Coverage for colour/models/rgb/transfer_functions/itur_bt_1361.py: 100%

1""" 

2Recommendation ITU-R BT.1361 

3============================ 

4 

5Define the *Recommendation ITU-R BT.1361* opto-electrical transfer function 

6(OETF) and its inverse. 

7 

8- :func:`colour.models.oetf_BT1361` 

9- :func:`colour.models.oetf_inverse_BT1361` 

10 

11References 

12---------- 

13- :cite:`InternationalTelecommunicationUnion1998` : International 

14 Telecommunication Union. (1998). Recommendation ITU-R BT.1361 - Worldwide 

15 unified colorimetry and related characteristics of future television and 

16 imaging systems (pp. 1-32). https://www.itu.int/dms_pubrec/itu-r/rec/bt/\ 

17R-REC-BT.1361-0-199802-W!!PDF-E.pdf 

18""" 

19 

20from __future__ import annotations 

21 

22import numpy as np 

23 

24from colour.algebra import spow 

25from colour.hints import ( # noqa: TC001 

26 Domain1, 

27 Range1, 

28) 

29from colour.models.rgb.transfer_functions import oetf_BT709, oetf_inverse_BT709 

30from colour.utilities import as_float, domain_range_scale, from_range_1, to_domain_1 

31 

32__author__ = "Colour Developers" 

33__copyright__ = "Copyright 2013 Colour Developers" 

34__license__ = "BSD-3-Clause - https://opensource.org/licenses/BSD-3-Clause" 

35__maintainer__ = "Colour Developers" 

36__email__ = "colour-developers@colour-science.org" 

37__status__ = "Production" 

38 

39__all__ = [ 

40 "oetf_BT1361", 

41 "oetf_inverse_BT1361", 

42] 

43 

44 

45def oetf_BT1361(L: Domain1) -> Range1: 

46 """ 

47 Apply the *Recommendation ITU-R BT.1361* extended colour gamut system 

48 opto-electronic transfer function (OETF). 

49 

50 Parameters 

51 ---------- 

52 L 

53 Scene *Luminance* :math:`L`. 

54 

55 Returns 

56 ------- 

57 :class:`numpy.ndarray` 

58 Non-linear primary signal :math:`E'`. 

59 

60 Notes 

61 ----- 

62 +------------+-----------------------+---------------+ 

63 | **Domain** | **Scale - Reference** | **Scale - 1** | 

64 +============+=======================+===============+ 

65 | ``L`` | 1 | 1 | 

66 +------------+-----------------------+---------------+ 

67 

68 +------------+-----------------------+---------------+ 

69 | **Range** | **Scale - Reference** | **Scale - 1** | 

70 +============+=======================+===============+ 

71 | ``E_p'`` | 1 | 1 | 

72 +------------+-----------------------+---------------+ 

73 

74 References 

75 ---------- 

76 :cite:`InternationalTelecommunicationUnion1998` 

77 

78 Examples 

79 -------- 

80 >>> oetf_BT1361(0.18) # doctest: +ELLIPSIS 

81 0.4090077288641... 

82 >>> oetf_BT1361(-0.25) # doctest: +ELLIPSIS 

83 -0.25 

84 >>> oetf_BT1361(1.33) # doctest: +ELLIPSIS 

85 1.1504846663972... 

86 """ 

87 

88 L = to_domain_1(L) 

89 

90 with domain_range_scale("ignore"): 

91 E_p = np.where( 

92 L >= 0, 

93 oetf_BT709(L), 

94 np.where( 

95 L <= -0.0045, 

96 # L in [-0.25, -0.0045] range 

97 -(1.099 * spow(-4 * L, 0.45) - 0.099) / 4, 

98 # L in [-0.0045, 0] range 

99 4.500 * L, 

100 ), 

101 ) 

102 

103 return as_float(from_range_1(E_p)) 

104 

105 

106def oetf_inverse_BT1361(E_p: Domain1) -> Range1: 

107 """ 

108 Apply the *Recommendation ITU-R BT.1361* extended colour gamut system 

109 inverse opto-electronic transfer function (OETF). 

110 

111 Parameters 

112 ---------- 

113 E_p 

114 Non-linear primary signal :math:`E'`. 

115 

116 Returns 

117 ------- 

118 :class:`numpy.ndarray` 

119 Scene *Luminance* :math:`L`. 

120 

121 Notes 

122 ----- 

123 +------------+-----------------------+---------------+ 

124 | **Domain** | **Scale - Reference** | **Scale - 1** | 

125 +============+=======================+===============+ 

126 | ``E_p`` | 1 | 1 | 

127 +------------+-----------------------+---------------+ 

128 

129 +------------+-----------------------+---------------+ 

130 | **Range** | **Scale - Reference** | **Scale - 1** | 

131 +============+=======================+===============+ 

132 | ``L`` | 1 | 1 | 

133 +------------+-----------------------+---------------+ 

134 

135 References 

136 ---------- 

137 :cite:`InternationalTelecommunicationUnion1998` 

138 

139 Examples 

140 -------- 

141 >>> oetf_inverse_BT1361(0.4090077288641) # doctest: +ELLIPSIS 

142 0.1799999... 

143 >>> oetf_inverse_BT1361(-0.25) # doctest: +ELLIPSIS 

144 -0.25 

145 >>> oetf_inverse_BT1361(1.1504846663972) # doctest: +ELLIPSIS 

146 1.3299999... 

147 """ 

148 

149 E_p = to_domain_1(E_p) 

150 

151 with domain_range_scale("ignore"): 

152 L = np.where( 

153 E_p >= 0, 

154 oetf_inverse_BT709(E_p), 

155 np.where( 

156 E_p <= 4.500 * -0.0045, 

157 # L in [-0.25, -0.0045] range 

158 -spow((-4 * E_p + 0.099) / 1.099, 1 / 0.45) / 4, 

159 # L in [-0.0045, 0] range 

160 E_p / 4.500, 

161 ), 

162 ) 

163 

164 return as_float(from_range_1(L))