Coverage for python/lsst/daf/butler/core/regions.py : 29%

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1# This file is part of daf_butler.
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/>.
22__all__ = ("makeBoxWcsRegion", )
24import lsst.sphgeom
25import lsst.geom
28def makeBoxWcsRegion(box, wcs, margin):
29 """Construct a spherical ConvexPolygon from a WCS and a bounding box.
31 Parameters
32 ----------
33 box : `lsst.geom.Box2I` or `lsst.geom.Box2D`
34 A box in the pixel coordinate system defined by the WCS.
35 wcs : `lsst.afw.image.Wcs`
36 A mapping from a pixel coordinate system to the sky.
37 margin : `float`
38 A buffer in pixels to grow the box by (in all directions) before
39 transforming it to sky coordinates.
41 Returns
42 -------
43 polygon : `lsst.sphgeom.ConvexPolygon`
44 A convex polygon.
45 """
46 box = lsst.geom.Box2D(box)
47 box.grow(margin)
48 vertices = []
49 for point in box.getCorners():
50 coord = wcs.pixelToSky(point)
51 lonlat = lsst.sphgeom.LonLat.fromRadians(coord.getRa().asRadians(),
52 coord.getDec().asRadians())
53 vertices.append(lsst.sphgeom.UnitVector3d(lonlat))
54 return lsst.sphgeom.ConvexPolygon(vertices)