i 
SI 
€ 
A APUD 
  
  
  
  
Fig. 9 PV1 image, size 128 z 256 consisting of a num- 
ber of signals in different sizes and orientations. The image 
is heavily corrupted by a computer generated o,, = 50 noise 
field, yielding a SNR = 4. The lower image shows the 
outlines of the detected regions after passing the entire pro- 
cedure. 
The parameters of the predictor are: w = 1.5, trunca- 
tion factor — 0.01, resulting in a half plane filter size of 6 
x 11. The confidence levels are, Stage I: 95%, Stage Ila: 
99.9% and Stage IIc: 99.996. In Stage IIb regions smaller 
than 3 pixels are removed; c, — 1. 
Stage I yields 239 regions, represented in fig. 8d, where 
each region is shown with different grey value. Stage Ila 
merges 230 of the 239 regions. In Stage IIb two regions are 
smaller than 3 pixels. They are merged with their most 
similar neighbours. In Stage IIc no insignificant regions 
are traced. The result of the entire procedure, where each 
region has received a grey value, is shown in fig. 8e. Fig. 8f 
displays the region outlines. 
Smoothing of the SB images corrupted by o, = 10 or 
20 doesn't improve the final result, since the predictor has 
already a smoothing effect. Heavy noise o, — 50 needs 
smoothing in Stage I and Stage II. Best performance in 
Stage I shows the extended Kuwahara filter and next best 
the Gaussian filter. The conditional filter shows worst be- 
700 
havior; the median and box filter lie in between. Our ex- 
periments confirmed out earlier considerations that the me- 
dian filter in Stage II gives best results, since it removes the 
tail parts of the noise enabling a more reliable decision on 
merging. 
The PV1 Images (fig. 9a) shows signals in a number 
of sizes and orientations, contaminated by a o, — 50 noise 
field. Predictor parameters: see SB image. The results 
of c, — 10 and o, — 20 images are good, even without 
previous smoothing. Smoothing of the 0, = 50 image by 
extended Kuwahara or Gaussian, showed, according our 
previous observation, the best results in Stage I. In Stage 
II the median filter shows best performance. 
Experiments on setting the confidence levels yielded: 
Stage I: 9596, Stage IIa: 99.996 and Stage IIc: 9596, as best 
options. Fig.9b shows the outlines of the regions obtained, 
where the extended Kuwahara in Stage I and the median 
filter in Stage II is applied, using the above best options.