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(c) Collinearity grouping (d) Pier areas 
T Figure 8: Low Resolution Harbor Scene 
scene. They suggest the global extension field as means of de- 
scribing the behavior of a curve segment, in terms of its con- 
tinuation. They also show that a directional convolution of an 
edge image with the above field can produce useful descriptions. 
In this technique all operations are parameter-free, non-iterative 
and the processing is linear in the number of edges in the in- 
put image. As an example of this technique consider the small 
image containing a building in figure 9a. The intensity edges ex- 
tracted from the image are shown in figure 9b. The saliency map (a) Image of 
constructed from these edges if shown in figure 9c. building edges 
  
     
  
  
(c) Saliency map 
Figure 9: Computation of saliency 
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