def parse_beam(header, pixelsize):
"""Read and return the beam properties bmaj, bmin and bpa values from
the fits header.
Returns:
- Beam parameters, (semimajor, semiminor, parallactic angle)
in (pixels,pixels, radians)
"""
bmaj, bmin, bpa = None, None, None
try:
# MIRIAD FITS file
bmaj = header['BMAJ']
bmin = header['BMIN']
bpa = header['BPA']
except KeyError:
for i, key in enumerate(header.ascardlist().keys()):
if key == 'HISTORY':
results = beam_regex.search(header[i])
if results:
bmaj, bmin, bpa = [float(results.group(key)) for
key in ('bmaj', 'bmin', 'bpa')]
break
beam = degrees2pixels(bmaj, bmin, bpa, pixelsize[0], pixelsize[1])
return beam
def __init__(self, url, plane=0, beam=None):
self._url = url
table = pyrap_table(self.url.encode(), ack=False)
self._data = parse_data(table, plane)
self._wcs = parse_coordinates(table)
self._centre_ra, self._centre_decl = parse_phase_centre(table)
self._freq_eff, self._freq_bw = parse_frequency(table)
if beam:
(bmaj, bmin, bpa) = beam
self._beam = degrees2pixels(
bmaj, bmin, bpa, self.pixelsize[0], self.pixelsize[1]
)
else:
self._beam = parse_beam(table, self.pixelsize)
def __init__(self, url, plane=0, beam=None):
super(CasaImage, self).__init__() # Set defaults
self.url = url
self.table = pyrap_table(self.url.encode(), ack=False)
self.telescope = self.table.getkeyword('coords')['telescope']
self.data = parse_data(self.table, plane)
self.wcs = parse_coordinates(self.table)
self.pixelsize = parse_pixelsize(self.wcs)
self.centre_ra, self.centre_decl = parse_phase_centre(self.table)
self.freq_eff, self.freq_bw = parse_frequency(self.table)
if beam:
(bmaj, bmin, bpa) = beam
self.beam = degrees2pixels(bmaj, bmin, bpa,
self.pixelsize[0], self.pixelsize[1])
else:
self.beam = parse_beam(self.table, self.pixelsize)
def __init__(self, url, plane=None, beam=None, hdu=0):
self._url = url
header = self._get_header(hdu)
self._wcs = parse_coordinates(header)
self._data = read_data(pyfits.open(self.url)[hdu], plane)
self._taustart_ts, self._tau_time = parse_times(header)
self._freq_eff, self._freq_bw = parse_frequency(header)
if beam:
(bmaj, bmin, bpa) = beam
self._beam = degrees2pixels(
bmaj, bmin, bpa, self.pixelsize[0], self.pixelsize[1]
)
else:
self._beam = parse_beam(header, self.pixelsize)
# Bonus attribute
if 'TELESCOP' in header:
# Otherwise, it defaults to None.
self.telescope = header['TELESCOP']
def parse_beam(table, pixelsize):
"""
Returns:
- Beam parameters, (semimajor, semiminor, parallactic angle) in
(pixels,pixels, radians).
"""
def ensure_degrees(quantity):
if quantity['unit'] == 'deg':
return quantity['value']
elif quantity['unit'] == 'arcsec':
return quantity['value'] / 3600
elif quantity['unit'] == 'rad':
return degrees(quantity['value'])
else:
raise Exception("Beam units (%s) unknown" % quantity['unit'])
restoringbeam = table.getkeyword('imageinfo')['restoringbeam']
bmaj = ensure_degrees(restoringbeam['major'])
bmin = ensure_degrees(restoringbeam['minor'])
bpa = ensure_degrees(restoringbeam['positionangle'])
beam_pixels = degrees2pixels(bmaj, bmin, bpa, pixelsize[0], pixelsize[1])
return beam_pixels
def __init__(self, url, plane=None, beam=None, hdu=0):
"""
Args:
- url: location of FITS file
- beam: (optional) beam parameters in degrees, in the form
(bmaj, bmin, bpa). Will attempt to read from header if
not supplied.
"""
# NB: pyfits bogs down reading parameters from FITS files with very
# long headers. This code should run in a fraction of a second on most
# files, but can take several seconds given a huge header.
super(FitsImage, self).__init__() # Set defaults
self.url = url
self.beam = beam
hdulist = pyfits.open(url)
hdu = hdulist[hdu]
self.header = hdu.header.copy()
if 'TELESCOP' in self.header:
# Otherwise, it defaults to None.
self.telescope = self.header['TELESCOP']
self.data = read_data(hdu, plane)
hdulist.close()
self.wcs = parse_coordinates(self.header)
self.pixelsize = parse_pixelsize(self.wcs)
self.centre_ra, self.centre_decl = calculate_phase_centre(self.data.shape,
self.wcs)
self.freq_eff, self.freq_bw = parse_frequency(self.header)
if beam:
(bmaj, bmin, bpa) = beam
self.beam = degrees2pixels(bmaj, bmin, bpa,
self.pixelsize[0], self.pixelsize[1])
else:
self.beam = parse_beam(self.header, self.pixelsize)
self.taustart_ts, self.tau_time = parse_times(self.header)
def parse_beam(header, pixelsize):
"""Read and return the beam properties bmaj, bmin and bpa values from
the fits header.
Returns:
- Beam parameters, (semimajor, semiminor, position angle)
in (pixels, pixels, radians)
"""
bmaj, bmin, bpa = None, None, None
try:
# MIRIAD FITS file
bmaj = header['BMAJ']
bmin = header['BMIN']
bpa = header['BPA']
except KeyError:
def get_history(hdr):
"""
Returns all history cards in FITS header hdr as a list of strings.
"""
# Appropriate method to get the HISTORY from a FITS header varies with
# PyFITS version. See discussion at
# <http://pythonhosted.org/pyfits/appendix/header_transition.html>.
# This is quite ugly, so deliberately limited to this scope.
if pyfits.__version__ < 3.2:
return hdr.get_history()
else:
return hdr['HISTORY']
for hist_entry in get_history(header):
results = beam_regex.search(hist_entry)
if results:
bmaj, bmin, bpa = [float(results.group(key)) for
key in ('bmaj', 'bmin', 'bpa')]
break
beam = degrees2pixels(bmaj, bmin, bpa, pixelsize[0], pixelsize[1])
return beam
