<i,) into a black pixel. This kind of transform is 
called horizontal RLS transform and signed as H, 
G,j). 
Defination 2 Suppose A(i,j;) and B(i,j;) are two 
black pixels in column i, if |j; —j;| &n, then turn 
an arbitray pixel C(1,j) between A and B (i.e. jj 
j« à) into a black pixel. This kind of transform is 
called vertical RLS transform and signed as V, Gi, 
p. 
- Defination 3 Suppose A Ci; »j,) and BCi25j2) G2—11 
=jJ;) are two black pixels in the diagonal direc- 
tion of down — left to up— right, if |i, —i;| Xn, 
then turn an arbitrary pixel C(i,j) between A and 
B (i.e. i,<i<i,) into a black pixel. This trans- : 
form is called down — left to up — right diagonal 
RLS transform and signed as D,G,)). 
Defination 4 Suppose A (i; ,j;) and B(i;,j;) (i;—i 
—]j—j2 are two black pixels in the diagonal direc- 
tion of up — left to down — right, if |i, —i;| n, 
then turn an arbitrary pixel C(i,j) between A and 
B into a black pixel. This kind of transform is 
called up —left to down—right diagonal RLS trans- 
form and signed as C, (i,j). : : 
For the original binary map images I(1,j) shown in 
Figure 1, the corresponding results of its H, (G»j) » 
V. G, D, D,G,p and C,G,j transforms (e.g. n= 
10) are respectively shown in Figure2, Figure 3, 
Figure 4 and Figure 5. Then a new image PG,)) is 
obtained from 
PG. m OL, V. DU GLV.n co 
IH YD, ACI U VV. YD. 1TC.YG.D 
An example of P(1,j) is shown in Figure 6, which 
is correspondant to I(i,j) shown in Figure 1. 
In image P (i,j), all of the hatched polygons are 
segmented into black bolcks. However, some Chi- 
nese characters which is much similar to hatched 
polygons in shape are segmented into blocks too. 
Other parts of the image remain the same as in the 
original map image. 
3. SERIES SHRINKING TRANSFORMS 
As shown in Figure 6, image P(i,j) includes black 
blocks as well as lines and other graphics. By per- 
forming series shrinking transforms, the graphics 
except black blocks can be deleted from image PG, 
j). Shrinking tramsfrom is defined as follows; For 
a black pixel, if more than two among its 8 neigh- 
  
  
Fig. 4 The result of D,(i,j) transform for IG»)) 
338 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996 
  
  
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