Grok is an open-source JPEG 2000 codec licensed under AGPL v3.

Grok is integrated into GDAL. Benchmark results (16 threads, GDAL release build, Fedora 42):

• 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

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

• 2,000+ unit tests
• Continuous fuzzing via OSS-Fuzz

• Python, C#, Java (SWIG)
• Rust (bindgen)

• Installation
• Testing
• Tile Cache Architecture
• S3 / Cloud Storage
• Language Bindings
• Wiki & Docs
• GitHub

git clone --recursive https://github.com/GrokImageCompression/grok.git
cd grok
cmake -B build
cmake --build build --parallel