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#!/usr/bin/env python
from pydrizzle import process_input
import pywcs, pyfits, numpy as np
from stwcs.distortion import utils
from pytools import fileutil as fu
from stwcs import wcsutil
def align_wcs(input, shiftfile=None, writeasn=False, asnname=None):
"""
Purpose
=======
Correct the WCS of a fits file, so that multidrizzle aligns the images.
To view the format of the shift file:
>>>from pytools.asnutil import ShiftFile
>>>print ShiftFile.__doc__
Example
=======
>>>import alignwcs
>>>alignwcs.align_wcs('*flt.fits', shiftfile='shifts.txt')
It works also on the command line:
%./alignwcs.py *flt.fits shifts.txt
Dependencies
============
`pytools`
`pyfits`
`pywcs`
`numpy`
`pydrizzle`
:Parameters:
`input`: a python list of file names or a string (wild card characters allowed)
input files may be in fits, geis or waiver fits format
`shiftfile`: a shift file, as the output of tweakshifts
`writeasn`: boolean
defines whether to write out the asn table updated with shift information
`asnname`: string
name for the output asn table
"""
if shiftfile == None:
print 'A shift file is required but was not provided\n'
return
asndict,b,c = process_input.process_input(input, shiftfile=shiftfile, updatewcs=False)
if writeasn:
if asnname == None:
asnname = c.split('.fits')[0] + '_shifts' + '.fits'
a.write(asnname)
outwcs = get_outwcs(asndict)
apply_shifts(asndict, outwcs)
def apply_shifts(asndict, outwcs):
for mem in asndict['members']:
filename = fu.buildRootname(mem)
xsh = asndict['members'][mem]['xshift']
ysh = asndict['members'][mem]['yshift']
shifts = np.array([[xsh, ysh]])
f = pyfits.open(filename)
for extn in f:
if extn.header.has_key('extname') and extn.header['extname'].lower() == 'sci':
extver = extn.header['extver']
owcs = pywcs.WCS(extn.header, f)
crvals = np.array([owcs.wcs.crval])
px = outwcs.wcs.s2p(crvals, 1)['pixcrd'] + shifts
ncrvals = outwcs.all_pix2sky(px, 1)
pyfits.setval(filename, 'CRVAL1', value=ncrvals[0,0], ext=extver)
pyfits.setval(filename, 'CRVAL2', value=ncrvals[0,1], ext=extver)
print 'Updated %s with shifts ' % filename, shifts
f.close()
def get_outwcs(asndict):
wcslist = []
for mem in asndict['members']:
filename = fu.buildRootname(mem)
f = pyfits.open(filename)
hdr0 = f[0].header
for extn in f:
if extn.header.has_key('extname') and extn.header['extname'].lower() == 'sci':
owcs = wcsutil.HSTWCS(hdr0, extn.header,f)
wcslist.append(owcs)
f.close()
outwcs = utils.output_wcs(wcslist)
return outwcs
if __name__ == '__main__':
import sys
args = sys.argv[1:]
input = args[:-1]
shifts = args[-1]
align_wcs(input, shiftfile=shifts)
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