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Hybrid Median Filtering of Color and Monochrome Images

A valuable tool for removing noise in digital images is the median filter. Although it does not shift edges, the median filter does remove fine lines and detail, and round corners. A more advanced version of this filter, which avoids these problems, is the hybrid median. This performs ranking in multiple sub-neighborhoods for each pixel, takes the median values from those rankings and performs a final ranking to select the final result. This procedure better preserves fine details while removing the noise. This interactive Java tutorial illustrates the effects of a hybrid median filter on shot and speckle noise in grayscale or color images.

Interactive Java Tutorial
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The tutorial initializes with a randomly selected specimen appearing in the Specimen Image window. The Choose A Specimen pull-down menu provides a selection of specimen images, in addition to the initial randomly chosen one. The Noise Level slider controls the amount of noise that is added, while the Noise Type radio buttons select either Shot or Speckle noise. For color images, the noise can be added either to the individual color Channels or to the Monochrome brightness only. The Choose An Operation pull-down menu determines the size of the neighborhood used for the hybrid median filter. The result of the filtering operation appears in the Filtered Image window.

Contributing Authors

John C. Russ - Materials Science and Engineering Dept., North Carolina State University, Raleigh, North Carolina, 27695.

Matthew Parry-Hill, and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.


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