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blitspin(6)		       XScreenSaver manual		     blitspin(6)

NAME
     blitspin - rotate a bitmap in an interesting way

SYNOPSIS
     blitspin [--display host:display.screen] [--foreground color] [--background
     color] [--window] [--root] [--window-id number] [--mono] [--install] [--vi-
     sual  visual] [--bitmap filename] [--delay usecs] [--delay2 usecs] [--dura-
     tion secs]

DESCRIPTION
     The blitspin program repeatedly rotates a bitmap by  90  degrees  by  using
     logical operations: the bitmap is divided into quadrants, and the quadrants
     are  shifted  clockwise.	Then  the same thing is done again with progres-
     sively smaller quadrants, except that all sub-quadrants of a given size are
     rotated in parallel.  So this takes O(16*log2(N)) blits of size  NxN,  with
     the  limitation that the image must be square, and the size must be a power
     of 2.

OPTIONS
     blitspin accepts the following options:

     --window
	     Draw on a newly-created window.  This is the default.

     --root  Draw on the root window.

     --window-id number
	     Draw on the specified window.

     --mono  If on a color display, pretend we're on a monochrome display.

     --install
	     Install a private colormap for the window.

     --visual visual
	     Specify which visual to use.  Legal values are the name of a visual
	     class, or the id number (decimal or hex) of a specific visual.

     --bitmap filename
	     The file name of a bitmap to rotate.  It need  not  be  square:  it
	     will  be  padded  with the background color.  If unspecified or the
	     string (default), a builtin bitmap is used.

	     If support for the XPM library was  enabled  at  compile-time,  the
	     specified file may be in XPM format as well as XBM, and thus may be
	     a color image.

	     The *bitmapFilePath resource will be searched if the bitmap name is
	     not a fully-qualified pathname.

     --grab-screen
	     If  this  option is specified, then the image which is spun will be
	     grabbed from the portion of the screen underlying the blitspin win-
	     dow, or from the system's video input, or from  a	random	file  on
	     disk,  as	indicated by the grabDesktopImages, grabVideoFrames, and
	     chooseRandomImages  options  in  the  ~/.xscreensaver   file;   see
	     xscreensaver-settings(1) for more details.

     --delay microseconds
	     How  long	to  delay  between steps of the rotation process, in mi-
	     croseconds.  Default is 500000, one-half second.

     --duration seconds
	     How long to run before loading a new image.  Default 120 seconds.

     --delay2 microseconds
	     How long to delay between each 90-degree rotation, in microseconds.
	     Default is 500000, one-half second.  DISPLAY  to  get  the  default
	     host and display number.

     --fps   Display the current frame rate and CPU load.

ENVIRONMENT
     XENVIRONMENT  to  get the name of a resource file that overrides the global
     resources stored in the RESOURCE_MANAGER property.

     XSCREENSAVER_WINDOW
	     The window ID to use with --root.

SEE ALSO
     X(1), xscreensaver(1), xscreensaver-settings(1), xscreensaver-getimage(6)

COPYRIGHT
     Copyright (C) 1992, 1993, 1997, 2001 by Jamie Zawinski.  Permission to use,
     copy, modify, distribute, and sell this software and its documentation  for
     any  purpose  is  hereby granted without fee, provided that the above copy-
     right notice appear in all copies and that both that copyright  notice  and
     this  permission notice appear in supporting documentation.  No representa-
     tions are made about the suitability of this software for any purpose.   It
     is provided "as is" without express or implied warranty.

AUTHOR
     Jamie Zawinski <jwz@jwz.org>, 17-aug-92.

     Based  on	SmallTalk  code  which appeared in the August 1981 issue of Byte
     magazine.

X Version 11		       6.15 (30-Mar-2026)		     blitspin(6)

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