zenresize 0.2.1

//! Color space conversion and alpha handling.
//!
//! Provides sRGB↔linear conversion and alpha premultiply/unpremultiply
//! for use in the resize pipeline.

/// Convert a row of sRGB u8 pixels to linear f32.
///
/// Dispatches through archmage `incant!` for token-based SIMD dispatch.
pub fn srgb_u8_to_linear_f32(input: &[u8], output: &mut [f32], channels: usize, has_alpha: bool) {
    crate::simd::srgb_u8_to_linear_f32(input, output, channels, has_alpha);
}

/// Convert a row of linear f32 pixels to sRGB u8.
///
/// Dispatches through archmage `incant!` for token-based SIMD dispatch.
pub fn linear_f32_to_srgb_u8(input: &[f32], output: &mut [u8], channels: usize, has_alpha: bool) {
    crate::simd::linear_f32_to_srgb_u8(input, output, channels, has_alpha);
}

/// Implementation: sRGB u8 → linear f32 using LUT.
///
/// Called by all dispatch tiers (scalar, x86, neon, wasm128).
pub(crate) fn srgb_u8_to_linear_f32_impl(
    input: &[u8],
    output: &mut [f32],
    channels: usize,
    has_alpha: bool,
) {
    debug_assert_eq!(input.len(), output.len());

    // Batch LUT conversion: all channels including alpha go through sRGB curve
    linear_srgb::default::srgb_u8_to_linear_slice(input, output);

    // Fix alpha: should be linear scale (v/255), not sRGB curve
    if has_alpha && channels == 4 {
        for (chunk_in, chunk_out) in input.chunks_exact(4).zip(output.chunks_exact_mut(4)) {
            chunk_out[3] = chunk_in[3] as f32 / 255.0;
        }
    }
}

/// Implementation: linear f32 → sRGB u8 using LUT.
///
/// Called by all dispatch tiers (scalar, x86, neon, wasm128).
pub(crate) fn linear_f32_to_srgb_u8_impl(
    input: &[f32],
    output: &mut [u8],
    channels: usize,
    has_alpha: bool,
) {
    debug_assert_eq!(input.len(), output.len());

    // LUT batch conversion: all channels including alpha go through sRGB curve
    linear_srgb::default::linear_to_srgb_u8_slice(input, output);

    // Fix alpha: should be linear scale (v*255+0.5), not sRGB curve
    if has_alpha && channels == 4 {
        for (chunk_in, chunk_out) in input.chunks_exact(4).zip(output.chunks_exact_mut(4)) {
            chunk_out[3] = (chunk_in[3] * 255.0 + 0.5) as u8;
        }
    }
}

/// Convert a row of sRGB u8 pixels to f32 without gamma conversion (sRGB space).
#[cfg(test)]
pub fn srgb_u8_to_f32(input: &[u8], output: &mut [f32]) {
    debug_assert_eq!(input.len(), output.len());
    for (inp, out) in input.iter().zip(output.iter_mut()) {
        *out = *inp as f32 / 255.0;
    }
}

/// Convert a row of f32 pixels to u8 without gamma conversion (sRGB space).
#[cfg(test)]
pub fn f32_to_srgb_u8(input: &[f32], output: &mut [u8]) {
    debug_assert_eq!(input.len(), output.len());
    for (inp, out) in input.iter().zip(output.iter_mut()) {
        *out = (*inp * 255.0 + 0.5).clamp(0.0, 255.0) as u8;
    }
}

/// Premultiply alpha in-place on a row of f32 RGBA pixels.
///
/// Multiplies RGB channels by the alpha value.
#[cfg(test)]
pub fn premultiply_alpha_f32(row: &mut [f32], channels: usize) {
    debug_assert_eq!(channels, 4);
    for pixel in row.chunks_exact_mut(4) {
        let a = pixel[3];
        pixel[0] *= a;
        pixel[1] *= a;
        pixel[2] *= a;
    }
}

/// Unpremultiply alpha in-place on a row of f32 RGBA pixels.
///
/// Divides RGB channels by the alpha value. Transparent pixels (alpha ≈ 0) are left as-is.
#[cfg(test)]
pub fn unpremultiply_alpha_f32(row: &mut [f32], channels: usize) {
    debug_assert_eq!(channels, 4);
    for pixel in row.chunks_exact_mut(4) {
        let a = pixel[3];
        if a > 1.0 / 1024.0 {
            let inv_a = 1.0 / a;
            pixel[0] *= inv_a;
            pixel[1] *= inv_a;
            pixel[2] *= inv_a;
        }
    }
}

// =============================================================================
// Integer (i12) linear-light lookup tables
// =============================================================================

/// sRGB u8 (0-255) → 12-bit linear (0-4095).
/// Computed as: `(srgb_to_linear(v/255.0) * 4095.0 + 0.5) as i16`
#[rustfmt::skip]
pub(crate) const SRGB_U8_TO_LINEAR_I12: [i16; 256] = [
       0,    1,    2,    4,    5,    6,    7,    9,   10,   11,   12,   14,   15,   16,   18,   20,
      21,   23,   25,   27,   29,   31,   33,   35,   37,   40,   42,   45,   48,   50,   53,   56,
      59,   62,   66,   69,   72,   76,   79,   83,   87,   91,   95,   99,  103,  107,  112,  116,
     121,  126,  131,  136,  141,  146,  151,  156,  162,  168,  173,  179,  185,  191,  197,  204,
     210,  216,  223,  230,  237,  244,  251,  258,  265,  273,  280,  288,  296,  304,  312,  320,
     329,  337,  346,  354,  363,  372,  381,  390,  400,  409,  419,  428,  438,  448,  458,  469,
     479,  490,  500,  511,  522,  533,  544,  555,  567,  578,  590,  602,  614,  626,  639,  651,
     664,  676,  689,  702,  715,  728,  742,  755,  769,  783,  797,  811,  825,  840,  854,  869,
     884,  899,  914,  929,  945,  960,  976,  992, 1008, 1024, 1041, 1057, 1074, 1091, 1108, 1125,
    1142, 1159, 1177, 1195, 1213, 1231, 1249, 1267, 1286, 1304, 1323, 1342, 1361, 1381, 1400, 1420,
    1440, 1459, 1480, 1500, 1520, 1541, 1562, 1582, 1603, 1625, 1646, 1668, 1689, 1711, 1733, 1755,
    1778, 1800, 1823, 1846, 1869, 1892, 1916, 1939, 1963, 1987, 2011, 2035, 2059, 2084, 2109, 2133,
    2159, 2184, 2209, 2235, 2260, 2286, 2312, 2339, 2365, 2392, 2419, 2446, 2473, 2500, 2527, 2555,
    2583, 2611, 2639, 2668, 2696, 2725, 2754, 2783, 2812, 2841, 2871, 2901, 2931, 2961, 2991, 3022,
    3052, 3083, 3114, 3146, 3177, 3209, 3240, 3272, 3304, 3337, 3369, 3402, 3435, 3468, 3501, 3535,
    3568, 3602, 3636, 3670, 3705, 3739, 3774, 3809, 3844, 3879, 3915, 3950, 3986, 4022, 4059, 4095,
];

/// 12-bit linear (0-4095) → sRGB u8 (0-255).
/// Computed as: `(linear_to_srgb(v/4095.0) * 255.0 + 0.5) as u8`
#[rustfmt::skip]
pub(crate) const LINEAR_I12_TO_SRGB_U8: [u8; 4096] = [
      0,   1,   2,   2,   3,   4,   5,   6,   6,   7,   8,   9,  10,  10,  11,  12,  13,  13,  14,  15,  15,  16,  16,  17,  18,  18,  19,  19,  20,  20,  21,  21,
     22,  22,  23,  23,  23,  24,  24,  25,  25,  25,  26,  26,  27,  27,  27,  28,  28,  29,  29,  29,  30,  30,  30,  31,  31,  31,  32,  32,  32,  33,  33,  33,
     34,  34,  34,  34,  35,  35,  35,  36,  36,  36,  37,  37,  37,  37,  38,  38,  38,  38,  39,  39,  39,  40,  40,  40,  40,  41,  41,  41,  41,  42,  42,  42,
     42,  43,  43,  43,  43,  43,  44,  44,  44,  44,  45,  45,  45,  45,  46,  46,  46,  46,  46,  47,  47,  47,  47,  48,  48,  48,  48,  48,  49,  49,  49,  49,
     49,  50,  50,  50,  50,  50,  51,  51,  51,  51,  51,  52,  52,  52,  52,  52,  53,  53,  53,  53,  53,  54,  54,  54,  54,  54,  55,  55,  55,  55,  55,  55,
     56,  56,  56,  56,  56,  57,  57,  57,  57,  57,  57,  58,  58,  58,  58,  58,  58,  59,  59,  59,  59,  59,  59,  60,  60,  60,  60,  60,  60,  61,  61,  61,
     61,  61,  61,  62,  62,  62,  62,  62,  62,  63,  63,  63,  63,  63,  63,  64,  64,  64,  64,  64,  64,  64,  65,  65,  65,  65,  65,  65,  66,  66,  66,  66,
     66,  66,  66,  67,  67,  67,  67,  67,  67,  67,  68,  68,  68,  68,  68,  68,  68,  69,  69,  69,  69,  69,  69,  69,  70,  70,  70,  70,  70,  70,  70,  71,
     71,  71,  71,  71,  71,  71,  72,  72,  72,  72,  72,  72,  72,  72,  73,  73,  73,  73,  73,  73,  73,  74,  74,  74,  74,  74,  74,  74,  74,  75,  75,  75,
     75,  75,  75,  75,  75,  76,  76,  76,  76,  76,  76,  76,  77,  77,  77,  77,  77,  77,  77,  77,  78,  78,  78,  78,  78,  78,  78,  78,  78,  79,  79,  79,
     79,  79,  79,  79,  79,  80,  80,  80,  80,  80,  80,  80,  80,  81,  81,  81,  81,  81,  81,  81,  81,  81,  82,  82,  82,  82,  82,  82,  82,  82,  83,  83,
     83,  83,  83,  83,  83,  83,  83,  84,  84,  84,  84,  84,  84,  84,  84,  84,  85,  85,  85,  85,  85,  85,  85,  85,  85,  86,  86,  86,  86,  86,  86,  86,
     86,  86,  87,  87,  87,  87,  87,  87,  87,  87,  87,  88,  88,  88,  88,  88,  88,  88,  88,  88,  88,  89,  89,  89,  89,  89,  89,  89,  89,  89,  90,  90,
     90,  90,  90,  90,  90,  90,  90,  90,  91,  91,  91,  91,  91,  91,  91,  91,  91,  91,  92,  92,  92,  92,  92,  92,  92,  92,  92,  92,  93,  93,  93,  93,
     93,  93,  93,  93,  93,  93,  94,  94,  94,  94,  94,  94,  94,  94,  94,  94,  95,  95,  95,  95,  95,  95,  95,  95,  95,  95,  96,  96,  96,  96,  96,  96,
     96,  96,  96,  96,  96,  97,  97,  97,  97,  97,  97,  97,  97,  97,  97,  98,  98,  98,  98,  98,  98,  98,  98,  98,  98,  98,  99,  99,  99,  99,  99,  99,
     99,  99,  99,  99,  99, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101, 102, 102, 102, 102, 102,
    102, 102, 102, 102, 102, 102, 103, 103, 103, 103, 103, 103, 103, 103, 103, 103, 103, 103, 104, 104, 104, 104, 104, 104, 104, 104, 104, 104, 104, 105, 105, 105,
    105, 105, 105, 105, 105, 105, 105, 105, 105, 106, 106, 106, 106, 106, 106, 106, 106, 106, 106, 106, 106, 107, 107, 107, 107, 107, 107, 107, 107, 107, 107, 107,
    107, 108, 108, 108, 108, 108, 108, 108, 108, 108, 108, 108, 108, 109, 109, 109, 109, 109, 109, 109, 109, 109, 109, 109, 109, 110, 110, 110, 110, 110, 110, 110,
    110, 110, 110, 110, 110, 111, 111, 111, 111, 111, 111, 111, 111, 111, 111, 111, 111, 111, 112, 112, 112, 112, 112, 112, 112, 112, 112, 112, 112, 112, 113, 113,
    113, 113, 113, 113, 113, 113, 113, 113, 113, 113, 113, 114, 114, 114, 114, 114, 114, 114, 114, 114, 114, 114, 114, 114, 115, 115, 115, 115, 115, 115, 115, 115,
    115, 115, 115, 115, 115, 116, 116, 116, 116, 116, 116, 116, 116, 116, 116, 116, 116, 116, 117, 117, 117, 117, 117, 117, 117, 117, 117, 117, 117, 117, 117, 117,
    118, 118, 118, 118, 118, 118, 118, 118, 118, 118, 118, 118, 118, 119, 119, 119, 119, 119, 119, 119, 119, 119, 119, 119, 119, 119, 119, 120, 120, 120, 120, 120,
    120, 120, 120, 120, 120, 120, 120, 120, 120, 121, 121, 121, 121, 121, 121, 121, 121, 121, 121, 121, 121, 121, 122, 122, 122, 122, 122, 122, 122, 122, 122, 122,
    122, 122, 122, 122, 122, 123, 123, 123, 123, 123, 123, 123, 123, 123, 123, 123, 123, 123, 123, 124, 124, 124, 124, 124, 124, 124, 124, 124, 124, 124, 124, 124,
    124, 125, 125, 125, 125, 125, 125, 125, 125, 125, 125, 125, 125, 125, 125, 125, 126, 126, 126, 126, 126, 126, 126, 126, 126, 126, 126, 126, 126, 126, 127, 127,
    127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 127, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 129, 129, 129, 129,
    129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 130, 130, 130, 130, 130, 130, 130, 130, 130, 130, 130, 130, 130, 130, 130, 131, 131, 131, 131, 131, 131,
    131, 131, 131, 131, 131, 131, 131, 131, 131, 131, 132, 132, 132, 132, 132, 132, 132, 132, 132, 132, 132, 132, 132, 132, 132, 133, 133, 133, 133, 133, 133, 133,
    133, 133, 133, 133, 133, 133, 133, 133, 133, 134, 134, 134, 134, 134, 134, 134, 134, 134, 134, 134, 134, 134, 134, 134, 134, 135, 135, 135, 135, 135, 135, 135,
    135, 135, 135, 135, 135, 135, 135, 135, 135, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 137, 137, 137, 137, 137, 137, 137,
    137, 137, 137, 137, 137, 137, 137, 137, 137, 138, 138, 138, 138, 138, 138, 138, 138, 138, 138, 138, 138, 138, 138, 138, 138, 139, 139, 139, 139, 139, 139, 139,
    139, 139, 139, 139, 139, 139, 139, 139, 139, 139, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 140, 141, 141, 141, 141, 141,
    141, 141, 141, 141, 141, 141, 141, 141, 141, 141, 141, 141, 142, 142, 142, 142, 142, 142, 142, 142, 142, 142, 142, 142, 142, 142, 142, 142, 142, 143, 143, 143,
    143, 143, 143, 143, 143, 143, 143, 143, 143, 143, 143, 143, 143, 143, 144, 144, 144, 144, 144, 144, 144, 144, 144, 144, 144, 144, 144, 144, 144, 144, 144, 145,
    145, 145, 145, 145, 145, 145, 145, 145, 145, 145, 145, 145, 145, 145, 145, 145, 145, 146, 146, 146, 146, 146, 146, 146, 146, 146, 146, 146, 146, 146, 146, 146,
    146, 146, 147, 147, 147, 147, 147, 147, 147, 147, 147, 147, 147, 147, 147, 147, 147, 147, 147, 147, 148, 148, 148, 148, 148, 148, 148, 148, 148, 148, 148, 148,
    148, 148, 148, 148, 148, 148, 149, 149, 149, 149, 149, 149, 149, 149, 149, 149, 149, 149, 149, 149, 149, 149, 149, 149, 150, 150, 150, 150, 150, 150, 150, 150,
    150, 150, 150, 150, 150, 150, 150, 150, 150, 150, 150, 151, 151, 151, 151, 151, 151, 151, 151, 151, 151, 151, 151, 151, 151, 151, 151, 151, 151, 152, 152, 152,
    152, 152, 152, 152, 152, 152, 152, 152, 152, 152, 152, 152, 152, 152, 152, 152, 153, 153, 153, 153, 153, 153, 153, 153, 153, 153, 153, 153, 153, 153, 153, 153,
    153, 153, 154, 154, 154, 154, 154, 154, 154, 154, 154, 154, 154, 154, 154, 154, 154, 154, 154, 154, 154, 155, 155, 155, 155, 155, 155, 155, 155, 155, 155, 155,
    155, 155, 155, 155, 155, 155, 155, 155, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 156, 157, 157, 157, 157,
    157, 157, 157, 157, 157, 157, 157, 157, 157, 157, 157, 157, 157, 157, 157, 158, 158, 158, 158, 158, 158, 158, 158, 158, 158, 158, 158, 158, 158, 158, 158, 158,
    158, 158, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 159, 160, 160, 160, 160, 160, 160, 160, 160, 160, 160,
    160, 160, 160, 160, 160, 160, 160, 160, 160, 160, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 161, 162, 162,
    162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 162, 163, 163, 163, 163, 163, 163, 163, 163, 163, 163, 163, 163, 163, 163,
    163, 163, 163, 163, 163, 163, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 164, 165, 165, 165, 165, 165,
    165, 165, 165, 165, 165, 165, 165, 165, 165, 165, 165, 165, 165, 165, 165, 165, 166, 166, 166, 166, 166, 166, 166, 166, 166, 166, 166, 166, 166, 166, 166, 166,
    166, 166, 166, 166, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 167, 168, 168, 168, 168, 168, 168, 168,
    168, 168, 168, 168, 168, 168, 168, 168, 168, 168, 168, 168, 168, 168, 168, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169, 169,
    169, 169, 169, 169, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 170, 171, 171, 171, 171, 171, 171, 171,
    171, 171, 171, 171, 171, 171, 171, 171, 171, 171, 171, 171, 171, 171, 171, 172, 172, 172, 172, 172, 172, 172, 172, 172, 172, 172, 172, 172, 172, 172, 172, 172,
    172, 172, 172, 172, 172, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 173, 174, 174, 174, 174, 174,
    174, 174, 174, 174, 174, 174, 174, 174, 174, 174, 174, 174, 174, 174, 174, 174, 174, 175, 175, 175, 175, 175, 175, 175, 175, 175, 175, 175, 175, 175, 175, 175,
    175, 175, 175, 175, 175, 175, 175, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 176, 177, 177,
    177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 177, 178, 178, 178, 178, 178, 178, 178, 178, 178, 178, 178, 178,
    178, 178, 178, 178, 178, 178, 178, 178, 178, 178, 178, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179, 179,
    179, 179, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 180, 181, 181, 181, 181, 181, 181, 181,
    181, 181, 181, 181, 181, 181, 181, 181, 181, 181, 181, 181, 181, 181, 181, 181, 182, 182, 182, 182, 182, 182, 182, 182, 182, 182, 182, 182, 182, 182, 182, 182,
    182, 182, 182, 182, 182, 182, 182, 182, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 183, 184,
    184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 184, 185, 185, 185, 185, 185, 185, 185, 185, 185,
    185, 185, 185, 185, 185, 185, 185, 185, 185, 185, 185, 185, 185, 185, 185, 186, 186, 186, 186, 186, 186, 186, 186, 186, 186, 186, 186, 186, 186, 186, 186, 186,
    186, 186, 186, 186, 186, 186, 186, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187, 187,
    188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 188, 189, 189, 189, 189, 189, 189, 189, 189,
    189, 189, 189, 189, 189, 189, 189, 189, 189, 189, 189, 189, 189, 189, 189, 189, 189, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190, 190,
    190, 190, 190, 190, 190, 190, 190, 190, 190, 190, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191, 191,
    191, 191, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 193, 193, 193, 193,
    193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 193, 194, 194, 194, 194, 194, 194, 194, 194, 194, 194, 194,
    194, 194, 194, 194, 194, 194, 194, 194, 194, 194, 194, 194, 194, 194, 195, 195, 195, 195, 195, 195, 195, 195, 195, 195, 195, 195, 195, 195, 195, 195, 195, 195,
    195, 195, 195, 195, 195, 195, 195, 195, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196, 196,
    196, 196, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 197, 198, 198, 198, 198,
    198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 198, 199, 199, 199, 199, 199, 199, 199, 199, 199, 199,
    199, 199, 199, 199, 199, 199, 199, 199, 199, 199, 199, 199, 199, 199, 199, 199, 200, 200, 200, 200, 200, 200, 200, 200, 200, 200, 200, 200, 200, 200, 200, 200,
    200, 200, 200, 200, 200, 200, 200, 200, 200, 200, 200, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201,
    201, 201, 201, 201, 201, 201, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202, 202,
    202, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 203, 204, 204, 204, 204,
    204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 204, 205, 205, 205, 205, 205, 205, 205, 205, 205,
    205, 205, 205, 205, 205, 205, 205, 205, 205, 205, 205, 205, 205, 205, 205, 205, 205, 205, 206, 206, 206, 206, 206, 206, 206, 206, 206, 206, 206, 206, 206, 206,
    206, 206, 206, 206, 206, 206, 206, 206, 206, 206, 206, 206, 206, 206, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207,
    207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208, 208,
    208, 208, 208, 208, 208, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209, 209,
    209, 209, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 210, 211, 211,
    211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 212, 212, 212, 212, 212, 212,
    212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 212, 213, 213, 213, 213, 213, 213, 213, 213, 213,
    213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 213, 214, 214, 214, 214, 214, 214, 214, 214, 214, 214, 214, 214,
    214, 214, 214, 214, 214, 214, 214, 214, 214, 214, 214, 214, 214, 214, 214, 214, 214, 215, 215, 215, 215, 215, 215, 215, 215, 215, 215, 215, 215, 215, 215, 215,
    215, 215, 215, 215, 215, 215, 215, 215, 215, 215, 215, 215, 215, 215, 216, 216, 216, 216, 216, 216, 216, 216, 216, 216, 216, 216, 216, 216, 216, 216, 216, 216,
    216, 216, 216, 216, 216, 216, 216, 216, 216, 216, 216, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217, 217,
    217, 217, 217, 217, 217, 217, 217, 217, 217, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218, 218,
    218, 218, 218, 218, 218, 218, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219, 219,
    219, 219, 219, 219, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220, 220,
    220, 220, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221, 221,
    221, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 222, 223,
    223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 223, 224, 224,
    224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 224, 225, 225, 225, 225,
    225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 225, 226, 226, 226, 226, 226,
    226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 226, 227, 227, 227, 227, 227, 227,
    227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 228, 228, 228, 228, 228, 228,
    228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 229, 229, 229, 229, 229, 229, 229,
    229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 229, 230, 230, 230, 230, 230, 230, 230,
    230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 230, 231, 231, 231, 231, 231, 231, 231,
    231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 231, 232, 232, 232, 232, 232, 232, 232,
    232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 232, 233, 233, 233, 233, 233, 233, 233,
    233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 233, 234, 234, 234, 234, 234, 234,
    234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 234, 235, 235, 235, 235, 235, 235,
    235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 235, 236, 236, 236, 236, 236,
    236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 236, 237, 237, 237, 237,
    237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 237, 238, 238, 238,
    238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 238, 239, 239,
    239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239, 239,
    240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240, 240,
    240, 240, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241, 241,
    241, 241, 241, 241, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242, 242,
    242, 242, 242, 242, 242, 242, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243, 243,
    243, 243, 243, 243, 243, 243, 243, 243, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 244,
    244, 244, 244, 244, 244, 244, 244, 244, 244, 244, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245,
    245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 245, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246,
    246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 246, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247,
    247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 247, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248,
    248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 248, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249,
    249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 249, 250, 250, 250, 250, 250, 250, 250,
    250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 250, 251, 251, 251,
    251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251, 251,
    251, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252, 252,
    252, 252, 252, 252, 252, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253, 253,
    253, 253, 253, 253, 253, 253, 253, 253, 253, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254,
    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
];

/// Convert a row of sRGB u8 pixels to 12-bit linear i16 values using LUT.
///
/// All channels are converted (no alpha special-casing).
/// Output values are in range 0-4095.
pub(crate) fn srgb_u8_to_linear_i12_row(input: &[u8], output: &mut [i16]) {
    debug_assert_eq!(input.len(), output.len());
    for (inp, out) in input.iter().zip(output.iter_mut()) {
        *out = SRGB_U8_TO_LINEAR_I12[*inp as usize];
    }
}

/// Convert a row of 12-bit linear i16 pixels to sRGB u8 using LUT.
///
/// Input values are clamped to 0-4095 before lookup.
pub(crate) fn linear_i12_to_srgb_u8_row(input: &[i16], output: &mut [u8]) {
    debug_assert_eq!(input.len(), output.len());
    for (inp, out) in input.iter().zip(output.iter_mut()) {
        *out = LINEAR_I12_TO_SRGB_U8[(*inp).clamp(0, 4095) as usize];
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    #[cfg(not(feature = "std"))]
    use alloc::{vec, vec::Vec};

    #[test]
    fn test_i12_lut_roundtrip() {
        // sRGB u8 → linear i12 → sRGB u8 should have max error ≤ 1
        for i in 0u8..=255 {
            let i12 = SRGB_U8_TO_LINEAR_I12[i as usize];
            assert!(
                (0..=4095).contains(&i12),
                "i12 out of range for input {}: {}",
                i,
                i12
            );
            let back = LINEAR_I12_TO_SRGB_U8[i12 as usize];
            let diff = (i as i16 - back as i16).unsigned_abs();
            assert!(
                diff <= 1,
                "i12 roundtrip mismatch at {}: {} -> {} -> {}, diff {}",
                i,
                i,
                i12,
                back,
                diff
            );
        }
    }

    #[test]
    fn test_i12_row_conversion() {
        let input: Vec<u8> = (0..=255).collect();
        let mut i12_buf = vec![0i16; 256];
        let mut output = vec![0u8; 256];

        srgb_u8_to_linear_i12_row(&input, &mut i12_buf);
        linear_i12_to_srgb_u8_row(&i12_buf, &mut output);

        for i in 0..256 {
            let diff = (input[i] as i16 - output[i] as i16).unsigned_abs();
            assert!(
                diff <= 1,
                "Row roundtrip mismatch at {}: {} -> {} -> {}",
                i,
                input[i],
                i12_buf[i],
                output[i]
            );
        }
    }

    #[test]
    fn test_srgb_u8_roundtrip() {
        let input: Vec<u8> = (0..=255).collect();
        let mut linear = vec![0.0f32; 256];
        let mut output = vec![0u8; 256];

        srgb_u8_to_linear_f32(&input, &mut linear, 1, false);
        linear_f32_to_srgb_u8(&linear, &mut output, 1, false);

        for i in 0..256 {
            let diff = (input[i] as i16 - output[i] as i16).unsigned_abs();
            assert!(
                diff <= 1,
                "Roundtrip mismatch at {}: {} -> {} -> {}",
                i,
                input[i],
                linear[i],
                output[i]
            );
        }
    }

    #[test]
    fn test_alpha_premultiply_roundtrip() {
        let mut row = [0.5f32, 0.3, 0.8, 0.5];
        let original = row;

        premultiply_alpha_f32(&mut row, 4);
        assert!((row[0] - 0.25).abs() < 1e-6);
        assert!((row[3] - 0.5).abs() < 1e-6);

        unpremultiply_alpha_f32(&mut row, 4);
        for i in 0..4 {
            assert!(
                (row[i] - original[i]).abs() < 1e-5,
                "Channel {} mismatch: {} vs {}",
                i,
                row[i],
                original[i]
            );
        }
    }

    #[test]
    fn test_transparent_pixel_unpremultiply() {
        let mut row = [0.0f32, 0.0, 0.0, 0.0];
        unpremultiply_alpha_f32(&mut row, 4);
        // Should not produce NaN or Inf
        for v in &row {
            assert!(v.is_finite());
        }
    }

    #[test]
    fn test_srgb_space_roundtrip() {
        let input: Vec<u8> = (0..=255).collect();
        let mut f32_buf = vec![0.0f32; 256];
        let mut output = vec![0u8; 256];

        srgb_u8_to_f32(&input, &mut f32_buf);
        f32_to_srgb_u8(&f32_buf, &mut output);

        for i in 0..256 {
            assert_eq!(
                input[i], output[i],
                "sRGB space roundtrip mismatch at {}",
                i
            );
        }
    }
}