In the

X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wi ...

, the program xwd (X Window dump) captures the content of a screen or of a

window A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent mat ...

and optionally saves it into a

file File or filing may refer to: Mechanical tools and processes * File (tool), a tool used to ''remove'' fine amounts of material from a workpiece **Filing (metalworking), a material removal process in manufacturing ** Nail file, a tool used to gent ...

. xwd runs in one of two ways: if a user specifies the whole screen or the name or identifier of a window as an argument, the program captures the content of the window; otherwise, it changes the shape of the

cursor Cursor may refer to: * Cursor (user interface), an indicator used to show the current position for user interaction on a computer monitor or other display device * Cursor (databases), a control structure that enables traversal over the records in ...

and waits for the user to click in a window, whose content is then captured.

Operation

At the X Window core protocol level, xwd uses the fact that any X client can request the content of an arbitrary window, including ones it did not create, using the GetImage request (this is done by the XGetImage function in the

Xlib Xlib (also known as libX11) is an X Window System protocol client library written in the C programming language. It contains functions for interacting with an X server. These functions allow programmers to write programs without knowing the ...

library). The content of the whole screen is obtained by requesting the content of the

root window {{Unreferenced, date=September 2008 In the X Window System, every window is contained within another window, called its parent. This makes the windows form a hierarchy. The root window is the root of this hierarchy. It is as large as the screen/di ...

. The file generated by xwd can then be read by various other X utilities such as ''xwud'', ''sxwd'', xv, and the GIMP, or converted to other formats; the

netpbm Netpbm (formerly Pbmplus) is an open-source package of graphics programs and a programming library. It is used mainly in the Unix world, where one can find it included in all major open-source operating system distributions, but also works on Micr ...

suite allows the construction of a useful pipeline: $ xwd , xwdtopnm , pnmtopng > Screenshot.png The dumps are larger in size than files in most

image file format An Image file format is a file format for a digital image. There are many formats that can be used, such as JPEG, PNG, and GIF. Most formats up until 2022 were for storing 2D images, not 3D ones. The data stored in an image file format may be ...

s – not only compressed formats such as PNG, but also uncompressed bitmap formats like BMP.

Image format

Various image viewers and tools support the X11 .xwd format, among others the GIMP,

ImageMagick ImageMagick, invoked from the command line as magick, is a free and open-source cross-platform software suite for displaying, creating, converting, modifying, and editing raster images. Created in 1987 by John Cristy, it can read and write ov ...

Netpbm Netpbm (formerly Pbmplus) is an open-source package of graphics programs and a programming library. It is used mainly in the Unix world, where one can find it included in all major open-source operating system distributions, but also works on Micr ...

, and

XnView XnView is an image organizer and general-purpose file manager used for viewing, converting, organizing and editing raster images, as well as general purpose file management. It comes with built-in hex inspection, batch renaming and screen ...

. In version 2.1.4

FFmpeg FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing of vid ...

supported pixel formats ''bgra, rgba, argb, abgr, rgb24, bgr24, rgb565be, rgb565le, bgr565be, bgr565le, rgb555be, rgb555le, bgr555be, bgr555le, rgb8, bgr8, rgb4_byte, bgr4_byte, pal8, gray,'' and ''monow.'' In these abbreviations ''555'' means 32768=32×32×32 colors, ''565'' means 65536 colors (6 bits for green), ''rgba'' is red-green-blue-alpha, ''4'' or ''8'' stands for 16 or 256 colors, ''le'' or ''be'' is the

endianness In computing, endianness, also known as byte sex, is the order or sequence of bytes of a word of digital data in computer memory. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). A big-endian system stores the mos ...

, ''pal'' is an input palette, etc. as listed by ffmpeg –pix_fmts. Details of the .xwd format in xwdfile.h depend on the platform, therefore it is unsuited for cross-platform applications and has no

MIME Multipurpose Internet Mail Extensions (MIME) is an Internet standard that extends the format of email messages to support text in character sets other than ASCII, as well as attachments of audio, video, images, and application programs. Message ...

image type.

References

External links

* xwd is part of

X11 The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wi ...

's standard distribution, but its

source Source may refer to: Research * Historical document * Historical source * Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence * Source (journalism), a person, publication, publishing institute o ...

can also be downloaded separately a
tar.bz2
o
tar.gz

Image::XWD

Perl Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offic ...

package at CPAN {{Graphics file formats Graphics file formats X Window System X Window programs Screenshot software 1985 introductions

Operation

Image format

See also

References

External links