(a)

(b)

(c)

(d)

(e)

Figure 4: Snake deformation with repulsive force. (a) A synthetic image of multiple objects in black and initialization in red color. (b) Its associated gradient flow. (c) An initial curve at a distance from the legitimate object will deform to a wrong object. (d) However, adding external repulsive force in image (a) will revise the gradient flow and guarantee the initial curve deform to the correct object (e).