diff --git a/runtime/lib/piwigo-derivative-call.php b/runtime/lib/piwigo-derivative-call.php
new file mode 100644
index 0000000..4baf58a
--- /dev/null
+++ b/runtime/lib/piwigo-derivative-call.php
@@ -0,0 +1,46 @@
+<?php
+if (PHP_SAPI !== 'cli')
+{
+  http_response_code(404);
+  exit;
+}
+
+$request = '';
+foreach ($argv as $arg)
+{
+  if (strpos($arg, '--request=') === 0)
+  {
+    $request = substr($arg, strlen('--request='));
+  }
+}
+if ($request === '' || strpos($request, '/i.php?/') !== 0)
+{
+  fwrite(STDERR, "Ungültige Piwigo-Derivatanforderung.\n");
+  exit(2);
+}
+
+$piwigo_root = realpath(dirname(__DIR__, 3));
+if ($piwigo_root === false || !is_file($piwigo_root.'/i.php'))
+{
+  fwrite(STDERR, "Piwigo i.php wurde nicht gefunden.\n");
+  exit(3);
+}
+
+chdir($piwigo_root);
+$_SERVER['REMOTE_ADDR'] = '127.0.0.1';
+$_SERVER['SERVER_ADDR'] = '127.0.0.1';
+$_SERVER['SERVER_NAME'] = 'localhost';
+$_SERVER['HTTP_HOST'] = 'localhost';
+$_SERVER['SERVER_PORT'] = '80';
+$_SERVER['REQUEST_METHOD'] = 'GET';
+$_SERVER['REQUEST_URI'] = $request;
+$_SERVER['SCRIPT_NAME'] = '/i.php';
+$_SERVER['PHP_SELF'] = '/i.php';
+$_SERVER['QUERY_STRING'] = ltrim((string)parse_url($request, PHP_URL_QUERY), '?');
+$_SERVER['HTTP_USER_AGENT'] = 'Bratonien-WebDAV-Warmup-Piwigo-Caller/0.9.7.1.8';
+$_SERVER['HTTPS'] = 'off';
+
+// Piwigo selbst erzeugt das Derivat. Der Warmup benötigt den ausgelieferten
+// Bild-Body nicht und prüft danach ausschließlich Piwigos Cache-Datei.
+ob_start(function ($buffer) { return ''; }, 1);
+include $piwigo_root.'/i.php';