lsst.afw g4d73512994+c357e897d2
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_makePixelToTanPixel.py
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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
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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.
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21
22__all__ = ["makePixelToTanPixel"]
23
24import lsst.geom
25import lsst.afw.geom
26
27
28def 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.
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 -------
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)
Describe a detector's orientation in the focal plane.
Definition: Orientation.h:51
Transform LSST spatial data, such as lsst::geom::Point2D and lsst::geom::SpherePoint,...
Definition: Transform.h:68
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.