JXL to JP2 Converter

Encoding: the JXL uses lossy VarDCT or lossless modular coding; existing JPEGs can be repacked without loss; JP2 uses wavelet coding: reversible 5/3 for lossless files, irreversible 9/7 for lossy ones, and the download is a lossless JPEG 2000 (.jp2) using the reversible 5/3 wavelet.

Bit depth: 8 to 16 bits per channel, or floating point in the JXL; JP2 allows up to 16 bits per channel is common, more is possible, and the JP2 written here has 8 bits per channel. High-bit-depth JPEG XL files are reduced to 8 bits per channel.

Colour: sRGB, Display P3, linear and other spaces described in the codestream in the JXL; JP2 supports sRGB, greyscale, YCC or a space described by an ICC profile, written here as 8-bit sRGB.

Transparency: the JXL stores it as an extra channel in the codestream; the JP2 keeps it as an extra component flagged as opacity.

Animation: frames inside a single codestream; the JP2 holds one image, so only the first frame is converted.

Metadata: the JXL can carry EXIF and XMP boxes in the container form, often stripped by encoders; JP2 can carry XML, ICC and resolution boxes, but nothing is copied across.

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 files usually come from image editors, archival pipelines and lossless JPEG recompression.

JPEG 2000 is a wavelet-based format that can be truly lossless or lossy, handles very high bit depths and huge images, and is used where long-term fidelity matters: archives, medicine, satellites and digital cinema.

A .jp2 file is a box structure: a 12-byte signature box, an 'ftyp' box, a 'jp2h' header box with the size and colour specification, then the 'jp2c' box holding the codestream, which begins with FF 4F FF 51.

JP2 is the better choice for archival masters and specialist imaging, while JXL suits archiving and future-proof high quality storage.

JP2 strengths: True lossless mode; High bit depths and very large images; Standardised for archives and digital cinema. Drawbacks to weigh: Browsers do not display it; Slow to encode and decode; Patchy support in everyday apps.