lsst.afw  22.0.0-22-gf1d71818e+ba3de87e18
_calculateSipWcsHeader.py
Go to the documentation of this file.
1 # This file is part of afw.
2 #
3 # Developed for the LSST Data Management System.
4 # This product includes software developed by the LSST Project
5 # (https://www.lsst.org).
6 # See the COPYRIGHT file at the top-level directory of this distribution
7 # for details of code ownership.
8 #
9 # This program is free software: you can redistribute it and/or modify
10 # it under the terms of the GNU General Public License as published by
11 # the Free Software Foundation, either version 3 of the License, or
12 # (at your option) any later version.
13 #
14 # This program is distributed in the hope that it will be useful,
15 # but WITHOUT ANY WARRANTY; without even the implied warranty of
16 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 # GNU General Public License for more details.
18 #
19 # You should have received a copy of the GNU General Public License
20 # along with this program. If not, see <https://www.gnu.org/licenses/>.
21 
22 
23 from lsst.geom import Extent2I, Box2D
24 from ._geom import SipApproximation, getPixelToIntermediateWorldCoords
25 from ._geom import makeTanSipMetadata
26 
27 __all__ = ("calculateSipWcsHeader",)
28 
29 
30 def calculateSipWcsHeader(wcs, order, bbox, spacing, header=None):
31  """Generate a SIP WCS header approximating a given ``SkyWcs``
32 
33  Parameters
34  ----------
35  wcs : `lsst.afw.geom.SkyWcs`
36  World Coordinate System to approximate as SIP.
37  order : `int`
38  SIP order (equal to the maximum sum of the polynomial exponents).
39  bbox : `lsst.geom.Box2I`
40  Bounding box over which to approximate the ``wcs``.
41  spacing : `float`
42  Spacing between sample points.
43  header : `lsst.daf.base.PropertyList`, optional
44  Header to which to add SIP WCS keywords.
45 
46  Returns
47  -------
48  header : `lsst.daf.base.PropertyList`
49  Header including SIP WCS keywords.
50 
51  Examples
52  --------
53  >>> header = calculateSipWcsHeader(exposure.getWcs(), 3, exposure.getBBox(), 20)
54  >>> sipWcs = SkyWcs(header)
55  """
56  transform = getPixelToIntermediateWorldCoords(wcs)
57  crpix = wcs.getPixelOrigin()
58  cdMatrix = wcs.getCdMatrix()
59  crval = wcs.getSkyOrigin()
60  gridNum = Extent2I(int(bbox.getWidth()/spacing + 0.5), int(bbox.getHeight()/spacing + 0.5))
61 
62  sip = SipApproximation(transform, crpix, cdMatrix, Box2D(bbox), gridNum, order)
63 
64  md = makeTanSipMetadata(sip.getPixelOrigin(), crval, sip.getCdMatrix(), sip.getA(), sip.getB(),
65  sip.getAP(), sip.getBP())
66 
67  if header is not None:
68  header.combine(md)
69  else:
70  header = md
71 
72  return header
def calculateSipWcsHeader(wcs, order, bbox, spacing, header=None)
std::shared_ptr< TransformPoint2ToPoint2 > getPixelToIntermediateWorldCoords(SkyWcs const &wcs, bool simplify=true)
Return a transform from pixel coordinates to intermediate world coordinates.
Definition: SkyWcs.cc:564
std::shared_ptr< daf::base::PropertyList > makeTanSipMetadata(lsst::geom::Point2D const &crpix, lsst::geom::SpherePoint const &crval, Eigen::Matrix2d const &cdMatrix, Eigen::MatrixXd const &sipA, Eigen::MatrixXd const &sipB)
Make metadata for a TAN-SIP WCS without inverse matrices.
Definition: wcsUtils.cc:197