Grok
April 16, 2026 · View on GitHub
Grok is an open-source JPEG 2000 codec licensed under AGPL v3.
Performance
Grok is integrated into GDAL. Benchmark results (16 threads, GDAL release build, Fedora 42):
| Workflow | Grok (JP2Grok) | Kakadu (JP2KAK) | OpenJPEG |
|---|---|---|---|
| Spot 6 (Network Storage) | 35.17 s | 344 s | 85 s |
| Spot 6 (Local Storage) | 26.92 s | 30.57 s | 52.09 s |
| Pleiades (Region) | 0.74 s | 1.41 s | 4.28 s |
Features
- High Throughput JPEG 2000 (HTJ2K) support
- Random-access sub-image decoding (TLM + PLT markers)
- Multi-level tile cache with LRU eviction and compressed chunk caching
- S3 / cloud storage with network fetch caching and disk spillover
- ICC color profiles, XML/IPTC/XMP/EXIF metadata
- Monochrome, sRGB, palette, YCC, extended YCC, CIELab, CMYK
- 1–16 bit precision
- JPEG/PNG/BMP/TIFF/RAW/PNM/PAM I/O
- Linux (x86-64/AArch64), Windows, macOS, WebAssembly
Transcoding (grk_transcode)
grk_transcode rewrites JP2/J2K files at the packet level — no full decompression required. Supported operations:
- Insert TLM (Tile-part Length) and PLT (Packet Length) markers for random access
- Inject SOP / EPH markers
- Truncate quality layers (
--max-layers) - Strip resolution levels (
--max-res) - Reorder packet progression (LRCP, RLCP, RPCL, PCRL, CPRL)
Example — add TLM + PLT markers to an existing file:
grk_transcode -i input.jp2 -o output.jp2 -X -L
Testing
- 2,000+ unit tests
- Continuous fuzzing via OSS-Fuzz
Language Bindings
- Python, C#, Java (SWIG)
- Rust (bindgen)
Links
- Installation
- Testing
- Tile Cache Architecture
- S3 / Cloud Storage
- Language Bindings
- Wiki & Docs
- GitHub
Quick Build
git clone --recursive https://github.com/GrokImageCompression/grok.git
cd grok
cmake -B build
cmake --build build --parallel