Coverage for python/lsst/atmospec/dispersion.py: 34%

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1# This file is part of atmospec. 

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 

22import logging 

23import numpy as np 

24 

25 

26__all__ = ['DispersionRelation'] 

27 

28 

29class DispersionRelation: 

30 def __init__(self, observedLines, spectralLines): 

31 """The dispersion relation, relating pixel to wavelength and vice versa 

32 

33 Parameters: 

34 ----------- 

35 observedLines : `list` of `float` 

36 The central wavelength of the observed lines in the spectrum in pix 

37 

38 spectralLines : `list` of `float` 

39 The central wavelength of the spectral lines present in the source 

40 in nm. 

41 

42 Notes: 

43 ------ 

44 The current implementation just supplies linear transformations 

45 but future extensions can support higher order polynomials, 

46 spline-fits, distortions etc 

47 """ 

48 self.observedLines = observedLines 

49 self.spectralLines = spectralLines 

50 

51 self.log = logging.getLogger('lsst.atmospec.dispersionRelation') 

52 self.pix2wlCoeffs = self._calcCoefficients() 

53 

54 def _calcCoefficients(self): 

55 if((self.observedLines is None) or (self.spectralLines is None)): 

56 self.log.warn('Missing input for _calcCoefficients, default transformation: 1 to 1 ') 

57 self.observedLines = [1, 2] 

58 self.spectralLines = [1, 2] 

59 pix2wlCoeffs = np.polyfit(self.observedLines, self.spectralLines, deg=1) 

60 

61 # xxx change to debug 

62 self.log.info('Pixel -> Wavelength linear transformation coefficients : ' + str(pix2wlCoeffs)) 

63 return pix2wlCoeffs 

64 

65 def Wavelength2Pixel(self, wavelength): 

66 """Currently just a linear transform""" 

67 wavelength = np.asarray(wavelength, dtype=np.float64) 

68 coef = self.pix2wlCoeffs 

69 return (wavelength-coef[1]) / coef[0] 

70 

71 def Pixel2Wavelength(self, pixel): 

72 """Currently just a linear transform""" 

73 pixel = np.asarray(pixel, dtype=np.float64) 

74 coef = self.pix2wlCoeffs 

75 return np.array(coef[1] + coef[0] * pixel)