Shared via Rust Playground

playground.rs

fn old() -> Vec<u8> {
    let mut hash = vec![0u8; 8]; // vec of u8 representing the bits and bytes of the hash computed for the image.
    let raw: Vec<_> = (0..8).flat_map(|_| (0 .. 9).rev()).collect(); // vec of u8 representing gray pixels of an 9x8 image.
    

    for x in 0..8 {
        for y in 0..8 {
            if raw[x*9+y] > raw[x*9+y+1] {
                hash[x] |= 0x1 << y
            }
        }
    }
    
    hash
}

fn new() -> Vec<u8> {
    let mut hash = vec![0u8; 8]; // vec of u8 representing the bits and bytes of the hash computed for the image.
    let raw: Vec<_> = (0..8).flat_map(|_| (0 .. 9).rev()).collect(); // vec of u8 representing gray pixels of an 9x8 image.

    for (row, hash_byte) in raw.chunks(9).zip(&mut hash) {
        *hash_byte = row.windows(2).enumerate().filter_map(|(i, window)| {
            if window[0] > window[1] { Some(i) } else { None }
        }).fold(0, |accum, i| accum | 0x1 << i);
    }
    
    hash    
}

fn main(){
    println!("old: {:?}", old());
    println!("new: {:?}", new());
}