Some mobile phones can shoot photos in raw by using applications which use Camera2 API. Usually they write raw shots in DNG format and without any compression.

I tried to search the web for free software which can be used directly to convert uncompressed DNG to lossless-compressed DNG, but only found a library named liblj92, which implements Lossless JPEG compression scheme used in DNG, but if I understood correctly, it doesn't deal with DNG format itself, so it's not the whole thing.

There's also a proprietary converter from Adobe, but this doesn't qualify because I'm searching for free software (free = as in freedom, when I can inspect and modify source code and distribute derivative works under same free license)

  • Wikipedia says that this format, which is called Digital Negative, is under one or more patents. That would explain a lack of free software for doing something with it. – Kodiologist Jul 11 '17 at 0:31
  • @Kodiologist well I guess at least a useful subset of it is patent free, otherwise it wouldn't be used at all in free software which can produce it. Also Wikipedia says that it's "Documented to have no known intellectual property encumbrances or license requirements", and also there are some countries where software patents are not recognized, including mine, so there's no problem at all if someone from these countries develops something. Maybe I have to do it… – Display Name Jul 11 '17 at 4:13

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