Understanding the rules for centering a sign

[Steve Slevinski]

  Hi Val,

I'd like to discuss the way SignPuddle centers a sign?  The center is 
used to align signs for text layout.

To determine the center of a sign with an algorithm, select the 
important symbols and create a smallest possible rectangle (a bounding 
box) around only those symbols.  This bounding box represents the center 
of the sign.  The absolute center of the bounding box is the center of 
the sign.

I'm currently using 2 levels of symbol detection.  Either there are head 
& trunk symbols or not.  If there are head or trunk symbols in a sign, 
only the head and trunk symbols are selected and enclosed by the 
centering bounding box.  If there are no head or trunk symbols, then all 
symbols are selected and the absolute center is used.


The current method is good enough, but I was considering a refinement 
based on SignSpelling rule #2: "Every sign has a center":
http://www.signwriting.org/lessons/elessons/less064.html

There could be 4 levels of centering:
Head or trunk symbols in sign - select head and trunk symbols.
Contact symbols in sign - select hand and contact symbols.
Hand symbols in sign - select hand symbols.
Otherwise - select everything.

Try these levels while reading SignSpelling Rule #1, "Write the position 
of contact":
http://www.signwriting.org/lessons/elessons/less063.html

You can see that a well written sign has a smaller centering bounding 
box than a poorly written sign.

I believe this new centering algorithm can improve text layout for both 
vertical and horizontal writing.

Regards,
-Steve