Fractal Parameters (fRAc)

• Status:   officially registered (PNG Extensions)
• Location:   anywhere
• Multiple:   yes

The fRAc chunk is unique in that it was officially registered as a PNG extension in 1995 but, as of early 1999, still had not actually been specified. Intended to store parameters pertaining to the generation of fractal images, the chunk is clearly useful only to a very specialized set of programs. As a result, its design was left in the hands of experts--specifically, the authors of Fractint, which is one of the most general fractal programs ever written and probably the most popular. But for technical reasons relating to Fractint's 16-bit origins, PNG support was not added as planned, so design of the fRAc chunk was deferred pending a rewrite of the program as a 32-bit application.