let dst = &mut ddata[doff..];
let copy_size = sstride.min(dstride);
for (dline, sline) in dst.chunks_exact_mut(dstride).take(h).zip(src.chunks_exact(sstride)) {
let dst = &mut ddata[doff..];
let copy_size = sstride.min(dstride);
for (dline, sline) in dst.chunks_exact_mut(dstride).take(h).zip(src.chunks_exact(sstride)) {