Horizontally flip png images and overlay an png image on top of them, then convert the png images to an animated webp image

convert.sh

#!/usr/bin/env bash

# Horizontally flip png images and overlay an png image on top of them
for filename in frame_*.png
do
  echo "Update $filename"
  # Horizontal flip
  magick "$filename" -flop "$filename"
  # Add overlay image
  magick convert "$filename" "../overlay.webp" -gravity Center -composite "$filename"
done

# Convert png images to an animated webp image
FILES=$(echo frame_*.png | sort)
echo "Merge $FILES"
magick $FILES -quality 50 -define webp:lossless=true animation.webp