Let’s see how much space this lossless “incantation” for JPEG XL could save for my 50 gigantic images.
| Size | Command | Time |
| 2,615,247,628 bytes | oxipng -o 0 | |
| 1,590,449,934 bytes | cjxl -d 0 | ~22 minutes |
| 1,355,276,849 bytes | cjxl -d 0 -e 10 -E 4 -I 100 -g 3 | ~61 hours |
Tested with the cjxl command of libjxl v0.11.1. All original JPEG XL files were converted to PNG via the djxl command and optimised with OxiPNG v9.1.3 again.
Effort 7 (default) is good enough that reduced 39.2% comparing to PNG, and that Effort 10 command reduced 48.2% comparing to PNG. Even between the two JPEG XL efforts, e10 reduced additional 14.8% from e7.
But we also need to see the slowest speed of each.
e7 5859 x 7680, 2.498 MP/s [2.50, 2.50]
e10 10500 x 10500, 0.002 MP/s [0.00, 0.00]
Even based on the total time, the default effort is still 166 times faster. I would not recommend using the e10 incantation due to how much more time it could take. The default is enough good for daily or normal usages.
Yes the 50 images available for download now are all made by cjxl -d 0 -e 10 -E 4 -I 100 -g 3 on my computer.