EP O 1 79 291  B1
T8ble  l
T. _ Two-d__ens_onal code table
_        _ode          Ele_ent_ to be coded     Notat_on      COde WOrd
pass               b l, bz              P    OOO l                    .
Hor_zontal         aoal, ala2            H    OOl?_(aoa l)_M(8 la2)
_          Vert_cal   al _ us t under b l     a lb l = O  V (,O)    l
__              .    al to the right of b l alb l -- l  Vg( l)   O. _l l
alb l -- 2  Vg(2)   OOOO l l
_                                   a lb l = 3  Vg(3)   OOOOO l l
a l to the left of b l  alb l E l  VL( l)   O IO
.     alb l _ 2  VL (2)   OOOOIO  _
_                      alb l E 3  VL (3)   OOOOO IO
Extens_on                   2-D  (extens_ons)  OOOOOOlxxx
l-D  (extens_ons)  OOOOOOOO IXXX
_5    Referring to Fig. 2, an exemplary- panern is shown for describ_ing the coding scheme wherein the pel
Ipi CtUre element) ''ao'' fep FeSentS the Feferen Ce OF Sta_ing element on the COdíng linel the ''a_'' representS
_          the ne Xt Changing element tO the Fight Of ao on the COd._ng l._nel and the ''b_'' fepfeSentS the fifSt Changing
element On the feferen Ce l__ne tO the right Of ao and Of OppOSite COIOUF tO ao. AS appafent ffOm Table 1, the
code words for la_b_ l _ 3 are of relatively short length.
__        50    Describing the basic concept of a first embodiment of the present invention with reference to Figs. 3A
thFOUgh 6D, the inVentiOn deteCtS a Chang__ng element C_ in a fiFSt SCan line, a Chang._ng element C2 in a
SeCOnd SCan l._ne and a Changing element C_ in a thi Fd sCan line.
F__gs. 3A-B, QA-D, 5A-D 6A-D show panerns which are pre-processed in accordance with the
pfeSent._nVention, and               _
55    Fig. 7 shows a circuit block diagram for performing the pre-process in accordance with the present
_invention.
Fig. 8 shows an example of an oríginal image used for the descr__ption of a second embodiment of the
pfeSent invention.                  _
Fig. 9 shows panerns which are pre-processed in the second embod__ment ofthe present invention, and
6o    Fig. IO shows the pre-process operation in the second embodiment of the present __nvention.
.       J Descripton of First Embodiment
The invent__on performs a pre-process of bi-level image data to reduce the amount of compressed data,
wh._ch are compressed under a conventional two-dimensional coding scheme, such as provided bv the
65  CCl_ Recommendatíon T.Q.
_                  _.3_-_           _,...    .                 .  .