.TH XScreenSaver 1 "24-Nov-97" "X Version 11"
.SH NAME
blitspin - rotate a bitmap in an interesting way
.SH SYNOPSIS
.B blitspin
[\-display \fIhost:display.screen\fP]
[\-foreground \fIcolor\fP] [\-background \fIcolor\fP] [\-window] [\-root]
[\-mono] [\-install] [\-visual \fIvisual\fP] [\-bitmap \fIfilename\fP]
[\-delay \fIusecs\fP] [\-delay2 \fIusecs\fP] [\-duration \fIsecs\fP]
.SH DESCRIPTION
The \fIblitspin\fP 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 \fBO(16*log2(N))\fP
blits of size NxN, with the limitation that the image must be square,
and the size must be a power of 2.
.SH OPTIONS
.I blitspin
accepts the following options:
.TP 8
.B \-window
Draw on a newly-created window. This is the default.
.TP 8
.B \-root
Draw on the root window.
.TP 8
.B \-mono
If on a color display, pretend we're on a monochrome display.
.TP 8
.B \-install
Install a private colormap for the window.
.TP 8
.B \-visual \fIvisual\fP
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.
.TP 8
.B \-bitmap \fIfilename\fP
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 \fI(default)\fP, a builtin bitmap is used.
If support for the \fIXPM\fP library was enabled at compile-time,
the specified file may be in \fIXPM\fP format as well as \fIXBM\fP, and
thus may be a color image.
The \fB*bitmapFilePath\fP resource will be searched if the bitmap
name is not a fully-qualified pathname.
.TP 8
.B \-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 \fIgrabDesktopImages\fP, \fIgrabVideoFrames\fP,
and \fIchooseRandomImages\fP options in the \fI~/.xscreensaver\fP file;
see
.BR xscreensaver-demo (1)
for more details.
.TP 8
.B \-delay \fImicroseconds\fP
How long to delay between steps of the rotation process, in microseconds.
Default is 500000, one-half second.
.TP 8
.B \-duration \fIseconds\fP
How long to run before loading a new image. Default 120 seconds.
.TP 8
.B \-delay2 \fImicroseconds\fP
How long to delay between each 90-degree rotation, in microseconds.
Default is 500000, one-half second.
.B DISPLAY
to get the default host and display number.
.TP 8
.B \-fps
Display the current frame rate and CPU load.
.SH ENVIRONMENT
.B XENVIRONMENT
to get the name of a resource file that overrides the global resources
stored in the RESOURCE_MANAGER property.
.SH SEE ALSO
.BR X (1),
.BR xscreensaver (1),
.BR xscreensaver-demo (1),
.BR xscreensaver-getimage (1)
.SH COPYRIGHT
Copyright \(co 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.
.SH AUTHOR
Jamie Zawinski <jwz@jwz.org>, 17-aug-92.
Based on SmallTalk code which appeared in the August 1981 issue of Byte
magazine.
