colr-types 0.3.1

Color model ZSTs and marker traits for colr.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163

//! Signal decoding (EOTF): encoded signal to linear light.

use crate::math::Float;
use crate::transfer::*;

/// Decode a value from a stored signal to linear light (inverse OETF / EOTF).
///
/// Implement for scalar `F: Float` to get a transfer function at any precision.
/// A blanket impl provides `Decode<[F; N]>` automatically for any `Decode<F>`.
///
/// Note: the HLG EOTF per ITU-R BT.2100 additionally applies an OOTF.
/// This returns inverse-OETF scene-linear, correct for scene-referred
/// pipelines that apply the OOTF separately.
pub trait Decode<T>: TransferFunction {
    /// Convert an encoded signal value to a linear-light value.
    fn decode(v: T) -> T;
}

impl<F: Float, TF: Decode<F>, const N: usize> Decode<[F; N]> for TF {
    #[inline(always)]
    fn decode(v: [F; N]) -> [F; N] {
        v.map(|x| TF::decode(x))
    }
}

impl<F: Float> Decode<F> for Linear {
    #[inline(always)]
    fn decode(v: F) -> F {
        v
    }
}

impl<F: Float> Decode<F> for Srgb {
    #[inline(always)]
    fn decode(x: F) -> F {
        let threshold = F::from_f64(Self::ENCODED_THRESHOLD as f64);
        let slope = F::from_f64(Self::LINEAR_SLOPE as f64);
        let alpha = F::from_f64(Self::ALPHA as f64);
        let gamma = F::from_f64(Self::GAMMA as f64);
        let one = F::ONE;
        if x <= threshold {
            x / slope
        } else {
            ((x + (alpha - one)) / alpha).powf(gamma)
        }
    }
}

impl<F: Float> Decode<F> for Rec709 {
    #[inline(always)]
    fn decode(x: F) -> F {
        let threshold = F::from_f64(Self::ENCODED_THRESHOLD as f64);
        let slope = F::from_f64(Self::LINEAR_SLOPE as f64);
        let alpha = F::from_f64(Self::ALPHA as f64);
        let inv_power = F::from_f64(1.0 / Self::POWER as f64);
        let one = F::ONE;
        if x <= threshold {
            x / slope
        } else {
            ((x + (alpha - one)) / alpha).powf(inv_power)
        }
    }
}

impl<F: Float> Decode<F> for Pq {
    #[inline(always)]
    fn decode(x: F) -> F {
        let zero = F::ZERO;
        let one = F::ONE;
        let m1 = F::from_f64(Self::M1 as f64);
        let m2 = F::from_f64(Self::M2 as f64);
        let c1 = F::from_f64(Self::C1 as f64);
        let c2 = F::from_f64(Self::C2 as f64);
        let c3 = F::from_f64(Self::C3 as f64);
        let v_m2 = x.max(zero).powf(one / m2);
        let num = (v_m2 - c1).max(zero);
        let den = c2 - c3 * v_m2;
        (num / den).powf(one / m1)
    }
}

impl<F: Float> Decode<F> for Hlg {
    #[inline(always)]
    fn decode(x: F) -> F {
        let zero = F::ZERO;
        let one = F::ONE;
        let neg_one = zero - one;
        let threshold = F::from_f64(Self::ENCODED_THRESHOLD as f64);
        let a = F::from_f64(Self::A as f64);
        let b = F::from_f64(Self::B as f64);
        let c = F::from_f64(Self::C as f64);
        let three = F::from_f64(3.0);
        let twelve = F::from_f64(12.0);
        if x.abs() <= threshold {
            x * x.abs() / three
        } else {
            let sign = if x < zero { neg_one } else { one };
            sign * ((x.abs() - c) / a).exp() + b / twelve
        }
    }
}

impl<F: Float> Decode<F> for ProPhoto {
    #[inline(always)]
    fn decode(x: F) -> F {
        let zero = F::ZERO;
        let one = F::ONE;
        let neg_one = zero - one;
        let sign = if x < zero { neg_one } else { one };
        let abs = x.abs();
        let threshold = F::from_f64(Self::ENCODED_THRESHOLD as f64);
        let slope = F::from_f64(Self::LINEAR_SLOPE as f64);
        let gamma = F::from_f64(Self::GAMMA as f64);
        sign * if abs <= threshold {
            abs / slope
        } else {
            abs.powf(gamma)
        }
    }
}

impl<F: Float> Decode<F> for AcesCc {
    #[inline(always)]
    fn decode(x: F) -> F {
        let cut1 = F::from_f64(Self::CUT1 as f64);
        let scale = F::from_f64(Self::LOG_SCALE as f64);
        let offset = F::from_f64(Self::LOG_OFFSET as f64);
        let ln2 = F::from_f64(core::f64::consts::LN_2);
        let neg16: F = F::from_f64(2.0f64.powi(-16));
        let two = F::from_f64(2.0);
        let linear = x * scale - offset;
        if x < cut1 {
            ((linear * ln2).exp() - neg16) * two
        } else {
            (linear * ln2).exp()
        }
    }
}

impl<F: Float> Decode<F> for AcesCct {
    #[inline(always)]
    fn decode(x: F) -> F {
        let y_brk = F::from_f64(Self::Y_BRK as f64);
        let a = F::from_f64(Self::A as f64);
        let b = F::from_f64(Self::B as f64);
        let scale = F::from_f64(Self::LOG_SCALE as f64);
        let offset = F::from_f64(Self::LOG_OFFSET as f64);
        let ln2 = F::from_f64(core::f64::consts::LN_2);
        if x <= y_brk {
            (x - b) / a
        } else {
            ((x * scale - offset) * ln2).exp()
        }
    }
}

impl<F: Float> Decode<F> for DciP3 {
    #[inline(always)]
    fn decode(x: F) -> F {
        let gamma = F::from_f64(Self::GAMMA as f64);
        x.max(F::ZERO).powf(gamma)
    }
}