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In theX Window System, theprogramxwd (X Window dump) captures the content of a screen or of awindow and optionally saves it into afile.[1]
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 thecursor and waits for the user to click in a window, whose content is then captured.
At theX 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 theGetImage request (this is done by theXGetImage function in theXlib library). The content of the whole screen is obtained by requesting the content of theroot window.
The file generated by xwd can then be read by various other X utilities such asxwud,sxwd,xv, and theGIMP, or converted to other formats; theImageMagick suite allows the construction of a usefulpipeline:
$ xwd | convert xwd:- screenshot.png
The dumps are larger in size than files in mostimage file formats – not only compressed formats such asPNG, but also uncompressed bitmap formats likeBMP.
| Filename extension | .xwd |
|---|---|
| Developed by | X Window System |
| Initial release | X10 / 1985; 40 years ago (1985) |
| Latest release | X11 September 1987; 37 years ago (1987-09) |
| Type of format | Image file formats |
| Standard | xwdfile.h[2] |
| Open format? | MIT license |
Various image viewers and tools support the X11.xwd format, among others theGIMP,ImageMagick,Netpbm, andXnView. In version 2.1.4FFmpeg supported pixel formatsbgra, rgba, argb, abgr, rgb24, bgr24, rgb565be, rgb565le, bgr565be, bgr565le, rgb555be, rgb555le, bgr555be, bgr555le, rgb8, bgr8, rgb4_byte, bgr4_byte, pal8, gray, andmonow. In these abbreviations555 means 32768=32×32×32 colors,565 means65536 colors (6 bits for green),rgba isred-green-blue-alpha,4 or8 stands for 16 or 256 colors,le orbe is theendianness,pal is an inputpalette, etc. as listed byffmpeg –pix_fmts.[3]
Details of the.xwd format inXWDFile.h depend on the platform, therefore it is unsuited for cross-platform applications and has noMIME image type.[2]
The X window dump (xwd) tool takes a snapshot of the current screen, a manually selected window or a window designated by its numeric ID, and outputs the image to standard output or to a file.
| Raster | |
|---|---|
| Raw | |
| Vector | |
| Compound | |
| Metadata |
|
