GROB is a raster graphics format associated with HP-48 and HP-49 series calculators.
There are at least two ways to encode a GROB image: "binary" and "ASCII". There may also be a third encoding called "text" or "ASC".
A binary GROB file begins with "HPHP48" or "HPHP49", and has bytes
1E 2B at offset 8.
ASCII format apparently begins with "