Coverage for colour/models/rgb/ycocg.py: 100%

1""" 

2YCoCg Colour Encoding 

3===================== 

4 

5Define the *YCoCg* colour encoding related transformations: 

6 

7- :func:`colour.RGB_to_YCoCg` 

8- :func:`colour.YCoCg_to_RGB` 

9 

10References 

11---------- 

12- :cite:`Malvar2003` : Malvar, H., & Sullivan, G. (2003). YCoCg-R: A Color 

13 Space with RGB Reversibility and Low Dynamic Range. 

14 https://www.microsoft.com/en-us/research/wp-content/uploads/2016/06/\ 

15Malvar_Sullivan_YCoCg-R_JVT-I014r3-2.pdf 

16""" 

17 

18from __future__ import annotations 

19 

20import typing 

21 

22import numpy as np 

23 

24from colour.algebra import vecmul 

25 

26if typing.TYPE_CHECKING: 

27 from colour.hints import ArrayLike, NDArrayFloat 

28 

29__author__ = "Colour Developers" 

30__copyright__ = "Copyright 2013 Colour Developers" 

31__license__ = "BSD-3-Clause - https://opensource.org/licenses/BSD-3-Clause" 

32__maintainer__ = "Colour Developers" 

33__email__ = "colour-developers@colour-science.org" 

34__status__ = "Development" 

35 

36__all__ = [ 

37 "MATRIX_RGB_TO_YCOCG", 

38 "MATRIX_YCOCG_TO_RGB", 

39 "RGB_to_YCoCg", 

40 "YCoCg_to_RGB", 

41] 

42 

43MATRIX_RGB_TO_YCOCG: NDArrayFloat = np.array( 

44 [ 

45 [1 / 4, 1 / 2, 1 / 4], 

46 [1 / 2, 0, -1 / 2], 

47 [-1 / 4, 1 / 2, -1 / 4], 

48 ] 

49) 

50"""*R'G'B'* colourspace to *YCoCg* colour encoding matrix.""" 

51 

52MATRIX_YCOCG_TO_RGB: NDArrayFloat = np.array( 

53 [ 

54 [1, 1, -1], 

55 [1, 0, 1], 

56 [1, -1, -1], 

57 ] 

58) 

59"""*YCoCg* colour encoding to *R'G'B'* colourspace matrix.""" 

60 

61 

62def RGB_to_YCoCg(RGB: ArrayLike) -> NDArrayFloat: 

63 """ 

64 Convert an array of *R'G'B'* values to the corresponding *YCoCg* colour 

65 encoding values array. 

66 

67 Parameters 

68 ---------- 

69 RGB 

70 Input *R'G'B'* array. 

71 

72 Returns 

73 ------- 

74 :class:`numpy.ndarray` 

75 *YCoCg* colour encoding array. 

76 

77 References 

78 ---------- 

79 :cite:`Malvar2003` 

80 

81 Examples 

82 -------- 

83 >>> RGB_to_YCoCg(np.array([1.0, 1.0, 1.0])) 

84 array([ 1., 0., 0.]) 

85 >>> RGB_to_YCoCg(np.array([0.75, 0.5, 0.5])) 

86 array([ 0.5625, 0.125 , -0.0625]) 

87 """ 

88 

89 return vecmul(MATRIX_RGB_TO_YCOCG, RGB) 

90 

91 

92def YCoCg_to_RGB(YCoCg: ArrayLike) -> NDArrayFloat: 

93 """ 

94 Convert an array of *YCoCg* colour encoding values to the corresponding 

95 *R'G'B'* values array. 

96 

97 Parameters 

98 ---------- 

99 YCoCg 

100 *YCoCg* colour encoding array. 

101 

102 Returns 

103 ------- 

104 :class:`numpy.ndarray` 

105 Output *R'G'B'* array. 

106 

107 References 

108 ---------- 

109 :cite:`Malvar2003` 

110 

111 Examples 

112 -------- 

113 >>> YCoCg_to_RGB(np.array([1.0, 0.0, 0.0])) 

114 array([ 1., 1., 1.]) 

115 >>> YCoCg_to_RGB(np.array([0.5625, 0.125, -0.0625])) 

116 array([ 0.75, 0.5 , 0.5 ]) 

117 """ 

118 

119 return vecmul(MATRIX_YCOCG_TO_RGB, YCoCg)