j2k-transcode 0.7.1

JPEG-to-HTJ2K coefficient-domain transcode primitives for j2k
Documentation 
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// SPDX-License-Identifier: MIT OR Apache-2.0

//! In-place reversible integer 5/3 lifting primitives.

pub(crate) fn reversible_lift_53_i32(values: &mut [i32]) {
    let n = values.len();
    if n < 2 {
        return;
    }

    if n.is_multiple_of(2) {
        for i in (1..n - 1).step_by(2) {
            values[i] -= floor_div_i32(values[i - 1] + values[i + 1], 2);
        }
        values[n - 1] -= values[n - 2];

        values[0] += floor_div_i32(values[1] + 1, 2);
        for i in (2..n).step_by(2) {
            values[i] += floor_div_i32(values[i - 1] + values[i + 1] + 2, 4);
        }
        return;
    }

    let last_even = n - 1;
    for i in (1..n).step_by(2) {
        let right = values.get(i + 1).copied().unwrap_or(values[last_even]);
        values[i] -= floor_div_i32(values[i - 1] + right, 2);
    }
    for i in (0..n).step_by(2) {
        let left = if i > 0 { values[i - 1] } else { values[1] };
        let right = values.get(i + 1).copied().unwrap_or(left);
        values[i] += floor_div_i32(left + right + 2, 4);
    }
}

pub(crate) fn floor_div_i32(numerator: i32, denominator: i32) -> i32 {
    numerator.div_euclid(denominator)
}