#
# stub function definition file for docstring parsing
#
[docs]def importfits(fitsimage, imagename='', whichrep=0, whichhdu=-1, zeroblanks=True, overwrite=False, defaultaxes=False, defaultaxesvalues='[]', beam='[]'):
r"""
Convert an image FITS file into a CASA image
[`Description`_] [`Examples`_] [`Development`_] [`Details`_]
Parameters
- fitsimage_ (path) - Name of input image FITS file
- imagename_ (string='') - Name of output CASA image
- whichrep_ (int=0) - If fits image has multiple coordinate reps, choose one.
- whichhdu_ (int=-1) - If fits file contains multiple images, choose one (0 = first HDU, -1 = first valid image).
- zeroblanks_ (bool=True) - Set blanked pixels to zero (not NaN)
- overwrite_ (bool=False) - Overwrite output file if it exists?
- defaultaxes_ (bool=False) - Add the default 4D coordinate axes where they are missing; value True requires setting defaultaxesvalues
- defaultaxesvalues_ (variant='[]') - List of values to assign to added degenerate axes when defaultaxes==True (ra,dec,freq,stokes)
- beam_ (variant='[]') - List of values to be used to define the synthesized beam [BMAJ,BMIN,BPA] (as in the FITS keywords)
.. _Description:
Description
You can use the **importfits** task to import a FITS image into
CASA image format. Note, the CASA viewer can read FITS images so
you don’t need to do this if you just want to look at the image.
The CASA FITS reader uses wcslib by Mark Calabretta and thus
implements the latest FITS standard (3.0). The intention of both
wcslib and the added CASA code is to accommodate certain common
deviations from the standard and be forgiving rather than
pedantic. In some cases, however, images deviating too far from
the standard will not be readable and you might see error
messages. Read these carefully and try to consult the FITS
documentation
( https://fits.gsfc.nasa.gov/standard30/fits_standard30aa.pdf ) to
see how you have to change the header of your FITS image to make
it sufficiently compliant with the standard.
The inputs for **importfits** are:
::
# importfits :: Convert an image FITS file into a CASA image
fitsimage = '' # Name of input image FITS file
imagename = '' # Name of output CASA image
whichrep = 0 # If fits image has multiple coordinate reps, choose one.
whichhdu = -1 # If its file contains multiple images, choose one
# (0 = first HDU, -1 = first valid image).
zeroblanks = True # Set blanked pixels to zero (not NaN)
overwrite = False # Overwrite pre-existing imagename
defaultaxes = False # Add the default 4D coordinate axes where they are missing;
# value True requires setting defaultaxesvalues
defaultaxesvalues = [] # List of values to assign to added degenerate axes when
# defaultaxes==True (ra,dec,freq,stokes)
beam = [] # List of values to be used to define the synthesized beam
# [BMAJ,BMIN,BPA] (as in the FITS keywords)
Here a description of the non-self-explanatory parameters:
*whichrep* -- If the FITS image has multiple coordinate
representations, this parameter lets you choose which one to use
(numbering starts at 0). Example: whichrep=1 .
*whichhdu* -- If the fits file contains multiple images, you can
choose the header data unit by number. The value "-1" (default)
chooses the first valid one.
CASA images by default have a 4D coordinate system (ra, dec,
stokes, freq). Your input image may not have that. Setting the
parameter *defaultaxes* to True, will make **importfits** add
the missing axes as degenerate (one-pixel) axes and will take
the coordinate values for these axes from the list in the
parameter *defaultaxesvalues* (ra,dec,stokes, freq). For
existing axes, empty strings can be given as values. For the
directions and spectral values, any valid angle/frequency
expressions can be given. Example:
defaultaxesvalues=['19h30m00', '-02d30m00', '88.5GHz', 'Q']. If
the order of the fits files ins not ra, dec, stokes, freq,
**imtrans** can be used to change the order.
If your input image does not provide a beam or you want to
override it, you can provde a list of values to be used to define
the synthesized beam [BMAJ,BMIN,BPA] (as in the FITS keywords) in
the parameter *beam*. Note that the FITS keywords typically list
the BMAJ, BMIN and BPA in degrees, but they can be specified with
other units in importfits. Example: beam=['0.35arcsec',
'0.24arcsec', '25deg']
.. _Examples:
Examples
A straightforward implementation of **importfits**:
::
importfits(fitsimage='ngc3256.fits', imagename='ngc3256.im',
overwrite=True)
Though the user may wish to explicitly set (or re-set), for
example, the beam characteristics:
::
importfits(fitsimage='ngc3256.fits', imagename='ngc3256.im',
overwrite=True, beam=['0.35arcsec', '0.24arcsec', '25deg'])
Which will force the BMIN, BMAX and BPA parameters to be 0.35",
0.24" and 25 degrees, respectively.
.. _Development:
Development
No additional development details
.. _Details:
Parameter Details
Detailed descriptions of each function parameter
.. _fitsimage:
| ``fitsimage (path)`` - Name of input image FITS file
| Default: none
| Example: fitsimage='3C273XC1.fits'
.. _imagename:
| ``imagename (string='')`` - Name of output CASA image
| Default: none
| Example: fitsimage='3C273XC1.image'
.. _whichrep:
| ``whichrep (int=0)`` - If fits image has multiple coordinate reps, choose one.
| Default: 0 (means first)
| Example: whichrep=1
.. _whichhdu:
| ``whichhdu (int=-1)`` - If fits file contains multiple images, choose one
| Default: -1 (use the first valid one)
| NOTE: 0 = first HDU, -1 = first valid image
| Example: whichhdu=1
.. _zeroblanks:
| ``zeroblanks (bool=True)`` - Set blanked pixels to zero (not NaN)
| Default: True
| Options: True|False
.. _overwrite:
| ``overwrite (bool=False)`` - Overwrite output file if it exists?
| Default: False
| Options: False|True
.. _defaultaxes:
| ``defaultaxes (bool=False)`` - Add the default 4D coordinate axes where they are
| missing
| Default: False
| Options: False|True
| IMPORTANT: value True requires setting defaultaxesvalues
.. _defaultaxesvalues:
| ``defaultaxesvalues (variant='[]')`` - List of values to assign to added degenerate axes when
| defaultaxes==True (ra,dec,freq,stokes)
| Default: []
| For existing axes, empty strings can be given as
| values. For the directions and spectral values,
| any valid angle/frequency expressions can be
| given.
| Example: defaultaxesvalues=['19h30m00',
| '-02d30m00', '88.5GHz', 'Q']
.. _beam:
| ``beam (variant='[]')`` - List of values to be used to define the synthesized beam
| [BMAJ,BMIN,BPA] (as in the FITS keywords)
| Default: [] (i.e.take from FITS file)
| Example: beam=['0.35arcsec', '0.24arcsec',
| '25deg']
"""
pass