fimg 0.4.55

fast image operations
Documentation 
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//! trait for packing pixels

use crate::pixels::convert::{PFrom, RGB, RGBA, Y, YA};

#[inline]
pub const fn pack(x: [u8; 4]) -> u32 {
    u32::from_le_bytes(x).rotate_left(8).swap_bytes()
}

#[inline]
pub const fn unpack(n: u32) -> [u8; 4] {
    n.rotate_left(8).to_be_bytes()
}

/// packs and unpacks this pixel
/// note that `unpack(pack(p))` may not equal `p`
pub trait Pack<P = u32> {
    /// pack this pixel
    fn pack(&self) -> P;
    /// unpacks this pixel
    fn unpack(from: P) -> Self;
}

macro_rules! simple {
    ($p:ident) => {
        impl Pack for $p {
            fn pack(&self) -> u32 {
                pack(PFrom::pfrom(*self))
            }

            fn unpack(from: u32) -> $p {
                PFrom::pfrom(unpack(from))
            }
        }
    };
}
simple!(RGBA);
simple!(RGB);
simple!(YA);
simple!(Y);

impl Pack<u8> for Y {
    fn pack(&self) -> u8 {
        self[0]
    }

    fn unpack(from: u8) -> Self {
        [from]
    }
}