blitspin man page on Tru64
[printable version]
XScreenSaver(1) XScreenSaver(1)
NAME
blitspin - rotate a bitmap in an interesting way
SYNOPSIS
blitspin [-display host:display.screen] [-foreground color] [-back‐
ground 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 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.
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 blit‐
spin window. (Or, it may come from an external video source:
see below.)
-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.
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 falling 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 setting grabVideoProba‐
bility 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 overrides the
global resources stored in the RESOURCE_MANAGER property.
SEE ALSO
X(1), xscreensaver(1)
COPYRIGHT
Copyright © 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 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 war‐
ranty.
AUTHOR
Jamie Zawinski <jwz@jwz.org>, 17-aug-92.
Based on SmallTalk code which appeared in the August 1981 issue of Byte
magazine.
X Version 11 24-Nov-97 XScreenSaver(1)
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