Function libheif_sys::heif_context_get_number_of_top_level_images

pub unsafe extern "C" fn heif_context_get_number_of_top_level_images(
    ctx: *mut heif_context
) -> c_int

Number of top-level images in the HEIF file. This does not include the thumbnails or the tile images that are composed to an image grid. You can get access to the thumbnails via the main image handle.