I`
    Pixel bounding box to check sky positions in.
wcs : `lsst.afw.image.SkyWcs`
    WCS associated with the bounding box.
ra : `astropy.Quantity`, (N,)
    Array of Right Ascension, angular units.
dec : `astropy.Quantity`, (N,)
    Array of Declination, angular units.
padding : `int`
   Pixel padding to ensure that bounding box is entirely contained
   within the resulting polygon.

Returns
-------
contained : `np.ndarray`, (N,)
   Boolean array indicating which points are contained in the
   bounding box.

Definition at line 60 of file exposureUtils.py.

def bbox_contains_sky_coords(bbox, wcs, ra, dec, padding=10):
    """Check if a set of sky positions are in the bounding box.
 
    This uses a two-step process: first check that the coordinates are
    inside a padded version of the bbox projected on the sky, and then
    project the remaining points onto the bbox, to avoid inverting
    the WCS outside of the valid region. The default padding
    size was chosen to be sufficient for the most warped detectors at
    the edges of the HyperSuprimeCam focal plane.
 
    Parameters
    ----------
    bbox : `lsst.geom.Box2I`
        Pixel bounding box to check sky positions in.
    wcs : `lsst.afw.image.SkyWcs`
        WCS associated with the bounding box.
    ra : `astropy.Quantity`, (N,)
        Array of Right Ascension, angular units.
    dec : `astropy.Quantity`, (N,)
        Array of Declination, angular units.
    padding : `int`
       Pixel padding to ensure that bounding box is entirely contained
       within the resulting polygon.
 
    Returns
    -------
    contained : `np.ndarray`, (N,)
       Boolean array indicating which points are contained in the
       bounding box.
    """
    poly = bbox_to_convex_polygon(bbox, wcs, padding=padding)
 
    _ra = np.atleast_1d(ra.to(units.radian).value).astype(np.float64)
    _dec = np.atleast_1d(dec.to(units.radian).value).astype(np.float64)
 
    radec_contained = poly.contains(_ra, _dec)
 
    contained = np.zeros_like(radec_contained, dtype=bool)
 
    x_in, y_in = wcs.skyToPixelArray(_ra[radec_contained], _dec[radec_contained], degrees=False)
    xy_contained = bbox.contains(x_in, y_in)
 
    # contained[not radec_contained] is already false
    contained[radec_contained] = xy_contained
    return contained

bbox_to_convex_polygon()

lsst.afw.image.exposure.exposureUtils.bbox_to_convex_polygon	(		bbox,
			wcs,
			padding = 10 )

Convert a bounding box and wcs to a convex polygon on the sky, with paddding.

The returned polygon has additional padding to ensure that the
bounding box is entirely contained within it.  The default padding
size was chosen to be sufficient for the most warped detectors at
the edges of the HyperSuprimeCam focal plane.

Parameters
----------
bbox : `lsst.geom.Box2I`
    Bounding box to convert.
wcs : `lsst.afw.image.SkyWcs`
    WCS associated with the bounding box.
padding : `int`
   Pixel padding to ensure that bounding box is entirely contained
   within the resulting polygon.

Returns
-------
convex_polygon : `lsst.sphgeom.ConvexPolygon`
   Will be None if wcs is not valid.

Definition at line 29 of file exposureUtils.py.

def bbox_to_convex_polygon(bbox, wcs, padding=10):
    """Convert a bounding box and wcs to a convex polygon on the sky, with paddding.
 
    The returned polygon has additional padding to ensure that the
    bounding box is entirely contained within it.  The default padding
    size was chosen to be sufficient for the most warped detectors at
    the edges of the HyperSuprimeCam focal plane.
 
    Parameters
    ----------
    bbox : `lsst.geom.Box2I`
        Bounding box to convert.
    wcs : `lsst.afw.image.SkyWcs`
        WCS associated with the bounding box.
    padding : `int`
       Pixel padding to ensure that bounding box is entirely contained
       within the resulting polygon.
 
    Returns
    -------
    convex_polygon : `lsst.sphgeom.ConvexPolygon`
       Will be None if wcs is not valid.
    """
    # Convert Box2I to Box2D, without modifying original.
    _bbox = lsst.geom.Box2D(bbox)
    _bbox.grow(padding)
    corners = [wcs.pixelToSky(corner).getVector()
               for corner in _bbox.getCorners()]
    return lsst.sphgeom.ConvexPolygon(corners)