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Local Contrast Enhancement

This interactive Java tutorial illustrates the process of local equalization. Local equalization functions just like the histogram equalization procedure, except that it takes place within a moving circular neighborhood and assigns a new value only to the central pixel. The result makes a pixel that is slightly brighter than its surroundings brighter still, and vice-versa, enhancing local contrast. The result is usually added back in some proportion to the original image to produce a more visually pleasing result, as shown in the tutorial.

Interactive Java Tutorial
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The tutorial initializes with a randomly selected specimen imaged in the microscope 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 Neighborhood Radius slider adjusts the size of the region around each pixel in which the histogram is summed and local equalization is performed, while the Blend Amount slider adjusts the fraction of the resulting enhanced contrast image that is added to the original to produce the resulting image shown in the Contrast-Expanded 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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