The MCF reader produces FME features for all feature data held in files that reside in a particular folder. For each file, the reader checks to see if that file is requested by looking at the list of IDs specified in the mapping file. If a match is made or no IDs were specified in the mapping file, then that file is opened to be read. The MCF reader extracts features one at a time and passes them on to the rest of the FME for further processing. When the file is exhausted, the MCF reader starts on the next file. When all MCF files in the folder have been read, then the reader is closed.
MCF uses an upper-left origin for its coordinates and FME uses a bottom-left origin. To compensate for this, all y values are multiplied by -1 to “flip” them over the x-axis.