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Merge pull request #411 from esheldon/seed-dither
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Seed dithering
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@esheldon
esheldon authored Aug 20, 2024
2 parents 5504852 + 76cf33e commit c2d5b5c
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Showing 5 changed files with 242 additions and 21 deletions.
21 changes: 2 additions & 19 deletions .github/workflows/tests.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -16,25 +16,8 @@ jobs:
fail-fast: false
matrix:
os: [macos-latest, ubuntu-latest]
pyver: ["3.8", "3.9", "3.10", "3.11", "3.12"]
npver: ["1.20", "1.21", "1.23", "1.26", "2.0"]
exclude:
- pyver: "3.11"
npver: "1.20"
- pyver: "3.11"
npver: "1.21"
- pyver: "3.10"
npver: "1.20"
- pyver: "3.12"
npver: "1.20"
- pyver: "3.12"
npver: "1.21"
- pyver: "3.12"
npver: "1.23"
- pyver: "3.8"
npver: "2.0"
- pyver: "3.8"
npver: "1.26"
pyver: ["3.12", "3.11"]
npver: ["1.26", "2.0"]

runs-on: ${{ matrix.os }}

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5 changes: 5 additions & 0 deletions CHANGES.md
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Original file line number Diff line number Diff line change
@@ -1,6 +1,11 @@
version 1.2.5 (not yet released)
-------------

New Features

- writing images supports the dither_seed keyword, to seed
the random number generator for subtractive dithering

Bug Fixes

- Fig bug slicing tables that have TBIT columns
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12 changes: 11 additions & 1 deletion fitsio/fitsio_pywrap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1395,6 +1395,7 @@ PyFITSObject_create_image_hdu(struct PyFITSObject* self, PyObject* args, PyObjec
int extver=0;
float qlevel=0;
int qmethod=0;
int dither_seed=0;
float hcomp_scale=0;
int hcomp_smooth=0;

Expand All @@ -1411,6 +1412,7 @@ PyFITSObject_create_image_hdu(struct PyFITSObject* self, PyObject* args, PyObjec

"qlevel",
"qmethod",
"dither_seed",

"hcomp_scale",
"hcomp_smooth",
Expand All @@ -1419,14 +1421,15 @@ PyFITSObject_create_image_hdu(struct PyFITSObject* self, PyObject* args, PyObjec
"extver",
NULL,
};
if (!PyArg_ParseTupleAndKeywords(args, kwds, "Oi|OiOfifisi", kwlist,
if (!PyArg_ParseTupleAndKeywords(args, kwds, "Oi|OiOfiifisi", kwlist,
&array_obj, &nkeys,
&dims_obj,
&comptype,
&tile_dims_obj,

&qlevel,
&qmethod,
&dither_seed,

&hcomp_scale,
&hcomp_smooth,
Expand Down Expand Up @@ -1495,6 +1498,13 @@ PyFITSObject_create_image_hdu(struct PyFITSObject* self, PyObject* args, PyObjec
goto create_image_hdu_cleanup;
}

// zero means to use the default (system clock).
if (dither_seed != 0) {
if (fits_set_dither_seed(self->fits, dither_seed, &status)) {
goto create_image_hdu_cleanup;
}
}

if (comptype == HCOMPRESS_1) {

if (fits_set_hcomp_scale(self->fits, hcomp_scale, &status)) {
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89 changes: 88 additions & 1 deletion fitsio/fitslib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -288,6 +288,7 @@ def write(filename, data, extname=None, extver=None, header=None,
names=None, write_bitcols=False, compress=None, tile_dims=None,
qlevel=DEFAULT_QLEVEL,
qmethod=DEFAULT_QMETHOD,
dither_seed=None,
hcomp_scale=DEFAULT_HCOMP_SCALE,
hcomp_smooth=False,
**keys):
Expand Down Expand Up @@ -377,6 +378,16 @@ def write(filename, data, extname=None, extver=None, header=None,
Defaults to 'SUBTRACTIVE_DITHER_1' which follows the fpack defaults
dither_seed: int or None
Seed for the subtractive dither. Seeding makes the lossy compression
reproducible. Allowed values are
None or 0 or 'clock':
do not set the seed explicitly, use the system clock
negative or 'checksum':
Set the seed based on the data checksum
1-10_000:
use the input seed
hcomp_scale: float
Scale value for HCOMPRESS, 0.0 means lossless compression. Default is
0.0 following the fpack defaults.
Expand Down Expand Up @@ -409,6 +420,7 @@ def write(filename, data, extname=None, extver=None, header=None,
tile_dims=tile_dims,
qlevel=qlevel,
qmethod=qmethod,
dither_seed=dither_seed,
hcomp_scale=hcomp_scale,
hcomp_smooth=hcomp_smooth,
)
Expand Down Expand Up @@ -624,6 +636,7 @@ def write(self, data, units=None, extname=None, extver=None,
tile_dims=None,
qlevel=DEFAULT_QLEVEL,
qmethod=DEFAULT_QMETHOD,
dither_seed=None,
hcomp_scale=DEFAULT_HCOMP_SCALE,
hcomp_smooth=False,
header=None, names=None,
Expand Down Expand Up @@ -686,6 +699,15 @@ def write(self, data, units=None, extname=None, extver=None,
Preserves zeros
Defaults to 'SUBTRACTIVE_DITHER_1' which follows the fpack defaults
dither_seed: int or None
Seed for the subtractive dither. Seeding makes the lossy
compression reproducible. Allowed values are
None or 0 or 'clock':
do not set the seed explicitly, use the system clock
negative or 'checksum':
Set the seed based on the data checksum
1-10_000:
use the input seed
hcomp_scale: float
Scale value for HCOMPRESS, 0.0 means lossless compression. Default
Expand Down Expand Up @@ -731,6 +753,7 @@ def write(self, data, units=None, extname=None, extver=None,
tile_dims=tile_dims,
qlevel=qlevel,
qmethod=qmethod,
dither_seed=dither_seed,
hcomp_scale=hcomp_scale,
hcomp_smooth=hcomp_smooth,
header=header)
Expand All @@ -745,6 +768,7 @@ def write_image(self, img, extname=None, extver=None,
compress=None, tile_dims=None,
qlevel=DEFAULT_QLEVEL,
qmethod=DEFAULT_QMETHOD,
dither_seed=None,
hcomp_scale=DEFAULT_HCOMP_SCALE,
hcomp_smooth=False,
header=None):
Expand Down Expand Up @@ -792,6 +816,15 @@ def write_image(self, img, extname=None, extver=None,
Preserves zeros
Defaults to 'SUBTRACTIVE_DITHER_1' which follows the fpack defaults
dither_seed: int or None
Seed for the subtractive dither. Seeding makes the lossy
compression reproducible. Allowed values are
None or 0 or 'clock':
do not set the seed explicitly, use the system clock
negative or 'checksum':
Set the seed based on the data checksum
1-10_000:
use the input seed
hcomp_scale: float
Scale value for HCOMPRESS, 0.0 means lossless compression. Default
Expand Down Expand Up @@ -823,6 +856,7 @@ def write_image(self, img, extname=None, extver=None,
tile_dims=tile_dims,
qlevel=qlevel,
qmethod=qmethod,
dither_seed=dither_seed,
hcomp_scale=hcomp_scale,
hcomp_smooth=hcomp_smooth,
)
Expand All @@ -844,6 +878,7 @@ def create_image_hdu(self,
tile_dims=None,
qlevel=DEFAULT_QLEVEL,
qmethod=DEFAULT_QMETHOD,
dither_seed=None,
hcomp_scale=DEFAULT_HCOMP_SCALE,
hcomp_smooth=False,
header=None):
Expand Down Expand Up @@ -917,7 +952,15 @@ def create_image_hdu(self,
Preserves zeros
Defaults to 'SUBTRACTIVE_DITHER_1' which follows the fpack defaults
dither_seed: int or None
Seed for the subtractive dither. Seeding makes the lossy
compression reproducible. Allowed values are
None or 0 or 'clock':
do not set the seed explicitly, use the system clock
negative or 'checksum':
Set the seed based on the data checksum
1-10_000:
use the input seed
hcomp_scale: float
Scale value for HCOMPRESS, 0.0 means lossless compression. Default
is 0.0 following the fpack defaults.
Expand Down Expand Up @@ -1002,6 +1045,7 @@ def create_image_hdu(self,

comptype = get_compress_type(compress)
qmethod = get_qmethod(qmethod)
dither_seed = get_dither_seed(dither_seed)

tile_dims = get_tile_dims(tile_dims, dims)
if qlevel is None:
Expand Down Expand Up @@ -1032,6 +1076,7 @@ def create_image_hdu(self,

qlevel=qlevel,
qmethod=qmethod,
dither_seed=dither_seed,

hcomp_scale=hcomp_scale,
hcomp_smooth=hcomp_smooth,
Expand Down Expand Up @@ -1800,6 +1845,48 @@ def get_qmethod(qmethod):
return _qmethod_map[qmethod]


def get_dither_seed(dither_seed):
"""
Convert a seed value or indicator to the approprate integer value for
cfitsio
Parameters
----------
dither_seed: number or string
Seed for the subtractive dither. Seeding makes the lossy compression
reproducible. Allowed values are
None or 0 or 'clock':
Return 0, do not set the seed explicitly, use the system clock
negative or 'checksum':
Return -1, means Set the seed based on the data checksum
1-10_000:
use the input seed
"""
if isinstance(dither_seed, bytes):
dither_seed = str(dither_seed, 'utf-8')

if isinstance(dither_seed, str):
dlow = dither_seed.lower()
if dlow == 'clock':
seed_out = 0
elif dlow == 'checksum':
seed_out = -1
else:
raise ValueError(f'Bad dither_seed {dither_seed}')
elif dither_seed is None:
seed_out = 0
else:
# must fit in an int
seed_out = numpy.int32(dither_seed)

if seed_out > 10_000:
raise ValueError(
f'Got dither_seed {seed_out}, expected avalue <= 10_000'
)

return seed_out


def check_comptype_img(comptype, dtype_str):

if comptype == NOCOMPRESS:
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