Filter registration and some simple filters (also descriptions). Desperate splitting of code into small shared libraries for historical reasons presumably (OS/2 and Windows 3.x). The libraries produced from the code in each subdirectory of filter/source/graphicfilter are graphic format import or export filters. But they don't have uniform API. Some have either an GraphicImport or GraphicExport entry point, and are loaded and used in a uniform fashion from code in svtools/source/filter/filter.cxx. Others have different API and are loaded from other places. For instance "icgm" has ImportCGM, and is loaded and used by sd/source/filter/cgm/sdcgmfilter.cxx (!). Svgreader is used for "File->Open" and then to choose the svg file. For "Insert->Picture->From File", see svgio/source/svgreader directory.