.pbm File — Portable Bitmap

PBM (Portable Bitmap) is the simplest image format in the Netpbm family, storing monochrome (black and white) images with no grayscale or color. PBM files have two variants: ASCII (P1) where each pixel is a 0 or 1 character, and raw binary (P4) where each byte contains 8 pixels. The header is minimal — just the magic number, width, and height. PBM's extreme simplicity makes it the easiest possible image format to understand, implement, and debug. In the ASCII variant, you can literally see the image as text — rows of 0s and 1s forming a visual pattern. This makes PBM ideal for teaching file format concepts, binary representation, and basic image processing. PBM is also used for scanned document storage, OCR preprocessing, fax data, and any context where binary (two-color) images are sufficient. The format is part of the broader Netpbm ecosystem of image processing tools that can convert between PBM, PGM, PPM, and hundreds of other formats. Despite its age and limitations, PBM remains relevant in text-mode visualization, ASCII art generation, and computational imaging research.