@param filter the filter to initialize
@param args A string of parameters to use when initializing the filter.
The format and meaning of this string varies by filter.
@param opaque Any extra non-string data needed by the filter. The meaning
of this parameter varies by filter.
@return zero on success
Initialize a filter.
@param filter the filter to initialize @param args A string of parameters to use when initializing the filter. The format and meaning of this string varies by filter. @param opaque Any extra non-string data needed by the filter. The meaning of this parameter varies by filter. @return zero on success