Coverage for models/rgb/transfer_functions/srgb.py: 33%

1""" 

2SRGB 

3==== 

4 

5Define the *sRGB* electro-optical transfer function (EOTF) and its 

6inverse. 

7 

8- :func:`colour.models.eotf_inverse_sRGB` 

9- :func:`colour.models.eotf_sRGB` 

10 

11References 

12---------- 

13- :cite:`InternationalElectrotechnicalCommission1999a` : International 

14 Electrotechnical Commission. (1999). IEC 61966-2-1:1999 - Multimedia 

15 systems and equipment - Colour measurement and management - Part 2-1: 

16 Colour management - Default RGB colour space - sRGB (p. 51). 

17 https://webstore.iec.ch/publication/6169 

18- :cite:`InternationalTelecommunicationUnion2015i` : International 

19 Telecommunication Union. (2015). Recommendation ITU-R BT.709-6 - Parameter 

20 values for the HDTV standards for production and international programme 

21 exchange BT Series Broadcasting service (pp. 1-32). 

22 https://www.itu.int/dms_pubrec/itu-r/rec/bt/\ 

23R-REC-BT.709-6-201506-I!!PDF-E.pdf 

24""" 

25 

26from __future__ import annotations 

27 

28import numpy as np 

29 

30from colour.algebra import spow 

31from colour.hints import ( # noqa: TC001 

32 Domain1, 

33 Range1, 

34) 

35from colour.utilities import as_float, domain_range_scale, from_range_1, to_domain_1 

36 

37__author__ = "Colour Developers" 

38__copyright__ = "Copyright 2013 Colour Developers" 

39__license__ = "BSD-3-Clause - https://opensource.org/licenses/BSD-3-Clause" 

40__maintainer__ = "Colour Developers" 

41__email__ = "colour-developers@colour-science.org" 

42__status__ = "Production" 

43 

44__all__ = [ 

45 "eotf_inverse_sRGB", 

46 "eotf_sRGB", 

47] 

48 

49 

50def eotf_inverse_sRGB(L: Domain1) -> Range1: 

51 """ 

52 Apply the *IEC 61966-2-1:1999* *sRGB* inverse electro-optical transfer 

53 function (EOTF). 

54 

55 Parameters 

56 ---------- 

57 L 

58 *Luminance* :math:`L` of the image. 

59 

60 Returns 

61 ------- 

62 :class:`numpy.ndarray` 

63 Electrical signal :math:`V`. 

64 

65 Notes 

66 ----- 

67 +------------+-----------------------+---------------+ 

68 | **Domain** | **Scale - Reference** | **Scale - 1** | 

69 +============+=======================+===============+ 

70 | ``L`` | 1 | 1 | 

71 +------------+-----------------------+---------------+ 

72 

73 +------------+-----------------------+---------------+ 

74 | **Range** | **Scale - Reference** | **Scale - 1** | 

75 +============+=======================+===============+ 

76 | ``V`` | 1 | 1 | 

77 +------------+-----------------------+---------------+ 

78 

79 References 

80 ---------- 

81 :cite:`InternationalElectrotechnicalCommission1999a`, 

82 :cite:`InternationalTelecommunicationUnion2015i` 

83 

84 Examples 

85 -------- 

86 >>> eotf_inverse_sRGB(0.18) # doctest: +ELLIPSIS 

87 0.4613561... 

88 """ 

89 

90 L = to_domain_1(L) 

91 

92 V = np.where(L <= 0.0031308, L * 12.92, 1.055 * spow(L, 1 / 2.4) - 0.055) 

93 

94 return as_float(from_range_1(V)) 

95 

96 

97def eotf_sRGB(V: Domain1) -> Range1: 

98 """ 

99 Apply the *IEC 61966-2-1:1999* *sRGB* electro-optical transfer function 

100 (EOTF). 

101 

102 Parameters 

103 ---------- 

104 V 

105 Electrical signal :math:`V`. 

106 

107 Returns 

108 ------- 

109 :class:`numpy.ndarray` 

110 *Luminance* :math:`L` of the image. 

111 

112 Notes 

113 ----- 

114 +------------+-----------------------+---------------+ 

115 | **Domain** | **Scale - Reference** | **Scale - 1** | 

116 +============+=======================+===============+ 

117 | ``V`` | 1 | 1 | 

118 +------------+-----------------------+---------------+ 

119 

120 +------------+-----------------------+---------------+ 

121 | **Range** | **Scale - Reference** | **Scale - 1** | 

122 +============+=======================+===============+ 

123 | ``L`` | 1 | 1 | 

124 +------------+-----------------------+---------------+ 

125 

126 References 

127 ---------- 

128 :cite:`InternationalElectrotechnicalCommission1999a`, 

129 :cite:`InternationalTelecommunicationUnion2015i` 

130 

131 Examples 

132 -------- 

133 >>> eotf_sRGB(0.461356129500442) # doctest: +ELLIPSIS 

134 0.1... 

135 """ 

136 

137 V = to_domain_1(V) 

138 

139 with domain_range_scale("ignore"): 

140 L = np.where( 

141 eotf_inverse_sRGB(0.0031308) >= V, 

142 V / 12.92, 

143 spow((V + 0.055) / 1.055, 2.4), 

144 ) 

145 

146 return as_float(from_range_1(L))