PGM to WBMP Converter

WBMP (Wireless Bitmap) is a monochrome (1-bit, black and white) image format defined as part of the Wireless Application Protocol (WAP) specification, developed by the WAP Forum (later consolidated into the Open Mobile Alliance) around 1998. The format was designed for the extremely constrained mobile devices of the late 1990s and early 2000s — phones with small monochrome screens, minimal processing power, and narrow bandwidth GSM data connections. WBMP uses the simplest possible encoding: a type identifier byte (always 0 for the only defined type), width and height encoded as multi-byte integers using a variable-length scheme, and the raw pixel data where each bit represents one pixel (0 for white, 1 for black) packed eight per byte. There is no compression, no metadata, and no color — the format is purely a minimal container for delivering small monochrome graphics to WAP-era mobile browsers. One advantage was extreme efficiency on constrained devices — WBMP images could be decoded with virtually zero CPU overhead and minimal memory, critical on early mobile hardware running at single-digit megahertz clock speeds. The tiny file sizes are another strength: a typical WBMP icon occupied just a few hundred bytes, practical for transfer over 9.6 kbps GSM data channels. While the WAP ecosystem has been entirely superseded by modern mobile web browsers capable of rendering full-color JPEG, PNG, and WebP images, WBMP files remain encountered in archived mobile content from that transitional era.