[FFmpeg-user] Converting hdmv_pgs_subtitle to image sequence

[Markus Amalthea Magnuson]

I'm trying to convert an hdmv_pgs_subtitle stream in a .sup file to a
sequence of images, one for every new subtitle in the stream. Running the
following will output a huge number of images of varying size, but they are
all corrupt:

ffmpeg -i test.sup -scodec copy test_%04d.png

Is this conversion from bitmap subtitles to images supported?