The XPM (X PixMap) format is an image file format used primarily for icons and pixmap images within the X Window System, the default windowing system for Unix-like operating systems. Introduced in the late 1980s, XPM is particularly noteworthy for its plain text declarations of pixel colors, which enables easy editing and sharing. It is a highly portable format, and being ASCII text-based, it is largely immune to compatibility issues that may affect binary formats.
History of the XPM Filetype
XPM was developed as a part of the X Windows System to facilitate the display of bitmap images in a portability-minded environment. The plain text structure was designed for ease of modification and human readability, catering to the needs of window system interfaces and applications of the time.
How XPM Works
The XPM file encodes an image in an array of strings, where each string represents a line of pixels. Characters in the strings correspond to colors defined in a symbol table within the file itself. This approach provides the flexibility to define a wide range of colors without increasing file complexity.
Software That Utilizes XPM
Software for Unix and Linux systems often use the XPM format for icons and button graphics. Image processing programs like GIMP and image viewers such as Eye of GNOME support the XPM format. Developers working with desktop environments like XFCE or window managers for Unix systems frequently encounter and manipulate XPM files.
Alternatives to XPM
Despite its early adoption and ease of use, the XPM format has been largely supplanted by modern formats like PNG and SVG. These alternatives offer better compression, alpha transparency, and are widely supported across different platforms, including web browsers. Yet, XPM remains a simple, editable format for icon graphics where complexity and color depth are not paramount.