Thanks for the compliment.
A filter works as follows:
The numbers in the box are weighting factors.
The center pixel is replaced by the weighted sum of all
pixels in the box (empty=zero weight)
E.g. a blurring filter, sort of primitive Gaussian:
1 2 1
2 7 2
1 2 1
The problem in PhS is the scaling – doesn´t work automatically: Scale by the sum of all factors: 7+4*2+4*1 =19
Offset 0
The most "stupid" blur filter is the box filter: 1 1 1
1 1 1
1 1 1
Scale=9
This is a highpass, the sum of all factors is 0. A bad highpass. -1 -1 -1
-1 +8 -1
-1 -1 -1
Scale=1 (not understandable), offset=128.
Sharpening filters are a little more complex.
A rather simple illustrated explanation is here.
<
http://www.fho-emden.de/~hoffmann/gauss25092001.pdf>
Best regards –Gernot