#!/bin/bash

mkdir result

find . -maxdepth 1 \( -iname "*.jpg" -o -iname "*.jpeg" -o -iname "*.png" \) -print0 | 
xargs -0 -P "$(sysctl -n hw.logicalcpu)" -I{} sh -c '
f="$1"
cwebp -quiet \
    -q 70 \
    -metadata all \
    "$f" \
    -o "result/$(basename "${f%.*}").webp"
' _ {}