There are several problems:
1) The documentation on the options page says
-statistic type value
but it should really be
-statistic type WidthxHeight
I can change that if you want?
2) You don't define the option "Nonpeak". What does that do? If you tell me, I can change the documents, if you want.
3) Min and Max produce the same result on my test and give a compare of 0
4) Mean and Median produce the same results on my test and give a compare of 0
Test image zelda3.png and WidthxHeight=9x9 also WidthxHeight=3x3
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Fred