cd ~/Desktop/Screenshot || exit 1

for f in *.png; do
  [ -f "$f" ] || continue

  # 已經是「已修改」開頭就跳過，避免重複處理
  case "$f" in
    已修改*) continue ;;
  esac

  out="已修改$f"
  magick "$f" -background white -alpha remove -alpha off -fuzz 12% -trim +repage "$out"
done