GROB

Latest revision as of 17:48, 28 December 2023

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.

[edit] Format details

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

[edit] 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.

[edit] 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.

[edit] Software

• Konvertor
• XnView
• grob.to.bitmap
• grob2eps.c
• My HP48 and HP49 software → hp48-mf-0.6.zip → hp48.dtx → grob2eps.c
• Farbfeld Utilities

[edit] Sample files

• dexvert samples — image/grob

[edit] Binary

• http://cd.textfiles.com/hhot/CALCUL~5/HP48G/GRAPHICS/ ...
• GROBS1.ZIP, GROBS2.ZIP
• grobs49.zip

[edit] ASCII

• supercarsgrob.zip