How to detect tree annual ring contour?

[panovr]

Hi,
  I have a tree Cross-sectional image:
[http://www.flickr.com/photos/47804888@N07/4383897306/in/photostream/]
  I want to process the image to obtain
the result as:
[http://www.flickr.com/photos/47804888@N07/4383138069/in/photostream/]
  So, I want to write a custom ImageJ plugin to complete
the task automatically or semi-automatically.
  In concretely, I need to do these:
  1. detect the tree annual ring contour
  2. draw a horizontal line through tree center
  3. compute the intersect point between the horizontal line and the every
annual ring.
  4. draw vertical line from every intersect point, so I can obtain
experimental data from the blue background image.  
  I have some thought:
  1. do contrast enhancement
  2. do edge detection to find the annual ring
  3. transform the edge image to binary image using threshold method.
  4. draw a horizontal line through tree center
  5. compute the intersect points
 
  Any suggest is appreciate.

[amrishchawla]

Hi,

i am a new user of image J.
i have an image with a grid in it. the grid contains several circular pieces of gels from a gas diffusion experiment. kind of like a big micro array. the control gel is all blue in color but the treated ones have a decreasing intensity of the blue color, from the periphery to the center as the dye turns colorless during my treatments. i  need to measure this change in intensity on several pieces at the same time and record them.
i have tried the plot profile and micro array commands but the problem with those is that the plot profile only allows me to draw straight lines and the micro array changes the diameter of all circles at the same time. my gels are circular but have different diameters.

can you help me wiht this. i have uploaded an image for clarity

thank you for your help in advance