lsst.afw  22.0.0-22-gf1d71818e+649249edd3
_makePixelToTanPixel.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 __all__ = ["makePixelToTanPixel"]
23 
24 import lsst.geom
25 import lsst.afw.geom
26 
27 
28 def makePixelToTanPixel(bbox, orientation, focalPlaneToField, pixelSizeMm):
29  """Make a Transform whose forward direction converts PIXELS to TAN_PIXELS
30  for one detector.
31 
32  Parameters
33  ----------
34  bbox : `lsst.geom.Box2I`
35  Detector bounding box.
36  orientation : `lsst.afw.cameraGeom.Orientation`
37  Orientation of detector in focal plane.
38  focalPlaneToField : `lsst.afw.geom.TransformPoint2ToPoint2`
39  A transform that converts from focal plane (mm) to field angle
40  coordinates (radians) in the forward direction.
41  pixelSizeMm : `lsst.geom.Extent2D`
42  Size of the pixel in mm in X and Y.
43 
44  Returns
45  -------
46  transform : `lsst.afw.geom.TransformPoint2ToPoint2`
47  A transform whose forward direction converts PIXELS to TAN_PIXELS.
48 
49  Notes
50  -----
51  PIXELS and TAN_PIXELS are described in the CameraGeom documentation under
52  :ref:`camera coordinate systems<section_Camera_Coordinate_Systems>`.
53  """
54  pixelToFocalPlane = orientation.makePixelFpTransform(pixelSizeMm)
55  pixelToField = pixelToFocalPlane.then(focalPlaneToField)
56  # fieldToTanPix is affine and matches fieldToPix at field center
57  # Note: focal plane to field angle is typically a radial transform,
58  # and linearizing the inverse transform of that may fail,
59  # so linearize the forward direction instead. (pixelToField is pixelToFocalPlane,
60  # an affine transform, followed by focalPlaneToField,
61  # so the same consideration applies to pixelToField)
62  pixAtFieldCtr = pixelToField.applyInverse(lsst.geom.Point2D(0, 0))
63  tanPixToFieldAffine = lsst.afw.geom.linearizeTransform(pixelToField, pixAtFieldCtr)
64  fieldToTanPix = lsst.afw.geom.makeTransform(tanPixToFieldAffine.inverted())
65 
66  return pixelToField.then(fieldToTanPix)
def makePixelToTanPixel(bbox, orientation, focalPlaneToField, pixelSizeMm)
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.