Combinations of Digital Filters

All the filters described above can be combined. By collecting best parts of every filter one can create, at least in theory, a very good hybrid filter. Thresholding and equalization, for example, could be combined with derivatives. Simple heuristic rules can also be appended to the filters to make them more intelligent, to react only to certain patterns.

Combinations of a few selected digital filters are presented here. Thresholding and histogram equalization with some edge-enhancing algorithms prove as quite useful combinations.

Figure 49: Variance of a median filtered sample image.

Figure 50: Sum of thresholded horizontal and vertical derivatives, equalized.

Figure 51: Thresholded square-environent derivative, equalized.

Figure 52: Thresholded deviation.

Antti Nurminen, 34044T,