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from __future__ import division # confidence high
import time
import pyfits
from pytools import fileutil
import utils
import logging
logger = logging.getLogger('stwcs.updatewcs.Det2IM')
class DET2IMCorr(object):
"""
Stores a small correction to the detector coordinates as a d2imarr
extension in the science file.
Notes
-----
For the case of ACS/WFC every 68th column is wider than the rest.
To compensate for this a small correction needs to be applied to the
detector coordinates. We call this a detector to image transformation.
The so obtained image coordinates are the input to all other distortion
corrections. The correction is originally stored in an external
reference file pointed to by 'D2IMFILE' keyword in the primary header.
This class attaches the correction array as an extension to the science
file with extname = `d2imarr`.
Other keywords used in this correction are:
`AXISCORR`: integer (1 or 2) - axis to which the detector to image
correction is applied
`D2IMEXT`: string = name of reference file which was used to create
the lookup table extension
`D2IMERR`: float, optional - maximum value of the correction
"""
def updateWCS(cls, fobj):
"""
Parameters
----------
fobj: pyfits object
Science file, for which a detector to image correction
is available
Notes
-----
Uses the file pointed to in the primary header keyword 'D2IMFILE'
to create an extension with a detector to image correction.
"""
logger.info("\n\tStarting Det2IM Correction: %s" % time.asctime())
try:
assert isinstance(fobj, pyfits.HDUList)
except AssertionError:
logger.exception('\n\tInput must be a pyfits.HDUList object')
raise
d2imfile = fileutil.osfn(fobj[0].header['D2IMFILE'])
axiscorr = cls.getAxisCorr(d2imfile)
d2imerr = pyfits.getdata(d2imfile, ext=1).max()
if axiscorr == None:
new_kw = {}
else:
new_kw = {'D2IMEXT': d2imfile, 'AXISCORR': axiscorr, 'D2IMERR': d2imerr}
cls.applyDet2ImCorr(fobj,axiscorr)
cls.updatehdr(fobj, new_kw)
updateWCS = classmethod(updateWCS)
def getAxisCorr(cls, refname):
try:
direction = pyfits.getval(refname, ext=1, key='EXTNAME')
if direction == 'DX': return 1
elif direction == 'DY': return 2
else:
logger.warning('\n\tDET2IM correction expects the reference file to have \
an EXTNAME keyword of value "DX" or "DY", EXTNAMe %s detected' % direction)
return None
except KeyError:
logger.exception("\n\tD2IMFILE %s is missing EXTNAME keyword. Unable to determine axis \
to which to apply the correction." % refname)
direction = None
return direction
getAxisCorr = classmethod(getAxisCorr)
def applyDet2ImCorr(cls,fobj, axiscorr):
binned = utils.getBinning(fobj)
hdu = cls.createDgeoHDU(fobj, axiscorr, binned)
d2imarr_ind = cls.getD2imIndex(fobj)
if d2imarr_ind:
fobj[d2imarr_ind] = hdu
else:
fobj.append(hdu)
applyDet2ImCorr = classmethod(applyDet2ImCorr)
def getD2imIndex(cls,fobj):
index = None
for e in range(len(fobj)):
try:
ename = fobj[e].header['EXTNAME']
except KeyError:
continue
if ename == 'D2IMARR':
index = e
return index
getD2imIndex = classmethod(getD2imIndex)
def createDgeoHDU(cls, fobj, axiscorr, binned=1):
d2imfile = fileutil.osfn(fobj[0].header['D2IMFILE'])
d2im_data = pyfits.getdata(d2imfile, ext=1)
sci_hdr = fobj['sci',1].header
d2im_hdr = cls.createDet2ImHdr(fobj, binned)
hdu = pyfits.ImageHDU(header=d2im_hdr, data=d2im_data)
return hdu
createDgeoHDU = classmethod(createDgeoHDU)
def createDet2ImHdr(cls, fobj, binned=1):
"""
Creates a header for the D2IMARR extension based on the
reference file recorded in D2IMFILE keyword in the primary header.
fobj - the science file
"""
d2imfile = fileutil.osfn(fobj[0].header['D2IMFILE'])
axiscorr = cls.getAxisCorr(d2imfile)
sci_hdr = fobj[1].header
data_shape = pyfits.getdata(d2imfile, ext=1).shape
naxis = pyfits.getval(d2imfile, ext=1, key='NAXIS')
kw = { 'NAXIS': 'Size of the axis',
'CRPIX': 'Coordinate system reference pixel',
'CRVAL': 'Coordinate system value at reference pixel',
'CDELT': 'Coordinate increment along axis'}
kw_comm1 = {}
kw_val1 = {}
for key in kw.keys():
for i in range(1, naxis+1):
si = str(i)
kw_comm1[key+si] = kw[key]
for i in range(1, naxis+1):
si = str(i)
kw_val1['NAXIS'+si] = data_shape[i-1]
kw_val1['CRPIX'+si] = data_shape[i-1]/2.
kw_val1['CDELT'+si] = 1./binned
kw_val1['CRVAL'+si] = (sci_hdr.get('NAXIS'+si, 1)/2. + \
sci_hdr.get('LTV'+si, 0.)) / binned
kw_comm0 = {'XTENSION': 'Image extension',
'BITPIX': 'IEEE floating point',
'NAXIS': 'Number of axes',
'EXTNAME': 'WCS distortion array',
'EXTVER': 'Distortion array version number',
'PCOUNT': 'Special data area of size 0',
'GCOUNT': 'One data group',
'AXISCORR': 'Direction in which the det2im correction is applied'}
kw_val0 = { 'XTENSION': 'IMAGE',
'BITPIX': -32,
'NAXIS': naxis,
'EXTNAME': 'D2IMARR',
'EXTVER': 1,
'PCOUNT': 0,
'GCOUNT': 1,
'AXISCORR': axiscorr
}
cdl = pyfits.CardList()
for key in kw_comm0.keys():
cdl.append(pyfits.Card(key=key, value=kw_val0[key], comment=kw_comm0[key]))
for key in kw_comm1.keys():
cdl.append(pyfits.Card(key=key, value=kw_val1[key], comment=kw_comm1[key]))
hdr = pyfits.Header(cards=cdl)
return hdr
createDet2ImHdr = classmethod(createDet2ImHdr)
def updatehdr(cls, fobj, kwdict):
"""
Update extension headers to keep record of the files used for the
detector to image correction.
"""
for ext in fobj:
try:
extname = ext.header['EXTNAME'].lower()
except KeyError:
continue
if extname == 'sci':
for kw in kwdict:
ext.header.update(kw, kwdict[kw])
else:
continue
updatehdr = classmethod(updatehdr)
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