Function encode_png

native/linux/src/lib.rs:2842–2877

Minimal PNG encoder (no external dependency). Matches the macOS implementation byte-for-byte so screenshots are identical across platforms.

(width: u32, height: u32, rgba: &[u8])

/// implementation byte-for-byte so screenshots are identical across
/// platforms.
fn encode_png(width: u32, height: u32, rgba: &[u8]) -> Option<Vec<u8>> {
    use std::io::Write;

    let mut png = Vec::new();
    png.write_all(&[137, 80, 78, 71, 13, 10, 26, 10]).ok()?;

    let mut ihdr = Vec::new();
    ihdr.extend_from_slice(&width.to_be_bytes());
    ihdr.extend_from_slice(&height.to_be_bytes());
    ihdr.push(8);
    ihdr.push(6);
    ihdr.push(0);
    ihdr.push(0);
    ihdr.push(0);
    write_png_chunk(&mut png, b"IHDR", &ihdr);

    let row_bytes = (width * 4) as usize;
    let mut raw = Vec::with_capacity((row_bytes + 1) * height as usize);
    for y in 0..height as usize {
        raw.push(0);
        let start = y * row_bytes;
        for x in 0..width as usize {
            let idx = start + x * 4;
            // wgpu Bgra8UnormSrgb: byte order is B, G, R, A
            raw.push(rgba[idx + 2]);
            raw.push(rgba[idx + 1]);
            raw.push(rgba[idx + 0]);
            raw.push(255);
        }
    }

    let deflated = deflate_store(&raw);
    write_png_chunk(&mut png, b"IDAT", &deflated);
    write_png_chunk(&mut png, b"IEND", &[]);
    Some(png)
}

fn write_png_chunk(out: &mut Vec<u8>, chunk_type: &[u8; 4], data: &[u8]) {
    let len = data.len() as u32;