lsst.afw  21.0.0-23-g03fb9f672+f385fa6f38
wcsUtils.py
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21 
22 __all__ = ["getSipMatrixFromMetadata", "computePixelToDistortedPixel",
23  "createTrivialWcsMetadata", "deleteBasicWcsMetadata", "getCdMatrixFromMetadata",
24  "getImageXY0FromMetadata", "hasSipMatrix", "makeSipMatrixMetadata",
25  "makeTanSipMetadata"]
26 
27 import lsst.geom
28 from ._geom import (_getSipMatrixFromMetadata, makeTransform, linearizeTransform,
29  createTrivialWcsMetadata, deleteBasicWcsMetadata, getCdMatrixFromMetadata,
30  getImageXY0FromMetadata, hasSipMatrix, makeSipMatrixMetadata,
31  makeTanSipMetadata)
32 
33 
34 def getSipMatrixFromMetadata(metadata, name):
35  """Extract a SIP matrix from FITS TAN-SIP WCS metadata.
36 
37  Omitted coefficients are set to 0 and all coefficients may be omitted.
38 
39  Parameters
40  ----------
41  metadata : `lsst.daf.base.PropertySet`
42  FITS metadata.
43  name : `str`
44  Name of TAN-SIP matrix (``"A"``, ``"B"``, ``"Ap"``, or ``"Bp"``).
45 
46  Returns
47  -------
48  `numpy.array`
49  The SIP matrix.
50 
51  Raises
52  ------
53  TypeError
54  If the order keyword ``<name>_ORDER`` (e.g. ``AP_ORDER``) is not found,
55  the value of the order keyword cannot be read as an integer,
56  the value of the order keyword is negative,
57  or if a matrix parameter (e.g. ``AP_5_0``) cannot be read as a float.
58  """
59  arr = _getSipMatrixFromMetadata(metadata, name)
60  if arr.shape == (): # order=0
61  arr.shape = (1, 1)
62  return arr
63 
64 
65 def computePixelToDistortedPixel(pixelToFocalPlane, focalPlaneToFieldAngle):
66  """Compute the transform ``pixelToDistortedPixel``, which applies optical
67  distortion specified by ``focalPlaneToFieldAngle``.
68 
69  The resulting transform is designed to be used to convert a pure TAN WCS
70  to a WCS that includes a model for optical distortion. In detail,
71  the initial WCS will contain these frames and transforms::
72 
73  PIXELS frame -> pixelToIwc -> IWC frame -> gridToIwc -> SkyFrame
74 
75  To produce the WCS with distortion, replace ``pixelToIwc`` with::
76 
77  pixelToDistortedPixel -> pixelToIwc
78 
79  Parameters
80  ----------
81  pixelToFocalPlane : `lsst.afw.geom.TransformPoint2ToPoint2`
82  Transform parent pixel coordinates to focal plane coordinates
83  focalPlaneToFieldAngle : `lsst.afw.geom.TransformPoint2ToPoint2`
84  Transform focal plane coordinates to field angle coordinates
85 
86  Returns
87  -------
88  pixelToDistortedPixel : `lsst.afw.geom.TransformPoint2ToPoint2`
89  A transform that applies the effect of the optical distortion model.
90  """
91  # return pixelToFocalPlane -> focalPlaneToFieldAngle -> tanFieldAngleToocalPlane -> focalPlaneToPixel
92  focalPlaneToTanFieldAngle = makeTransform(linearizeTransform(focalPlaneToFieldAngle,
93  lsst.geom.Point2D(0, 0)))
94  return pixelToFocalPlane.then(focalPlaneToFieldAngle) \
95  .then(focalPlaneToTanFieldAngle.inverted()) \
96  .then(pixelToFocalPlane.inverted())
def computePixelToDistortedPixel(pixelToFocalPlane, focalPlaneToFieldAngle)
Definition: wcsUtils.py:65
def getSipMatrixFromMetadata(metadata, name)
Definition: wcsUtils.py:34
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.