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Diffstat (limited to 'distortion/coeff_converter.py')
| -rw-r--r-- | distortion/coeff_converter.py | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/distortion/coeff_converter.py b/distortion/coeff_converter.py new file mode 100644 index 0000000..e31854d --- /dev/null +++ b/distortion/coeff_converter.py @@ -0,0 +1,137 @@ +import numpy as np +import pyfits +import pywcs + +def sip2idc(wcs): + """ + Converts SIP style coefficients to IDCTAB coefficients. + + :Parameters: + `wcs`: pyfits.Header or pywcs.WCS object + """ + if isinstance(wcs,pyfits.Header): + ocx10 = wcs.get('OCX10', None) + ocx11 = wcs.get('OCX11', None) + ocy10 = wcs.get('OCY10', None) + ocy11 = wcs.get('OCY11', None) + order = hdr.get('A_ORDER', None) + sipa, sipb = _read_sip_kw(header) + if sipa == None or sipb == None: + print 'SIP coefficients are not available.\n' + print 'Cannot convert SIP to IDC coefficients.\n' + return + elif isinstance(wcs,pywcs.WCS): + try: + ocx10 = wcs.ocx10 + ocx11 = wcs.ocx11 + ocy10 = wcs.ocy10 + ocy11 = wcs.ocy11 + except AttributeError: + print 'First order IDCTAB coefficients are not available.\n' + print 'Cannot convert SIP to IDC coefficients.\n' + return + try: + sipa = wcs.sip.a + sipb = wcs.sip.b + except AttributeError: + print 'SIP coefficients are not available.\n' + print 'Cannot convert SIP to IDC coefficients.\n' + return + else: + print 'Input to sip2idc must be a PyFITS header or a wcsutil.HSTWCS object\n' + return + + try: + order = wcs.sip.a_order + except AttributeError: + print 'SIP model order unknown, exiting ...\n' + return + + if None in [ocx10, ocx11, ocy10, ocy11]: + print 'First order IDC coefficients not found, exiting ...\n' + return + idc_coeff = np.array([[ocx11, ocx10], [ocy11, ocy10]]) + cx = np.zeros((order+1,order+1), dtype=np.double) + cy = np.zeros((order+1,order+1), dtype=np.double) + for n in range(order+1): + for m in range(order+1): + if n >= m and n>=2: + sipval = np.array([[sipa[m,n-m]],[sipb[m,n-m]]]) + idcval = np.dot(idc_coeff, sipval) + cx[n,m] = idcval[0] + cy[n,m] = idcval[1] + + cx[1,0] = ocx10 + cx[1,1] = ocx11 + cy[1,0] = ocy10 + cy[1,1] = ocy11 + + return cx, cy + +def _read_sip_kw(header): + """ + Reads SIP header keywords and returns an array of coefficients. + + If no SIP header keywords are found, None is returned. + """ + if header.has_key("A_ORDER"): + if not header.has_key("B_ORDER"): + raise ValueError( + "A_ORDER provided without corresponding B_ORDER " + "keyword for SIP distortion") + + m = int(header["A_ORDER"]) + a = np.zeros((m+1, m+1), np.double) + for i in range(m+1): + for j in range(m-i+1): + a[i, j] = header.get("A_%d_%d" % (i, j), 0.0) + + m = int(header["B_ORDER"]) + b = np.zeros((m+1, m+1), np.double) + for i in range(m+1): + for j in range(m-i+1): + b[i, j] = header.get("B_%d_%d" % (i, j), 0.0) + elif header.has_key("B_ORDER"): + raise ValueError( + "B_ORDER provided without corresponding A_ORDER " + "keyword for SIP distortion") + else: + a = None + b = None + + return a , b +""" +def idc2sip(wcsobj, idctab = None): + if isinstance(wcs,pywcs.WCS): + try: + cx10 = wcsobj.ocx10 + cx11 = wcsobj.cx11 + cy10 = wcsobj.cy10 + cy11 = wcsobj.cy11 + except AttributeError: + print + try: + order = wcs.sip.a_order + except AttributeError: + print 'SIP model order unknown, exiting ...\n' + return + else: + print 'Input to sip2idc must be a PyFITS header or a wcsutil.HSTWCS object\n' + return + + if None in [ocx10, ocx11, ocy10, ocy11]: + print 'First order IDC coefficients not found, exiting ...\n' + return + idc_coeff = np.array([[wcsobj.cx11, wcsobj.cx10], [wcsobj.cy11, wcsobj.cy10]]) + cx = numpy.zeros((order+1,order+1), dtype=numpy.double) + cy = numpy.zeros((order+1,order+1), dtype=numpy.double) + for n in range(order+1): + for m in range(order+1): + if n >= m and n>=2: + sipval = numpy.array([[wcsobj.sip.a[n,m]],[wcsobj.sip.b[n,m]]]) + idcval = numpy.dot(idc_coeff, sipval) + cx[m,n-m] = idcval[0] + cy[m,n-m] = idcval[1] + + return cx, cy +"""
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