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NAME
     blitspin - rotate a bitmap in an interesting way

SYNOPSIS
     blitspin [-display host:display.screen] [-foreground  color]
     [-background  color]  [-window]  [-root]  [-mono] [-install]
     [-visual visual] [-bitmap filename] [-delay usecs]  [-delay2
     usecs]

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.

     -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 for-
             mat 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,  it  may  come
             from an external video source: see below.)

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

     -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.

RESOURCES
     On some systems (currently, only SGIs),  this  program  can,
     instead  of  grabbing a desktop image, grab a frame of video
     from an external camera and manipulate  that  instead.   The
     following resources control that.

     grabVideoProbability (Float)
             What portion of the time to grab video rather than a
             screen image, between 0.0 and 1.0.  Defaults to 0.5,
             or half the time.

     videoDevice (Integer)
             The number of the  default  video  input  device  to
             check  first.   If  unspecified,  the default camera
             (from videopanel(1)) will be checked  first.   After
             that,  all  other available video input devices will
             be checked in order.

             The first one which produces a non-black image  will
             be  used.   If all images are black, the others will
             be re-checked a few times before giving up and  fal-
             ling  back  to  simply grabbing a desktop image (but
             note that this takes a few seconds, so if you  don't
             actually  have  any  video  sources  hooked  up, you
             should consider turning off video grabbing  by  set-
             ting grabVideoProbability to 0.0.)

     videoGain (Float)
             The amount by which to brighten the  grabbed  image.
             This defaults to 2.2.

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

SEE ALSO
     X(1), xscreensaver(1)

COPYRIGHT
     Copyright O 1992, 1993, 1997 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  permis-
     sion   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 <[email protected]>, 17-aug-92.

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

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