HP Labs Technical Reports

Shape Preserving Local Histogram Modification

Caselles, Vicent; Lisani, Jose-Luis; Morel, Jean-Michel; Sapiro, Guillermo

HPL-97-58

Keyword(s):histogram equalization; local operations; mathematical morphology; level-sets; connected components

Abstract: A novel approach for shape preserving contrast enhancement is presented in this paper. Contrast enhancement is achieved by means of a local histogram equalization algorithm which preserves the level-sets of the image. This basic property is violated by common local schemes, thereby introducing spurious objects and modifying the image information. The scheme is based on equalizing the histogram in all the connected components of the image, which are defined based both on the grey-values and spatial relations between pixels in the image, and following mathematical morphology, constitute the basic objects in the scene. We give examples for both grey-value and color images.

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