Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Texture
SLA_PROJECTOR_TEXTUREParameter: Projection
SLA_PROJECTOR_PROJECTIONParameter: Offset X
SLA_PROJECTOR_OFFSET_XParameter: Offset Y
SLA_PROJECTOR_OFFSET_YParameter: Length X
SLA_PROJECTOR_LENGTH_XParameter: Length Y
SLA_PROJECTOR_LENGTH_YParameter: Tiles X
SLA_PROJECTOR_TILES_XParameter: Tiles Y
SLA_PROJECTOR_TILES_YParameter: Tile
SLA_PROJECTOR_TILEParameter: Seamless
SLA_PROJECTOR_SEAMLESSParameter: Position
SLA_PROJECTOR_POSITIONParameter: Rotation
SLA_PROJECTOR_ROTATIONParameter: Scale
SLA_PROJECTOR_SIZEParameter: Paste Tag
SLA_PROJECTOR_PASTE_TAG