Function default_chunk_use 

pub fn default_chunk_use(
    w: &Walk<'_>,
    ifd: &Ifd,
    tiles: bool,
    offs: &[u64],
    cnts: &[u64],
) -> Vec<ChunkUse>

Rules::chunk_use’s default, after image-tiff’s expand_chunk: it reads whole chunk rows (right-edge padding included, then discarded) for the rows inside the image only. Uncompressed and PackBits chunks are split at that point; for other compression the end of the coded data is not found.