Convert Ghost CMS images to WebP

ghost_img2webp.sh

#!/bin/sh

apk update
apk add coreutils mariadb-client mariadb-connector-c libwebp-tools

MYSQL_HOST=db
MYSQL_USER=root
MYSQL_PASS=example
MYSQL_DB=ghost
GHOST_PATH=/var/lib/ghost
QUALITY=70

ABSOLUTE_CONTENT_PATH=$(realpath "$GHOST_PATH/content") || exit 1

printf "select feature_image from posts where feature_image not regexp '^__GHOST_URL__/content/images/.*\.webp$';\n" | \
    mariadb --skip-ssl-verify-server-cert -h"$MYSQL_HOST" -u"$MYSQL_USER" -p"$MYSQL_PASS" "$MYSQL_DB" | \
    grep '__GHOST_URL__' | sed "s|__GHOST_URL__|$GHOST_PATH|" | \
    while IFS= read -r IMAGE; do
  [ -z "$IMAGE" ] && continue
  case "$(realpath "$IMAGE")" in
    "$ABSOLUTE_CONTENT_PATH"/*) ;;
    *)
      printf "Path traversal detected! Please investigate! %s\n" "$IMAGE" >&2
      break
      ;;
  esac
  CONVERTED_IMAGE="$(dirname "$IMAGE")/$(basename "${IMAGE%.*}").webp"
  SQL_IMAGE=$(printf "%s" "$IMAGE" | sed -e "s|$GHOST_PATH|__GHOST_URL__|" -e "s/'/''/g")
  SQL_CONVERTED_IMAGE=$(printf "%s" "$CONVERTED_IMAGE" | sed -e "s|$GHOST_PATH|__GHOST_URL__|" -e "s/'/''/g")
  cwebp -quiet -q "$QUALITY" "$IMAGE" -o "$CONVERTED_IMAGE" &&
    printf "update posts set feature_image = '%s' where feature_image = '%s';\n" "$SQL_CONVERTED_IMAGE" "$SQL_IMAGE" | \
        mariadb --skip-ssl-verify-server-cert -h"$MYSQL_HOST" -u"$MYSQL_USER" -p"$MYSQL_PASS" "$MYSQL_DB" &&
    printf "Successfully converted %s to %s\n" "$IMAGE" "$CONVERTED_IMAGE"
done