diff options
Diffstat (limited to 'lib/stwcs/distortion/utils.py')
| -rw-r--r-- | lib/stwcs/distortion/utils.py | 63 |
1 files changed, 31 insertions, 32 deletions
diff --git a/lib/stwcs/distortion/utils.py b/lib/stwcs/distortion/utils.py index b70f474..6cff569 100644 --- a/lib/stwcs/distortion/utils.py +++ b/lib/stwcs/distortion/utils.py @@ -1,8 +1,7 @@ -from __future__ import division # confidence high -import os +from __future__ import division # confidence high +import os import numpy as np import pywcs -import pyfits from stwcs import wcsutil from numpy import sqrt, arctan2 from stsci.tools import fileutil @@ -10,14 +9,14 @@ from stsci.tools import fileutil def output_wcs(list_of_wcsobj, ref_wcs=None, owcs=None, undistort=True): """ Create an output WCS. - + Parameters ---------- list_of_wcsobj: Python list a list of HSTWCS objects - ref_wcs: an HSTWCS object + ref_wcs: an HSTWCS object to be used as a reference WCS, in case outwcs is None. - if ref_wcs is None (default), the first member of the list + if ref_wcs is None (default), the first member of the list is used as a reference outwcs: an HSTWCS object the tangent plane defined by this object is used as a reference @@ -26,16 +25,16 @@ def output_wcs(list_of_wcsobj, ref_wcs=None, owcs=None, undistort=True): """ fra_dec = np.vstack([w.calcFootprint() for w in list_of_wcsobj]) wcsname = list_of_wcsobj[0].wcs.name - - # This new algorithm may not be strictly necessary, but it may be more + + # This new algorithm may not be strictly necessary, but it may be more # robust in handling regions near the poles or at 0h RA. - crval1,crval2 = computeFootprintCenter(fra_dec) + crval1,crval2 = computeFootprintCenter(fra_dec) crval = np.array([crval1,crval2], dtype=np.float64) # this value is now zero-based if owcs is None: if ref_wcs == None: ref_wcs = list_of_wcsobj[0].deepcopy() - if undistort: + if undistort: outwcs = undistortWCS(ref_wcs) else: outwcs = ref_wcs.deepcopy() @@ -58,7 +57,7 @@ def output_wcs(list_of_wcsobj, ref_wcs=None, owcs=None, undistort=True): tanpix = outwcs.wcs.s2p(fra_dec, 0)['pixcrd'] # shift crpix to take into account (floating-point value of) position of - # corner pixel relative to output frame size: no rounding necessary... + # corner pixel relative to output frame size: no rounding necessary... newcrpix = np.array([crpix[0]+tanpix[:,0].min(), crpix[1]+ tanpix[:,1].min()]) @@ -71,37 +70,37 @@ def output_wcs(list_of_wcsobj, ref_wcs=None, owcs=None, undistort=True): def computeFootprintCenter(edges): """ Geographic midpoint in spherical coords for points defined by footprints. Algorithm derived from: http://www.geomidpoint.com/calculation.html - - This algorithm should be more robust against discontinuities at the poles. + + This algorithm should be more robust against discontinuities at the poles. """ alpha = np.deg2rad(edges[:,0]) dec = np.deg2rad(edges[:,1]) - + xmean = np.mean(np.cos(dec)*np.cos(alpha)) ymean = np.mean(np.cos(dec)*np.sin(alpha)) zmean = np.mean(np.sin(dec)) - + crval1 = np.rad2deg(np.arctan2(ymean,xmean))%360.0 crval2 = np.rad2deg(np.arctan2(zmean,np.sqrt(xmean*xmean+ymean*ymean))) - + return crval1,crval2 def undistortWCS(wcsobj): """ Creates an undistorted linear WCS by applying the IDCTAB distortion model - to a 3-point square. The new ORIENTAT angle is calculated as well as the + to a 3-point square. The new ORIENTAT angle is calculated as well as the plate scale in the undistorted frame. """ assert isinstance(wcsobj, pywcs.WCS) import coeff_converter - + cx, cy = coeff_converter.sip2idc(wcsobj) - # cx, cy can be None because either there is no model available + # cx, cy can be None because either there is no model available # or updatewcs was not run. if cx == None or cy == None: if foundIDCTAB(wcsobj.idctab): m = """IDCTAB is present but distortion model is missing. - Run updatewcs() to update the headers or + Run updatewcs() to update the headers or pass 'undistort=False' keyword to output_wcs().\n """ raise RuntimeError, m @@ -116,7 +115,7 @@ def undistortWCS(wcsobj): #order = wcsobj.sip.a_order pscale = wcsobj.idcscale #pixref = np.array([wcsobj.sip.SIPREF1, wcsobj.sip.SIPREF2]) - + tan_pix = apply_idc(px, cx, cy, wcsobj.wcs.crpix, pscale, order=1) xc = tan_pix[:,0] yc = tan_pix[:,1] @@ -131,8 +130,8 @@ def undistortWCS(wcsobj): if ( _det == 0.0): print 'Singular matrix in updateWCS, aborting ...' return - - lin_wcsobj = pywcs.WCS() + + lin_wcsobj = pywcs.WCS() cd_inv = np.linalg.inv(cd_mat) cd = np.dot(wcsobj.wcs.cd, cd_inv).astype(np.float64) lin_wcsobj.wcs.cd = cd @@ -149,16 +148,16 @@ def apply_idc(pixpos, cx, cy, pixref, pscale= None, order=None): """ Apply the IDCTAB polynomial distortion model to pixel positions. pixpos must be already corrected for ltv1/2. - + Parameters ---------- pixpos: a 2D numpy array of (x,y) pixel positions to be distortion corrected cx, cy: IDC model distortion coefficients pixref: reference opixel position - + """ if cx == None: - return pixpos + return pixpos if order is None: print 'Unknown order of distortion model \n' @@ -166,23 +165,23 @@ def apply_idc(pixpos, cx, cy, pixref, pscale= None, order=None): if pscale is None: print 'Unknown model plate scale\n' return pixpos - + # Apply in the same way that 'drizzle' would... _cx = cx/pscale _cy = cy/ pscale _p = pixpos - + # Do NOT include any zero-point terms in CX,CY here # as they should not be scaled by plate-scale like rest # of coeffs... This makes the computations consistent # with 'drizzle'. WJH 17-Feb-2004 _cx[0,0] = 0. _cy[0,0] = 0. - + dxy = _p - pixref # Apply coefficients from distortion model here... - - c = _p * 0. + + c = _p * 0. for i in range(order+1): for j in range(i+1): c[:,0] = c[:,0] + _cx[i][j] * pow(dxy[:,0],j) * pow(dxy[:,1],(i-j)) @@ -194,7 +193,7 @@ def foundIDCTAB(idctab): idctab_found = True try: idctab = fileutil.osfn(idctab) - if idctab == 'N/A' or idctab == "": + if idctab == 'N/A' or idctab == "": idctab_found = False if os.path.exists(idctab): idctab_found = True |