Rich asked:
I'm not sure if the contents of the fRAc chunk were ever defined. Tim, can you comment on that?
Not defined, but I am the owner, so we can define it it. I don't think defining fRAc is that urgent. I would rather do any temporary thing to store data, and when we are clear what we want to store, then define fRAc. The hardest part is honoring the PNG philosophy of "no versions". This means that we decompose the data into subsets that once defined and named will never change. Change is accomplished by creating new items with new names. At one time my thought was to define the notion of "subchunk" within fRAc, and support PNG's philosophy that way. That is, do define a number of never-changing subchunks such as "corners". A real simple way to proceed at first is to write something like a PAR into a comment field or application-specific chunk. Since fRAc has been reserved, I really want to do it right. Originally I imagined that fRAc would be application-independent. That may be a pipe dream. On another subject, it would be very exciting to see what 3D functionality you could contribute. Tim