Why the MNG format support plugins are not shipped with Qt 5.7-msvc2015 build? The qmng.dll and qmngd.dll.
Format Description Support 3rd Party Codec MNG Multiple-image Network Graphics Read Yes (bundled, unmaintained)
Note: Some bundled third party codecs are not maintained anymore. They are provided for manual builds only, and not used as a fallback in case system libraries are unavailable.