Coverage for python/lsst/sphgeom/_healpixPixelization.py: 25%
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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
24import healpy as hp
26from ._sphgeom import RangeSet, Region, UnitVector3d
27from ._sphgeom import Box, Circle, ConvexPolygon, Ellipse
28from .pixelization_abc import PixelizationABC
31class HealpixPixelization(PixelizationABC):
32 """HEALPix pixelization class.
34 Parameters
35 ----------
36 level : `int`
37 Pixelization level. HEALPix nside = 2**level
38 """
39 MAX_LEVEL = 17
41 def __init__(self, level: int):
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 # This is arbitrarily returning 4 points on a side
69 # to approximate the pixel shape.
70 varr = hp.boundaries(self._nside, i, step=4, nest=True).T
71 return ConvexPolygon([UnitVector3d(*c) for c in varr])
73 def index(self, v: UnitVector3d) -> int:
74 return hp.vec2pix(self._nside, v.x(), v.y(), v.z(), nest=True)
76 def toString(self, i: int) -> str:
77 return str(i)
79 def envelope(self, region: Region, maxRanges: int = 0):
80 if maxRanges > 0:
81 # If this is important, the rangeset can be consolidated.
82 raise NotImplementedError("HealpixPixelization: maxRanges not implemented")
83 pixels_highres = self._interior_pixels_from_region(self._nside_highres, region)
85 # Dilate the high resolution pixels by one to ensure that the full
86 # region is completely covered at high resolution.
87 neighbors = hp.get_all_neighbours(self._nside_highres,
88 pixels_highres,
89 nest=True)
90 # Shift back to the original resolution and uniquify
91 pixels = np.unique(np.right_shift(neighbors, self._bit_shift))
93 return RangeSet(pixels)
95 def interior(self, region: Region, maxRanges: int = 0):
96 if maxRanges > 0:
97 # If this is important, the rangeset can be consolidated.
98 raise NotImplementedError("HealpixPixelization: maxRanges not implemented")
99 pixels = self._interior_pixels_from_region(self._nside, region)
101 # Check that the corners of the pixels are entirely enclosed in
102 # the region
104 # Returns array [npixels, 3, ncorners], where ncorners is 4, and
105 # the center index points to x, y, z.
106 corners = hp.boundaries(self._nside, pixels, step=1, nest=True)
108 corners_int = region.contains(corners[:, 0, :].ravel(),
109 corners[:, 1, :].ravel(),
110 corners[:, 2, :].ravel()).reshape((len(pixels), 4))
111 interior = (np.sum(corners_int, axis=1) == 4)
112 pixels = pixels[interior]
114 return RangeSet(pixels)
116 def _interior_pixels_from_region(self, nside: int, region: Region):
117 """Get interior pixels from a region.
119 Parameters
120 ----------
121 nside : `int`
122 Healpix nside to retrieve interior pixels.
123 region : `lsst.sphgeom.Region`
124 Sphgeom region to find interior pixels.
126 Returns
127 -------
128 pixels : `np.ndarray`
129 Array of pixels at resolution nside, nest ordering.
130 """
131 _circle = None
132 _poly = None
133 if isinstance(region, (Box, Ellipse)):
134 _circle = region.getBoundingCircle()
135 elif isinstance(region, Circle):
136 _circle = region
137 elif isinstance(region, ConvexPolygon):
138 _poly = region
139 else:
140 raise ValueError("Invalid region.")
142 # Find all pixels at an arbitrarily higher resolution
143 if _circle is not None:
144 center = _circle.getCenter()
145 vec = np.array([center.x(), center.y(), center.z()]).T
146 pixels = hp.query_disc(nside,
147 vec,
148 _circle.getOpeningAngle().asRadians(),
149 inclusive=False,
150 nest=True)
151 else:
152 vertices = np.array([[v.x(), v.y(), v.z()] for v in _poly.getVertices()])
153 pixels = hp.query_polygon(nside,
154 vertices,
155 inclusive=False,
156 nest=True)
158 return pixels
160 def __eq__(self, other):
161 if isinstance(other, HealpixPixelization):
162 return (self._level == other._level)
164 def __repr__(self):
165 return f"HealpixPixelization({self._level})"
167 def __reduce__(self):
168 return (self.__class__, (self._level, ))