Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: File Format
ID_PAINTTEXTURE_SAVEFORMAT
Parameter: Filename
ID_PAINTTEXTURE_FILENAME
Parameter: Color Profile
ID_PAINTTEXTURE_ICCPROFILE
Parameter: DPI
ID_PAINTTEXTURE_DPI
Parameter: Aspect Ratio
ID_PAINTTEXTURE_ASPECTRATIO