Error: Call to undefined function Drupal\imageapi_optimize_avif_webp\Plugin\ImageAPIOptimizeProcessor\imageavif() in Drupal\imageapi_optimize_avif_webp\Plugin\ImageAPIOptimizeProcessor\AvifWebp->applyToImage()

Please try https://stackoverflow.com/questions/70965543/how-to-enable-imageavif-in-...

Module Requirements:
1. If using ImageMagick tookit then latest version of ImageMagick extension with 'Images format' AVIF must be enabled.
2. If using GD toolkit then PHP 8.1+ and php-gd extension must be enabled.

Related 🐛 Error: Call to undefined function AvifWebp->applyToImage() (line 85 Active

The requirements above aren't enough - you have to have ImageMagik at a version that supports AVIF. For GD it has to be built with AVIF support. Just having it installed is not enough.

https://php.watch/versions/8.1/gd-avif

https://stackoverflow.com/questions/71739530/php-8-1-imageavif-avif-imag...

Check your PHP version. https://www.php.net/manual/en/function.imageavif.php