How to dilate foreground only if it's surrounded by background?

[nicolai.rostov]

Yep, black and white, at least this is how the documentation makes me see what morphology (originally) sees as background and foreground.

On the other hand, doesn't IM already have a similar feature? How does the '-despeckle' operator decide what is, and what is not, a speckle? There must be a way to generalize this to other operations.

[fmw42]

From the code:


% DespeckleImage() reduces the speckle noise in an image while perserving the
% edges of the original image. A speckle removing filter uses a complementary
% hulling technique (raising pixels that are darker than their surrounding
% neighbors, then complementarily lowering pixels that are brighter than their
% surrounding neighbors) to reduce the speckle index of that image (reference
% Crimmins speckle removal).


So again simply looking at the graylevels of the neighborhood.

See effect.c at line 916