In this discussion on the Commons village pump, I got pretty solid support for a proposal to enable uploads of DNG raw image files to Commons:
This is a royalty-free open specification format that fulfills a useful role that existing permitted formats do not, in that it allows other users to create new versions of a photo. See the thread above for details.
All I need from the devs is to enact this by adding 'dng' to $wgFileExtensions for Commons. I would take care of everything else: adding templates to link DNG files with their JPEG versions, adding project pages to explain them, how to use them, and link
software support for them. There's no need for thumbnail support for these files, nor would such support make a lot of sense.
- For those interested in adding support for a new file type to MediaWiki, please read: https://www.mediawiki.org/wiki/Manual:Adding_support_for_new_filetypes
- DNG is patented with a free (but revokable) license. It is also 17 years old now, so Adobe's patents will expire in 3 years or so.
- DNGs are TIFF files, specifically TIFF/EP compliant files with additional metadata and algo's
- Spec: https://helpx.adobe.com/camera-raw/digital-negative.html
- Tags can be located in EXIF or TIFF-EP EXIF, IPTC or XMP
- Unique identifier for DNG files seem to be the tag DNGVersion
- File extension can be .DNG or .TIF (this might pose some problems for our implementation)
- Mime type for DNG is image/x-adobe-dng
- ImageMagick supports DNG, but you have to prefix the file being read with DNG: or otherwise it will treat it as a tiff file. See also: https://imagemagick.org/script/formats.php
- Note, we will have to split tiff from dng handler in any thumbor implementation for this, so maybe force dng files are uploaded with DNG file extension?)
- I can't find information on how well imagemagick implements DNG. Like does it even do opcode processing before making a thumbnail ?
- Still needed, multiple examples of freely licensed (preferably public domain) DNG images from multiple camera brands.
There is a whole list of mime types for various raw image formats at: https://github.com/angryziber/gnome-raw-thumbnailer/blob/master/data/raw-thumbnailer.xml
It looks like there are lots of RAW manufacturers specific formats, all TIFF based but few are DNG compliant ?