Sanitize WordPress filenames on upload

functions.php

/**
 * WordPress allows UTF8 characters such as copyright symbol in filenames but these break in Safari
 *
 * @see https://wordpress.org/support/topic/uploaded-image-with-accents-in-name-image-dont-show-in-safari-6 for original function
 * @see https://core.trac.wordpress.org/ticket/22363 for progress on fixing this bug
 *
 * #wordpress
 */
function sanitize_filename_on_upload($filename) {
  $ext = end(explode('.',$filename));
  $sanitized = preg_replace('/[^a-zA-Z0-9-_.]/','', substr($filename, 0, -(strlen($ext)+1)));
  $sanitized = str_replace('.','-', $sanitized);
  return strtolower($sanitized.'.'.$ext);
}
add_filter('sanitize_file_name', 'sanitize_filename_on_upload', 10);