XScreenSaver(1)                                                XScreenSaver(1)


       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]


       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:


       -root   Draw on the root window.


               Install a private colormap for the window.

       -visual 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.

               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.

       -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.


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




       Copyright  ©  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

X Version 11                       24-Nov-97                   XScreenSaver(1)

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