preferred.mediaobject.role — Select which mediaobject to use based on
this value of an object's
A mediaobject may contain several objects such as imageobjects.
If the parameter
is non-zero, then the
role attribute on
imageobjects and other objects within a
mediaobject container will be used to select which object will be
used. If one of the objects has a role value that matches the
preferred.mediaobject.role parameter, then it has first
priority for selection. If more than one has such a
role value, the first one is used.
for the sequence of selection.