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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/>. 

21 

22__all__ = ("makeBoxWcsRegion", ) 

23 

24import lsst.sphgeom 

25import lsst.geom 

26 

27 

28def makeBoxWcsRegion(box, wcs, margin): 

29 """Construct a spherical ConvexPolygon from a WCS and a bounding box. 

30 

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. 

40 

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)