blink1rs 0.2.0

Control the blink(1) USB RGB LED. Simple sync API over hidapi, with hardware watchdog support for alerting.
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// SPDX-FileCopyrightText: 2026 Tod Kurt
// SPDX-License-Identifier: MIT

//! Gamma correction, off by default.

/// `255 * (x/255)^(1/0.45)`, transcribed from `blink1-lib.c` `GammaE[]`,
/// originally from rgb-123.com/ws2812-color-output.
static GAMMA_E: [u8; 256] = [
    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, 2, 2, 2,
    2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 11,
    11, 11, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, 19, 20, 21, 21, 22, 22,
    23, 23, 24, 25, 25, 26, 27, 27, 28, 29, 29, 30, 31, 31, 32, 33, 34, 34, 35, 36, 37, 37, 38, 39,
    40, 40, 41, 42, 43, 44, 45, 46, 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, 76, 77, 78, 79, 80, 81, 83, 84, 85, 86, 88,
    89, 90, 91, 93, 94, 95, 96, 98, 99, 100, 102, 103, 104, 106, 107, 109, 110, 111, 113, 114, 116,
    117, 119, 120, 121, 123, 124, 126, 128, 129, 131, 132, 134, 135, 137, 138, 140, 142, 143, 145,
    146, 148, 150, 151, 153, 155, 157, 158, 160, 162, 163, 165, 167, 169, 170, 172, 174, 176, 178,
    179, 181, 183, 185, 187, 189, 191, 193, 194, 196, 198, 200, 202, 204, 206, 208, 210, 212, 214,
    216, 218, 220, 222, 224, 227, 229, 231, 233, 235, 237, 239, 241, 244, 246, 248, 250, 252, 255,
];

pub(crate) fn degamma(n: u8) -> u8 {
    GAMMA_E[n as usize]
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn matches_c_table_endpoints() {
        assert_eq!(degamma(0), 0);
        assert_eq!(degamma(21), 0);
        assert_eq!(degamma(22), 1);
        assert_eq!(degamma(128), 55);
        assert_eq!(degamma(255), 255);
    }

    #[test]
    fn is_monotonic() {
        assert!(GAMMA_E.windows(2).all(|w| w[0] <= w[1]));
    }
}