class SkyGroup:
"""
Holds multiple :py:class:`SkyImage` objects whose sky background values
must be adjusted together.
`SkyGroup` provides methods for obtaining bounding polygon of the group
of :py:class:`SkyImage` objects and to compute sky value of the group.
"""
def __init__(self, images, id=None, sky=0.0):
if isinstance(images, SkyImage):
self._images = [images]
elif hasattr(images, '__iter__'):
self._images = []
for im in images:
if not isinstance(im, SkyImage):
raise TypeError("Each element of the 'images' parameter "
"must be an 'SkyImage' object.")
self._images.append(im)
else:
raise TypeError(
"Parameter 'images' must be either a single "
"'SkyImage' object or a list of 'SkyImage' objects")
self._id = id
self._update_bounding_polygon()
self._sky = sky
for im in self._images:
im.sky += sky
@property
def id(self):
""" Set or get `SkyImage`'s `id`.
While `id` can be of any type, it is prefereble that `id` be
of a type with nice string representation.
"""
return self._id
@id.setter
def id(self, id):
self._id = id
@property
def sky(self):
""" Sky background value. See `calc_sky` for more details.
"""
return self._sky
@sky.setter
def sky(self, sky):
delta_sky = sky - self._sky
self._sky = sky
for im in self._images:
im.sky += delta_sky
@property
def radec(self):
"""
Get RA and DEC of the verteces of the bounding polygon as a
`~numpy.ndarray` of shape (N, 2) where N is the number of verteces + 1.
"""
return self._radec
@property
def polygon(self):
""" Get image's bounding polygon.
"""
return self._polygon
def intersection(self, skyimage):
"""
Compute intersection of this `SkyImage` object and another
`SkyImage`, `SkyGroup`, or
:py:class:`~spherical_geometry.polygon.SphericalPolygon`
object.
Parameters
----------
skyimage : SkyImage, SkyGroup, SphericalPolygon
Another object that should be intersected with this `SkyImage`.
Returns
-------
polygon : SphericalPolygon
A :py:class:`~spherical_geometry.polygon.SphericalPolygon` that is
the intersection of this `SkyImage` and `skyimage`.
"""
if isinstance(skyimage, (SkyImage, SkyGroup)):
return self._polygon.intersection(skyimage.polygon)
else:
return self._polygon.intersection(skyimage)
def _update_bounding_polygon(self):
polygons = [im.polygon for im in self._images]
if len(polygons) == 0:
self._polygon = SphericalPolygon([])
self._radec = []
else:
self._polygon = SphericalPolygon.multi_union(polygons)
self._radec = list(self._polygon.to_radec())
def __len__(self):
return len(self._images)
def __getitem__(self, idx):
return self._images[idx]
def __setitem__(self, idx, value):
if not isinstance(value, SkyImage):
raise TypeError("Item must be of 'SkyImage' type")
value.sky += self._sky
self._images[idx] = value
self._update_bounding_polygon()
def __delitem__(self, idx):
del self._images[idx]
if len(self._images) == 0:
self._sky = 0.0
self._id = None
self._update_bounding_polygon()
def __iter__(self):
for image in self._images:
yield image
def insert(self, idx, value):
"""Inserts a `SkyImage` into the group.
"""
if not isinstance(value, SkyImage):
raise TypeError("Item must be of 'SkyImage' type")
value.sky += self._sky
self._images.insert(idx, value)
self._update_bounding_polygon()
def append(self, value):
"""Appends a `SkyImage` to the group.
"""
if not isinstance(value, SkyImage):
raise TypeError("Item must be of 'SkyImage' type")
value.sky += self._sky
self._images.append(value)
self._update_bounding_polygon()
def calc_sky(self, overlap=None, delta=True):
"""
Compute sky background value.
Parameters
----------
overlap : SkyImage, SkyGroup, SphericalPolygon, list of tuples, \
None, optional
Another `SkyImage`, `SkyGroup`,
:py:class:`spherical_geometry.polygons.SphericalPolygon`, or
a list of tuples of (RA, DEC) of vertices of a spherical
polygon. This parameter is used to indicate that sky statistics
should computed only in the region of intersection of *this*
image with the polygon indicated by `overlap`. When `overlap` is
`None`, sky statistics will be computed over the entire image.
delta : bool, optional
Should this function return absolute sky value or the difference
between the computed value and the value of the sky stored in the
`sky` property.
Returns
-------
skyval : float, None
Computed sky value (absolute or relative to the `sky` attribute).
If there are no valid data to perform this computations (e.g.,
because this image does not overlap with the image indicated by
`overlap`), `skyval` will be set to `None`.
npix : int
Number of pixels used to compute sky statistics.
polyarea : float
Area (in srad) of the polygon that bounds data used to compute
sky statistics.
"""
if len(self._images) == 0:
return (None, 0, 0.0)
wght = 0
area = 0.0
if overlap is None:
# compute minimum sky across all images in the group:
wsky = None
for image in self._images:
# make sure all images have the same background:
image.background = self._sky
sky, npix, imarea = image.calc_sky(overlap=None, delta=delta)
if sky is None:
continue
if wsky is None or wsky > sky:
wsky = sky
wght = npix
area = imarea
return (wsky, wght, area)
################################################
## compute weighted sky in various overlaps: ##
################################################
wsky = 0.0
for image in self._images:
# make sure all images have the same background:
image.background = self._sky
sky, npix, area1 = image.calc_sky(overlap=overlap, delta=delta)
area += area1
if sky is not None and npix > 0:
pix_area = npix * image.pix_area
wsky += sky * pix_area
wght += pix_area
if wght == 0.0 or area == 0.0:
return (None, wght, area)
else:
return (wsky / wght, wght, area)
class SkyGroup:
"""
Holds multiple :py:class:`SkyImage` objects whose sky background values
must be adjusted together.
`SkyGroup` provides methods for obtaining bounding polygon of the group
of :py:class:`SkyImage` objects and to compute sky value of the group.
"""
def __init__(self, images, id=None, sky=0.0):
if isinstance(images, SkyImage):
self._images = [images]
elif hasattr(images, '__iter__'):
self._images = []
for im in images:
if not isinstance(im, SkyImage):
raise TypeError("Each element of the 'images' parameter "
"must be an 'SkyImage' object.")
self._images.append(im)
else:
raise TypeError("Parameter 'images' must be either a single "
"'SkyImage' object or a list of 'SkyImage' objects")
self._id = id
self._update_bounding_polygon()
self._sky = sky
for im in self._images:
im.sky += sky
@property
def id(self):
""" Set or get `SkyImage`'s `id`.
While `id` can be of any type, it is prefereble that `id` be
of a type with nice string representation.
"""
return self._id
@id.setter
def id(self, id):
self._id = id
@property
def sky(self):
""" Sky background value. See `calc_sky` for more details.
"""
return self._sky
@sky.setter
def sky(self, sky):
delta_sky = sky - self._sky
self._sky = sky
for im in self._images:
im.sky += delta_sky
@property
def radec(self):
"""
Get RA and DEC of the verteces of the bounding polygon as a
`~numpy.ndarray` of shape (N, 2) where N is the number of verteces + 1.
"""
return self._radec
@property
def polygon(self):
""" Get image's bounding polygon.
"""
return self._polygon
def intersection(self, skyimage):
"""
Compute intersection of this `SkyImage` object and another
`SkyImage`, `SkyGroup`, or
:py:class:`~spherical_geometry.polygon.SphericalPolygon`
object.
Parameters
----------
skyimage : SkyImage, SkyGroup, SphericalPolygon
Another object that should be intersected with this `SkyImage`.
Returns
-------
polygon : SphericalPolygon
A :py:class:`~spherical_geometry.polygon.SphericalPolygon` that is
the intersection of this `SkyImage` and `skyimage`.
"""
if isinstance(skyimage, (SkyImage, SkyGroup)):
return self._polygon.intersection(skyimage.polygon)
else:
return self._polygon.intersection(skyimage)
def _update_bounding_polygon(self):
polygons = [im.polygon for im in self._images]
if len(polygons) == 0:
self._polygon = SphericalPolygon([])
self._radec = []
else:
self._polygon = SphericalPolygon.multi_union(polygons)
self._radec = list(self._polygon.to_radec())
def __len__(self):
return len(self._images)
def __getitem__(self, idx):
return self._images[idx]
def __setitem__(self, idx, value):
if not isinstance(value, SkyImage):
raise TypeError("Item must be of 'SkyImage' type")
value.sky += self._sky
self._images[idx] = value
self._update_bounding_polygon()
def __delitem__(self, idx):
del self._images[idx]
if len(self._images) == 0:
self._sky = 0.0
self._id = None
self._update_bounding_polygon()
def __iter__(self):
for image in self._images:
yield image
def insert(self, idx, value):
"""Inserts a `SkyImage` into the group.
"""
if not isinstance(value, SkyImage):
raise TypeError("Item must be of 'SkyImage' type")
value.sky += self._sky
self._images.insert(idx, value)
self._update_bounding_polygon()
def append(self, value):
"""Appends a `SkyImage` to the group.
"""
if not isinstance(value, SkyImage):
raise TypeError("Item must be of 'SkyImage' type")
value.sky += self._sky
self._images.append(value)
self._update_bounding_polygon()
def calc_sky(self, overlap=None, delta=True):
"""
Compute sky background value.
Parameters
----------
overlap : SkyImage, SkyGroup, SphericalPolygon, list of tuples, \
None, optional
Another `SkyImage`, `SkyGroup`,
:py:class:`spherical_geometry.polygons.SphericalPolygon`, or
a list of tuples of (RA, DEC) of vertices of a spherical
polygon. This parameter is used to indicate that sky statistics
should computed only in the region of intersection of *this*
image with the polygon indicated by `overlap`. When `overlap` is
`None`, sky statistics will be computed over the entire image.
delta : bool, optional
Should this function return absolute sky value or the difference
between the computed value and the value of the sky stored in the
`sky` property.
Returns
-------
skyval : float, None
Computed sky value (absolute or relative to the `sky` attribute).
If there are no valid data to perform this computations (e.g.,
because this image does not overlap with the image indicated by
`overlap`), `skyval` will be set to `None`.
npix : int
Number of pixels used to compute sky statistics.
polyarea : float
Area (in srad) of the polygon that bounds data used to compute
sky statistics.
"""
if len(self._images) == 0:
return (None, 0, 0.0)
wght = 0
area = 0.0
if overlap is None:
# compute minimum sky across all images in the group:
wsky = None
for image in self._images:
# make sure all images have the same background:
image.background = self._sky
sky, npix, imarea = image.calc_sky(overlap=None, delta=delta)
if sky is None:
continue
if wsky is None or wsky > sky:
wsky = sky
wght = npix
area = imarea
return (wsky, wght, area)
################################################
## compute weighted sky in various overlaps: ##
################################################
wsky = 0.0
for image in self._images:
# make sure all images have the same background:
image.background = self._sky
sky, npix, area1 = image.calc_sky(overlap=overlap, delta=delta)
area += area1
if sky is not None and npix > 0:
pix_area = npix * image.pix_area
wsky += sky * pix_area
wght += pix_area
if wght == 0.0 or area == 0.0:
return (None, wght, area)
else:
return (wsky / wght, wght, area)
