ImageJ: Measuring distances of points using growth lines as a guide in bivalve shells

[M]

Hello everybody,

I am trying to measure distance of laser ablation holes from the outer margin (0) of bivalve shells. The holes are not distributed linearly across the growth lines (see the figure). Thus I cannot measure the distance of a hole to the outer margin directly. I have to use the visible growth lines as a help in these measurements.

I am new to ImageJ macros, but have used the program a little bit. I did some measurements using ObjectJ plugin and presume that it comes in handy with this problem too. Obviously I have to write some macros to get these measurements. It’s difficult to start without help and thus I’d like to ask a hand from more experienced users.

Ideally the desired distance measure (D) for a hole (magenta numbers) would be the distance of the closest red line [a-e] from 0 along the Purple line plus or minus the shortest distance from the center of the hole (or a point) to the closest red line (d). Plus, if the hole is below the closest red line and minus, if it's above it. Perhaps I would have to standardize d, so that D’s would be evenly distributed along the Purple line (otherwise they would be clumped near [a-e]).

I guess it's not possible/feasible to make ImageJ to do all of these calculations, but I would like to get at least following information for each hole:

1) The closest red line
2) The shortest distance from the center of a hole to the closest red line
3) The shortest distance from the center of a hole to the second closest red line (for standardization)

And of course I am looking for an easy way drawing these red lines too.

The rest I probably manage to calculate on my own using R.

I have quite a few of these photos and would like to make the process as painless as possible in case I decide to add or remove red lines for some photos.

Any ideas how to start with this?

Best regards and many thanks for any answer,
-Mikko