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# 

# LSST Data Management System 

# Copyright 2008, 2009, 2010 LSST Corporation. 

# 

# This product includes software developed by the 

# LSST Project (http://www.lsst.org/). 

# 

# 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 LSST License Statement and 

# the GNU General Public License along with this program. If not, 

# see <http://www.lsstcorp.org/LegalNotices/>. 

# 

 

__all__ = ['WcsFactory'] 

 

import lsst.afw.geom as afwGeom 

 

 

class WcsFactory: 

"""A factory for creating Wcs objects for the sky tiles. 

 

Parameters 

---------- 

pixelScale : `lsst.geom.Angle` 

Desired scale, as sky/pixel. 

projection : `str` 

FITS-standard 3-letter name of projection, e.g.: TAN (tangent), 

STG (stereographic), MOL (Mollweide's), AIT (Hammer-Aitoff) 

see Representations of celestial coordinates in FITS 

(Calabretta and Greisen, 2002). 

rotation : `lsst.geom.Angle` 

Rotation relative to cardinal. 

flipX : `bool` 

Flip the X axis? 

""" 

 

def __init__(self, pixelScale, projection, rotation=0*afwGeom.radians, flipX=False): 

if len(projection) != 3: 

raise RuntimeError("projection=%r; must have length 3" % (projection,)) 

self._projection = projection 

self._cdMatrix = afwGeom.makeCdMatrix(scale=pixelScale, orientation=rotation, flipX=flipX) 

 

def makeWcs(self, crPixPos, crValCoord): 

"""Make a Wcs. 

 

Parameters 

---------- 

crPixPos : `lsst.geom.Point2D` 

crPix for WCS, using the LSST standard. 

crValCoord : `lsst.geom.SpherePoint` 

ICRS crVal for WCS. 

 

Returns 

------- 

results : `lsst.afw.geom.SkyWcs` 

The new SkyWcs object. 

""" 

return afwGeom.makeSkyWcs(crpix=crPixPos, crval=crValCoord, 

cdMatrix=self._cdMatrix, projection=self._projection)