pub fn mip_chain(img: &Image) -> Vec<(u32, u32, Vec<u8>)>Expand description
The smaller levels of img’s mipmap chain, each half the one before
(at least one pixel), down to 1 x 1: alpha-weighted 2 x 2 averages in
linear light, in sRGB values like the picture. The viewer uploads
them under the full picture.