How Does Lossless Compression in Fuji RAF Files Work?
4 days ago
- #digital photography
- #Fuji RAF
- #compression algorithms
- The author spent three months at the Recurse Center in New York, focusing on digital photography fundamentals.
- Fuji's lossless image compression algorithm reduces file sizes by about 50% without quality loss, but requires complex decompression for custom processing.
- The algorithm is adaptive and differential, changing based on past data and storing differences from expected values.
- Images are split into vertical stripes for parallel processing, significantly improving performance.
- Pixels are collated by color to improve compression efficiency by reducing differences between neighboring pixels.
- The encoding process involves interleaving color vectors, computing expected values, and encoding differences using variable-length codes.
- The algorithm adapts the number of bits used for encoding based on local image contrast, optimizing compression for different areas.
- Decompression follows a similar process but in reverse, with the adaptive coding system operating in the same direction for both compression and decompression.
- The project took about four weeks, including research, implementation, and writing, and was considered a valuable learning experience.
- Future digital archeologists might find this information useful for decoding Fuji's compressed RAW files.