These ImageJ macros (link) measure the minimum wall thickness of open or closed objects from the perspective of each pixel on the interior or exterior of a wall. If the wall is broken (incomplete) there is a version that uses an interior object to define the open and closed regions (this also allows a measurement of the percent of wall that is open). A detailed explanation of the two macros is provided in this presentation: PDF. In the illustration below we illustrate the impact of the choice of direction for this macro.
Legal Notice:
These macros have been developed to demonstrate the power of the ImageJ macro language and we assume no responsibility whatsoever for its use by other parties, and make no guarantees, expressed or implied, about its quality, reliability, or any other characteristic. On the other hand we hope you do have fun with them without causing harm.
The macros are continually being tweaked and new features and options are frequently added, meaning that not all of these are fully tested. Please contact me if you have any problems, questions or requests for new modifications.