X BitMap

An X BitMap, often abbreviated as XBM, is a plain text, black and white (monochrome) image file format used primarily in the X Window System. XBM files are not raster graphics in the traditional sense; instead, they contain C source code declaring a static array of bytes (unsigned chars). This array represents the pixels of the image, with each bit corresponding to a single pixel. A '1' bit typically represents a black pixel, while a '0' bit represents a white pixel.

The XBM format is defined by two C preprocessor macros: width and height, specifying the dimensions of the image. A third macro, containing the pixel data itself, is declared as an array of unsigned characters. These macros are used by C or C++ programs to include and display the bitmap within a graphical user interface.

The XBM format's main advantage lies in its simplicity and portability, as it can be easily included in C code without requiring external libraries for image decoding. Its disadvantage is its limited color depth (only black and white) and relatively larger file size compared to compressed image formats. While largely superseded by more advanced image formats, XBM still sees occasional use in niche applications or where minimal dependencies are desired.