Coverage for python/lsst/sphgeom/_healpixPixelization.py: 24%
75 statements
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« prev ^ index » next coverage.py v6.4.2, created at 2022-07-15 02:30 -0700
1# This file is part of sphgeom.
2#
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (http://www.lsst.org).
6# See the COPYRIGHT file at the top-level directory of this distribution
7# for details of code ownership.
8#
9# This program is free software: you can redistribute it and/or modify
10# it under the terms of the GNU General Public License as published by
11# the Free Software Foundation, either version 3 of the License, or
12# (at your option) any later version.
13#
14# This program is distributed in the hope that it will be useful,
15# but WITHOUT ANY WARRANTY; without even the implied warranty of
16# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17# GNU General Public License for more details.
18#
19# You should have received a copy of the GNU General Public License
20# along with this program. If not, see <http://www.gnu.org/licenses/>.
21__all__ = ["HealpixPixelization"]
23import numpy as np
25from ._sphgeom import Box, Circle, ConvexPolygon, Ellipse, RangeSet, Region, UnitVector3d
26from .pixelization_abc import PixelizationABC
29class HealpixPixelization(PixelizationABC):
30 """HEALPix pixelization class.
32 Parameters
33 ----------
34 level : `int`
35 Pixelization level. HEALPix nside = 2**level
36 """
38 MAX_LEVEL = 17
40 def __init__(self, level: int):
41 import healpy as hp
43 if level < 0:
44 raise ValueError("HealPix level must be >= 0.")
46 self._level = level
47 self._nside = 2**level
49 self._npix = hp.nside2npix(self._nside)
51 # Values used to do pixel/region intersections
52 self._bit_shift = 8
53 self._nside_highres = self._nside * (2 ** (self._bit_shift // 2))
55 @property
56 def nside(self):
57 return self._nside
59 def getLevel(self):
60 return self._level
62 level = property(getLevel)
64 def universe(self) -> RangeSet:
65 return RangeSet(0, self._npix)
67 def pixel(self, i) -> Region:
68 import healpy as hp
70 # This is arbitrarily returning 4 points on a side
71 # to approximate the pixel shape.
72 varr = hp.boundaries(self._nside, i, step=4, nest=True).T
73 return ConvexPolygon([UnitVector3d(*c) for c in varr])
75 def index(self, v: UnitVector3d) -> int:
76 import healpy as hp
78 return hp.vec2pix(self._nside, v.x(), v.y(), v.z(), nest=True)
80 def toString(self, i: int) -> str:
81 return str(i)
83 def envelope(self, region: Region, maxRanges: int = 0):
84 import healpy as hp
86 if maxRanges > 0:
87 # If this is important, the rangeset can be consolidated.
88 raise NotImplementedError("HealpixPixelization: maxRanges not implemented")
89 pixels_highres = self._interior_pixels_from_region(self._nside_highres, region)
91 # Dilate the high resolution pixels by one to ensure that the full
92 # region is completely covered at high resolution.
93 neighbors = hp.get_all_neighbours(self._nside_highres, pixels_highres, nest=True)
94 # Shift back to the original resolution and uniquify
95 pixels = np.unique(np.right_shift(neighbors, self._bit_shift))
97 return RangeSet(pixels)
99 def interior(self, region: Region, maxRanges: int = 0):
100 import healpy as hp
102 if maxRanges > 0:
103 # If this is important, the rangeset can be consolidated.
104 raise NotImplementedError("HealpixPixelization: maxRanges not implemented")
105 pixels = self._interior_pixels_from_region(self._nside, region)
107 # Check that the corners of the pixels are entirely enclosed in
108 # the region
110 # Returns array [npixels, 3, ncorners], where ncorners is 4, and
111 # the center index points to x, y, z.
112 corners = hp.boundaries(self._nside, pixels, step=1, nest=True)
114 corners_int = region.contains(
115 corners[:, 0, :].ravel(), corners[:, 1, :].ravel(), corners[:, 2, :].ravel()
116 ).reshape((len(pixels), 4))
117 interior = np.sum(corners_int, axis=1) == 4
118 pixels = pixels[interior]
120 return RangeSet(pixels)
122 def _interior_pixels_from_region(self, nside: int, region: Region):
123 """Get interior pixels from a region.
125 Parameters
126 ----------
127 nside : `int`
128 Healpix nside to retrieve interior pixels.
129 region : `lsst.sphgeom.Region`
130 Sphgeom region to find interior pixels.
132 Returns
133 -------
134 pixels : `np.ndarray`
135 Array of pixels at resolution nside, nest ordering.
136 """
137 import healpy as hp
139 _circle = None
140 _poly = None
141 if isinstance(region, (Box, Ellipse)):
142 _circle = region.getBoundingCircle()
143 elif isinstance(region, Circle):
144 _circle = region
145 elif isinstance(region, ConvexPolygon):
146 _poly = region
147 else:
148 raise ValueError("Invalid region.")
150 # Find all pixels at an arbitrarily higher resolution
151 if _circle is not None:
152 center = _circle.getCenter()
153 vec = np.array([center.x(), center.y(), center.z()]).T
154 pixels = hp.query_disc(
155 nside, vec, _circle.getOpeningAngle().asRadians(), inclusive=False, nest=True
156 )
157 else:
158 vertices = np.array([[v.x(), v.y(), v.z()] for v in _poly.getVertices()])
159 pixels = hp.query_polygon(nside, vertices, inclusive=False, nest=True)
161 return pixels
163 def __eq__(self, other):
164 if isinstance(other, HealpixPixelization):
165 return self._level == other._level
167 def __repr__(self):
168 return f"HealpixPixelization({self._level})"
170 def __reduce__(self):
171 return (self.__class__, (self._level,))