We use OpenCV on linux to read and process regular 8-bit JPGs.
We are now receiving 12-bit JPGs from a specific piece of hardware. OpenCV cannot read these, nor can anything else I've tried. Is there a utility or library for linux that would enable us to process these? Perhaps converting to an 8-bit format?
The latest libjpeg supports 12-bit JPG as a compile-time option. Meaning it would not be easy to write software that supports regular 8-bit and 12-bit jpg at the same time. But I'm wondering if someone has solved this already.
I have a couple of improvements to your proposed technique.
Firstly, you can simplify your process and remove the need to install and be reliant on ImageMagick by making djpeg emit a PPM file, because OpenCV can read them anyway without any libraries. So your command would become:
djpeg > result.ppm < some12bitBadBoy.jpg
Secondly, if you do that, you actually get a 12/16-bit PPM file, so you retain more colour resolution into the process!
identify -verbose result.ppm
Image: a.ppm
Format: PPM (Portable pixmap format (color))
Mime type: image/x-portable-pixmap
Class: DirectClass
Geometry: 227x149+0+0
Units: Undefined
Type: TrueColor
Endianess: Undefined
Colorspace: sRGB
Depth: 12-bit <---
Channel depth:
Red: 12-bit <---
Green: 12-bit <---
Blue: 12-bit <---
Channel statistics:
Pixels: 33823
Red:
min: 514 (0.125519)
max: 4095 (1)
mean: 2350.62 (0.574022)
standard deviation: 1102.04 (0.269119)
kurtosis: -1.39076
skewness: 0.13609
entropy: 0.971255
Green:
min: 305 (0.0744811)
max: 4095 (1)
mean: 1453.69 (0.354991)
standard deviation: 852.147 (0.208095)
kurtosis: 2.42348
skewness: 1.77043
entropy: 0.918006
Blue:
min: 213 (0.0520147)
max: 4095 (1)
mean: 1309.16 (0.319698)
standard deviation: 890.453 (0.217449)
kurtosis: 2.74961
skewness: 1.92239
...
...
For anyone else trying to find an elusive 12-bit JPEG, I eventually found one here.
A further suggestion, to simplify your workflow, might be to use inotify (man page) to monitor filesystem events on your image storage area. So you could effectively be notified whenever new JPEGs arrive for analysis, then you could automagically check if 12-bit and generate a corresponding PPM file using the procedure above and move the 12-bit JPEG off to some other holding area on disk in case you need to refer back to it.
In case you use Macs, the equivalent is fswatch which can be installed with homebrew.