...

'Wetware' springs to mind.

Open source? Freeware?  Would you like an AI with that?

...

Possibly almost as much as people who refrain from
multi-posting.  Please refrain from multi-posting,
in future.

(X-post to c.l.j.p./h., w/ f-u to c.l.j.p. only)

--
Andrew T.

Length in pixels? How do you *define* the length of a "curve" of pixels?
How do you define "curve", even?

Here you go:
 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Scale to fit :)

If you can straighten it to a vertical line, then you already know the
length.

Try searching for "edge detection". The first thing you need is to
find the pixels that comprise the curve. When you have those, you'll
have to define how length is measured.

/L

Gee, thanks for posing the question.  The first result of a web search
produced a link to Straighten Curved Objects plugin for ImageJ.
I had no idea such existed.  A good bit of user interaction is involved
so probably will not be much good for batch straightening.

<http://rsb.info.nih.gov/ij/plugins/straighten.html>

Maybe java.awt.Shape, and java.awt.geom.PathIterator will help.
Probably not for auto-finding curved shapes in an image though.

JH

If you have some constraints such as that the image is made of lines
with a constant width, then you could just measure the area of the image.

I'm not even sure who to solve it for the general case, say you have a
figure that looks as a line 2 pixels wide and 2 pixels long how long
would it be if you straighten it? Say we label the pixels like this:

ab
cd

One solution would be 2 pixels if it is a line 2 pixels wide, the line
goes left to right from (ac) to (bd). Another could be 4 pixels if the
line is 1 pixel wide and goes travels (a)->(b)->(d)->(c). I'm not sure
how we would measure the length if the line instead traveled
(a)->(d)->(c)->(b).

//Roger Lindsjö