seven_seg - a simple way to decode numbers from a 7-segment display image

Copyright (C) 2010 Andrew H. Armenia.

This program is free software; you are free to distribute copies under
the terms of the GNU General Public License, version 3. Please see
the file COPYING for a copy of that license.

The purpose of this program is in broadcasting of sporting events. It
will eventually be usable to match the graphical scoreboard used in the 
broadcast to the venue's official scoreboard. This will occur without 
need for any manual intervention.

Build dependencies include cairo (for now) and pangocairo 
(due to some dependencies in code borrowed from openreplay).
SDL is also used for the GUI. To build, just run "make."

Currently, video input is not actually supported. So the image is read from
a hard-coded file ("hockey_scoreboard.png").

This program must be run in an environment supported by SDL. Once the program
has been started, a window should appear. Press "s" to enter setup mode.
To set up the decoder, markers must be placed on each segment of the four
digits of the display. Begin with the rightmost (least significant) digit.
Click the center horizontal segment first. Then move left and down to click
on the bottom-left vertical segment. From there, proceed in a counterclockwise
fashion, marking each segment of the display.

Press "n" to advance to the "n"ext digit. Mark all of its segments in the same
fashion. Once all segments are marked, you're ready to start. Press "r" for 
"r"un. This will begin the actual decoding process. The decoded data will be
transmitted via UDPv4 multicast to 239.160.181.93 port 30004. The setup mode
can be re-entered at any time by pressing the "s" key again.

The UDP protocol is dirt simple: just a signed 32-bit integer, in network
byte order, transmitted via UDP. This is obviously highly insecure, so
production systems using this network protocol should be firewalled 
externally.

The author has developed patches to the scoreboard-display program HockeyBoard
(http://sourceforge.net/projects/hockeyboard) to enable it to receive clock
synchronization information via the UDP socket. A patched version may be
released once the author of HockeyBoard provides additional license details.