Median Filter - Boundary Issues

Boundary Issues

Note that, in the example above, because there is no entry preceding the first value, the first value is repeated, as with the last value, to obtain enough entries to fill the window. This is one way of handling missing window entries at the boundaries of the signal, but there are other schemes that have different properties that might be preferred in particular circumstances:

• Avoid processing the boundaries, with or without cropping the signal or image boundary afterwards,
• Fetching entries from other places in the signal. With images for example, entries from the far horizontal or vertical boundary might be selected,
• Shrinking the window near the boundaries, so that every window is full.