diff --git a/webdav-derivative.php b/webdav-derivative.php
new file mode 100644
index 0000000..999945a
--- /dev/null
+++ b/webdav-derivative.php
@@ -0,0 +1,126 @@
+<?php
+define('PHPWG_ROOT_PATH', '../../');
+include_once(PHPWG_ROOT_PATH.'include/common.inc.php');
+
+if (!defined('BRATONIEN_TOOLS_PATH'))
+{
+  define('BRATONIEN_TOOLS_ID', basename(__DIR__));
+  define('BRATONIEN_TOOLS_PATH', PHPWG_ROOT_PATH.'plugins/'.BRATONIEN_TOOLS_ID.'/');
+}
+
+require_once(BRATONIEN_TOOLS_PATH.'include/webdav_image_runtime.inc.php');
+require_once(BRATONIEN_TOOLS_PATH.'include/webdav_gallery_runtime.inc.php');
+
+function bratonien_tools_webdav_derivative_abort($status, $message)
+{
+  http_response_code((int)$status);
+  header('Content-Type: text/plain; charset=utf-8');
+  header('Cache-Control: no-store');
+  echo $message;
+  exit;
+}
+
+$image_id = (int)($_GET['id'] ?? 0);
+$type = trim((string)($_GET['type'] ?? ''));
+if ($image_id < 1 || $type === '')
+{
+  bratonien_tools_webdav_derivative_abort(400, 'Bild-ID oder Derivattyp fehlt.');
+}
+
+$permission_condition = get_sql_condition_FandF(array('forbidden_categories'=>'category_id'), null, true);
+$access_result = pwg_query('SELECT 1 FROM '.IMAGE_CATEGORY_TABLE.' WHERE image_id='.$image_id.' AND '.$permission_condition.' LIMIT 1');
+if (!pwg_db_num_rows($access_result))
+{
+  bratonien_tools_webdav_derivative_abort(403, 'Kein Zugriff auf dieses Bild.');
+}
+
+if (!class_exists('ImageStdParams') || !class_exists('DerivativeImage') || !class_exists('SrcImage'))
+{
+  require_once(PHPWG_ROOT_PATH.'include/derivative.inc.php');
+}
+
+$params = @ImageStdParams::get_by_type($type);
+if (!$params)
+{
+  bratonien_tools_webdav_derivative_abort(404, 'Unbekannter Piwigo-Derivattyp.');
+}
+
+$result = pwg_query('SELECT * FROM '.IMAGES_TABLE.' WHERE id='.$image_id.' LIMIT 1');
+if (!pwg_db_num_rows($result))
+{
+  bratonien_tools_webdav_derivative_abort(404, 'Bild wurde nicht gefunden.');
+}
+$row = pwg_db_fetch_assoc($result);
+$src = new SrcImage($row);
+$info = bratonien_tools_webdav_image_source_info($image_id);
+if (!$info)
+{
+  bratonien_tools_webdav_derivative_abort(404, 'Keine WebDAV-Quelle fuer dieses Bild gefunden.');
+}
+
+$preview = bratonien_tools_webdav_preview_path($info);
+if (!$preview || !is_file($preview) || !is_readable($preview))
+{
+  bratonien_tools_webdav_derivative_abort(404, 'Nextcloud-Preview ist noch nicht vorbereitet.');
+}
+
+$derivative = new DerivativeImage($params, $src);
+if ($derivative->same_as_source())
+{
+  bratonien_tools_webdav_derivative_abort(404, 'Derivat entspricht der Platzhalterquelle und wird nicht ausgeliefert.');
+}
+
+$target = $derivative->get_path();
+if ($target === '')
+{
+  bratonien_tools_webdav_derivative_abort(500, 'Derivat-Zielpfad fehlt.');
+}
+
+if (!bratonien_tools_webdav_derivative_matches_preview($target, $params, $image_id))
+{
+  if (is_file($target))
+  {
+    @unlink($target);
+    clearstatcache(true, $target);
+  }
+
+  $detail = '';
+  if (!bratonien_tools_webdav_generate_derivative($params, $src, $detail))
+  {
+    error_log('Bratonien WebDAV on-demand derivative #'.$image_id.' type='.$type.': '.$detail);
+    bratonien_tools_webdav_derivative_abort(503, 'Derivat konnte noch nicht erzeugt werden.');
+  }
+}
+
+if (!bratonien_tools_webdav_derivative_matches_preview($target, $params, $image_id))
+{
+  bratonien_tools_webdav_derivative_abort(503, 'Erzeugtes Derivat ist noch nicht gueltig.');
+}
+
+$size = @filesize($target);
+$mtime = @filemtime($target) ?: time();
+$etag = sha1($target.'|'.$mtime.'|'.($size ?: 0));
+$extension = strtolower(pathinfo($target, PATHINFO_EXTENSION));
+$content_type = 'image/jpeg';
+if ($extension === 'png') $content_type = 'image/png';
+elseif ($extension === 'gif') $content_type = 'image/gif';
+elseif ($extension === 'webp') $content_type = 'image/webp';
+
+header('Content-Type: '.$content_type);
+if ($size !== false) header('Content-Length: '.(string)$size);
+header('ETag: "'.$etag.'"');
+header('Last-Modified: '.gmdate('D, d M Y H:i:s', $mtime).' GMT');
+header('Cache-Control: private, max-age=86400, must-revalidate');
+header('X-Content-Type-Options: nosniff');
+
+$client_etag = trim((string)($_SERVER['HTTP_IF_NONE_MATCH'] ?? ''), " \t\r\n\"");
+if ($client_etag !== '' && hash_equals($etag, $client_etag))
+{
+  http_response_code(304);
+  exit;
+}
+
+if (($_SERVER['REQUEST_METHOD'] ?? 'GET') !== 'HEAD')
+{
+  readfile($target);
+}