def load_moments_data(results_dir):
"""Load the full-Stokes images into memory.
Args:
results_dir (str): directory to save results.
Returns:
image_temp: ARL image data.
weights: array of weights per channel (1/sigma**2).
"""
try:
if os.path.isdir(results_dir):
try:
# Load the channel 0 data as an image template:
image_temp = import_image_from_fits(
'%s/imaging_clean_WStack-%s.fits' % (results_dir, 0))
# Fill image_temp with the multi-frequency data:
image_temp.data = np.concatenate(([
import_image_from_fits('%s/imaging_clean_WStack-%s.fits' %
(results_dir, channel)).data
for channel in range(0, 40)
]))
# Calculate the weights, in the form [channel, stokes, npix, npix]:
# Initially using std for weights, should consider more robust options.
weights = np.array([
1.0 / (np.std(image_temp.data[channel, 0, :, :])**2)
for channel in range(0, 40)
])
except:
print("Unexpected error:", sys.exc_info()[0])
raise
except:
print("Input directory does not exist:", sys.exc_info()[0])
raise
return image_temp, weights
def create_test_image(
canonical=True,
cellsize=None,
frequency=None,
channel_bandwidth=None,
phasecentre=None,
polarisation_frame=PolarisationFrame("stokesI")) -> Image:
"""Create a useful test image
This is the test image M31 widely used in ALMA and other simulations. It is actually part of an Halpha region in
M31.
:param canonical: Make the image into a 4 dimensional image
:param cellsize:
:param frequency: Frequency (array) in Hz
:param channel_bandwidth: Channel bandwidth (array) in Hz
:param phasecentre: Phase centre of image (SkyCoord)
:param polarisation_frame: Polarisation frame
:return: Image
"""
if frequency is None:
frequency = [1e8]
im = import_image_from_fits(arl_path("data/models/M31.MOD"))
if canonical:
if polarisation_frame is None:
im.polarisation_frame = PolarisationFrame("stokesI")
elif isinstance(polarisation_frame, PolarisationFrame):
im.polarisation_frame = polarisation_frame
else:
raise ValueError("polarisation_frame is not valid")
im = replicate_image(im,
frequency=frequency,
polarisation_frame=im.polarisation_frame)
if cellsize is not None:
im.wcs.wcs.cdelt[0] = -180.0 * cellsize / numpy.pi
im.wcs.wcs.cdelt[1] = +180.0 * cellsize / numpy.pi
if frequency is not None:
im.wcs.wcs.crval[3] = frequency[0]
if channel_bandwidth is not None:
im.wcs.wcs.cdelt[3] = channel_bandwidth[0]
else:
if len(frequency) > 1:
im.wcs.wcs.cdelt[3] = frequency[1] - frequency[0]
else:
im.wcs.wcs.cdelt[3] = 0.001 * frequency[0]
im.wcs.wcs.radesys = 'ICRS'
im.wcs.wcs.equinox = 2000.00
if phasecentre is not None:
im.wcs.wcs.crval[0] = phasecentre.ra.deg
im.wcs.wcs.crval[1] = phasecentre.dec.deg
# WCS is 1 relative
im.wcs.wcs.crpix[0] = im.data.shape[3] // 2 + 1
im.wcs.wcs.crpix[1] = im.data.shape[2] // 2 + 1
return im
def create_low_test_beam(model: Image) -> Image:
"""Create a test power beam for LOW using an image from OSKAR
:param model: Template image
:return: Image
"""
beam = import_image_from_fits(arl_path('data/models/SKA1_LOW_beam.fits'))
# Scale the image cellsize to account for the different in frequencies. Eventually we will want to
# use a frequency cube
log.info("create_low_test_beam: primary beam is defined at %.3f MHz" %
(beam.wcs.wcs.crval[2] * 1e-6))
nchan, npol, ny, nx = model.shape
# We need to interpolate each frequency channel separately. The beam is assumed to just scale with
# frequency.
reprojected_beam = create_empty_image_like(model)
for chan in range(nchan):
model2dwcs = model.wcs.sub(2).deepcopy()
model2dshape = [model.shape[2], model.shape[3]]
beam2dwcs = beam.wcs.sub(2).deepcopy()
# The frequency axis is the second to last in the beam
frequency = model.wcs.sub(['spectral']).wcs_pix2world([chan], 0)[0]
fscale = beam.wcs.wcs.crval[2] / frequency
beam2dwcs.wcs.cdelt = fscale * beam.wcs.sub(2).wcs.cdelt
beam2dwcs.wcs.crpix = beam.wcs.sub(2).wcs.crpix
beam2dwcs.wcs.crval = model.wcs.sub(2).wcs.crval
beam2dwcs.wcs.ctype = model.wcs.sub(2).wcs.ctype
model2dwcs.wcs.crpix = [
model.shape[2] // 2 + 1, model.shape[3] // 2 + 1
]
beam2d = create_image_from_array(beam.data[0, 0, :, :], beam2dwcs,
model.polarisation_frame)
reprojected_beam2d, footprint = reproject_image(beam2d,
model2dwcs,
shape=model2dshape)
assert numpy.max(
footprint.data) > 0.0, "No overlap between beam and model"
reprojected_beam2d.data *= reprojected_beam2d.data
reprojected_beam2d.data[footprint.data <= 0.0] = 0.0
for pol in range(npol):
reprojected_beam.data[chan,
pol, :, :] = reprojected_beam2d.data[:, :]
return reprojected_beam
def moments_save_to_disk(moments_im,
stokes_type='q',
results_dir='./results_dir',
outname='mean'):
"""Save the Faraday moments images to disk.
Args:
rmsynth (numpy array): array of complex numbers from RM Synthesis.
cellsize (float): advised cellsize in Faraday space.
maxrm_est (float): maximum observable RM (50 percent sensitivity).
rmtype (str): the component of the complex numbers to process and save.
results_dir (str): directory to save results.
outname (str): outname for saved file.
Returns:
None
"""
# Read in the first channel image, and appropriate it as the new moments image:
im_moments = import_image_from_fits('%s/imaging_clean_WStack-%s.fits' %
(results_dir, 0))
# Place the data into the open image:
im_moments.data = moments_im
try:
if stokes_type == 'p':
stokes_val = 0.0
elif stokes_type == 'q':
stokes_val = 2.0
elif stokes_type == 'u':
stokes_val = 3.0
except:
print("Unknown value for stokes_type:", sys.exc_info()[0])
raise
# This line also adjusts the listed Stokes parameter (use 0.0=? for P):
im_moments.wcs.wcs.crval = [
im_moments.wcs.wcs.crval[0], im_moments.wcs.wcs.crval[1], stokes_val,
im_moments.wcs.wcs.crval[3]
]
# Output the file to disk:
export_image_to_fits(im_moments,
'%s/%s_%s.fits' % (results_dir, outname, stokes_type))
return