lsst.afw  21.0.0-13-g512c41855+47cba9fc36
wcsUtilsContinued.py
Go to the documentation of this file.
1 #
2 # LSST Data Management System
3 # Copyright 2017 LSST Corporation.
4 #
5 # This product includes software developed by the
6 # LSST Project (http://www.lsst.org/).
7 #
8 # This program is free software: you can redistribute it and/or modify
9 # it under the terms of the GNU General Public License as published by
10 # the Free Software Foundation, either version 3 of the License, or
11 # (at your option) any later version.
12 #
13 # This program is distributed in the hope that it will be useful,
14 # but WITHOUT ANY WARRANTY; without even the implied warranty of
15 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 # GNU General Public License for more details.
17 #
18 # You should have received a copy of the LSST License Statement and
19 # the GNU General Public License along with this program. If not,
20 # see <http://www.lsstcorp.org/LegalNotices/>.
21 #
22 
23 __all__ = ["getSipMatrixFromMetadata", "computePixelToDistortedPixel"]
24 
25 import lsst.geom
26 from ..transformFactory import linearizeTransform, makeTransform
27 from .wcsUtils import _getSipMatrixFromMetadata
28 
29 
30 def getSipMatrixFromMetadata(metadata, name):
31  """Extract a SIP matrix from FITS TAN-SIP WCS metadata.
32 
33  Omitted coefficients are set to 0 and all coefficients may be omitted.
34 
35  Parameters
36  ----------
37  metadata : `lsst.daf.base.PropertySet`
38  FITS metadata.
39  name : `str`
40  Name of TAN-SIP matrix (``"A"``, ``"B"``, ``"Ap"``, or ``"Bp"``).
41 
42  Returns
43  -------
44  `numpy.array`
45  The SIP matrix.
46 
47  Raises
48  ------
49  TypeError
50  If the order keyword ``<name>_ORDER`` (e.g. ``AP_ORDER``) is not found,
51  the value of the order keyword cannot be read as an integer,
52  the value of the order keyword is negative,
53  or if a matrix parameter (e.g. ``AP_5_0``) cannot be read as a float.
54  """
55  arr = _getSipMatrixFromMetadata(metadata, name)
56  if arr.shape == (): # order=0
57  arr.shape = (1, 1)
58  return arr
59 
60 
61 def computePixelToDistortedPixel(pixelToFocalPlane, focalPlaneToFieldAngle):
62  """Compute the transform ``pixelToDistortedPixel``, which applies optical
63  distortion specified by ``focalPlaneToFieldAngle``.
64 
65  The resulting transform is designed to be used to convert a pure TAN WCS
66  to a WCS that includes a model for optical distortion. In detail,
67  the initial WCS will contain these frames and transforms::
68 
69  PIXELS frame -> pixelToIwc -> IWC frame -> gridToIwc -> SkyFrame
70 
71  To produce the WCS with distortion, replace ``pixelToIwc`` with::
72 
73  pixelToDistortedPixel -> pixelToIwc
74 
75  Parameters
76  ----------
77  pixelToFocalPlane : `lsst.afw.geom.TransformPoint2ToPoint2`
78  Transform parent pixel coordinates to focal plane coordinates
79  focalPlaneToFieldAngle : `lsst.afw.geom.TransformPoint2ToPoint2`
80  Transform focal plane coordinates to field angle coordinates
81 
82  Returns
83  -------
84  pixelToDistortedPixel : `lsst.afw.geom.TransformPoint2ToPoint2`
85  A transform that applies the effect of the optical distortion model.
86  """
87  # return pixelToFocalPlane -> focalPlaneToFieldAngle -> tanFieldAngleToocalPlane -> focalPlaneToPixel
88  focalPlaneToTanFieldAngle = makeTransform(linearizeTransform(focalPlaneToFieldAngle,
89  lsst.geom.Point2D(0, 0)))
90  return pixelToFocalPlane.then(focalPlaneToFieldAngle) \
91  .then(focalPlaneToTanFieldAngle.inverted()) \
92  .then(pixelToFocalPlane.inverted())
def computePixelToDistortedPixel(pixelToFocalPlane, focalPlaneToFieldAngle)
std::shared_ptr< TransformPoint2ToPoint2 > makeTransform(lsst::geom::AffineTransform const &affine)
Wrap an lsst::geom::AffineTransform as a Transform.
lsst::geom::AffineTransform linearizeTransform(TransformPoint2ToPoint2 const &original, lsst::geom::Point2D const &inPoint)
Approximate a Transform by its local linearization.