Source code for drizzlepac.tweakback

"""
`tweakback` - propagate the "tweaked" solutions back to the original
input files.

Version 0.4.0 - replaced previous algorithm that used fitting of WCS
footprints to reconstruct the transformation that was applied to the
old drizzled image (to align it with another image) to obtain the new
drizzled image WCS with an algorithm that is based on linearization of
the exact compound operator that transforms current image coordinates to
the "aligned" (to the new drizzled WCS) image coordinates.

:Authors: Warren Hack, Mihai Cara

:License: :doc:`LICENSE`

"""
import os

import numpy as np
from astropy.io import fits

from stwcs import wcsutil
from stsci.tools import parseinput, logutil
from stsci.skypac.utils import get_ext_list, ext2str

from . import updatehdr
from . import linearfit
from . import util


__taskname__ = 'tweakback' # unless someone comes up with anything better

# This is specifically NOT intended to match the package-wide version information.
__version__ = '0.4.1'
__version_date__ = '13-July-2020'


log = logutil.create_logger(__name__, level=logutil.logging.NOTSET)

if hasattr(np, 'float128'):
    ndfloat128 = np.float128
elif hasattr(np, 'float96'):
    ndfloat128 = np.float96
else:
    ndfloat128 = np.float64


#### Primary function
[docs]def tweakback(drzfile, input=None, origwcs = None, newname = None, wcsname = None, extname='SCI', force=False, verbose=False): """ Apply WCS solution recorded in drizzled file to distorted input images (``_flt.fits`` files) used to create the drizzled file. This task relies on the original WCS and updated WCS to be recorded in the drizzled image's header as the last 2 alternate WCSs. Parameters ---------- drzfile : str (Default = '') filename of undistorted image which contains the new WCS and WCS prior to being updated newname : str (Default = None) Value of ``WCSNAME`` to be used to label the updated solution in the output (eq., ``_flt.fits``) files. If left blank or None, it will default to using the current ``WCSNAME`` value from the input drzfile. input : str (Default = '') filenames of distorted images to be updated using new WCS from 'drzfile'. These can be provided either as an ``@-file``, a comma-separated list of filenames or using wildcards. .. note:: A blank value will indicate that the task should derive the filenames from the 'drzfile' itself, if possible. The filenames will be derived from the ``D*DATA`` keywords written out by ``AstroDrizzle``. If they can not be found, the task will quit. origwcs : str (Default = None) Value of ``WCSNAME`` keyword prior to the drzfile image being updated by ``TweakReg``. If left blank or None, it will default to using the second to last ``WCSNAME*`` keyword value found in the header. wcsname : str (Default = None) Value of WCSNAME for updated solution written out by ``TweakReg`` as specified by the `wcsname` parameter from ``TweakReg``. If this is left blank or `None`, it will default to the current ``WCSNAME`` value from the input drzfile. extname : str (Default = 'SCI') Name of extension in `input` files to be updated with new WCS force : bool (Default = False) This parameters specified whether or not to force an update of the WCS even though WCS already exists with this solution or `wcsname`? verbose : bool (Default = False) This parameter specifies whether or not to print out additional messages during processing. Notes ----- The algorithm used by this function is based on linearization of the exact compound operator that converts input image coordinates to the coordinates (in the input image) that would result in alignment with the new drizzled image WCS. If no input distorted files are specified as input, this task will attempt to generate the list of filenames from the drizzled input file's own header. EXAMPLES -------- An image named ``acswfc_mos2_drz.fits`` was created from 4 images using astrodrizzle. This drizzled image was then aligned to another image using tweakreg and the header was updated using the ``WCSNAME`` = ``TWEAK_DRZ``. The new WCS can then be used to update each of the 4 images that were combined to make up this drizzled image using: >>> from drizzlepac import tweakback >>> tweakback.tweakback('acswfc_mos2_drz.fits') If the same WCS should be applied to a specific set of images, those images can be updated using: >>> tweakback.tweakback('acswfc_mos2_drz.fits', ... input='img_mos2a_flt.fits,img_mos2e_flt.fits') See Also -------- stwcs.wcsutil.altwcs: Alternate WCS implementation """ print("TweakBack Version {:s}({:s}) started at: {:s}\n" .format(__version__,__version_date__,util._ptime()[0])) # Interpret input list/string into list of filename(s) fltfiles = parseinput.parseinput(input)[0] if fltfiles is None or len(fltfiles) == 0: # try to extract the filenames from the drizzled file's header fltfiles = extract_input_filenames(drzfile) if fltfiles is None: print('*'*60) print('*') print('* ERROR:') print('* No input filenames found! ') print('* Please specify "fltfiles" or insure that input drizzled') print('* image contains D*DATA keywords. ') print('*') print('*'*60) raise ValueError if not isinstance(fltfiles,list): fltfiles = [fltfiles] sciext = determine_extnum(drzfile, extname='SCI') scihdr = fits.getheader(drzfile, ext=sciext, memmap=False) ### Step 1: Read in updated and original WCS solutions # determine keys for all alternate WCS solutions in drizzled image header wkeys = wcsutil.altwcs.wcskeys(drzfile, ext=sciext) wnames = wcsutil.altwcs.wcsnames(drzfile, ext=sciext) if not util.is_blank(newname): final_name = newname else: final_name = wnames[wkeys[-1]] # Read in HSTWCS objects for final,updated WCS and previous WCS from # from drizzled image header # The final solution also serves as reference WCS when using updatehdr if not util.is_blank(wcsname): for k in wnames: if wnames[k] == wcsname: wcskey = k break else: wcskey = wkeys[-1] final_wcs = wcsutil.HSTWCS(drzfile, ext=sciext, wcskey=wkeys[-1]) if not util.is_blank(origwcs): for k in wnames: if wnames[k] == origwcs: orig_wcskey = k orig_wcsname = origwcs break else: orig_wcsname,orig_wcskey = determine_orig_wcsname(scihdr,wnames,wkeys) orig_wcs = wcsutil.HSTWCS(drzfile,ext=sciext,wcskey=orig_wcskey) # read in RMS values reported for new solution crderr1kw = 'CRDER1'+wkeys[-1] crderr2kw = 'CRDER2'+wkeys[-1] if crderr1kw in scihdr: crderr1 = fits.getval(drzfile, crderr1kw, ext=sciext, memmap=False) else: crderr1 = 0.0 if crderr2kw in scihdr: crderr2 = fits.getval(drzfile, crderr2kw, ext=sciext, memmap=False) else: crderr2 = 0.0 del scihdr ### Step 2: Apply solution to input file headers for fname in fltfiles: logstr = "....Updating header for {:s}...".format(fname) if verbose: print("\n{:s}\n".format(logstr)) else: log.info(logstr) # reset header WCS keywords to original (OPUS generated) values imhdulist = fits.open(fname, mode='update', memmap=False) extlist = get_ext_list(imhdulist, extname='SCI') if not extlist: extlist = [0] # Process MEF images... for ext in extlist: logstr = "Processing {:s}[{:s}]".format(imhdulist.filename(), ext2str(ext)) if verbose: print("\n{:s}\n".format(logstr)) else: log.info(logstr) chip_wcs = wcsutil.HSTWCS(imhdulist, ext=ext) update_chip_wcs(chip_wcs, orig_wcs, final_wcs, xrms=crderr1, yrms = crderr2) # Update FITS file with newly updated WCS for this chip extnum = imhdulist.index(imhdulist[ext]) updatehdr.update_wcs(imhdulist, extnum, chip_wcs, wcsname=final_name, reusename=False, verbose=verbose) imhdulist.close()
[docs]def linearize(wcsim, wcsima, wcs_olddrz, wcs_newdrz, imcrpix, hx=1.0, hy=1.0): # linearization using 5-point formula for first order derivative x0 = imcrpix[0] y0 = imcrpix[1] p = np.asarray([[x0, y0], [x0 - hx, y0], [x0 - hx * 0.5, y0], [x0 + hx * 0.5, y0], [x0 + hx, y0], [x0, y0 - hy], [x0, y0 - hy * 0.5], [x0, y0 + hy * 0.5], [x0, y0 + hy]], dtype=np.float64) # convert image coordinates to old drizzled image coordinates: p = wcs_olddrz.wcs_world2pix(wcsim.wcs_pix2world(p, 1), 1) # convert to sky coordinates using the new drizzled image's WCS: p = wcs_newdrz.wcs_pix2world(p, 1) # convert back to image coordinate system using partially (CRVAL only) # aligned image's WCS: p = wcsima.wcs_world2pix(p, 1).astype(ndfloat128) # derivative with regard to x: u1 = ((p[1] - p[4]) + 8 * (p[3] - p[2])) / (6*hx) # derivative with regard to y: u2 = ((p[5] - p[8]) + 8 * (p[7] - p[6])) / (6*hy) return (np.asarray([u1, u2]).T, p[0])
[docs]def update_chip_wcs(chip_wcs, drz_old_wcs, drz_new_wcs, xrms=None, yrms=None): cd_eye = np.eye(chip_wcs.wcs.cd.shape[0]) # estimate precision necessary for iterative processes: naxis1, naxis2 = chip_wcs.pixel_shape maxiter = 100 crpix2corners = np.dstack([i.flatten() for i in np.meshgrid( [1, naxis1], [1, naxis2])])[0] - chip_wcs.wcs.crpix maxUerr = 1.0e-5 / np.amax(np.linalg.norm(crpix2corners, axis=1)) # estimate step for numerical differentiation. We need a step # large enough to avoid rounding errors and small enough to get a # better precision for numerical differentiation. # TODO: The logic below should be revised at a later time so that it # better takes into account the two competing requirements. hx = max(1.0, min(20.0, (chip_wcs.wcs.crpix[0] - 1.0)/100.0, (naxis1 - chip_wcs.wcs.crpix[0])/100.0)) hy = max(1.0, min(20.0, (chip_wcs.wcs.crpix[1] - 1.0)/100.0, (naxis2 - chip_wcs.wcs.crpix[1])/100.0)) # compute new CRVAL for the image WCS: chip_wcs_orig = chip_wcs.deepcopy() crpix_in_old_drz = drz_old_wcs.wcs_world2pix([chip_wcs.wcs.crval], 1) chip_wcs.wcs.crval = drz_new_wcs.wcs_pix2world(crpix_in_old_drz, 1)[0] chip_wcs.wcs.set() # initial approximation for CD matrix of the image WCS: (U, u) = linearize(chip_wcs_orig, chip_wcs, drz_old_wcs, drz_new_wcs, chip_wcs_orig.wcs.crpix, hx=hx, hy=hy) err0 = np.amax(np.abs(U-cd_eye)).astype(np.float64) chip_wcs.wcs.cd = np.dot(chip_wcs.wcs.cd.astype(ndfloat128), U).astype(np.float64) chip_wcs.wcs.set() # NOTE: initial solution is the exact mathematical solution (modulo numeric # differentiation). However, e.g., due to rounding errors, approximate # numerical differentiation, the solution may be improved by performing # several iterations. The next step will try to perform # fixed-point iterations to "improve" the solution # but this is not really required. # Perform fixed-point iterations to improve the approximation # for CD matrix of the image WCS (actually for the U matrix). for i in range(maxiter): (U, u) = linearize(chip_wcs_orig, chip_wcs, drz_old_wcs, drz_new_wcs, chip_wcs_orig.wcs.crpix, hx=hx, hy=hy) err = np.amax(np.abs(U-cd_eye)).astype(np.float64) if err > err0: break chip_wcs.wcs.cd = np.dot(chip_wcs.wcs.cd, U).astype(np.float64) chip_wcs.wcs.set() if err < maxUerr: break err0 = err if xrms is not None: chip_wcs.wcs.crder = np.array([xrms,yrms])
#### TEAL Interfaces to run this task
[docs]def run(configobj): # Interpret user-input from TEAL GUI and call function tweakback(configobj['drzfile'], newname = configobj['newname'], input=configobj['input'], origwcs = configobj['origwcs'], wcsname = configobj['wcsname'], extname=configobj['extname'],verbose=configobj['verbose'], force=configobj['force'])
#### Utility functions #
[docs]def extract_input_filenames(drzfile): """ Generate a list of filenames from a drizzled image's header """ data_kws = fits.getval(drzfile, 'd*data', ext=0, memmap=False) if len(data_kws) == 0: return None fnames = [] for kw in data_kws.cards: f = kw.value.split('[')[0] if f not in fnames: fnames.append(f) return fnames
[docs]def determine_extnum(drzfile, extname='SCI'): # Determine what kind of drizzled file input has been provided: MEF or single hdulist = fits.open(drzfile, memmap=False) numext = len(hdulist) sciext = 0 for e,i in zip(hdulist,list(range(numext))): if 'extname' in e.header and e.header['extname'] == extname: sciext = i break hdulist.close() return sciext
[docs]def determine_orig_wcsname(header, wnames, wkeys): """ Determine the name of the original, unmodified WCS solution """ orig_wcsname = None orig_key = " " if orig_wcsname is None: for k,w in wnames.items(): if w[:4] == 'IDC_': orig_wcsname = w orig_key = k break if orig_wcsname is None: # No IDC_ wcsname found... revert to second to last if available if len(wnames) > 1: orig_key = wkeys[-2] orig_wcsname = wnames[orig_key] return orig_wcsname,orig_key
[docs]def help(file=None): """ Print out syntax help for running astrodrizzle Parameters ---------- file : str (Default = None) If given, write out help to the filename specified by this parameter Any previously existing file with this name will be deleted before writing out the help. """ helpstr = getHelpAsString(docstring=True, show_ver = True) if file is None: print(helpstr) else: if os.path.exists(file): os.remove(file) f = open(file, mode = 'w') f.write(helpstr) f.close()
[docs]def getHelpAsString(docstring = False, show_ver = True): """ return useful help from a file in the script directory called __taskname__.help """ install_dir = os.path.dirname(__file__) taskname = util.base_taskname(__taskname__, '') htmlfile = os.path.join(install_dir, 'htmlhelp', taskname + '.html') helpfile = os.path.join(install_dir, taskname + '.help') if docstring or (not docstring and not os.path.exists(htmlfile)): if show_ver: helpString = os.linesep + \ ' '.join([__taskname__, 'Version', __version__, ' updated on ', __version_date__]) + 2*os.linesep else: helpString = '' if os.path.exists(helpfile): helpString += teal.getHelpFileAsString(taskname, __file__) else: if __doc__ is not None: helpString += tweakback.__doc__ + os.linesep else: helpString = 'file://' + htmlfile return helpString