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LSST Data Management Base Package
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utils.py
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1# This file is part of afw.
2#
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (https://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 <https://www.gnu.org/licenses/>.
21
22"""Utilities that should be imported into the lsst.afw.geom namespace when lsst.afw.geom is used
23
24In the case of the assert functions, importing them makes them available in lsst.utils.tests.TestCase
25"""
26__all__ = ["wcsAlmostEqualOverBBox"]
27
28import itertools
29import math
30
31import numpy as np
32
34import lsst.geom
35from ._geom import GenericEndpoint, Point2Endpoint, SpherePointEndpoint
36
37
38def _compareWcsOverBBox(wcs0, wcs1, bbox, maxDiffSky=0.01*lsst.geom.arcseconds,
39 maxDiffPix=0.01, nx=5, ny=5, doShortCircuit=True):
40 """Compare two :py:class:`WCS <lsst.afw.geom.SkyWcs>` over a rectangular grid of pixel positions
41
42 Parameters
43 ----------
44 wcs0 : `lsst.afw.geom.SkyWcs`
45 WCS 0
46 wcs1 : `lsst.afw.geom.SkyWcs`
47 WCS 1
48 bbox : `lsst.geom.Box2I` or `lsst.geom.Box2D`
49 boundaries of pixel grid over which to compare the WCSs
50 maxDiffSky : `lsst.geom.Angle`
51 maximum separation between sky positions computed using Wcs.pixelToSky
52 maxDiffPix : `float`
53 maximum separation between pixel positions computed using Wcs.skyToPixel
54 nx : `int`
55 number of points in x for the grid of pixel positions
56 ny : `int`
57 number of points in y for the grid of pixel positions
58 doShortCircuit : `bool`
59 if True then stop at the first error, else test all values in the grid
60 and return information about the worst violations found
61
62 Returns
63 -------
64 msg : `str`
65 an empty string if the WCS are sufficiently close; else return a string describing
66 the largest error measured in pixel coordinates (if sky to pixel error was excessive)
67 and sky coordinates (if pixel to sky error was excessive). If doShortCircuit is true
68 then the reported error is likely to be much less than the maximum error across the
69 whole pixel grid.
70 """
71 if nx < 1 or ny < 1:
72 raise RuntimeError(f"nx = {nx} and ny = {ny} must both be positive")
73 if maxDiffSky < 0*lsst.geom.arcseconds:
74 raise RuntimeError(f"maxDiffSky = {maxDiffSky} must not be negative")
75 if maxDiffPix < 0:
76 raise RuntimeError(f"maxDiffPix = {maxDiffPix} must not be negative")
77
78 bboxd = lsst.geom.Box2D(bbox)
79 xList = np.linspace(bboxd.getMinX(), bboxd.getMaxX(), nx)
80 yList = np.linspace(bboxd.getMinY(), bboxd.getMaxY(), ny)
81 # we don't care about measured error unless it is too large, so initialize
82 # to max allowed
83 measDiffSky = (maxDiffSky, "?") # (sky diff, pix pos)
84 measDiffPix = (maxDiffPix, "?") # (pix diff, sky pos)
85 for x, y in itertools.product(xList, yList):
86 fromPixPos = lsst.geom.Point2D(x, y)
87 sky0 = wcs0.pixelToSky(fromPixPos)
88 sky1 = wcs1.pixelToSky(fromPixPos)
89 diffSky = sky0.separation(sky1)
90 if diffSky > measDiffSky[0]:
91 measDiffSky = (diffSky, fromPixPos)
92 if doShortCircuit:
93 break
94
95 toPixPos0 = wcs0.skyToPixel(sky0)
96 toPixPos1 = wcs1.skyToPixel(sky0)
97 diffPix = math.hypot(*(toPixPos0 - toPixPos1))
98 if diffPix > measDiffPix[0]:
99 measDiffPix = (diffPix, sky0)
100 if doShortCircuit:
101 break
102
103 msgList = []
104 if measDiffSky[0] > maxDiffSky:
105 msgList.append(f"{measDiffSky[0].asArcseconds()} arcsec max measured sky error "
106 f"> {maxDiffSky.asArcseconds()} arcsec max allowed sky error "
107 f"at pix pos=measDiffSky[1]")
108 if measDiffPix[0] > maxDiffPix:
109 msgList.append(f"{measDiffPix[0]} max measured pix error "
110 f"> {maxDiffPix} max allowed pix error "
111 f"at sky pos={measDiffPix[1]}")
112
113 return "; ".join(msgList)
114
115
116def wcsAlmostEqualOverBBox(wcs0, wcs1, bbox, maxDiffSky=0.01*lsst.geom.arcseconds,
117 maxDiffPix=0.01, nx=5, ny=5):
118 """Test if two :py:class:`WCS <lsst.afw.geom.SkyWcs>` are almost equal over a grid of pixel positions.
119
120 Parameters
121 ----------
122 wcs0 : `lsst.afw.geom.SkyWcs`
123 WCS 0
124 wcs1 : `lsst.afw.geom.SkyWcs`
125 WCS 1
126 bbox : `lsst.geom.Box2I` or `lsst.geom.Box2D`
127 boundaries of pixel grid over which to compare the WCSs
128 maxDiffSky : `lsst.geom.Angle`
129 maximum separation between sky positions computed using Wcs.pixelToSky
130 maxDiffPix : `float`
131 maximum separation between pixel positions computed using Wcs.skyToPixel
132 nx : `int`
133 number of points in x for the grid of pixel positions
134 ny : `int`
135 number of points in y for the grid of pixel positions
136
137 Returns
138 -------
139 almostEqual: `bool`
140 `True` if two WCS are almost equal over a grid of pixel positions, else `False`
141 """
142 return not bool(_compareWcsOverBBox(
143 wcs0=wcs0,
144 wcs1=wcs1,
145 bbox=bbox,
146 maxDiffSky=maxDiffSky,
147 maxDiffPix=maxDiffPix,
148 nx=nx,
149 ny=ny,
150 doShortCircuit=True,
151 ))
152
153
154@lsst.utils.tests.inTestCase
155def assertWcsAlmostEqualOverBBox(testCase, wcs0, wcs1, bbox, maxDiffSky=0.01*lsst.geom.arcseconds,
156 maxDiffPix=0.01, nx=5, ny=5, msg="WCSs differ"):
157 """Assert that two :py:class:`WCS <lsst.afw.geom.SkyWcs>` are almost equal over a grid of pixel positions
158
159 Compare pixelToSky and skyToPixel for two WCS over a rectangular grid of pixel positions.
160 If the WCS are too divergent at any point, call testCase.fail; the message describes
161 the largest error measured in pixel coordinates (if sky to pixel error was excessive)
162 and sky coordinates (if pixel to sky error was excessive) across the entire pixel grid.
163
164 Parameters
165 ----------
166 testCase : `unittest.TestCase`
167 test case the test is part of; an object supporting one method: fail(self, msgStr)
168 wcs0 : `lsst.afw.geom.SkyWcs`
169 WCS 0
170 wcs1 : `lsst.afw.geom.SkyWcs`
171 WCS 1
172 bbox : `lsst.geom.Box2I` or `lsst.geom.Box2D`
173 boundaries of pixel grid over which to compare the WCSs
174 maxDiffSky : `lsst.geom.Angle`
175 maximum separation between sky positions computed using Wcs.pixelToSky
176 maxDiffPix : `float`
177 maximum separation between pixel positions computed using Wcs.skyToPixel
178 nx : `int`
179 number of points in x for the grid of pixel positions
180 ny : `int`
181 number of points in y for the grid of pixel positions
182 msg : `str`
183 exception message prefix; details of the error are appended after ": "
184 """
185 errMsg = _compareWcsOverBBox(
186 wcs0=wcs0,
187 wcs1=wcs1,
188 bbox=bbox,
189 maxDiffSky=maxDiffSky,
190 maxDiffPix=maxDiffPix,
191 nx=nx,
192 ny=ny,
193 doShortCircuit=False,
194 )
195 if errMsg:
196 testCase.fail(f"{msg}: {errMsg}")
197
198
199@lsst.utils.tests.inTestCase
200def makeEndpoints(testCase):
201 """Generate a representative sample of ``Endpoints``.
202
203 Parameters
204 ----------
205 testCase : `unittest.TestCase`
206 test case the test is part of; an object supporting one method: fail(self, msgStr)
207
208 Returns
209 -------
210 endpoints : `list`
211 List of endpoints with enough diversity to exercise ``Endpoint``-related
212 code. Each invocation of this method shall return independent objects.
213 """
214 return [GenericEndpoint(n) for n in range(1, 6)] + \
215 [Point2Endpoint(), SpherePointEndpoint()]
A floating-point coordinate rectangle geometry.
Definition Box.h:413
assertWcsAlmostEqualOverBBox(testCase, wcs0, wcs1, bbox, maxDiffSky=0.01 *lsst.geom.arcseconds, maxDiffPix=0.01, nx=5, ny=5, msg="WCSs differ")
Definition utils.py:156
wcsAlmostEqualOverBBox(wcs0, wcs1, bbox, maxDiffSky=0.01 *lsst.geom.arcseconds, maxDiffPix=0.01, nx=5, ny=5)
Definition utils.py:117
_compareWcsOverBBox(wcs0, wcs1, bbox, maxDiffSky=0.01 *lsst.geom.arcseconds, maxDiffPix=0.01, nx=5, ny=5, doShortCircuit=True)
Definition utils.py:39
makeEndpoints(testCase)
Definition utils.py:200