Writing · 2026-04-27
Lossless JPEG to JPEG XL transcoding, explained
Re-encode a JPEG as JXL, save ~20% storage, decode back to a pixel-perfect JPEG later. How it works and when to use it.
Most image compression has a one-way door. You pick a quality setting, you save the file, and the original detail is gone forever. Lossless JPEG to JPEG XL transcoding breaks that rule.
What lossless transcoding actually means
A JPEG file is not just pixel data. It is the result of a specific encoding pipeline: DCT transforms, quantization tables, Huffman coding. JPEG XL’s libjxl can read every byte of a JPEG, re-encode the same data using better entropy coding, and write a smaller JXL file that, when decoded back, produces a bit-identical JPEG.
You save space. You keep the file. You can restore the original any time.
(Full post coming soon.)
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#jxl
#lossless
#archival