your script doesn't deal with offset'd web2p

[marcespie]

See for instance:
https://mathiasbynens.be/demo/animated-webp

webpmux -info shows that two frames have x/yoffsets... and after running your script,
the resulting image is broken

the solution is complicated. It would mean parsing the full webpmux -info output, and using graphicsmagick to properly offset frames that require it.

[elsonwx]

@marcespie fixed in 5322308