函数 sws_getDefaultFilter 

pub unsafe extern "C" fn sws_getDefaultFilter(
    lumaGBlur: f32,
    chromaGBlur: f32,
    lumaSharpen: f32,
    chromaSharpen: f32,
    chromaHShift: f32,
    chromaVShift: f32,
    verbose: c_int,
) -> *mut SwsFilter