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] [--visual visual] [--bitmap filename] [--delay usecs] [--delay2
       usecs] [--duration 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
       progressively  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 window, 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  microseconds.   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(6x)

COPYRIGHT

       Copyright  ©  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  copyright  notice  appear  in  all  copies and that both that copyright notice and this permission
       notice appear in supporting documentation.  No representations 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.