add ignore edge function in pdiff.

README.google

+URL: http://pdiff.sourceforge.net/
+Version: 1.1.1
+License: GNU General Public License
+License File: files/source/gpl.txt
+
+Description:
+PerceptualDiff is an image comparison utility that makes use of a 
+computational model of the human visual system to compare two images.
+
+Local Modifications:
+A "-noedge e (0.0 to 1.0)" option is added to the original version, 

[vangelis, 2009/07/09 02:43:29]

flag is now called 'ignoreEdges'

+which can turn on the edge detection function and prevent edges in 
+the images to be checked during comparison.
+Parameter e is the threshold in edge detection, if e is 1.0, all

[vangelis, 2009/07/09 02:43:29]

please update the description of the values for 'e'

+possible edges would be ignored during comparison, if e is a small 
+value near 0, only scattered points would be ignored from being 
+checked. Edge detection function employs convolution with a 
+3-by-3 kernel:
+-1 -1 -1
+-1  8 -1
+-1 -1 -1
+It will first detect edges in the original pdiff output image,
+and create a new pdiff result by substracting edges from the original
+output image, and also recalculate unmatched pixels to make results
+consistent.