< Picture data's MIME type, in ASCII printable characters
0x20-0x7e, NUL terminated. For best compatibility with players,
use picture data of MIME type \c image/jpeg or \c image/png. A
MIME type of '-->' is also allowed, in which case the picture
data should be a complete URL. In file storage, the MIME type is
stored as a 32-bit length followed by the ASCII string with no NUL
terminator, but is converted to a plain C string in this structure
for convenience.
< Picture data's MIME type, in ASCII printable characters 0x20-0x7e, NUL terminated. For best compatibility with players, use picture data of MIME type \c image/jpeg or \c image/png. A MIME type of '-->' is also allowed, in which case the picture data should be a complete URL. In file storage, the MIME type is stored as a 32-bit length followed by the ASCII string with no NUL terminator, but is converted to a plain C string in this structure for convenience.