Function heif_image_scale_image 

pub unsafe extern "C" fn heif_image_scale_image(
    input: *const heif_image,
    output: *mut *mut heif_image,
    width: c_int,
    height: c_int,
    options: *const heif_scaling_options,
) -> heif_error

Currently, heif_scaling_options is not defined yet. Pass a NULL pointer.