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Disable FITS image compression by default #138

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merged 1 commit into from
Jan 24, 2024
+36 −6
Merged

Disable FITS image compression by default #138

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42 changes: 36 additions & 6 deletions maps/python/fitsio.py
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Original file line number Diff line number Diff line change
Expand Up @@ -481,7 +481,7 @@ def parse_wcs_header(header):

@core.usefulfunc
def save_skymap_fits(filename, T, Q=None, U=None, W=None, overwrite=False,
compress='GZIP_2', hdr=None):
compress=False, quantize_level=16.0, hdr=None):
"""
Save G3 map objects to a fits file.

Expand Down Expand Up @@ -515,7 +515,13 @@ def save_skymap_fits(filename, T, Q=None, U=None, W=None, overwrite=False,
FITS readers (e.g. idlastro). If defined, the compression algorithm to
be used by the Astropy class astropy.io.fits.CompImageHDU.
Can be: 'RICE_1', 'RICE_ONE', 'PLIO_1', 'GZIP_1', 'GZIP_2' or
'HCOMPRESS_1'. Only GZIP_1 and GZIP_2 are lossless.
'HCOMPRESS_1'. Only GZIP_1 and GZIP_2 are lossless, although only
for integer data.
quantize_level : float
Floating point quantization level for compression. Higher values result
in more accurate floating point representation, but worse compression
ratio. See the astropy FITS image documention for details:
https://docs.astropy.org/en/stable/io/fits/api/images.html
hdr : dict
If defined, extra keywords to be appened to the FITS header. The dict
can contain entries such as ``hdr['NEWKEY'] = 'New value'`` or
Expand Down Expand Up @@ -612,7 +618,12 @@ def save_skymap_fits(filename, T, Q=None, U=None, W=None, overwrite=False,
for m, name in zip(maps, names):
if flat:
if compress:
hdu = astropy.io.fits.CompImageHDU(np.asarray(m), header=header, compression_type=ctype)
hdu = astropy.io.fits.CompImageHDU(
np.asarray(m),
header=header,
compression_type=ctype,
quantize_level=quantize_level,
)
else:
hdu = astropy.io.fits.ImageHDU(np.asarray(m), header=header)
hdu.header['ISWEIGHT'] = False
Expand Down Expand Up @@ -672,7 +683,12 @@ def save_skymap_fits(filename, T, Q=None, U=None, W=None, overwrite=False,

if flat:
if compress:
hdu = astropy.io.fits.CompImageHDU(np.asarray(m), header=header, compression_type=ctype)
hdu = astropy.io.fits.CompImageHDU(
np.asarray(m),
header=header,
compression_type=ctype,
quantize_level=quantize_level,
)
else:
hdu = astropy.io.fits.ImageHDU(np.asarray(m), header=header)
hdu.header['ISWEIGHT'] = True
Expand Down Expand Up @@ -729,7 +745,14 @@ def save_skymap_fits(filename, T, Q=None, U=None, W=None, overwrite=False,


@core.indexmod
def SaveMapFrame(frame, output_file=None, hdr=None, compress='GZIP_2', overwrite=False):
def SaveMapFrame(
frame,
output_file=None,
hdr=None,
compress=False,
quantize_level=16.0,
overwrite=False,
):
"""
Save a map frame to a FITS file. See ``save_skymap_fits`` for details. The
map frame should contain T maps and (optionally) unpolarized weights, or T/Q/U
Expand All @@ -752,7 +775,13 @@ def SaveMapFrame(frame, output_file=None, hdr=None, compress='GZIP_2', overwrite
FITS readers (e.g. idlastro). If defined, the compression algorithm to
be used by the Astropy class astropy.io.fits.CompImageHDU.
Can be: 'RICE_1', 'RICE_ONE', 'PLIO_1', 'GZIP_1', 'GZIP_2' or
'HCOMPRESS_1'. Only GZIP_1 and GZIP_2 are lossless.
'HCOMPRESS_1'. Only GZIP_1 and GZIP_2 are lossless, although only
for integer data.
quantize_level : float
Floating point quantization level for compression. Higher values result
in more accurate floating point representation, but worse compression
ratio. See the astropy FITS image documention for details:
https://docs.astropy.org/en/stable/io/fits/api/images.html
overwrite : bool
If True, any existing file with the same name will be ovewritten.
"""
Expand All @@ -776,5 +805,6 @@ def SaveMapFrame(frame, output_file=None, hdr=None, compress='GZIP_2', overwrite
W=W,
overwrite=overwrite,
compress=compress,
quantize_level=quantize_level,
hdr=hdr,
)
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