let bw_ = (if comp > 0 { bw/2 } else { bw }) + ((pre + post) as usize);
let bh_ = (if comp > 0 { bh/2 } else { bh }) + ((pre + post) as usize);
edge_emu(src, sx_ - pre, sy_ - pre, bw_, bh_,
let bw_ = (if comp > 0 { bw/2 } else { bw }) + ((pre + post) as usize);
let bh_ = (if comp > 0 { bh/2 } else { bh }) + ((pre + post) as usize);
edge_emu(src, sx_ - pre, sy_ - pre, bw_, bh_,