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# 

# LSST Data Management System 

# Copyright 2017 AURA/LSST 

# 

# 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__ = ('InitialSkyWcsError', 'createInitialSkyWcs', 'bboxFromIraf') 

 

import re 

import lsst.geom as geom 

 

from lsst.afw.cameraGeom import PIXELS, FIELD_ANGLE 

from lsst.afw.image import RotType 

from lsst.afw.geom.skyWcs import makeSkyWcs 

import lsst.pex.exceptions 

 

 

class InitialSkyWcsError(Exception): 

"""For handling failures when creating a SkyWcs from a camera geometry and 

boresight. 

 

Typically used as a chained exception from a lower level exception. 

""" 

pass 

 

 

def createInitialSkyWcs(visitInfo, detector, flipX=False): 

"""Create a SkyWcs from the telescope boresight and detector geometry. 

 

A typical usecase for this is to create the initial WCS for a newly-read 

raw exposure. 

 

 

Parameters 

---------- 

visitInfo : `lsst.afw.image.VisitInfo` 

Where to get the telescope boresight and rotator angle from. 

detector : `lsst.afw.cameraGeom.Detector` 

Where to get the camera geomtry from. 

flipX : `bool`, optional 

If False, +X is along W, if True +X is along E. 

 

Returns 

------- 

skyWcs : `lsst.afw.geom.SkyWcs` 

The new composed WCS. 

 

Raises 

------ 

InitialSkyWcsError 

Raised if there is an error generating the SkyWcs, chained from the 

lower-level exception if available. 

""" 

if visitInfo.getRotType() != RotType.SKY: 

msg = (f"Cannot create SkyWcs from camera geometry: rotator angle defined using " 

f"RotType={visitInfo.getRotType()} instead of SKY.") 

raise InitialSkyWcsError(msg) 

orientation = visitInfo.getBoresightRotAngle() 

boresight = visitInfo.getBoresightRaDec() 

try: 

pixelsToFieldAngle = detector.getTransform(detector.makeCameraSys(PIXELS), 

detector.makeCameraSys(FIELD_ANGLE)) 

except lsst.pex.exceptions.InvalidParameterError as e: 

raise InitialSkyWcsError("Cannot compute PIXELS to FIELD_ANGLE Transform.") from e 

return makeSkyWcs(pixelsToFieldAngle, orientation, flipX, boresight) 

 

 

def bboxFromIraf(irafBBoxStr): 

"""Return a Box2I corresponding to an IRAF-style BBOX 

 

[x0:x1,y0:y1] where x0 and x1 are the one-indexed start and end columns, and correspondingly 

y0 and y1 are the start and end rows. 

""" 

 

mat = re.search(r"^\[([-\d]+):([-\d]+),([-\d]+):([-\d]+)\]$", irafBBoxStr) 

if not mat: 

raise RuntimeError("Unable to parse IRAF-style bbox \"%s\"" % irafBBoxStr) 

x0, x1, y0, y1 = [int(_) for _ in mat.groups()] 

 

return geom.BoxI(geom.PointI(x0 - 1, y0 - 1), geom.PointI(x1 - 1, y1 - 1))