fn write_signature(out: &mut Vec<u8>) {
    out.push(137u8);
    out.push(80u8);
    out.push(78u8);
    out.push(71u8);
    out.push(13u8);
    out.push(10u8);
    out.push(26u8);
    out.push(10u8);
}
/*8 bytes PNG signature, aka the magic bytes*/
8 bytes PNG signature, aka the magic bytes
8 bytes PNG signature aka the magic bytes
fn write_signature(out: &mut Vec<u8>) {
    out.push(137u8);
    out.push(80u8);
    out.push(78u8);
    out.push(71u8);
    out.push(13u8);
    out.push(10u8);
    out.push(26u8);
    out.push(10u8);
}
fn write_signature ( out : & mut Vec < u8 > ) { out . push ( 137u8 ) ; out . push ( 80u8 ) ; out . push ( 78u8 ) ; out . push ( 71u8 ) ; out . push ( 13u8 ) ; out . push ( 10u8 ) ; out . push ( 26u8 ) ; out . push ( 10u8 ) ; }
8 bytes PNG signature, aka the magic bytes
8 bytes PNG signature aka the magic bytes
out
&mut Vec<u8>