XWD to FAX Converter

XWD (X Window Dump) is a screen capture image format defined as part of the X Window System by the MIT X Consortium, dating to approximately 1987. The xwd command-line utility captures the contents of an X window or the entire screen and saves it as an XWD file — functionally equivalent to a screenshot utility but predating the concept by years. XWD files contain a detailed header specifying the X server's visual type, bit depth, byte order, bitmap unit and padding, the window's dimensions, border width, and color map information, followed by the raw pixel data exactly as represented in the X server's framebuffer. This means XWD files faithfully capture the exact pixel representation used by the display hardware — including server-specific byte ordering, padding, and color organization — making them primarily useful on the system where they were captured or on systems with compatible display configurations. The header also stores the window name string and the full color map entries for indexed-color visuals. XWD supports all X11 visual types: StaticGray, GrayScale, StaticColor, PseudoColor, TrueColor, and DirectColor, at any bit depth supported by the X server. One advantage is exact framebuffer fidelity: XWD captures the window's pixel data in its native format without any color space conversion or compression, making it the definitive record of what the X server was actually displaying. The format's integration with the X11 command-line toolkit provides another practical benefit — xwd can capture specific windows by ID or name, be triggered remotely via SSH, and piped directly to format converters. XWD files are handled by ImageMagick, GIMP, xwud (the viewer companion to xwd), and xv.