Image Processing Reference
In-Depth Information
fies the design strategy. They also show that when the optimum filter output lies
within the envelope, the constraint can only be beneficial.
An example demonstrating the benefit of envelope filtering taken from the
above paper is presented here. Figure 8.2(a) shows a corrupted image that has been
created by adding both 10 percent salt-and-pepper noise and a series of horizontal
Envelope filtering example. The above figures show the benefit of envelope filter-
ing. The noisy image is shown in (a) and its restoration with a 17-point stack filter is shown in
(b). Envelope filtering using openings and closings by a cross results in the image in (c). En-
velope filtering to within a fixed distance of the median is shown in (d). The MSE for each im-
age is (a) 1912; (b) 106; (c) 79; and (d) 55, respectively.
Figure 8.2
