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### Patents

The field of data compression is mined with patents, and fractal image compression is no exception. Most patents are owned by Iterated Systems, Inc. US patent 4,941,193 covers the “graduate student algorithm” for fractal compression with IFS, which is not practical as we have seen.

US patent 5,065,447 (continued in 5,347,600) covers fractal compression with the “Fractal Transform”, that is, with Partitioned Iterated Function Systems. The sample program given in the chapter is provided only for educational purposes, as it may be affected by these patents. If you wish to use it for other purposes, you must contact Iterated Systems at the following address in the USA:

5550A Peachtree Parkway, Suite 650
Norcross, GA 30092

Iterated Systems also owns US patent 5,384,867 (continued in 5,430,812) on hardware boards performing fractal compression.

US patent 5,416,856, filed by Jacobs, Boss, and Fisher, covers a refinement of fractal compression with PIFS, where at least one of the domain to range transformations is non-contractive. The inventors observed that it is not necessary to impose contractivity on any given transformation, as long as the PIFS consisting of the union of all transformations is eventually contractive after some iterations. The contractive transformations may dominate the expansive ones after two or more iterations. Our sample program does not use this refinement.

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