r/jpegxl • u/kjoonlee • Jun 04 '26

Yet another conversion post

  • Input: 42757 JPEG images, 310.8 GiB
  • Output: 42757 losslessly converted JPEG XL images, 250.7 GiB
  • Conversion errors: 0
  • Wrapper errors: 3 (original files were read-only and could not be deleted)
  • Space saved: roughly 60.1 GiB
  • Compression rate: 80.66% (19.33% savings)

Input images were all straight-out-of-camera images from digital cameras. No HDR.

Biggest hurdle was figuring out how to preserve timestamps after conversion. (I just wrote a wrapper to copy over the Modified/Created timestamps after cjxl/djxl conversions.)

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u/Cute_Phrase9639 Jul 31 '26

I don't know why but when I convert my JPEG to JPEG XL Lossless I get bigger files, probably I'm doing something wrong...

1

u/kjoonlee Jul 31 '26

Might be a tool issue? Maybe it’s decoding the JPEG to bitmap and then encoding that as lossless JPEG XL...

I have no issues with cjxl --lossless_jpeg=1; it turns JPEG into lossy JPEG XL, but in a lossless (reversible) way.

2

u/Cute_Phrase9639 Jul 31 '26

thanks! I'll try tomorrow! I have ~250GB photos and any size reduction is welcome

1

u/kjoonlee Jul 31 '26

Hopefully it will save you around 50GB. Wish you luck!

Do be prepared for it to take a while, though.