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ift
NIFTy
Commits
4fae9924
Commit
4fae9924
authored
Mar 13, 2019
by
Philipp Arras
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Add NFFTOperator
parent
9f8bd423
Pipeline
#45187
passed with stages
in 8 minutes and 6 seconds
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nfft.py
nifty5/library/nfft.py
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nifty5/library/nfft.py
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4fae9924
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
# Copyright(C) 20182019 MaxPlanckSociety
#
# Resolve is being developed at the MaxPlanckInstitut fuer Astrophysik.
import
numpy
as
np
import
nifty5
as
ift
class
NFFTOperator
(
ift
.
LinearOperator
):
"""Performs a nonequidistant Fourier transform, i.e. a Fourier transform
followed by a degridding operation.
Parameters

domain : RGSpace
Domain of the operator. It has to be twodimensional and have shape
`(2N, 2N)`. The coordinates of the lower left pixel of the dirty image
are `(N,N)`, and of the upper right pixel `(N1,N1)`.
uv : numpy.ndarray
2D numpy array of type float64 and shape (M,2), where M is the number
of measurements. uv[i,0] and uv[i,1] contain the u and v coordinates
of measurement #i, respectively. All coordinates must lie in the range
`[0.5; 0,5[`.
"""
def
__init__
(
self
,
domain
,
uv
):
from
pynfft.nfft
import
NFFT
npix
=
domain
.
shape
[
0
]
assert
npix
==
domain
.
shape
[
1
]
assert
len
(
domain
.
shape
)
==
2
assert
type
(
npix
)
==
int
,
"npix must be integer"
assert
npix
>
0
and
(
npix
%
2
)
==
0
,
"npix must be an even, positive integer"
assert
isinstance
(
uv
,
np
.
ndarray
),
"uv must be a Numpy array"
assert
uv
.
dtype
==
np
.
float64
,
"uv must be an array of float64"
assert
uv
.
ndim
==
2
,
"uv must be a 2D array"
assert
uv
.
shape
[
0
]
>
0
,
"at least one point needed"
assert
uv
.
shape
[
1
]
==
2
,
"the second dimension of uv must be 2"
assert
np
.
all
(
uv
>=

0.5
)
and
np
.
all
(
uv
<=
0.5
),
\
"all coordinates must lie between 0.5 and 0.5"
self
.
_domain
=
ift
.
DomainTuple
.
make
(
domain
)
self
.
_target
=
ift
.
DomainTuple
.
make
(
ift
.
UnstructuredDomain
(
uv
.
shape
[
0
]))
self
.
_capability
=
self
.
TIMES

self
.
ADJOINT_TIMES
self
.
npt
=
uv
.
shape
[
0
]
self
.
plan
=
NFFT
(
self
.
domain
.
shape
,
self
.
npt
,
m
=
6
)
self
.
plan
.
x
=
uv
self
.
plan
.
precompute
()
def
apply
(
self
,
x
,
mode
):
self
.
_check_input
(
x
,
mode
)
if
mode
==
self
.
TIMES
:
self
.
plan
.
f_hat
=
x
.
to_global_data
()
res
=
self
.
plan
.
trafo
()
.
copy
()
else
:
self
.
plan
.
f
=
x
.
to_global_data
()
res
=
self
.
plan
.
adjoint
()
.
copy
()
return
ift
.
Field
.
from_global_data
(
self
.
_tgt
(
mode
),
res
)
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