GROB

From Just Solve the File Format Problem
Revision as of 07:27, 8 December 2019 by Zzo38 (Talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search
File Format
Name GROB
Ontology
Extension(s) .grb, .gro, others
Released ~1990

GROB is a (usually) bi-level raster graphics format associated with HP-48 and HP-49 series calculators.

There are two ways to encode a GROB image: "binary" and "ASCII". Sometimes, GROB images are also ASC-encoded.

Contents

Format details

Binary format has an 18-byte header, followed by the pixel data.

Grayscale images

Although the format only really supports bi-level images, some images are intended to be interpreted as grayscale with 2 bits/pixel (or perhaps more). The physical image consists of the bit-planes stacked vertically. Unfortunately, there does not seem to be any way to detect whether this is the case.

Identification

A binary GROB file begins with "HPHP48" or "HPHP49", and has bytes 1E 2B at offset 8.

ASCII format apparently begins with "GROB ". An ASCII GROB might be embedded inside a script, or preceded by a "%%HP" header line, so it won't necessarily start at the beginning of the file.

Software

Sample files

Binary

ASCII

Personal tools
Namespaces

Variants
Actions
Navigation
Toolbox