extern const struct output_driver_factory pdf_driver_factory;
extern const struct output_driver_factory ps_driver_factory;
extern const struct output_driver_factory svg_driver_factory;
+extern const struct output_driver_factory png_driver_factory;
#endif
extern const struct output_driver_factory tex_driver_factory;
&pdf_driver_factory,
&ps_driver_factory,
&svg_driver_factory,
+ &png_driver_factory,
#endif
&tex_driver_factory,
NULL