gemtoppm
SYNOPSIS
gemtoppm [gemfile]
or
gemtoppm < gemfile > ppmfile
DESCRIPTION
The gemtoppm command is a specialized utility within the extensive Netpbm image manipulation toolkit. Its primary function is to convert image files created by the GEM (Graphics Environment Manager) desktop environment into the Netpbm Portable Pixmap (PPM) format. GEM was a popular graphical user interface in the 1980s and early 1990s, particularly on systems like the Atari ST, Amiga, and early PC compatibles.
While GEM images stored in the .IMG format often contained various data types, gemtoppm specifically targets and processes the bitmap image data. The resulting PPM file can then be easily manipulated by other Netpbm tools or converted to a wide array of different image formats, integrating older GEM content into modern workflows. It serves as a crucial bridge for preserving and utilizing legacy graphics.
CAVEATS
gemtoppm has a significant limitation: it can only process monochrome (1-bit deep) GEM image files. If a GEM .IMG file contains color information, gemtoppm will not be able to correctly interpret or convert it, potentially leading to errors or corrupted output. Users should ensure their GEM input files are strictly black and white bitmaps.
INPUT/OUTPUT BEHAVIOR
If no gemfile is specified, gemtoppm reads the GEM image data from standard input. The converted PPM image is always written to standard output. This allows for flexible piping with other commands, such as `cat old.img | gemtoppm > new.ppm`.
HISTORY
The gemtoppm utility is part of the Netpbm project, a comprehensive set of graphics tools with roots in the original Pbmplus package developed by Jef Poskanzer in the late 1980s. Netpbm continued to evolve, integrating and expanding upon these initial tools. gemtoppm's inclusion reflects the project's dedication to interoperability and its ability to handle a vast array of historical and contemporary image formats. Its existence is particularly relevant to the era when GEM was a prominent graphical environment on various personal computers, making it a tool for legacy data migration and preservation.
