viewport-lib 0.14.0

/// Built-in colourmap LUT data (256 RGBA samples each).
///
/// Each function returns a `[[u8; 4]; 256]` array suitable for uploading to a
/// 256×1 GPU texture.  All values are in linear (non-sRGB) space to match the
/// `Rgba8Unorm` texture format used by the LUT sampler.

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

#[inline]
fn clamp01(x: f32) -> f32 {
    x.clamp(0.0, 1.0)
}

#[inline]
fn to_u8(x: f32) -> u8 {
    (clamp01(x) * 255.0 + 0.5) as u8
}

// ---------------------------------------------------------------------------
// Greyscale: linear ramp black -> white
// ---------------------------------------------------------------------------

/// Linear greyscale ramp from black (index 0) to white (index 255).
pub fn greyscale_rgba() -> [[u8; 4]; 256] {
    let mut lut = [[0u8; 4]; 256];
    for i in 0..256 {
        let v = i as u8;
        lut[i] = [v, v, v, 255];
    }
    lut
}

// ---------------------------------------------------------------------------
// Viridis: Smith 2015 polynomial approximation
// ---------------------------------------------------------------------------

/// Viridis colourmap : perceptually uniform, colourblind-friendly.
///
/// Uses the Smith 2015 polynomial approximation.
pub fn viridis_rgba() -> [[u8; 4]; 256] {
    let mut lut = [[0u8; 4]; 256];
    for i in 0..256 {
        let t = i as f32 / 255.0;
        // Degree-6 polynomial approximation (Zucker/Smith coefficients).
        // Range: dark purple (t=0) -> blue -> teal -> green -> yellow (t=1).
        let r = 0.277_727_33
            + t * (0.105_093_04
                + t * (-0.330_861_83
                    + t * (-4.634_230_5
                        + t * (6.228_269_9 + t * (4.776_385_0 - t * 5.435_455_9)))));
        let g = 0.005_407_345
            + t * (1.404_613_5
                + t * (0.214_847_56
                    + t * (-5.799_101_0 + t * (14.179_933 + t * (-13.745_145 + t * 4.645_852_6)))));
        let b = 0.334_099_81
            + t * (1.384_590_2
                + t * (0.095_095_16
                    + t * (-19.332_441 + t * (56.690_552 + t * (-65.353_033 + t * 26.312_435)))));
        lut[i] = [to_u8(r), to_u8(g), to_u8(b), 255];
    }
    lut
}

// ---------------------------------------------------------------------------
// Plasma: polynomial approximation
// ---------------------------------------------------------------------------

/// Plasma colourmap : perceptually uniform, colourblind-friendly.
///
/// Uses a polynomial approximation of the Matplotlib plasma colourmap.
pub fn plasma_rgba() -> [[u8; 4]; 256] {
    let mut lut = [[0u8; 4]; 256];
    for i in 0..256 {
        let t = i as f32 / 255.0;
        // Degree-6 polynomial approximation (Zucker/Kall coefficients).
        // Range: dark blue (t=0) -> pink (t=0.5) -> orange -> yellow (t=1).
        let r = 0.058_732_344
            + t * (2.176_514_6
                + t * (-2.689_460_5
                    + t * (6.130_348_3 + t * (-11.107_436 + t * (10.023_066 - t * 3.658_713_8)))));
        let g = 0.023_336_709
            + t * (0.238_383_42
                + t * (-7.455_851
                    + t * (42.346_188 + t * (-82.666_31 + t * (71.413_62 - t * 22.931_534)))));
        let b = 0.543_340_18
            + t * (0.753_960_46
                + t * (3.110_800
                    + t * (-28.518_854 + t * (60.139_847 + t * (-54.072_186 + t * 18.191_908)))));
        lut[i] = [to_u8(r), to_u8(g), to_u8(b), 255];
    }
    lut
}

// ---------------------------------------------------------------------------
// Coolwarm: diverging blue -> white -> red (cubic Hermite)
// ---------------------------------------------------------------------------

/// Diverging coolwarm colourmap: blue at t=0, white at t=0.5, red at t=1.
pub fn coolwarm_rgba() -> [[u8; 4]; 256] {
    let mut lut = [[0u8; 4]; 256];

    // Control points in linear [0,1] space.
    let cold = [59.0 / 255.0_f32, 76.0 / 255.0, 192.0 / 255.0]; // blue
    let mid = [220.0 / 255.0_f32, 220.0 / 255.0, 220.0 / 255.0]; // near-white
    let warm = [180.0 / 255.0_f32, 4.0 / 255.0, 38.0 / 255.0]; // red

    for i in 0..256 {
        let t = i as f32 / 255.0;
        // Piecewise smooth cubic Hermite blend across two halves.
        let (r, g, b) = if t <= 0.5 {
            let s = t * 2.0; // [0,1] in the cold half
            let h = s * s * (3.0 - 2.0 * s); // smoothstep
            (
                cold[0] + h * (mid[0] - cold[0]),
                cold[1] + h * (mid[1] - cold[1]),
                cold[2] + h * (mid[2] - cold[2]),
            )
        } else {
            let s = (t - 0.5) * 2.0; // [0,1] in the warm half
            let h = s * s * (3.0 - 2.0 * s);
            (
                mid[0] + h * (warm[0] - mid[0]),
                mid[1] + h * (warm[1] - mid[1]),
                mid[2] + h * (warm[2] - mid[2]),
            )
        };
        lut[i] = [to_u8(r), to_u8(g), to_u8(b), 255];
    }
    lut
}

// ---------------------------------------------------------------------------
// Rainbow: HSV hue sweep 240° (blue) -> 0° (red) at full saturation/value
// ---------------------------------------------------------------------------

/// Rainbow colourmap: HSV hue sweep from 240° (blue) at t=0 to 0° (red) at t=1.
pub fn rainbow_rgba() -> [[u8; 4]; 256] {
    let mut lut = [[0u8; 4]; 256];
    for i in 0..256 {
        let t = i as f32 / 255.0;
        // Hue sweeps from 240° down to 0° as t goes from 0 to 1.
        let hue = 240.0 * (1.0 - t); // degrees
        let (r, g, b) = hsv_to_rgb(hue, 1.0, 1.0);
        lut[i] = [to_u8(r), to_u8(g), to_u8(b), 255];
    }
    lut
}

/// Convert HSV (hue in degrees [0,360), saturation [0,1], value [0,1]) to RGB.
fn hsv_to_rgb(h: f32, s: f32, v: f32) -> (f32, f32, f32) {
    if s == 0.0 {
        return (v, v, v);
    }
    let h = h % 360.0;
    let sector = (h / 60.0).floor() as i32;
    let frac = h / 60.0 - sector as f32;
    let p = v * (1.0 - s);
    let q = v * (1.0 - s * frac);
    let t = v * (1.0 - s * (1.0 - frac));
    match sector {
        0 => (v, t, p),
        1 => (q, v, p),
        2 => (p, v, t),
        3 => (p, q, v),
        4 => (t, p, v),
        _ => (v, p, q),
    }
}

// ---------------------------------------------------------------------------
// Magma: exact 256-sample LUT sampled from matplotlib
// ---------------------------------------------------------------------------

/// Magma colourmap : perceptually uniform. Black/purple -> orange -> near-white.
pub fn magma_rgba() -> [[u8; 4]; 256] {
    [
        [0, 0, 4, 255],
        [1, 0, 5, 255],
        [1, 1, 6, 255],
        [1, 1, 8, 255],
        [2, 1, 9, 255],
        [2, 2, 11, 255],
        [2, 2, 13, 255],
        [3, 3, 15, 255],
        [3, 3, 18, 255],
        [4, 4, 20, 255],
        [5, 4, 22, 255],
        [6, 5, 24, 255],
        [6, 5, 26, 255],
        [7, 6, 28, 255],
        [8, 7, 30, 255],
        [9, 7, 32, 255],
        [10, 8, 34, 255],
        [11, 9, 36, 255],
        [12, 9, 38, 255],
        [13, 10, 41, 255],
        [14, 11, 43, 255],
        [16, 11, 45, 255],
        [17, 12, 47, 255],
        [18, 13, 49, 255],
        [19, 13, 52, 255],
        [20, 14, 54, 255],
        [21, 14, 56, 255],
        [22, 15, 59, 255],
        [24, 15, 61, 255],
        [25, 16, 63, 255],
        [26, 16, 66, 255],
        [28, 16, 68, 255],
        [29, 17, 71, 255],
        [30, 17, 73, 255],
        [32, 17, 75, 255],
        [33, 17, 78, 255],
        [34, 17, 80, 255],
        [36, 18, 83, 255],
        [37, 18, 85, 255],
        [39, 18, 88, 255],
        [41, 17, 90, 255],
        [42, 17, 92, 255],
        [44, 17, 95, 255],
        [45, 17, 97, 255],
        [47, 17, 99, 255],
        [49, 17, 101, 255],
        [51, 16, 103, 255],
        [52, 16, 105, 255],
        [54, 16, 107, 255],
        [56, 16, 108, 255],
        [57, 15, 110, 255],
        [59, 15, 112, 255],
        [61, 15, 113, 255],
        [63, 15, 114, 255],
        [64, 15, 116, 255],
        [66, 15, 117, 255],
        [68, 15, 118, 255],
        [69, 16, 119, 255],
        [71, 16, 120, 255],
        [73, 16, 120, 255],
        [74, 16, 121, 255],
        [76, 17, 122, 255],
        [78, 17, 123, 255],
        [79, 18, 123, 255],
        [81, 18, 124, 255],
        [82, 19, 124, 255],
        [84, 19, 125, 255],
        [86, 20, 125, 255],
        [87, 21, 126, 255],
        [89, 21, 126, 255],
        [90, 22, 126, 255],
        [92, 22, 127, 255],
        [93, 23, 127, 255],
        [95, 24, 127, 255],
        [96, 24, 128, 255],
        [98, 25, 128, 255],
        [100, 26, 128, 255],
        [101, 26, 128, 255],
        [103, 27, 128, 255],
        [104, 28, 129, 255],
        [106, 28, 129, 255],
        [107, 29, 129, 255],
        [109, 29, 129, 255],
        [110, 30, 129, 255],
        [112, 31, 129, 255],
        [114, 31, 129, 255],
        [115, 32, 129, 255],
        [117, 33, 129, 255],
        [118, 33, 129, 255],
        [120, 34, 129, 255],
        [121, 34, 130, 255],
        [123, 35, 130, 255],
        [124, 35, 130, 255],
        [126, 36, 130, 255],
        [128, 37, 130, 255],
        [129, 37, 129, 255],
        [131, 38, 129, 255],
        [132, 38, 129, 255],
        [134, 39, 129, 255],
        [136, 39, 129, 255],
        [137, 40, 129, 255],
        [139, 41, 129, 255],
        [140, 41, 129, 255],
        [142, 42, 129, 255],
        [144, 42, 129, 255],
        [145, 43, 129, 255],
        [147, 43, 128, 255],
        [148, 44, 128, 255],
        [150, 44, 128, 255],
        [152, 45, 128, 255],
        [153, 45, 128, 255],
        [155, 46, 127, 255],
        [156, 46, 127, 255],
        [158, 47, 127, 255],
        [160, 47, 127, 255],
        [161, 48, 126, 255],
        [163, 48, 126, 255],
        [165, 49, 126, 255],
        [166, 49, 125, 255],
        [168, 50, 125, 255],
        [170, 51, 125, 255],
        [171, 51, 124, 255],
        [173, 52, 124, 255],
        [174, 52, 123, 255],
        [176, 53, 123, 255],
        [178, 53, 123, 255],
        [179, 54, 122, 255],
        [181, 54, 122, 255],
        [183, 55, 121, 255],
        [184, 55, 121, 255],
        [186, 56, 120, 255],
        [188, 57, 120, 255],
        [189, 57, 119, 255],
        [191, 58, 119, 255],
        [192, 58, 118, 255],
        [194, 59, 117, 255],
        [196, 60, 117, 255],
        [197, 60, 116, 255],
        [199, 61, 115, 255],
        [200, 62, 115, 255],
        [202, 62, 114, 255],
        [204, 63, 113, 255],
        [205, 64, 113, 255],
        [207, 64, 112, 255],
        [208, 65, 111, 255],
        [210, 66, 111, 255],
        [211, 67, 110, 255],
        [213, 68, 109, 255],
        [214, 69, 108, 255],
        [216, 69, 108, 255],
        [217, 70, 107, 255],
        [219, 71, 106, 255],
        [220, 72, 105, 255],
        [222, 73, 104, 255],
        [223, 74, 104, 255],
        [224, 76, 103, 255],
        [226, 77, 102, 255],
        [227, 78, 101, 255],
        [228, 79, 100, 255],
        [229, 80, 100, 255],
        [231, 82, 99, 255],
        [232, 83, 98, 255],
        [233, 84, 98, 255],
        [234, 86, 97, 255],
        [235, 87, 96, 255],
        [236, 88, 96, 255],
        [237, 90, 95, 255],
        [238, 91, 94, 255],
        [239, 93, 94, 255],
        [240, 95, 94, 255],
        [241, 96, 93, 255],
        [242, 98, 93, 255],
        [242, 100, 92, 255],
        [243, 101, 92, 255],
        [244, 103, 92, 255],
        [244, 105, 92, 255],
        [245, 107, 92, 255],
        [246, 108, 92, 255],
        [246, 110, 92, 255],
        [247, 112, 92, 255],
        [247, 114, 92, 255],
        [248, 116, 92, 255],
        [248, 118, 92, 255],
        [249, 120, 93, 255],
        [249, 121, 93, 255],
        [249, 123, 93, 255],
        [250, 125, 94, 255],
        [250, 127, 94, 255],
        [250, 129, 95, 255],
        [251, 131, 95, 255],
        [251, 133, 96, 255],
        [251, 135, 97, 255],
        [252, 137, 97, 255],
        [252, 138, 98, 255],
        [252, 140, 99, 255],
        [252, 142, 100, 255],
        [252, 144, 101, 255],
        [253, 146, 102, 255],
        [253, 148, 103, 255],
        [253, 150, 104, 255],
        [253, 152, 105, 255],
        [253, 154, 106, 255],
        [253, 155, 107, 255],
        [254, 157, 108, 255],
        [254, 159, 109, 255],
        [254, 161, 110, 255],
        [254, 163, 111, 255],
        [254, 165, 113, 255],
        [254, 167, 114, 255],
        [254, 169, 115, 255],
        [254, 170, 116, 255],
        [254, 172, 118, 255],
        [254, 174, 119, 255],
        [254, 176, 120, 255],
        [254, 178, 122, 255],
        [254, 180, 123, 255],
        [254, 182, 124, 255],
        [254, 183, 126, 255],
        [254, 185, 127, 255],
        [254, 187, 129, 255],
        [254, 189, 130, 255],
        [254, 191, 132, 255],
        [254, 193, 133, 255],
        [254, 194, 135, 255],
        [254, 196, 136, 255],
        [254, 198, 138, 255],
        [254, 200, 140, 255],
        [254, 202, 141, 255],
        [254, 204, 143, 255],
        [254, 205, 144, 255],
        [254, 207, 146, 255],
        [254, 209, 148, 255],
        [254, 211, 149, 255],
        [254, 213, 151, 255],
        [254, 215, 153, 255],
        [254, 216, 154, 255],
        [253, 218, 156, 255],
        [253, 220, 158, 255],
        [253, 222, 160, 255],
        [253, 224, 161, 255],
        [253, 226, 163, 255],
        [253, 227, 165, 255],
        [253, 229, 167, 255],
        [253, 231, 169, 255],
        [253, 233, 170, 255],
        [253, 235, 172, 255],
        [252, 236, 174, 255],
        [252, 238, 176, 255],
        [252, 240, 178, 255],
        [252, 242, 180, 255],
        [252, 244, 182, 255],
        [252, 246, 184, 255],
        [252, 247, 185, 255],
        [252, 249, 187, 255],
        [252, 251, 189, 255],
        [252, 253, 191, 255],
    ]
}

// ---------------------------------------------------------------------------
// Inferno: exact 256-sample LUT sampled from matplotlib
// ---------------------------------------------------------------------------

/// Inferno colourmap : perceptually uniform. Black -> deep red -> orange -> light yellow.
pub fn inferno_rgba() -> [[u8; 4]; 256] {
    [
        [0, 0, 4, 255],
        [1, 0, 5, 255],
        [1, 1, 6, 255],
        [1, 1, 8, 255],
        [2, 1, 10, 255],
        [2, 2, 12, 255],
        [2, 2, 14, 255],
        [3, 2, 16, 255],
        [4, 3, 18, 255],
        [4, 3, 20, 255],
        [5, 4, 23, 255],
        [6, 4, 25, 255],
        [7, 5, 27, 255],
        [8, 5, 29, 255],
        [9, 6, 31, 255],
        [10, 7, 34, 255],
        [11, 7, 36, 255],
        [12, 8, 38, 255],
        [13, 8, 41, 255],
        [14, 9, 43, 255],
        [16, 9, 45, 255],
        [17, 10, 48, 255],
        [18, 10, 50, 255],
        [20, 11, 52, 255],
        [21, 11, 55, 255],
        [22, 11, 57, 255],
        [24, 12, 60, 255],
        [25, 12, 62, 255],
        [27, 12, 65, 255],
        [28, 12, 67, 255],
        [30, 12, 69, 255],
        [31, 12, 72, 255],
        [33, 12, 74, 255],
        [35, 12, 76, 255],
        [36, 12, 79, 255],
        [38, 12, 81, 255],
        [40, 11, 83, 255],
        [41, 11, 85, 255],
        [43, 11, 87, 255],
        [45, 11, 89, 255],
        [47, 10, 91, 255],
        [49, 10, 92, 255],
        [50, 10, 94, 255],
        [52, 10, 95, 255],
        [54, 9, 97, 255],
        [56, 9, 98, 255],
        [57, 9, 99, 255],
        [59, 9, 100, 255],
        [61, 9, 101, 255],
        [62, 9, 102, 255],
        [64, 10, 103, 255],
        [66, 10, 104, 255],
        [68, 10, 104, 255],
        [69, 10, 105, 255],
        [71, 11, 106, 255],
        [73, 11, 106, 255],
        [74, 12, 107, 255],
        [76, 12, 107, 255],
        [77, 13, 108, 255],
        [79, 13, 108, 255],
        [81, 14, 108, 255],
        [82, 14, 109, 255],
        [84, 15, 109, 255],
        [85, 15, 109, 255],
        [87, 16, 110, 255],
        [89, 16, 110, 255],
        [90, 17, 110, 255],
        [92, 18, 110, 255],
        [93, 18, 110, 255],
        [95, 19, 110, 255],
        [97, 19, 110, 255],
        [98, 20, 110, 255],
        [100, 21, 110, 255],
        [101, 21, 110, 255],
        [103, 22, 110, 255],
        [105, 22, 110, 255],
        [106, 23, 110, 255],
        [108, 24, 110, 255],
        [109, 24, 110, 255],
        [111, 25, 110, 255],
        [113, 25, 110, 255],
        [114, 26, 110, 255],
        [116, 26, 110, 255],
        [117, 27, 110, 255],
        [119, 28, 109, 255],
        [120, 28, 109, 255],
        [122, 29, 109, 255],
        [124, 29, 109, 255],
        [125, 30, 109, 255],
        [127, 30, 108, 255],
        [128, 31, 108, 255],
        [130, 32, 108, 255],
        [132, 32, 107, 255],
        [133, 33, 107, 255],
        [135, 33, 107, 255],
        [136, 34, 106, 255],
        [138, 34, 106, 255],
        [140, 35, 105, 255],
        [141, 35, 105, 255],
        [143, 36, 105, 255],
        [144, 37, 104, 255],
        [146, 37, 104, 255],
        [147, 38, 103, 255],
        [149, 38, 103, 255],
        [151, 39, 102, 255],
        [152, 39, 102, 255],
        [154, 40, 101, 255],
        [155, 41, 100, 255],
        [157, 41, 100, 255],
        [159, 42, 99, 255],
        [160, 42, 99, 255],
        [162, 43, 98, 255],
        [163, 44, 97, 255],
        [165, 44, 96, 255],
        [166, 45, 96, 255],
        [168, 46, 95, 255],
        [169, 46, 94, 255],
        [171, 47, 94, 255],
        [173, 48, 93, 255],
        [174, 48, 92, 255],
        [176, 49, 91, 255],
        [177, 50, 90, 255],
        [179, 50, 90, 255],
        [180, 51, 89, 255],
        [182, 52, 88, 255],
        [183, 53, 87, 255],
        [185, 53, 86, 255],
        [186, 54, 85, 255],
        [188, 55, 84, 255],
        [189, 56, 83, 255],
        [191, 57, 82, 255],
        [192, 58, 81, 255],
        [193, 58, 80, 255],
        [195, 59, 79, 255],
        [196, 60, 78, 255],
        [198, 61, 77, 255],
        [199, 62, 76, 255],
        [200, 63, 75, 255],
        [202, 64, 74, 255],
        [203, 65, 73, 255],
        [204, 66, 72, 255],
        [206, 67, 71, 255],
        [207, 68, 70, 255],
        [208, 69, 69, 255],
        [210, 70, 68, 255],
        [211, 71, 67, 255],
        [212, 72, 66, 255],
        [213, 74, 65, 255],
        [215, 75, 63, 255],
        [216, 76, 62, 255],
        [217, 77, 61, 255],
        [218, 78, 60, 255],
        [219, 80, 59, 255],
        [221, 81, 58, 255],
        [222, 82, 56, 255],
        [223, 83, 55, 255],
        [224, 85, 54, 255],
        [225, 86, 53, 255],
        [226, 87, 52, 255],
        [227, 89, 51, 255],
        [228, 90, 49, 255],
        [229, 92, 48, 255],
        [230, 93, 47, 255],
        [231, 94, 46, 255],
        [232, 96, 45, 255],
        [233, 97, 43, 255],
        [234, 99, 42, 255],
        [235, 100, 41, 255],
        [235, 102, 40, 255],
        [236, 103, 38, 255],
        [237, 105, 37, 255],
        [238, 106, 36, 255],
        [239, 108, 35, 255],
        [239, 110, 33, 255],
        [240, 111, 32, 255],
        [241, 113, 31, 255],
        [241, 115, 29, 255],
        [242, 116, 28, 255],
        [243, 118, 27, 255],
        [243, 120, 25, 255],
        [244, 121, 24, 255],
        [245, 123, 23, 255],
        [245, 125, 21, 255],
        [246, 126, 20, 255],
        [246, 128, 19, 255],
        [247, 130, 18, 255],
        [247, 132, 16, 255],
        [248, 133, 15, 255],
        [248, 135, 14, 255],
        [248, 137, 12, 255],
        [249, 139, 11, 255],
        [249, 140, 10, 255],
        [249, 142, 9, 255],
        [250, 144, 8, 255],
        [250, 146, 7, 255],
        [250, 148, 7, 255],
        [251, 150, 6, 255],
        [251, 151, 6, 255],
        [251, 153, 6, 255],
        [251, 155, 6, 255],
        [251, 157, 7, 255],
        [252, 159, 7, 255],
        [252, 161, 8, 255],
        [252, 163, 9, 255],
        [252, 165, 10, 255],
        [252, 166, 12, 255],
        [252, 168, 13, 255],
        [252, 170, 15, 255],
        [252, 172, 17, 255],
        [252, 174, 18, 255],
        [252, 176, 20, 255],
        [252, 178, 22, 255],
        [252, 180, 24, 255],
        [251, 182, 26, 255],
        [251, 184, 29, 255],
        [251, 186, 31, 255],
        [251, 188, 33, 255],
        [251, 190, 35, 255],
        [250, 192, 38, 255],
        [250, 194, 40, 255],
        [250, 196, 42, 255],
        [250, 198, 45, 255],
        [249, 199, 47, 255],
        [249, 201, 50, 255],
        [249, 203, 53, 255],
        [248, 205, 55, 255],
        [248, 207, 58, 255],
        [247, 209, 61, 255],
        [247, 211, 64, 255],
        [246, 213, 67, 255],
        [246, 215, 70, 255],
        [245, 217, 73, 255],
        [245, 219, 76, 255],
        [244, 221, 79, 255],
        [244, 223, 83, 255],
        [244, 225, 86, 255],
        [243, 227, 90, 255],
        [243, 229, 93, 255],
        [242, 230, 97, 255],
        [242, 232, 101, 255],
        [242, 234, 105, 255],
        [241, 236, 109, 255],
        [241, 237, 113, 255],
        [241, 239, 117, 255],
        [241, 241, 121, 255],
        [242, 242, 125, 255],
        [242, 244, 130, 255],
        [243, 245, 134, 255],
        [243, 246, 138, 255],
        [244, 248, 142, 255],
        [245, 249, 146, 255],
        [246, 250, 150, 255],
        [248, 251, 154, 255],
        [249, 252, 157, 255],
        [250, 253, 161, 255],
        [252, 255, 164, 255],
    ]
}

// ---------------------------------------------------------------------------
// Turbo: exact 256-sample LUT sampled from matplotlib
// ---------------------------------------------------------------------------

/// Turbo colourmap (Google 2019) : improved rainbow. Deep purple -> cyan -> green -> yellow -> red.
pub fn turbo_rgba() -> [[u8; 4]; 256] {
    [
        [48, 18, 59, 255],
        [50, 21, 67, 255],
        [51, 24, 74, 255],
        [52, 27, 81, 255],
        [53, 30, 88, 255],
        [54, 33, 95, 255],
        [55, 36, 102, 255],
        [56, 39, 109, 255],
        [57, 42, 115, 255],
        [58, 45, 121, 255],
        [59, 47, 128, 255],
        [60, 50, 134, 255],
        [61, 53, 139, 255],
        [62, 56, 145, 255],
        [63, 59, 151, 255],
        [63, 62, 156, 255],
        [64, 64, 162, 255],
        [65, 67, 167, 255],
        [65, 70, 172, 255],
        [66, 73, 177, 255],
        [66, 75, 181, 255],
        [67, 78, 186, 255],
        [68, 81, 191, 255],
        [68, 84, 195, 255],
        [68, 86, 199, 255],
        [69, 89, 203, 255],
        [69, 92, 207, 255],
        [69, 94, 211, 255],
        [70, 97, 214, 255],
        [70, 100, 218, 255],
        [70, 102, 221, 255],
        [70, 105, 224, 255],
        [70, 107, 227, 255],
        [71, 110, 230, 255],
        [71, 113, 233, 255],
        [71, 115, 235, 255],
        [71, 118, 238, 255],
        [71, 120, 240, 255],
        [71, 123, 242, 255],
        [70, 125, 244, 255],
        [70, 128, 246, 255],
        [70, 130, 248, 255],
        [70, 133, 250, 255],
        [70, 135, 251, 255],
        [69, 138, 252, 255],
        [69, 140, 253, 255],
        [68, 143, 254, 255],
        [67, 145, 254, 255],
        [66, 148, 255, 255],
        [65, 150, 255, 255],
        [64, 153, 255, 255],
        [62, 155, 254, 255],
        [61, 158, 254, 255],
        [59, 160, 253, 255],
        [58, 163, 252, 255],
        [56, 165, 251, 255],
        [55, 168, 250, 255],
        [53, 171, 248, 255],
        [51, 173, 247, 255],
        [49, 175, 245, 255],
        [47, 178, 244, 255],
        [46, 180, 242, 255],
        [44, 183, 240, 255],
        [42, 185, 238, 255],
        [40, 188, 235, 255],
        [39, 190, 233, 255],
        [37, 192, 231, 255],
        [35, 195, 228, 255],
        [34, 197, 226, 255],
        [32, 199, 223, 255],
        [31, 201, 221, 255],
        [30, 203, 218, 255],
        [28, 205, 216, 255],
        [27, 208, 213, 255],
        [26, 210, 210, 255],
        [26, 212, 208, 255],
        [25, 213, 205, 255],
        [24, 215, 202, 255],
        [24, 217, 200, 255],
        [24, 219, 197, 255],
        [24, 221, 194, 255],
        [24, 222, 192, 255],
        [24, 224, 189, 255],
        [25, 226, 187, 255],
        [25, 227, 185, 255],
        [26, 228, 182, 255],
        [28, 230, 180, 255],
        [29, 231, 178, 255],
        [31, 233, 175, 255],
        [32, 234, 172, 255],
        [34, 235, 170, 255],
        [37, 236, 167, 255],
        [39, 238, 164, 255],
        [42, 239, 161, 255],
        [44, 240, 158, 255],
        [47, 241, 155, 255],
        [50, 242, 152, 255],
        [53, 243, 148, 255],
        [56, 244, 145, 255],
        [60, 245, 142, 255],
        [63, 246, 138, 255],
        [67, 247, 135, 255],
        [70, 248, 132, 255],
        [74, 248, 128, 255],
        [78, 249, 125, 255],
        [82, 250, 122, 255],
        [85, 250, 118, 255],
        [89, 251, 115, 255],
        [93, 252, 111, 255],
        [97, 252, 108, 255],
        [101, 253, 105, 255],
        [105, 253, 102, 255],
        [109, 254, 98, 255],
        [113, 254, 95, 255],
        [117, 254, 92, 255],
        [121, 254, 89, 255],
        [125, 255, 86, 255],
        [128, 255, 83, 255],
        [132, 255, 81, 255],
        [136, 255, 78, 255],
        [139, 255, 75, 255],
        [143, 255, 73, 255],
        [146, 255, 71, 255],
        [150, 254, 68, 255],
        [153, 254, 66, 255],
        [156, 254, 64, 255],
        [159, 253, 63, 255],
        [161, 253, 61, 255],
        [164, 252, 60, 255],
        [167, 252, 58, 255],
        [169, 251, 57, 255],
        [172, 251, 56, 255],
        [175, 250, 55, 255],
        [177, 249, 54, 255],
        [180, 248, 54, 255],
        [183, 247, 53, 255],
        [185, 246, 53, 255],
        [188, 245, 52, 255],
        [190, 244, 52, 255],
        [193, 243, 52, 255],
        [195, 241, 52, 255],
        [198, 240, 52, 255],
        [200, 239, 52, 255],
        [203, 237, 52, 255],
        [205, 236, 52, 255],
        [208, 234, 52, 255],
        [210, 233, 53, 255],
        [212, 231, 53, 255],
        [215, 229, 53, 255],
        [217, 228, 54, 255],
        [219, 226, 54, 255],
        [221, 224, 55, 255],
        [223, 223, 55, 255],
        [225, 221, 55, 255],
        [227, 219, 56, 255],
        [229, 217, 56, 255],
        [231, 215, 57, 255],
        [233, 213, 57, 255],
        [235, 211, 57, 255],
        [236, 209, 58, 255],
        [238, 207, 58, 255],
        [239, 205, 58, 255],
        [241, 203, 58, 255],
        [242, 201, 58, 255],
        [244, 199, 58, 255],
        [245, 197, 58, 255],
        [246, 195, 58, 255],
        [247, 193, 58, 255],
        [248, 190, 57, 255],
        [249, 188, 57, 255],
        [250, 186, 57, 255],
        [251, 184, 56, 255],
        [251, 182, 55, 255],
        [252, 179, 54, 255],
        [252, 177, 54, 255],
        [253, 174, 53, 255],
        [253, 172, 52, 255],
        [254, 169, 51, 255],
        [254, 167, 50, 255],
        [254, 164, 49, 255],
        [254, 161, 48, 255],
        [254, 158, 47, 255],
        [254, 155, 45, 255],
        [254, 153, 44, 255],
        [254, 150, 43, 255],
        [254, 147, 42, 255],
        [254, 144, 41, 255],
        [253, 141, 39, 255],
        [253, 138, 38, 255],
        [252, 135, 37, 255],
        [252, 132, 35, 255],
        [251, 129, 34, 255],
        [251, 126, 33, 255],
        [250, 123, 31, 255],
        [249, 120, 30, 255],
        [249, 117, 29, 255],
        [248, 114, 28, 255],
        [247, 111, 26, 255],
        [246, 108, 25, 255],
        [245, 105, 24, 255],
        [244, 102, 23, 255],
        [243, 99, 21, 255],
        [242, 96, 20, 255],
        [241, 93, 19, 255],
        [240, 91, 18, 255],
        [239, 88, 17, 255],
        [237, 85, 16, 255],
        [236, 83, 15, 255],
        [235, 80, 14, 255],
        [234, 78, 13, 255],
        [232, 75, 12, 255],
        [231, 73, 12, 255],
        [229, 71, 11, 255],
        [228, 69, 10, 255],
        [226, 67, 10, 255],
        [225, 65, 9, 255],
        [223, 63, 8, 255],
        [221, 61, 8, 255],
        [220, 59, 7, 255],
        [218, 57, 7, 255],
        [216, 55, 6, 255],
        [214, 53, 6, 255],
        [212, 51, 5, 255],
        [210, 49, 5, 255],
        [208, 47, 5, 255],
        [206, 45, 4, 255],
        [204, 43, 4, 255],
        [202, 42, 4, 255],
        [200, 40, 3, 255],
        [197, 38, 3, 255],
        [195, 37, 3, 255],
        [193, 35, 2, 255],
        [190, 33, 2, 255],
        [188, 32, 2, 255],
        [185, 30, 2, 255],
        [183, 29, 2, 255],
        [180, 27, 1, 255],
        [178, 26, 1, 255],
        [175, 24, 1, 255],
        [172, 23, 1, 255],
        [169, 22, 1, 255],
        [167, 20, 1, 255],
        [164, 19, 1, 255],
        [161, 18, 1, 255],
        [158, 16, 1, 255],
        [155, 15, 1, 255],
        [152, 14, 1, 255],
        [149, 13, 1, 255],
        [146, 11, 1, 255],
        [142, 10, 1, 255],
        [139, 9, 2, 255],
        [136, 8, 2, 255],
        [133, 7, 2, 255],
        [129, 6, 2, 255],
        [126, 5, 2, 255],
        [122, 4, 3, 255],
    ]
}

// ---------------------------------------------------------------------------
// Jet: exact 256-sample LUT sampled from matplotlib
// ---------------------------------------------------------------------------

/// Jet colourmap : classic blue-cyan-green-yellow-red. Not perceptually uniform.
pub fn jet_rgba() -> [[u8; 4]; 256] {
    [
        [0, 0, 128, 255],
        [0, 0, 132, 255],
        [0, 0, 137, 255],
        [0, 0, 141, 255],
        [0, 0, 146, 255],
        [0, 0, 150, 255],
        [0, 0, 155, 255],
        [0, 0, 159, 255],
        [0, 0, 164, 255],
        [0, 0, 168, 255],
        [0, 0, 173, 255],
        [0, 0, 178, 255],
        [0, 0, 182, 255],
        [0, 0, 187, 255],
        [0, 0, 191, 255],
        [0, 0, 196, 255],
        [0, 0, 200, 255],
        [0, 0, 205, 255],
        [0, 0, 209, 255],
        [0, 0, 214, 255],
        [0, 0, 218, 255],
        [0, 0, 223, 255],
        [0, 0, 227, 255],
        [0, 0, 232, 255],
        [0, 0, 237, 255],
        [0, 0, 241, 255],
        [0, 0, 246, 255],
        [0, 0, 250, 255],
        [0, 0, 255, 255],
        [0, 0, 255, 255],
        [0, 0, 255, 255],
        [0, 0, 255, 255],
        [0, 1, 255, 255],
        [0, 4, 255, 255],
        [0, 9, 255, 255],
        [0, 13, 255, 255],
        [0, 17, 255, 255],
        [0, 20, 255, 255],
        [0, 25, 255, 255],
        [0, 29, 255, 255],
        [0, 33, 255, 255],
        [0, 36, 255, 255],
        [0, 41, 255, 255],
        [0, 45, 255, 255],
        [0, 49, 255, 255],
        [0, 52, 255, 255],
        [0, 57, 255, 255],
        [0, 61, 255, 255],
        [0, 65, 255, 255],
        [0, 68, 255, 255],
        [0, 73, 255, 255],
        [0, 77, 255, 255],
        [0, 81, 255, 255],
        [0, 84, 255, 255],
        [0, 89, 255, 255],
        [0, 93, 255, 255],
        [0, 97, 255, 255],
        [0, 100, 255, 255],
        [0, 105, 255, 255],
        [0, 109, 255, 255],
        [0, 113, 255, 255],
        [0, 116, 255, 255],
        [0, 121, 255, 255],
        [0, 125, 255, 255],
        [0, 129, 255, 255],
        [0, 133, 255, 255],
        [0, 136, 255, 255],
        [0, 141, 255, 255],
        [0, 145, 255, 255],
        [0, 149, 255, 255],
        [0, 153, 255, 255],
        [0, 157, 255, 255],
        [0, 161, 255, 255],
        [0, 165, 255, 255],
        [0, 168, 255, 255],
        [0, 173, 255, 255],
        [0, 177, 255, 255],
        [0, 181, 255, 255],
        [0, 185, 255, 255],
        [0, 189, 255, 255],
        [0, 193, 255, 255],
        [0, 197, 255, 255],
        [0, 200, 255, 255],
        [0, 205, 255, 255],
        [0, 209, 255, 255],
        [0, 213, 255, 255],
        [0, 217, 255, 255],
        [0, 221, 254, 255],
        [0, 225, 251, 255],
        [0, 229, 248, 255],
        [2, 232, 244, 255],
        [6, 237, 241, 255],
        [9, 241, 238, 255],
        [12, 245, 235, 255],
        [15, 249, 231, 255],
        [19, 253, 228, 255],
        [22, 255, 225, 255],
        [25, 255, 222, 255],
        [28, 255, 219, 255],
        [31, 255, 215, 255],
        [35, 255, 212, 255],
        [38, 255, 209, 255],
        [41, 255, 206, 255],
        [44, 255, 202, 255],
        [48, 255, 199, 255],
        [51, 255, 196, 255],
        [54, 255, 193, 255],
        [57, 255, 190, 255],
        [60, 255, 186, 255],
        [64, 255, 183, 255],
        [67, 255, 180, 255],
        [70, 255, 177, 255],
        [73, 255, 173, 255],
        [77, 255, 170, 255],
        [80, 255, 167, 255],
        [83, 255, 164, 255],
        [86, 255, 160, 255],
        [90, 255, 157, 255],
        [93, 255, 154, 255],
        [96, 255, 151, 255],
        [99, 255, 148, 255],
        [102, 255, 144, 255],
        [106, 255, 141, 255],
        [109, 255, 138, 255],
        [112, 255, 135, 255],
        [115, 255, 131, 255],
        [119, 255, 128, 255],
        [122, 255, 125, 255],
        [125, 255, 122, 255],
        [128, 255, 119, 255],
        [131, 255, 115, 255],
        [135, 255, 112, 255],
        [138, 255, 109, 255],
        [141, 255, 106, 255],
        [144, 255, 102, 255],
        [148, 255, 99, 255],
        [151, 255, 96, 255],
        [154, 255, 93, 255],
        [157, 255, 90, 255],
        [160, 255, 86, 255],
        [164, 255, 83, 255],
        [167, 255, 80, 255],
        [170, 255, 77, 255],
        [173, 255, 73, 255],
        [177, 255, 70, 255],
        [180, 255, 67, 255],
        [183, 255, 64, 255],
        [186, 255, 60, 255],
        [190, 255, 57, 255],
        [193, 255, 54, 255],
        [196, 255, 51, 255],
        [199, 255, 48, 255],
        [202, 255, 44, 255],
        [206, 255, 41, 255],
        [209, 255, 38, 255],
        [212, 255, 35, 255],
        [215, 255, 31, 255],
        [219, 255, 28, 255],
        [222, 255, 25, 255],
        [225, 255, 22, 255],
        [228, 255, 19, 255],
        [231, 255, 15, 255],
        [235, 255, 12, 255],
        [238, 255, 9, 255],
        [241, 252, 6, 255],
        [244, 248, 2, 255],
        [248, 245, 0, 255],
        [251, 241, 0, 255],
        [254, 237, 0, 255],
        [255, 234, 0, 255],
        [255, 230, 0, 255],
        [255, 226, 0, 255],
        [255, 222, 0, 255],
        [255, 219, 0, 255],
        [255, 215, 0, 255],
        [255, 211, 0, 255],
        [255, 208, 0, 255],
        [255, 204, 0, 255],
        [255, 200, 0, 255],
        [255, 196, 0, 255],
        [255, 193, 0, 255],
        [255, 189, 0, 255],
        [255, 185, 0, 255],
        [255, 182, 0, 255],
        [255, 178, 0, 255],
        [255, 174, 0, 255],
        [255, 171, 0, 255],
        [255, 167, 0, 255],
        [255, 163, 0, 255],
        [255, 159, 0, 255],
        [255, 156, 0, 255],
        [255, 152, 0, 255],
        [255, 148, 0, 255],
        [255, 145, 0, 255],
        [255, 141, 0, 255],
        [255, 137, 0, 255],
        [255, 134, 0, 255],
        [255, 130, 0, 255],
        [255, 126, 0, 255],
        [255, 122, 0, 255],
        [255, 119, 0, 255],
        [255, 115, 0, 255],
        [255, 111, 0, 255],
        [255, 108, 0, 255],
        [255, 104, 0, 255],
        [255, 100, 0, 255],
        [255, 96, 0, 255],
        [255, 93, 0, 255],
        [255, 89, 0, 255],
        [255, 85, 0, 255],
        [255, 82, 0, 255],
        [255, 78, 0, 255],
        [255, 74, 0, 255],
        [255, 71, 0, 255],
        [255, 67, 0, 255],
        [255, 63, 0, 255],
        [255, 59, 0, 255],
        [255, 56, 0, 255],
        [255, 52, 0, 255],
        [255, 48, 0, 255],
        [255, 45, 0, 255],
        [255, 41, 0, 255],
        [255, 37, 0, 255],
        [255, 34, 0, 255],
        [255, 30, 0, 255],
        [255, 26, 0, 255],
        [255, 22, 0, 255],
        [255, 19, 0, 255],
        [250, 15, 0, 255],
        [246, 11, 0, 255],
        [241, 8, 0, 255],
        [237, 4, 0, 255],
        [232, 0, 0, 255],
        [228, 0, 0, 255],
        [223, 0, 0, 255],
        [218, 0, 0, 255],
        [214, 0, 0, 255],
        [209, 0, 0, 255],
        [205, 0, 0, 255],
        [200, 0, 0, 255],
        [196, 0, 0, 255],
        [191, 0, 0, 255],
        [187, 0, 0, 255],
        [182, 0, 0, 255],
        [178, 0, 0, 255],
        [173, 0, 0, 255],
        [168, 0, 0, 255],
        [164, 0, 0, 255],
        [159, 0, 0, 255],
        [155, 0, 0, 255],
        [150, 0, 0, 255],
        [146, 0, 0, 255],
        [141, 0, 0, 255],
        [137, 0, 0, 255],
        [132, 0, 0, 255],
        [128, 0, 0, 255],
    ]
}

// ---------------------------------------------------------------------------
// RdBu (reversed): exact 256-sample LUT sampled from matplotlib
// ---------------------------------------------------------------------------

/// RdBu diverging colourmap (red -> white -> blue, reversed so blue is at t=0).
/// Suitable for signed quantities (negative = blue, zero = white, positive = red).
pub fn rdbu_r_rgba() -> [[u8; 4]; 256] {
    [
        [5, 48, 97, 255],
        [6, 50, 100, 255],
        [7, 52, 103, 255],
        [8, 54, 106, 255],
        [9, 56, 109, 255],
        [10, 59, 112, 255],
        [12, 61, 115, 255],
        [13, 63, 118, 255],
        [14, 65, 121, 255],
        [15, 67, 123, 255],
        [16, 69, 126, 255],
        [17, 71, 129, 255],
        [18, 73, 132, 255],
        [19, 76, 135, 255],
        [20, 78, 138, 255],
        [21, 80, 141, 255],
        [23, 82, 144, 255],
        [24, 84, 147, 255],
        [25, 86, 150, 255],
        [26, 88, 153, 255],
        [27, 90, 156, 255],
        [28, 92, 159, 255],
        [29, 95, 162, 255],
        [30, 97, 165, 255],
        [31, 99, 168, 255],
        [32, 101, 171, 255],
        [34, 103, 172, 255],
        [35, 105, 173, 255],
        [36, 106, 174, 255],
        [38, 108, 175, 255],
        [39, 110, 176, 255],
        [40, 112, 177, 255],
        [42, 113, 178, 255],
        [43, 115, 179, 255],
        [44, 117, 180, 255],
        [46, 119, 181, 255],
        [47, 121, 181, 255],
        [48, 122, 182, 255],
        [50, 124, 183, 255],
        [51, 126, 184, 255],
        [52, 128, 185, 255],
        [54, 129, 186, 255],
        [55, 131, 187, 255],
        [56, 133, 188, 255],
        [58, 135, 189, 255],
        [59, 136, 190, 255],
        [60, 138, 190, 255],
        [62, 140, 191, 255],
        [63, 142, 192, 255],
        [64, 143, 193, 255],
        [66, 145, 194, 255],
        [67, 147, 195, 255],
        [70, 149, 196, 255],
        [73, 151, 197, 255],
        [76, 153, 198, 255],
        [79, 155, 199, 255],
        [82, 157, 200, 255],
        [86, 159, 201, 255],
        [89, 161, 202, 255],
        [92, 163, 203, 255],
        [95, 165, 205, 255],
        [98, 167, 206, 255],
        [101, 169, 207, 255],
        [104, 171, 208, 255],
        [107, 172, 209, 255],
        [110, 174, 210, 255],
        [113, 176, 211, 255],
        [117, 178, 212, 255],
        [120, 180, 213, 255],
        [123, 182, 214, 255],
        [126, 184, 215, 255],
        [129, 186, 216, 255],
        [132, 188, 217, 255],
        [135, 190, 218, 255],
        [138, 192, 219, 255],
        [141, 194, 220, 255],
        [144, 196, 221, 255],
        [147, 198, 222, 255],
        [150, 199, 223, 255],
        [152, 200, 224, 255],
        [155, 201, 224, 255],
        [157, 203, 225, 255],
        [160, 204, 226, 255],
        [162, 205, 227, 255],
        [165, 206, 227, 255],
        [167, 208, 228, 255],
        [169, 209, 229, 255],
        [172, 210, 229, 255],
        [174, 211, 230, 255],
        [177, 213, 231, 255],
        [179, 214, 232, 255],
        [182, 215, 232, 255],
        [184, 216, 233, 255],
        [187, 218, 234, 255],
        [189, 219, 234, 255],
        [192, 220, 235, 255],
        [194, 221, 236, 255],
        [197, 223, 236, 255],
        [199, 224, 237, 255],
        [202, 225, 238, 255],
        [204, 226, 239, 255],
        [207, 228, 239, 255],
        [209, 229, 240, 255],
        [210, 230, 240, 255],
        [212, 230, 241, 255],
        [213, 231, 241, 255],
        [215, 232, 241, 255],
        [216, 233, 241, 255],
        [218, 233, 242, 255],
        [219, 234, 242, 255],
        [221, 235, 242, 255],
        [222, 235, 242, 255],
        [224, 236, 243, 255],
        [225, 237, 243, 255],
        [227, 237, 243, 255],
        [228, 238, 244, 255],
        [230, 239, 244, 255],
        [231, 240, 244, 255],
        [233, 240, 244, 255],
        [234, 241, 245, 255],
        [236, 242, 245, 255],
        [237, 242, 245, 255],
        [239, 243, 245, 255],
        [240, 244, 246, 255],
        [242, 245, 246, 255],
        [243, 245, 246, 255],
        [245, 246, 247, 255],
        [246, 247, 247, 255],
        [247, 246, 246, 255],
        [247, 245, 244, 255],
        [248, 244, 242, 255],
        [248, 243, 240, 255],
        [248, 242, 239, 255],
        [248, 241, 237, 255],
        [249, 240, 235, 255],
        [249, 239, 233, 255],
        [249, 238, 231, 255],
        [249, 237, 229, 255],
        [249, 235, 227, 255],
        [250, 234, 225, 255],
        [250, 233, 223, 255],
        [250, 232, 222, 255],
        [250, 231, 220, 255],
        [251, 230, 218, 255],
        [251, 229, 216, 255],
        [251, 228, 214, 255],
        [251, 227, 212, 255],
        [252, 226, 210, 255],
        [252, 224, 208, 255],
        [252, 223, 207, 255],
        [252, 222, 205, 255],
        [253, 221, 203, 255],
        [253, 220, 201, 255],
        [253, 219, 199, 255],
        [253, 217, 196, 255],
        [252, 215, 194, 255],
        [252, 213, 191, 255],
        [252, 211, 188, 255],
        [251, 208, 185, 255],
        [251, 206, 183, 255],
        [251, 204, 180, 255],
        [250, 202, 177, 255],
        [250, 200, 175, 255],
        [249, 198, 172, 255],
        [249, 196, 169, 255],
        [249, 194, 167, 255],
        [248, 191, 164, 255],
        [248, 189, 161, 255],
        [248, 187, 158, 255],
        [247, 185, 156, 255],
        [247, 183, 153, 255],
        [247, 181, 150, 255],
        [246, 179, 148, 255],
        [246, 177, 145, 255],
        [246, 175, 142, 255],
        [245, 172, 139, 255],
        [245, 170, 137, 255],
        [245, 168, 134, 255],
        [244, 166, 131, 255],
        [243, 164, 129, 255],
        [242, 161, 127, 255],
        [241, 158, 125, 255],
        [240, 156, 123, 255],
        [239, 153, 121, 255],
        [238, 150, 119, 255],
        [236, 147, 116, 255],
        [235, 145, 114, 255],
        [234, 142, 112, 255],
        [233, 139, 110, 255],
        [232, 137, 108, 255],
        [230, 134, 106, 255],
        [229, 131, 104, 255],
        [228, 128, 102, 255],
        [227, 126, 100, 255],
        [226, 123, 98, 255],
        [225, 120, 96, 255],
        [223, 118, 94, 255],
        [222, 115, 92, 255],
        [221, 112, 89, 255],
        [220, 110, 87, 255],
        [219, 107, 85, 255],
        [218, 104, 83, 255],
        [216, 101, 81, 255],
        [215, 99, 79, 255],
        [214, 96, 77, 255],
        [213, 93, 76, 255],
        [211, 90, 74, 255],
        [210, 88, 73, 255],
        [208, 85, 72, 255],
        [207, 82, 70, 255],
        [206, 79, 69, 255],
        [204, 76, 68, 255],
        [203, 73, 66, 255],
        [201, 71, 65, 255],
        [200, 68, 64, 255],
        [198, 65, 62, 255],
        [197, 62, 61, 255],
        [196, 59, 60, 255],
        [194, 56, 58, 255],
        [193, 54, 57, 255],
        [191, 51, 56, 255],
        [190, 48, 54, 255],
        [189, 45, 53, 255],
        [187, 42, 52, 255],
        [186, 40, 50, 255],
        [184, 37, 49, 255],
        [183, 34, 48, 255],
        [182, 31, 46, 255],
        [180, 28, 45, 255],
        [179, 25, 44, 255],
        [177, 24, 43, 255],
        [174, 23, 42, 255],
        [171, 22, 42, 255],
        [168, 21, 41, 255],
        [165, 20, 41, 255],
        [162, 19, 40, 255],
        [159, 18, 40, 255],
        [156, 17, 39, 255],
        [153, 16, 39, 255],
        [150, 15, 39, 255],
        [147, 14, 38, 255],
        [144, 13, 38, 255],
        [141, 12, 37, 255],
        [138, 11, 37, 255],
        [135, 10, 36, 255],
        [132, 9, 36, 255],
        [129, 8, 35, 255],
        [127, 8, 35, 255],
        [124, 7, 34, 255],
        [121, 6, 34, 255],
        [118, 5, 33, 255],
        [115, 4, 33, 255],
        [112, 3, 32, 255],
        [109, 2, 32, 255],
        [106, 1, 31, 255],
        [103, 0, 31, 255],
    ]
}

// ---------------------------------------------------------------------------
// Custom colourmap LUT generation
// ---------------------------------------------------------------------------

/// Linearly interpolate between colour stops to produce a 256-sample LUT.
///
/// `stops` is a slice of `(position, rgba)` pairs where `position` is in `[0, 1]`.
/// Stops are sorted by position before interpolation.
/// The result is clamped: the first stop colour fills `t < stops[0].0` and the last
/// stop colour fills `t > stops.last().0`.
///
/// Returns a `[[u8; 4]; 256]` suitable for uploading to a 256×1 GPU texture.
pub fn lerp_colourmap_lut(stops: &[(f32, [u8; 4])]) -> [[u8; 4]; 256] {
    let mut lut = [[0u8; 4]; 256];
    if stops.is_empty() {
        return lut;
    }
    // Sort by position.
    let mut sorted: Vec<(f32, [u8; 4])> = stops.to_vec();
    sorted.sort_by(|a, b| a.0.partial_cmp(&b.0).unwrap_or(std::cmp::Ordering::Equal));

    for i in 0..256 {
        let t = i as f32 / 255.0;

        // Find the surrounding stops.
        let first = sorted[0];
        let last = *sorted.last().unwrap();

        if t <= first.0 {
            lut[i] = first.1;
            continue;
        }
        if t >= last.0 {
            lut[i] = last.1;
            continue;
        }

        // Binary search for the lower stop.
        let pos = sorted.partition_point(|s| s.0 <= t);
        let lo = sorted[pos - 1];
        let hi = sorted[pos];

        let range = hi.0 - lo.0;
        let frac = if range > 1.0e-7 {
            (t - lo.0) / range
        } else {
            0.0
        };
        lut[i] = [
            (lo.1[0] as f32 + (hi.1[0] as f32 - lo.1[0] as f32) * frac + 0.5) as u8,
            (lo.1[1] as f32 + (hi.1[1] as f32 - lo.1[1] as f32) * frac + 0.5) as u8,
            (lo.1[2] as f32 + (hi.1[2] as f32 - lo.1[2] as f32) * frac + 0.5) as u8,
            (lo.1[3] as f32 + (hi.1[3] as f32 - lo.1[3] as f32) * frac + 0.5) as u8,
        ];
    }
    lut
}

/// Parse a ParaView XML colourmap file.
///
/// Supports the standard format:
/// ```xml
/// <ColourMaps>
///   <ColourMap name="MyMap" space="RGB">
///     <Point x="0.0" r="0.0" g="0.0" b="0.0" o="1.0"/>
///     <Point x="1.0" r="1.0" g="1.0" b="1.0" o="1.0"/>
///   </ColourMap>
/// </ColourMaps>
/// ```
///
/// Returns a list of `(name, stops)` pairs, where each stop is `(position_0_1, [r, g, b, a])`.
/// Uses simple string parsing without any XML library dependency.
pub fn parse_paraview_xml_colourmap(xml: &str) -> Vec<(String, Vec<(f32, [u8; 4])>)> {
    let mut result = Vec::new();
    let mut current_name: Option<String> = None;
    let mut current_stops: Vec<(f32, [u8; 4])> = Vec::new();

    for line in xml.lines() {
        let trimmed = line.trim();

        if trimmed.starts_with("<ColourMap") {
            // Extract name attribute.
            current_name = attr_value(trimmed, "name").map(|s| s.to_string());
            current_stops.clear();
        } else if trimmed.starts_with("</ColourMap>") {
            if let Some(name) = current_name.take() {
                if !current_stops.is_empty() {
                    result.push((name, current_stops.clone()));
                }
            }
            current_stops.clear();
        } else if trimmed.starts_with("<Point") {
            // Parse x, r, g, b, o attributes.
            if let (Some(x), Some(r), Some(g), Some(b)) = (
                attr_f32(trimmed, "x"),
                attr_f32(trimmed, "r"),
                attr_f32(trimmed, "g"),
                attr_f32(trimmed, "b"),
            ) {
                let a = attr_f32(trimmed, "o").unwrap_or(1.0);
                let stop = (
                    x,
                    [
                        (r.clamp(0.0, 1.0) * 255.0 + 0.5) as u8,
                        (g.clamp(0.0, 1.0) * 255.0 + 0.5) as u8,
                        (b.clamp(0.0, 1.0) * 255.0 + 0.5) as u8,
                        (a.clamp(0.0, 1.0) * 255.0 + 0.5) as u8,
                    ],
                );
                current_stops.push(stop);
            }
        }
    }

    result
}

/// Serialize a colourmap to the ParaView XML colourmap format.
pub fn export_paraview_xml_colourmap(name: &str, stops: &[(f32, [u8; 4])]) -> String {
    let mut out = String::new();
    out.push_str("<ColourMaps>\n");
    out.push_str(&format!("  <ColourMap name=\"{}\" space=\"RGB\">\n", name));
    for &(pos, rgba) in stops {
        let r = rgba[0] as f32 / 255.0;
        let g = rgba[1] as f32 / 255.0;
        let b = rgba[2] as f32 / 255.0;
        let o = rgba[3] as f32 / 255.0;
        out.push_str(&format!(
            "    <Point x=\"{:.6}\" r=\"{:.6}\" g=\"{:.6}\" b=\"{:.6}\" o=\"{:.6}\"/>\n",
            pos, r, g, b, o
        ));
    }
    out.push_str("  </ColourMap>\n");
    out.push_str("</ColourMaps>\n");
    out
}

// ---------------------------------------------------------------------------
// XML parsing helpers
// ---------------------------------------------------------------------------

/// Extract the string value of a named XML attribute from a tag line.
/// e.g. `attr_value(r#"<Point x="0.5"/>"#, "x")` returns `Some("0.5")`.
fn attr_value<'a>(tag: &'a str, name: &str) -> Option<&'a str> {
    let search = format!("{}=\"", name);
    let start = tag.find(search.as_str())? + search.len();
    let end = tag[start..].find('"')? + start;
    Some(&tag[start..end])
}

fn attr_f32(tag: &str, name: &str) -> Option<f32> {
    attr_value(tag, name)?.parse().ok()
}