Lossless JPEG compressor for RAW portion of Raspberry Pi Camera RAW format.
Uses a modified version of the lj92 library found here.
If you are using a Pi Camera V1, run make camera_v1
If you are using a Pi Camera V2, run make camera_v2
If you only want to make the merge_jpg program, run make lj92_merge
merge_jpg is not camera version dependent.
Designed to run on the Raspberry Pi. Splits a Raspberry Pi Camera JPEG+RAW file into the JPEG and the RAW portions, then compresses the RAW portion with Lossless JPEG (1992) format. This algorithm takes a fair bit of time to run on a Pi, so it's suggested to enable threaded lj92 execution on multicore Raspberry Pi systems.
To split a Raspberry Pi JPEG+RAW into a truncated JPEG and its compressed RAW portion (ljpg), run split_jpg jpeg_file.jpg. The original JPEG will be truncated to remove all compressed data. You may specify two-component or four-component compression by passing in split_jpg jpeg_file.jpg 2 or split_jpg jpeg_file.jpg 4, respectively. Two-component compression is the default.
Designed to combine a JPEG+RAW file split into JPEG and LJ92-compressed RAW portion back into a JPEG+RAW file. This makes the output compatible with most other programs that manipulate Raspberry Pi Camera RAW files.
To merge a truncated JPEG and a ljpg produced by split_jpg, just place the ljpg in the same directory as the truncated JPEG file, then run merge_jpg split_jpeg_file.jpg This will recreate the split_jpeg_file.jpg with the same RAW data that was stripped off and compressed by split_jpg.
Because this program needs to be fast, I've chosen to use #define to set the camera version and compile on the Raspberry Pi.
I've chosen to discard non-imaging RAW data in the original RAW. This includes unset padding pixels in the last vertical lines and the last few horizontal lines of RAW data. This reduces filesize without affecting imaging output.
If you are going to be using a multi-core Raspberry Pi, use this:
gcc lj92.c split_jpg.c -o split_jpg --std=gnu99 -O3 -march=native -funroll-loops -D${camera_version} -DTHREADED_LJ92 -lpthread
Using -march=native on Raspbian may trigger a compiler bug on the Raspberry Pi 3 (or Pi 2B2); use this instead:
gcc lj92.c split_jpg.c -o split_jpg --std=gnu99 -O3 -mcpu=cortex-a53 -funroll-loops -D${camera_version} -DTHREADED_LJ92 -lpthread
If you are using a Raspberry Pi A/B(+)/Zero (W):
gcc lj92.c split_jpg.c -o split_jpg --std=gnu99 -O3 -march=native -funroll-loops -D${camera_version}
Only the Lossless JPEG compression is threaded, and is split up per-component. Therefore, 4-component compression can be threaded better.
For a better explanation of "components", please see this article.
- Single thread, 2 components: ~619ms
- Multithreaded, 2 components: ~338ms (1.83x)
- Single thread, 4 components: ~619ms
- Multithreaded, 4 components: ~241ms (2.57x)
- Single thread, 2 components: ~1072ms
- Single thread, 4 components: ~1059ms
Tests were done on an ISO100, ISO400, and ISO800 source.
- 2 components: 70.7%, 73.6%, 84.8%
- 4 components: 70.1%, 73.8%, 84.4%
Compression performance is slightly worse than Adobe's DNG compressor.
lj92 library:
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.