When a FITS header is scanned in memory or read from a file several image values are retrieved from the header and stored in s FITSImage structure. This structure may be accesed with the following macros:
    #define ft_hasbscale(fits)        ( fits->image->has_bscale       )
    #define ft_bscale(fits)           ( fits->image->bscale           )
    #define ft_hasbzero(fits)         ( fits->image->has_bzero        )
    #define ft_bzero(fits)            ( fits->image->bzero            )
    #define ft_hasblank(fits)         ( fits->image->has_blank        )
    #define ft_blank(fits)            ( fits->image->blank            )
    typedef struct FITSImage {
        int       has_bscale;
        int       bscale;
        int       has_bzero;
        int       bzero;
        int       has_blank;
        int       blank;
    } *FITSImage;