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# LSST Data Management System
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"""Utilities that should be imported into the lsst.afw.geom namespace when lsst.afw.geom is used
In the case of the assert functions, importing them makes them available in lsst.utils.tests.TestCase
"""
__all__ = ["wcsAlmostEqualOverBBox"]
import itertools
import math
import numpy as np
import lsst.utils.tests
import lsst.geom
from .endpoint import GenericEndpoint, Point2Endpoint, SpherePointEndpoint
def _compareWcsOverBBox(wcs0, wcs1, bbox, maxDiffSky=0.01*lsst.geom.arcseconds,
maxDiffPix=0.01, nx=5, ny=5, doShortCircuit=True):
"""Compare two :py:class:`WCS <lsst.afw.geom.SkyWcs>` over a rectangular grid of pixel positions
Parameters
----------
wcs0 : `lsst.afw.geom.SkyWcs`
WCS 0
wcs1 : `lsst.afw.geom.SkyWcs`
WCS 1
bbox : `lsst.geom.Box2I` or `lsst.geom.Box2D`
boundaries of pixel grid over which to compare the WCSs
maxDiffSky : `lsst.geom.Angle`
maximum separation between sky positions computed using Wcs.pixelToSky
maxDiffPix : `float`
maximum separation between pixel positions computed using Wcs.skyToPixel
nx : `int`
number of points in x for the grid of pixel positions
ny : `int`
number of points in y for the grid of pixel positions
doShortCircuit : `bool`
if True then stop at the first error, else test all values in the grid
and return information about the worst violations found
Returns
-------
msg : `str`
an empty string if the WCS are sufficiently close; else return a string describing
the largest error measured in pixel coordinates (if sky to pixel error was excessive)
and sky coordinates (if pixel to sky error was excessive). If doShortCircuit is true
then the reported error is likely to be much less than the maximum error across the
whole pixel grid.
"""
if nx < 1 or ny < 1:
raise RuntimeError(
"nx = %s and ny = %s must both be positive" % (nx, ny))
if maxDiffSky <= 0*lsst.geom.arcseconds:
raise RuntimeError("maxDiffSky = %s must be positive" % (maxDiffSky,))
if maxDiffPix <= 0:
raise RuntimeError("maxDiffPix = %s must be positive" % (maxDiffPix,))
bboxd = lsst.geom.Box2D(bbox)
xList = np.linspace(bboxd.getMinX(), bboxd.getMaxX(), nx)
yList = np.linspace(bboxd.getMinY(), bboxd.getMaxY(), ny)
# we don't care about measured error unless it is too large, so initialize
# to max allowed
measDiffSky = (maxDiffSky, "?") # (sky diff, pix pos)
measDiffPix = (maxDiffPix, "?") # (pix diff, sky pos)
for x, y in itertools.product(xList, yList):
fromPixPos = lsst.geom.Point2D(x, y)
sky0 = wcs0.pixelToSky(fromPixPos)
sky1 = wcs1.pixelToSky(fromPixPos)
diffSky = sky0.separation(sky1)
if diffSky > measDiffSky[0]:
measDiffSky = (diffSky, fromPixPos)
if doShortCircuit:
break
toPixPos0 = wcs0.skyToPixel(sky0)
toPixPos1 = wcs1.skyToPixel(sky0)
diffPix = math.hypot(*(toPixPos0 - toPixPos1))
if diffPix > measDiffPix[0]:
measDiffPix = (diffPix, sky0)
if doShortCircuit:
break
msgList = []
if measDiffSky[0] > maxDiffSky:
msgList.append("%s arcsec max measured sky error > %s arcsec max allowed sky error at pix pos=%s" %
(measDiffSky[0].asArcseconds(), maxDiffSky.asArcseconds(), measDiffSky[1]))
if measDiffPix[0] > maxDiffPix:
msgList.append("%s max measured pix error > %s max allowed pix error at sky pos=%s" %
(measDiffPix[0], maxDiffPix, measDiffPix[1]))
return "; ".join(msgList)
[docs]def wcsAlmostEqualOverBBox(wcs0, wcs1, bbox, maxDiffSky=0.01*lsst.geom.arcseconds,
maxDiffPix=0.01, nx=5, ny=5):
"""Test if two :py:class:`WCS <lsst.afw.geom.SkyWcs>` are almost equal over a grid of pixel positions.
Parameters
----------
wcs0 : `lsst.afw.geom.SkyWcs`
WCS 0
wcs1 : `lsst.afw.geom.SkyWcs`
WCS 1
bbox : `lsst.geom.Box2I` or `lsst.geom.Box2D`
boundaries of pixel grid over which to compare the WCSs
maxDiffSky : `lsst.geom.Angle`
maximum separation between sky positions computed using Wcs.pixelToSky
maxDiffPix : `float`
maximum separation between pixel positions computed using Wcs.skyToPixel
nx : `int`
number of points in x for the grid of pixel positions
ny : `int`
number of points in y for the grid of pixel positions
Returns
-------
almostEqual: `bool`
`True` if two WCS are almost equal over a grid of pixel positions, else `False`
"""
return not bool(_compareWcsOverBBox(
wcs0=wcs0,
wcs1=wcs1,
bbox=bbox,
maxDiffSky=maxDiffSky,
maxDiffPix=maxDiffPix,
nx=nx,
ny=ny,
doShortCircuit=True,
))
@lsst.utils.tests.inTestCase
def assertWcsAlmostEqualOverBBox(testCase, wcs0, wcs1, bbox, maxDiffSky=0.01*lsst.geom.arcseconds,
maxDiffPix=0.01, nx=5, ny=5, msg="WCSs differ"):
"""Assert that two :py:class:`WCS <lsst.afw.geom.SkyWcs>` are almost equal over a grid of pixel positions
Compare pixelToSky and skyToPixel for two WCS over a rectangular grid of pixel positions.
If the WCS are too divergent at any point, call testCase.fail; the message describes
the largest error measured in pixel coordinates (if sky to pixel error was excessive)
and sky coordinates (if pixel to sky error was excessive) across the entire pixel grid.
Parameters
----------
testCase : `unittest.TestCase`
test case the test is part of; an object supporting one method: fail(self, msgStr)
wcs0 : `lsst.afw.geom.SkyWcs`
WCS 0
wcs1 : `lsst.afw.geom.SkyWcs`
WCS 1
bbox : `lsst.geom.Box2I` or `lsst.geom.Box2D`
boundaries of pixel grid over which to compare the WCSs
maxDiffSky : `lsst.geom.Angle`
maximum separation between sky positions computed using Wcs.pixelToSky
maxDiffPix : `float`
maximum separation between pixel positions computed using Wcs.skyToPixel
nx : `int`
number of points in x for the grid of pixel positions
ny : `int`
number of points in y for the grid of pixel positions
msg : `str`
exception message prefix; details of the error are appended after ": "
"""
errMsg = _compareWcsOverBBox(
wcs0=wcs0,
wcs1=wcs1,
bbox=bbox,
maxDiffSky=maxDiffSky,
maxDiffPix=maxDiffPix,
nx=nx,
ny=ny,
doShortCircuit=False,
)
if errMsg:
testCase.fail("%s: %s" % (msg, errMsg))
@lsst.utils.tests.inTestCase
def makeEndpoints(testCase):
"""Generate a representative sample of ``Endpoints``.
Parameters
----------
testCase : `unittest.TestCase`
test case the test is part of; an object supporting one method: fail(self, msgStr)
Returns
-------
endpoints : `list`
List of endpoints with enough diversity to exercise ``Endpoint``-related
code. Each invocation of this method shall return independent objects.
"""
return [GenericEndpoint(n) for n in range(1, 6)] + \
[Point2Endpoint(), SpherePointEndpoint()]