        \param dz Depth of images in the written file.
        \param dc Spectrum of images in the written file.
    **/
    static void save_empty_cimg(const char *const filename,
                                const unsigned int nb,
                                const unsigned int dx, const unsigned int dy=1,
        \param dz Depth of images in the written file.
        \param dc Spectrum of images in the written file.
    **/
    static void save_empty_cimg(const char *const filename,
                                const unsigned int nb,
                                const unsigned int dx, const unsigned int dy=1,