Image created and placed under CC0 licence (effectovely public domain) by
Damon Hart-Davis.

Interesting case where JXL is larger than source PNG and derived WEBP.

8130 img/data.png
6820 img/data.png.webp
8642 img/data.png.jxl

% cwebp -v -lossless -m 6 -q 100 img/data.png -o img/data.png.web
% cjxl -v -s 9 -q 100 -E 3 -I 1 img/data.png img/data.png.jxl

(cjxl at v0.3.7)

-E 2 -I 1 at suggestion of @jonsneyers

With V0.5.0:

% cjxl -e 9 -g 3 -I 0 -P 0 --patches 0
JPEG XL encoder v0.5.0 [AVX2,SSE4]
Read 800x153 image, 32.2 MP/s
Encoding [VarDCT, d1.000, tortoise], 2 threads.
Failed to compress to VarDCT.

and:
% cjxl -v -e 9 -q 100 img/data.png 
Compressed to 10485 bytes (0.685 bpp).
% cjxl -v -e 9 -q 100 -E 3 -I 1 img/data.png 
Compressed to 13508 bytes (0.883 bpp).


DHD20210922: used squoosh.app to make smaller webp
8130 img/data.png
5892 img/data.png.webp

Used effort 9, slight loss 100.