# Licensed under a 3-clause BSD style license - see LICENSE.rst
import logging
import numpy as np
from astropy import units as u
from astropy.coordinates import Angle
from regions import PixCoord
from gammapy.datasets import SpectrumDatasetOnOff
from gammapy.maps import RegionGeom, RegionNDMap, WcsNDMap
from gammapy.utils.regions import list_to_compound_region
from ..core import Maker
__all__ = ["ReflectedRegionsFinder", "ReflectedRegionsBackgroundMaker"]
log = logging.getLogger(__name__)
class ReflectedRegionsFinder:
"""Find reflected regions.
This class is responsible for placing :ref:`region_reflected` for a given
input region and pointing position. It converts to pixel coordinates
internally assuming a tangent projection at center position.
If the center lies inside the input region, no reflected regions
can be found.
If you want to make a
background estimate for an IACT observation using the reflected regions
method, see also `~gammapy.makers.ReflectedRegionsBackgroundMaker`
Parameters
----------
region : `~regions.SkyRegion`
Region to rotate
center : `~astropy.coordinates.SkyCoord`
Rotation point
angle_increment : `~astropy.coordinates.Angle`, optional
Rotation angle applied when a region falls in an excluded region.
min_distance : `~astropy.coordinates.Angle`, optional
Minimal distance between two consecutive reflected regions
min_distance_input : `~astropy.coordinates.Angle`, optional
Minimal distance from input region
max_region_number : int, optional
Maximum number of regions to use
exclusion_mask : `~gammapy.maps.WcsNDMap`, optional
Exclusion mask
binsz : `~astropy.coordinates.Angle`
Bin size of the reference map used for region finding.
Examples
--------
>>> from astropy.coordinates import SkyCoord, Angle
>>> from regions import CircleSkyRegion
>>> from gammapy.makers import ReflectedRegionsFinder
>>> pointing = SkyCoord(83.2, 22.7, unit='deg', frame='icrs')
>>> target_position = SkyCoord(80.2, 23.5, unit='deg', frame='icrs')
>>> theta = Angle(0.4, 'deg')
>>> on_region = CircleSkyRegion(target_position, theta)
>>> finder = ReflectedRegionsFinder(min_distance_input='1 rad', region=on_region, center=pointing)
>>> finder.run()
>>> print(finder.reflected_regions[0])
Region: CircleSkyRegion
center: <SkyCoord (Galactic): (l, b) in deg
( 184.9367087, -8.37920222)>
radius: 0.400147197682 deg
"""
def __init__(
self,
region,
center,
angle_increment="0.1 rad",
min_distance="0 rad",
min_distance_input="0.1 rad",
max_region_number=10000,
exclusion_mask=None,
binsz="0.01 deg",
):
self.region = region
self.center = center
self.angle_increment = Angle(angle_increment)
if self.angle_increment <= Angle(0, "deg"):
raise ValueError("angle_increment is too small")
self.min_distance = Angle(min_distance)
self.min_distance_input = Angle(min_distance_input)
self.exclusion_mask = exclusion_mask
self.max_region_number = max_region_number
self.reflected_regions = None
self.reference_map = None
self.binsz = Angle(binsz)
def run(self):
"""Run all steps.
"""
self.reference_map = self.make_reference_map(
self.region, self.center, self.binsz
)
if self.exclusion_mask is not None:
coords = self.reference_map.geom.get_coord()
vals = self.exclusion_mask.get_by_coord(coords)
self.reference_map.data += vals
else:
self.reference_map.data += 1
# Check if center is contained in region
if self.region.contains(self.center, self.reference_map.geom.wcs):
self.reflected_regions = []
else:
self.setup()
self.find_regions()
@staticmethod
def make_reference_map(region, center, binsz="0.01 deg", min_width="0.3 deg"):
"""Create empty reference map.
The size of the map is chosen such that all reflected regions are
contained on the image.
To do so, the reference map width is taken to be 4 times the distance between
the target region center and the rotation point. This distance is larger than
the typical dimension of the region itself (otherwise the rotation point would
lie inside the region). A minimal width value is added by default in case the
region center and the rotation center are too close.
The WCS of the map is the TAN projection at the `center` in the coordinate
system used by the `region` center.
Parameters
----------
region : `~regions.SkyRegion`
Region to rotate
center : `~astropy.coordinates.SkyCoord`
Rotation point
binsz : `~astropy.coordinates.Angle`
Reference map bin size.
min_width : `~astropy.coordinates.Angle`
Minimal map width.
Returns
-------
reference_map : `~gammapy.maps.WcsNDMap`
Map containing the region
"""
frame = region.center.frame.name
# width is the full width of an image (not the radius)
width = 4 * region.center.separation(center) + Angle(min_width)
return WcsNDMap.create(
skydir=center, binsz=binsz, width=width, frame=frame, proj="TAN"
)
@staticmethod
def _region_angular_size(pixels, center):
"""Compute maximum angular size of a group of pixels as seen from center.
This assumes that the center lies outside the group of pixel
Parameters
----------
pixels : `~astropy.regions.PixCoord`
the pixels coordinates
center : `~astropy.regions.PixCoord`
the center coordinate in pixels
Returns
-------
angular_size : `~astropy.coordinates.Angle`
the maximum angular size
"""
newX, newY = center.x - pixels.x, center.y - pixels.y
angles = Angle(np.arctan2(newX, newY), "rad")
angular_size = np.max(angles) - np.min(angles)
if angular_size.value > np.pi:
angular_size = np.max(angles.wrap_at(0 * u.rad)) - np.min(
angles.wrap_at(0 * u.rad)
)
return angular_size
def setup(self):
"""Compute parameters for reflected regions algorithm."""
geom = self.reference_map.geom
self._pix_region = self.region.to_pixel(geom.wcs)
self._pix_center = PixCoord.from_sky(self.center, geom.wcs)
# Make the ON reference map
mask = geom.region_mask([self.region], inside=True)
# on_reference_map = WcsNDMap(geom=geom, data=mask)
# Extract all pixcoords in the geom
X, Y = geom.get_pix()
ONpixels = PixCoord(X[mask], Y[mask])
# find excluded PixCoords
mask = self.reference_map.data == 0
self.excluded_pixcoords = PixCoord(X[mask], Y[mask])
# Minimum angle a region has to be moved to not overlap with previous one
min_ang = self._region_angular_size(ONpixels, self._pix_center)
# Add required minimal distance between two off regions
self._min_ang = min_ang + self.min_distance
# Maximum possible angle before regions is reached again
self._max_angle = Angle("360deg") - self._min_ang - self.min_distance_input
def find_regions(self):
"""Find reflected regions."""
curr_angle = self._min_ang + self.min_distance_input
reflected_regions = []
while curr_angle < self._max_angle:
test_reg = self._pix_region.rotate(self._pix_center, curr_angle)
if not np.any(test_reg.contains(self.excluded_pixcoords)):
region = test_reg.to_sky(self.reference_map.geom.wcs)
reflected_regions.append(region)
curr_angle += self._min_ang
if self.max_region_number <= len(reflected_regions):
break
else:
curr_angle = curr_angle + self.angle_increment
self.reflected_regions = reflected_regions
def plot(self, fig=None, ax=None):
"""Standard debug plot.
See example here: :ref:'regions_reflected'.
"""
fig, ax, cbar = self.reference_map.plot(
fig=fig, ax=ax, cmap="gray", vmin=0, vmax=1
)
wcs = self.reference_map.geom.wcs
on_patch = self.region.to_pixel(wcs=wcs).as_artist(edgecolor="red", alpha=0.6)
ax.add_patch(on_patch)
for off in self.reflected_regions:
tmp = off.to_pixel(wcs=wcs)
off_patch = tmp.as_artist(edgecolor="blue", alpha=0.6)
ax.add_patch(off_patch)
xx, yy = self.center.to_pixel(wcs)
ax.plot(xx, yy, marker="+", color="green", markersize=20, linewidth=5)
return fig, ax
[docs]class ReflectedRegionsBackgroundMaker(Maker):
"""Reflected regions background maker.
Parameters
----------
angle_increment : `~astropy.coordinates.Angle`, optional
Rotation angle applied when a region falls in an excluded region.
min_distance : `~astropy.coordinates.Angle`, optional
Minimal distance between two consecutive reflected regions
min_distance_input : `~astropy.coordinates.Angle`, optional
Minimal distance from input region
max_region_number : int, optional
Maximum number of regions to use
exclusion_mask : `~gammapy.maps.WcsNDMap`, optional
Exclusion mask
binsz : `~astropy.coordinates.Angle`
Bin size of the reference map used for region finding.
"""
tag = "ReflectedRegionsBackgroundMaker"
def __init__(
self,
angle_increment="0.1 rad",
min_distance="0 rad",
min_distance_input="0.1 rad",
max_region_number=10000,
exclusion_mask=None,
binsz="0.01 deg",
):
self.binsz = binsz
self.exclusion_mask = exclusion_mask
self.angle_increment = Angle(angle_increment)
self.min_distance = Angle(min_distance)
self.min_distance_input = Angle(min_distance_input)
self.max_region_number = max_region_number
def _get_finder(self, dataset, observation):
return ReflectedRegionsFinder(
binsz=self.binsz,
exclusion_mask=self.exclusion_mask,
center=observation.pointing_radec,
region=dataset.counts.geom.region,
min_distance=self.min_distance,
min_distance_input=self.min_distance_input,
max_region_number=self.max_region_number,
angle_increment=self.angle_increment,
)
[docs] def make_counts_off(self, dataset, observation):
"""Make off counts.
Parameters
----------
dataset : `SpectrumDataset`
Spectrum dataset.
observation : `DatastoreObservation`
Data store observation.
Returns
-------
counts_off : `RegionNDMap`
Off counts.
"""
finder = self._get_finder(dataset, observation)
finder.run()
energy_axis = dataset.counts.geom.axes["energy"]
if len(finder.reflected_regions) > 0:
region_union = list_to_compound_region(finder.reflected_regions)
wcs = finder.reference_map.geom.wcs
geom = RegionGeom.create(region=region_union, axes=[energy_axis], wcs=wcs)
counts_off = RegionNDMap.from_geom(geom=geom)
counts_off.fill_events(observation.events)
acceptance_off = len(finder.reflected_regions)
else:
# if no OFF regions are found, off is set to None and acceptance_off to zero
counts_off = None
acceptance_off = 0
return counts_off, acceptance_off
[docs] def run(self, dataset, observation):
"""Run reflected regions background maker
Parameters
----------
dataset : `SpectrumDataset`
Spectrum dataset.
observation : `DatastoreObservation`
Data store observation.
Returns
-------
dataset_on_off : `SpectrumDatasetOnOff`
On off dataset.
"""
counts_off, acceptance_off = self.make_counts_off(dataset, observation)
return SpectrumDatasetOnOff.from_spectrum_dataset(
dataset=dataset,
acceptance=1,
acceptance_off=acceptance_off,
counts_off=counts_off,
)