makeDNG

Simple tool for converting mosaiced (Bayer) TIFF files to Adobe DNG, specifically suited for the Point Grey BFLY-U3-23S6C-C camera.

Usage:

makeDNG input_tiff_file output_dng_file [cfa_pattern] [compression] [reelname] [frame number]

cfa_pattern can be from 0-3

• 0 BGGR
• 1 GBRG
• 2 GRBG
• 3 RGGB (default)

compression

• 1 none (default)
• 7 lossless JPEG
• 8 Adobe Deflate (16-bit float)

reelname

• An optional name for a sequence of images. Up to 31 characters.

frame number

• A number that designates an image's unique place within a sequence. The frame number will be converted to SMPTE time code and is hardcoded to 18fps. The frame number should match the sequencing field of the file name. See §6.2 of the CinemaDNG spec for details.

Notes:

Adobe Camera Raw sometimes decodes lossless JPEG files incorrectly, so this is why lossless JPEG is not the default. Both RawTherapee 5.5 and ffmpeg decode correctly, so I tend to think it is a bug in ACR. Use with caution if you care about ACR.

Deflate compression requires floating point data, so the original linear 16-bit data is scaled to [0, 1]. It might make sense to eventually change the scaling factor, since middle gray should be at 0.18 if we are following OpenEXR convention.

The dcp subfolder contains the spectral data for the U3-23S6C as well as a script to generate ForwardMatrix and ColorMatrix values with dcamprof. The spectral data is estimated from the graphic in the camera's data sheet, so don't put too much trust in it. A trivial patch is needed to add Ektaspace primaries to dcamprof if that interests you.

Build Instructions

Windows build (Visual Studio 2017):

• An MSVC project is included.
• libtiff newer than around 4.0.6 is required for some of the DNG tags. Even when compression is used, no optional libs (zlib/zstd/lzma/libjpeg) are needed. We compress each tile with LJ92 ourselves and write them with TIFFWriteRawTile, but having libjpeg will suppress a warning from libtiff.
• A patched libtiff is needed if you want to write some of the lens EXIF tags. This is very optional, but does avoid RawTherapee reporting your lens as "Unknown".

Linux build (tested on Ubuntu 20.04):

In the base directory for the project, build with:

gcc -std=c99 -g -oO *.c -o makedng -lz -ltiff -lm

TODO:

• Use threads to compress each tile
• Add support for non-mod16 tile sizes (use padding)
• Implement the floating point X2 predictor (34894)

References:

Thanks to the following for their previous work:

prng by Ben Pfaff https://benpfaff.org/writings/clc/random.html
elphel_dng by Dave Coffin http://community.elphel.com/files/jp4/elphel_dng.c
makeDNG from the Field project http://openendedgroup.com/field/images/makeDNG.zip
tiff2raw by Allan G. Weber http://sipi.usc.edu/database/tiff2raw.c
rawtiDNG by Kevin Lawson https://github.com/kelvinlawson/rawti-tools
Lossless JPEG by Andrew Baldwin https://bitbucket.org/baldand/mlrawviewer