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.TH XScreenSaver 1 "" "X Version 11"
.SH NAME
glitchpeg - glitched image screen saver.
.SH SYNOPSIS
.B glitchpeg
[\-display \fIhost:display.screen\fP]
[\-visual \fIvisual\fP]
[\-window]
[\-root]
[\-delay \fInumber\fP]
[\-duration \fInumber\fP]
[\-count \fInumber\fP]
.SH DESCRIPTION
Loads an image, corrupts it, and then displays the corrupted version,
several times a second. After a while, finds a new image to corrupt.
It glitches the image by altering random bytes in the compressed image
file before de-compressing it. This creates interesting visual effects
on JPEG files, but doesn't work well on PNG files, since PNG contains
checksums that detect simple corruption.
.SH OPTIONS
.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 \-window
Draw on a newly-created window. This is the default.
.TP 8
.B \-root
Draw on the root window.
.TP 8
.B \-delay \fInumber\fP
Per-frame delay, in microseconds. Default: 30000 (0.03 seconds).
.TP 8
.B \-duration \fInumber\fP
How many seconds before loading a new image. Default: 120.
.TP 8
.B \-count \fInumber\fP
Number of glitches to introduce per iteration. Default: 100.
.SH ENVIRONMENT
.PP
.TP 8
.B DISPLAY
to get the default host and display number.
.TP 8
.B XENVIRONMENT
to get the name of a resource file that overrides the global resources
stored in the RESOURCE_MANAGER property.
.SH SECURITY
Because this program is feeding intentionally-invalid data into your
operating system's image-decoding libraries, it is possible that it
may crash as a result of that corrupted data.
That should not be possible -- but it might be.
Please note that if this happens, that indicates a serious security
bug in your system's image libraries! It likely means that your
libraries are susceptible to buffer overflow attacks or similar, which
can lead to remote code execution. You should report that bug to the
maintainers of those image libraries.
In the context of xscreensaver, when configured to load only local
image files, this should not be a direct security concern: this screen
saver crashing will not affect the xscreensaver daemon and will not
unlock your screen.
.SH SEE ALSO
.BR X (1),
.BR xscreensaver (1)
.SH COPYRIGHT
Copyright \(co 2018 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.
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