The APIMAGE or separate raster option for ArcPress writes all raster information in the map to a separate file. ArcPress then only rasterizes the vector information. The separated raster information is added afterwards.
It was originally designed for use with ArcInfo workstation *.gra files. It does not work with *.eps file input.
APIMAGE has the added benefit of applying color adjust and saturation options to the vector and/or raster information in the map.
APIMAGE or separate raster is no longer available in ArcPress for ArcMap ArcGIS 9.x and above. It is only available in ArcPress for ArcInfo Workstation 9.x and above.