1. A method for segmenting an input image of an object, comprising the steps of: specifying, by a user, a set of labels for pixels in the input image to produce labeled pixels and remaining unlabeled pixel, wherein the set of labels identifies object pixels and background pixels; propagating the labels in the input image based on differences of intensities of neighboring pixels to produce an initial level set, wherein the initial level set is represented probabilistically; and evolving the initial level set using a cost function to produce a segment in an output image, and wherein the steps are performed in a processor.