Provided by: xscreensaver-data-extra_5.08-0ubuntu3_i386 bug


        blitspin - rotate a bitmap in an interesting way


        blitspin  [-display  host:display.screen]  [-foreground  color] [-back-
        ground color] [-window] [-root]  [-mono]  [-install]  [-visual  visual]
        [-bitmap filename] [-delay usecs] [-delay2 usecs] [-duration secs]


        The blitspin program repeatedly rotates a bitmap by 90 degrees by using
        logical operations: the bitmap is divided into quadrants, and the quad-
        rants  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.


        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 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
        -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.
                If this option is specified, then the image which is spun  will
                be  grabbed from the portion of the screen underlying the blit-
                spin window, or from the system's video input, or from a random
                file  on disk, as indicated by the grabDesktopImages, grabVide-
                oFrames, and chooseRandomImages options in the  ~/.xscreensaver
                file; see xscreensaver-demo(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  sec-
        -delay2 microseconds
                How long to delay between each 90-degree rotation, in microsec-
                onds.  Default is 500000, one-half second.  DISPLAY to get  the
                default host and display number.
        -fps    Display the current frame rate and CPU load.


        XENVIRONMENT  to  get  the  name  of a resource file that overrides the
        global resources stored in the RESOURCE_MANAGER property.
        X(1), xscreensaver(1), xscreensaver-demo(1), xscreensaver-getimage(1)


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


        Jamie Zawinski <>, 17-aug-92.
        Based on SmallTalk code which appeared in the August 1981 issue of Byte