Provided by: xscreensaver-data-extra_4.23-4ubuntu8_i386
blitspin - rotate a bitmap in an interesting way
blitspin [-display host:display.screen] [-foreground color]
[-background 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
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.
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.
Specify which visual to use. Legal values are the name of a
visual class, or the id number (decimal or hex) of a specific
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
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
How long to delay between steps of the rotation process, in
microseconds. Default is 500000, one-half second.
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.
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 © 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.
Jamie Zawinski <email@example.com>, 17-aug-92.
Based on SmallTalk code which appeared in the August 1981 issue of Byte