Qt 5.8 supported Image formats
here is list of supported image formats :
but in Qt 5.8 not support dds & jp2 formats.
in plugins/imageformats folder not exist qdds.dll & qjp2.dll files.
Qt app can't open dds & jp2 formats
If you refer to not having support for those formats in your installed Qt, then I recommend you to try to compile with proper options enabled. JP2 is a third party plugin, meaning you should probably download it on its own. If you can't compile, check that you have installed the plugins and they are enabled. Also, you might download a compiled version on its own.
dds was moved to unmaintained status in 5.8, you'll have to uncomment the dds line in src/plugins/imageformats/imageformats.pro if you want to build it manually (no compile flag exists to enable it).