I sent this message directly to the email address on Autotrace's
homepage, but, since it doesn't seem to have been actively developed
for quite a while, I decided to repost it here.

As an update, I made the changes the way they made sense to me and
things seem to work fine. I'm wondering if I'm dealing with a
cut-and-paste issue (centerline processing came after the
outline/contour functionality) or whether I'm just not understanding
something.

I will eventually be submitting my code changes to the project once
it's cleaned up and ready for general consumption.

Tom

-------- ORIGINAL EMAIL ----------

Hello Martin.

I'd like to start by thanking you for developing Autotrace. I am
currently making some modifications.
I have added support for the Stentiford thinning algorithm. I don't
know if it is better, but we were already using it elsewhere, so I
figured it would be faster to have it in Autotrace. I also added
support for just dumping the Splines to a text file for easy parsing
by other programs rather than all the other formats.

I have a question about the partial outline code (pxl-outline.c)

I have a situation where this is not working.

My text diagram:

X = already in the original open "outline"
W = I want this pixel too
U = Used in another curve

---U-
---WU
--X--
--X--
-X---

In this case, an open outline is found, starting from the upper-most X
going SOUTH.
When it is finished, it tries to find another partial outline to
combine with. Here is where I get confused.

If we're going SOUTH, it tries to find partial outlines in the
following directional order:
EAST
SOUTHEAST
SOUTHWEST
end-of-list

The comment states "If the outline is open (i.e., we didn't return to
the starting pixel), search from the starting pixel in the opposite
direction and concatenate the two outlines."

How is this the "opposite direction" ?

I would assume that it would use:
NORTH
NORTHEAST
NORTHWEST

Can you help me understand this? I don't want to break anything that
I don't understand.

Thank you in advance for any help you can give me.

Tom McKearney