pub unsafe extern "C" fn pixBlendColorByChannel(
    pixd: *mut PIX,
    pixs1: *mut PIX,
    pixs2: *mut PIX,
    x: l_int32,
    y: l_int32,
    rfract: l_float32,
    gfract: l_float32,
    bfract: l_float32,
    transparent: l_int32,
    transpix: l_uint32
) -> *mut PIX