Provided by: xscreensaver-data-extra_5.36-1ubuntu1_amd64 
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] [-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.
-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-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 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.
SEE ALSO
X(1), xscreensaver(1), xscreensaver-demo(1), xscreensaver-getimage(1)
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.