make a hexdump or do the reverse

-r | -revert
       reverse operation: convert (or patch) hexdump into binary.  If not writing to stdout,  xxd  writes
       into  its  output  file without truncating it. Use the combination -r -p to read plain hexadecimal
       dumps without  line  number  information  and  without  a  particular  column  layout.  Additional
       Whitespace and line-breaks are allowed anywhere.

-p | -ps | -postscript | -plain
       output in postscript continuous hexdump style. Also known as plain hexdump style.