Add support for DNG files

[pierotofy]

DNG files are a type of raw file supported by some DJI drones.

Using the rawpy (0.21.0) lib and exiftool it should be trivial to convert them to JPEG prior to processing.

[Saijin-Naib]

What if folks are using them for the wider dynamic range? Is it possible to pass DNG through as metadata-tagged TIFF (which internally, DNG is mostly just TIFF anyway)?

[pierotofy]

Probably, I'm just unsure what people's goal are for using DNGs. Maybe this would be a good discussion to have on the forum before implementing it.

[Saijin-Naib]

Probably, I'm just unsure what people's goal are for using DNGs. Maybe this would be a good discussion to have on the forum before implementing it.

From the Community posts and emails I've been involved with over the years about DNG, I summarize it like this:

The folks that know they are using DNGs want them for the extra radiometric resolution and lesser processing/artifacting.

The folks that don't know they are using DNGs just are taking whatever files and throwing them at WebODM and just expect it to work it out.

[pierotofy]

Makes sense, thanks for the insight. We should then process these as 16bit TIFFs, otherwise there's no point.