Isophote-based interpolation

Abstract
Standard methods for image interpolation are based on smoothly fitting the image intensity surface. Recent edge- directed interpolation methods add limited geometric infor- mation (edge maps) to build more accurate and visually ap- pealing interpolations at key contours in the image. This paper presents a method for geometry-based interpolation that smoothly fits the isophote (intensity level curve) con- tours at all points in the image rather than just at selected contours. By using level set methods for curve evolution, no explicit extraction or representation of these contours is re- quired (unlike earlier edge-directed methods). The method uses existing interpolation techniques as an initial approx- imation and then iteratively reconstructs the isophotes us- ing constrained smoothing. Results show that the technique produces results that are more visually realistic than stan- dard function-fitting methods.

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