I have a similar kind of a problem in measuring the length of the curved line.
When I use a free hand tool & draw a curved line & click measure (ctrl +M) gives length. Other wise it gives zero. If there are more than one such line in an image & try calculating measure it gives zero.
The first two measure are just when I draw them & click measure separately. Then 3,4 are those that I select these lines using magic wand tool & click measure. Why the length is 0.0? The 5 measurement is just by selecting the line tool & click measure. Also why other measure like area is looking different?
Here is the screen shot:
My second question is that I want to know how this measurements works (I mean mathematically, say want to know what formula they use). Where do I get such information?
Thanks in advance,