1. An apparatus for segmenting objects in an image, comprising: input means for receiving an input image containing at least one object ( 10 , 20 ), said image comprising pixel data sets of at least two dimensions; means for generating an edge-detected image from said input image; means for selecting markers in said edge-detected image, and for assigning respective fixed electrical potential values to said markers; computation means for generating an electrical potential map as a solution to an electrostatic flow problem in a resistive medium having a resistivity dependent on the edge-detected image, with the markers defining electrodes at the respective fixed potential values; and means for estimating object contours from said potential map.