Parent Topic: <A href="http://www.pcigeomatics.com/cgi-bin/pcihlp/IWORKS|Filter">Filter</a><hr>
<H4>Type 1/Type 2 - Laplacian Edge Detector Filter </H4>
The Laplacian edge detector generates sharp edge definition of an 
image. This filter can be used to highlight edges having both
positive and negative brightness slopes.<p>
The two Laplacian filters have different weight arrangements 
as shown below:<p>
Example of 3x3 Laplacian filters.
<P>
<PRE>
        Type 1                  Type 2
          
       0  1  0                 -1 -1 -1
       1 -4  1                 -1  8 -1
       0  1  0                 -1 -1 -1

       where sum of all the weights = 0
</PRE>
NOTE: In order to filter pixels located near the edges of the image,
edge pixel values are replicated to give sufficient data.
<P>
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