Hi @yuhx0914,
If you have used the filament tracer, then the output fields filament/start_frac and filament/end_frac store the coordinates of the start/end of the filament associated with each particle. These are fractional values scaled from 0 to 1, so you need the micrograph shape (in location/micrograph_shape) in order to convert them to indices of the micrograph image. Does this suit your needs?
PS: see a description of the data fields held in particle.filament in this comment.
Best,
Michael