DNG to JXL Converter

Encoding: the DNG uses lossless (or lossy) JPEG-compressed sensor data, plus optional JPEG previews; JXL uses lossy VarDCT or lossless modular coding; existing JPEGs can be repacked without loss, and the download is a JPEG XL encoded with libjxl compiled to WebAssembly, lossy at the quality you choose or lossless.

Bit depth: 8 to 16 bits per channel in the DNG; JXL allows 8 to 16 bits per channel, or floating point, and the JXL written here has 8 bits per channel. The raw data's 12 to 16 bits are not used: the embedded 8-bit preview is converted.

Colour: camera RGB plus the colour matrices that map it to XYZ (demosaiced linear RGB in a Linear DNG) in the DNG; JXL supports sRGB, Display P3, linear and other spaces described in the codestream, written here as 8-bit sRGB.

Metadata: the DNG can carry EXIF, XMP and DNG tags for colour matrices, calibration and lens corrections; JXL can carry EXIF and XMP boxes in the container form, often stripped by encoders, but nothing is copied across.

DNG is Adobe's openly documented raw format. Some cameras and phones record it directly, Adobe DNG Converter turns other brands' raw files into it, and a Linear DNG holds already-demosaiced RGB that raw editors treat like any other raw file.

DNG is built on TIFF/EP. The raw image sits in a sub-IFD marked as the main image, with tags for black and white levels, colour matrices and the colour filter pattern; a Linear DNG (PhotometricInterpretation 34892) stores demosaiced RGB instead of a mosaic. Previews are optional, and Adobe DNG Converter can write a medium (1024 px), full-size or no preview.

DNG files usually come from Leica, Pentax and Ricoh cameras, DJI drones, Google Pixel and iPhone ProRAW, and Adobe DNG Converter.

JPEG XL is a next-generation format designed to replace JPEG. It compresses better than JPEG and WebP, supports lossless, HDR and progressive decoding, and can losslessly repack existing JPEGs.

A JPEG XL file is either a bare codestream starting with FF 0A or an ISO base media container whose 'jxlc' box holds the codestream. A recompressed JPEG keeps a 'jbrd' box that lets the original JPEG bytes be rebuilt exactly.

JXL is the better choice for archiving and future-proof high quality storage, while DNG suits raw editing and archiving raw files in an open format.

JXL strengths: Excellent lossy and lossless compression; Progressive decoding and HDR; Huge image sizes. Drawbacks to weigh: Browser support is limited (Safari only by default); Few apps can open it yet.