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authorAaron LI <aly@aaronly.me>2017-08-13 11:17:03 +0800
committerAaron LI <aly@aaronly.me>2017-08-13 11:17:03 +0800
commit01ad6e91008d3e564861694289fc400311639b98 (patch)
treefb19aaf722ef72d5e1a691870f8b6c7414479c61 /fg21sim/utils/fits.py
parentf372ced0663836c4bde13794cafd25cb51111d3c (diff)
downloadfg21sim-01ad6e91008d3e564861694289fc400311639b98.tar.bz2
utils: Merge fits.py into io.py
Functions "{read,write}_fits_healpix()" merged into io.py Signed-off-by: Aaron LI <aly@aaronly.me>
Diffstat (limited to 'fg21sim/utils/fits.py')
-rw-r--r--fg21sim/utils/fits.py152
1 files changed, 0 insertions, 152 deletions
diff --git a/fg21sim/utils/fits.py b/fg21sim/utils/fits.py
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--- a/fg21sim/utils/fits.py
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-# Copyright (c) 2016 Weitian LI <liweitianux@live.com>
-# MIT license
-
-"""
-FITS utilities
---------------
-
-read_fits_healpix:
- Read the HEALPix map from a FITS file or a BinTableHDU to 1D array
- in *RING* ordering.
-
-write_fits_healpix:
- Write the HEALPix map to a FITS file with proper header as well
- as the user-provided header.
-"""
-
-from datetime import datetime, timezone
-
-import numpy as np
-from astropy.io import fits
-import healpy as hp
-
-
-# Column formats for FITS binary table
-# Reference:
-# http://docs.astropy.org/en/stable/io/fits/usage/table.html#column-creation
-FITS_COLUMN_FORMATS = {
- np.dtype("bool"): "L",
- np.dtype("uint8"): "B",
- np.dtype("int16"): "I",
- np.dtype("int32"): "J",
- np.dtype("int64"): "K",
- np.dtype("float32"): "E",
- np.dtype("float64"): "D",
- np.dtype("complex64"): "C",
- np.dtype("complex128"): "M",
-}
-
-
-def read_fits_healpix(filename):
- """Read the HEALPix map from a FITS file or a BinTableHDU to 1D array
- in *RING* ordering.
-
- Parameters
- ----------
- filename : str or `~astropy.io.fits.BinTableHDU`
- Filename of the HEALPix FITS file,
- or an `~astropy.io.fits.BinTableHDU` instance.
-
- Returns
- -------
- data : 1D `~numpy.ndarray`
- HEALPix data in *RING* ordering with same dtype as input
- header : `~astropy.io.fits.Header`
- Header of the input FITS file
-
- NOTE
- ----
- This function wraps on `healpy.read_map()`, but set the data type of
- data array to its original value as in FITS file, as well as return
- FITS header as `~astropy.io.fits.Header` instance.
- """
- if isinstance(filename, fits.BinTableHDU):
- hdu = filename
- else:
- # Read the first extended table
- hdu = fits.open(filename)[1]
- # Hack to ignore the dtype byteorder, use native endianness
- dtype = np.dtype(hdu.data.field(0).dtype.type)
- header = hdu.header
- data = hp.read_map(hdu, nest=False, verbose=False)
- return (data.astype(dtype), header)
-
-
-def write_fits_healpix(filename, hpmap, header=None, clobber=False,
- checksum=False):
- """Write the HEALPix map to a FITS file with proper header as well
- as the user-provided header.
-
- This function currently only support one style of HEALPix with the
- following specification:
- - Only one column: I (intensity)
- - ORDERING: RING
- - COORDSYS: G (Galactic)
- - OBJECT: FULLSKY
- - INDXSCHM: IMPLICIT
-
- Parameters
- ----------
- filename : str
- Filename of the output file to write the HEALPix map data
- hpmap : 1D `~numpy.ndarray`
- 1D array containing the HEALPix map data, and the ordering
- scheme should be "RING";
- The data type is preserved in the output FITS file.
- header : `~astropy.io.fits.Header`, optional
- Extra header to be appended to the output FITS
- clobber : bool, optional
- Whether overwrite the existing file?
- checksum : bool, optional
- Whether calculate the checksum for the output file, which is
- recorded as the "CHECKSUM" header keyword.
-
- NOTE
- ----
- - This function is intended to replace the most common case of
- `healpy.write_map()`, which still uses some deprecated functions of
- `numpy` and `astropy`, meanwhile, it interface/arguments is not very
- handy.
- - This function (currently) only implement the very basic feature of
- the `healpy.write_map()`.
- """
- hpmap = np.asarray(hpmap)
- if hpmap.ndim != 1:
- raise ValueError("Invalid HEALPix data: only support 1D array")
- # Hack to ignore the dtype byteorder, use native endianness
- dtype = np.dtype(hpmap.dtype.type)
- hpmap = hpmap.astype(dtype)
- #
- npix = hpmap.size
- nside = int((npix / 12) ** 0.5)
- colfmt = FITS_COLUMN_FORMATS.get(hpmap.dtype)
- if hpmap.size > 1024:
- hpmap = hpmap.reshape(int(hpmap.size/1024), 1024)
- colfmt = "1024" + colfmt
- #
- hdr = fits.Header()
- # set HEALPix parameters
- hdr["PIXTYPE"] = ("HEALPIX", "HEALPix pixelization")
- hdr["ORDERING"] = ("RING",
- "Pixel ordering scheme, either RING or NESTED")
- hdr["COORDSYS"] = ("G", "Ecliptic, Galactic or Celestial (equatorial)")
- hdr["NSIDE"] = (nside, "HEALPix resolution parameter")
- hdr["NPIX"] = (npix, "Total number of pixels")
- hdr["FIRSTPIX"] = (0, "First pixel # (0 based)")
- hdr["LASTPIX"] = (npix-1, "Last pixel # (0 based)")
- hdr["INDXSCHM"] = ("IMPLICIT", "Indexing: IMPLICIT or EXPLICIT")
- hdr["OBJECT"] = ("FULLSKY", "Sky coverage, either FULLSKY or PARTIAL")
- #
- hdr["EXTNAME"] = ("HEALPIX", "Name of the binary table extension")
- hdr["CREATOR"] = (__name__, "File creator")
- hdr["DATE"] = (datetime.now(timezone.utc).astimezone().isoformat(),
- "File creation date")
- # Merge user-provided header
- # NOTE: use the `.extend()` method instead of `.update()` method
- if header is not None:
- hdr.extend(fits.Header(header))
- #
- hdu = fits.BinTableHDU.from_columns([
- fits.Column(name="I", array=hpmap, format=colfmt)
- ], header=hdr)
- hdu.writeto(filename, clobber=clobber, checksum=checksum)