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# This file is part of daf_butler. 

# 

# Developed for the LSST Data Management System. 

# This product includes software developed by the LSST Project 

# (http://www.lsst.org). 

# See the COPYRIGHT file at the top-level directory of this distribution 

# for details of code ownership. 

# 

# This program is free software: you can redistribute it and/or modify 

# it under the terms of the GNU General Public License as published by 

# the Free Software Foundation, either version 3 of the License, or 

# (at your option) any later version. 

# 

# This program is distributed in the hope that it will be useful, 

# but WITHOUT ANY WARRANTY; without even the implied warranty of 

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

# GNU General Public License for more details. 

# 

# You should have received a copy of the GNU General Public License 

# along with this program. If not, see <http://www.gnu.org/licenses/>. 

 

import lsst.sphgeom 

import lsst.geom 

 

__all__ = ("makeBoxWcsRegion", ) 

 

 

def makeBoxWcsRegion(box, wcs, margin): 

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

 

Parameters 

---------- 

box : `lsst.geom.Box2I` or `lsst.geom.Box2D` 

A box in the pixel coordinate system defined by the WCS. 

wcs : `lsst.afw.image.Wcs` 

A mapping from a pixel coordinate system to the sky. 

margin : `float` 

A buffer in pixels to grow the box by (in all directions) before 

transforming it to sky coordinates. 

 

Returns 

------- 

polygon : `lsst.sphgeom.ConvexPolygon` 

A convex polygon. 

""" 

box = lsst.geom.Box2D(box) 

box.grow(margin) 

vertices = [] 

for point in box.getCorners(): 

coord = wcs.pixelToSky(point) 

lonlat = lsst.sphgeom.LonLat.fromRadians(coord.getRa().asRadians(), 

coord.getDec().asRadians()) 

vertices.append(lsst.sphgeom.UnitVector3d(lonlat)) 

return lsst.sphgeom.ConvexPolygon(vertices)