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

#![no_std]

pub mod colors;
pub mod hsv;

pub use smart_leds_trait::*;

/// An iterator that provides brightness reduction
pub struct Brightness<I> {
    iter: I,
    brightness: u8,
}

impl<'a, I> Iterator for Brightness<I>
where
    I: Iterator<Item = Color>,
{
    type Item = Color;

    fn next(&mut self) -> Option<Color> {
        self.iter.next().map(|a| Color {
            r: (a.r as u16 * (self.brightness as u16 + 1) / 256) as u8,
            g: (a.g as u16 * (self.brightness as u16 + 1) / 256) as u8,
            b: (a.b as u16 * (self.brightness as u16 + 1) / 256) as u8,
        })
    }
}

/// Pass your iterator into this function to get reduced brightness
pub fn brightness<I>(iter: I, brightness: u8) -> Brightness<I>
where
    I: Iterator<Item = Color>,
{
    Brightness { iter, brightness }
}

/// An iterator that provides gamma correction.
/// Makes the colour distribution non-linear, to match your eyes' perception 
/// In other words, makes orange look orange.
/// If using in combination with a brightness reduction, apply the gamma
/// correction first, then the brightness reduction
/// ie: brightness(gamma(data.iter().cloned()), 32)
pub struct Gamma<I> {
    iter: I,
}

impl<'a, I> Iterator for Gamma<I>
where
    I: Iterator<Item = Color>,
{
    type Item = Color;

    fn next(&mut self) -> Option<Color> {
        // This table remaps linear input values
        // (the numbers we’d like to use; e.g. 127 = half brightness)
        // to nonlinear gamma-corrected output values
        // (numbers producing the desired effect on the LED;
        // e.g. 36 = half brightness).
        const GAMMA8: [u8; 256] = [
            0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
            0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  1,  1,  1,  1,
            1,  1,  1,  1,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2,  2,  2,
            2,  3,  3,  3,  3,  3,  3,  3,  4,  4,  4,  4,  4,  5,  5,  5,
            5,  6,  6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  9,  9,  9, 10,
            10, 10, 11, 11, 11, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16,
            17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 24, 24, 25,
            25, 26, 27, 27, 28, 29, 29, 30, 31, 32, 32, 33, 34, 35, 35, 36,
            37, 38, 39, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 50,
            51, 52, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68,
            69, 70, 72, 73, 74, 75, 77, 78, 79, 81, 82, 83, 85, 86, 87, 89,
            90, 92, 93, 95, 96, 98, 99,101,102,104,105,107,109,110,112,114,
            115,117,119,120,122,124,126,127,129,131,133,135,137,138,140,142,
            144,146,148,150,152,154,156,158,160,162,164,167,169,171,173,175,
            177,180,182,184,186,189,191,193,196,198,200,203,205,208,210,213,
            215,218,220,223,225,228,231,233,236,239,241,244,247,249,252,255
        ];
        self.iter.next().map(|a| Color {
            r: GAMMA8[a.r as usize],
            g: GAMMA8[a.g as usize],
            b: GAMMA8[a.b as usize],
        })
    }
}

/// Pass your iterator into this function to get corrected gamma
pub fn gamma<I>(iter: I) -> Gamma<I>
where
    I: Iterator<Item = Color>,
{
    Gamma { iter }
}