Coverage for python/lsst/afw/cameraGeom/_makePixelToTanPixel.py: 40%

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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 

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 

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. 

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)