blitspin(6x)

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.