It looks like the OM_NEW or OM_SET methods import it and the OM_GET method exports it with the SGA_BitMap attribute . Though the autodocs seems unclear on getting the resultant bitmap. Like so: SGA_BitMap (struct BitMap *) Pointer to the source bitmap which will be copied from when used with OM_NEW, OM_SET and OM_UPDATE. This bitmap is only read from. The sketchboard object always uses its own internal bitmap for editing. The internal bitmap can be retrieved using this attribute and OM_GET. Set the gadget to GA_ReadOnly before invoking OM_GET and be ready to handle a NULL pointer if the gadget has not yet been layed out. Defaults to NULL (blank). Applicability is (OM_NEW, OM_SET, OM_UPDATE, OM_GET)