pbmtomda

Convert a PBM image to a MDA file

$ pbmtomda [path/to/image.pbm] > [path/to/output.mda]

$ pbmtomda -i [path/to/image.pbm] > [path/to/output.mda]

$ pbmtomda -d [path/to/image.pbm] > [path/to/output.mda]

pbmtomda [pbmfile]

pbmfile
    The path to the Portable Bitmap (PBM) image file to be converted. If this argument is omitted, pbmtomda reads the PBM image data from standard input (stdin). The output raw MDA/Hercules graphics data is always written to standard output (stdout).

pbmtomda is a specialized utility from the Netpbm suite, designed to convert a Portable Bitmap (PBM) image into a raw byte stream suitable for direct display on an IBM PC Monochrome Display Adapter (MDA) or Hercules graphics card. The Netpbm project provides a comprehensive toolkit for manipulating graphics files, often used in scripts due to its simple, stream-oriented design.

The MDA and Hercules cards were prevalent in early IBM PC systems, offering monochrome text and graphics capabilities. pbmtomda's output is not a standard image file format, but rather a sequence of bytes laid out exactly as required by the MDA/Hercules video memory, making it useful for emulators or niche applications requiring low-level hardware interaction. It typically expects the input PBM image to be 720x348 pixels for Hercules compatibility or 640x200 for MDA, though it will process other dimensions, potentially with scaling or cropping.

The output of pbmtomda is a raw byte stream directly mapping to MDA/Hercules video memory; it is not a standard image file format and cannot be viewed directly by typical image viewers.

This command is highly specialized for very old hardware (IBM PC MDA/Hercules graphics cards) or emulators of such hardware. Its practical use in modern computing environments is limited.

The command expects input PBM images to be specific dimensions (720x348 for Hercules, 640x200 for MDA). Input images of other sizes will be scaled or clipped, potentially leading to undesired visual distortion.

There are no options to control scaling, positioning, or color inversion directly within the command, which simplifies its interface but limits flexibility.

The raw byte stream produced by pbmtomda is structured according to the video memory layout of the IBM PC MDA/Hercules cards. For Hercules, this means a 720x348 pixel monochrome image where pixels are packed 8 per byte. The layout can be complex, involving interleaved scanlines and specific byte ordering for video memory addressing, which is crucial for emulators or direct hardware programming that needs to interact with the MDA/Hercules video buffer.

pbmtomda is an integral part of the Netpbm suite of graphics utilities. The Netpbm project itself evolved from the PBMplus toolkit, which was created by Jef Poskanzer in the late 1980s. The command's existence reflects the computing landscape of that era, where the IBM PC and its variants, equipped with Monochrome Display Adapter (MDA) and later Hercules graphics cards, were dominant. These cards provided basic monochrome text and graphics capabilities, and pbmtomda was developed to facilitate the conversion of standard bitmap images into a format directly usable by this specific hardware. Its purpose remains largely historical and for niche applications like DOS emulation or hardware preservation.

pbm(5), netpbm(1), anytopnm(1), pnmtoany(1), pbmtopgm(1)