Multi-scale midline extraction using creaseness

Applying the divergence operator on the gradient vector field is known as a robust method for computing the local creaseness, defined as the level set extrinsic curvature. Based on this measure, we present a multi-scale method to extract continuous midlines of elongated objects of various widths simultaneously. The scale-space is not built on the input image, but on the gradient vector field. During the iterative construction of the scale-space the current solution keeps thin objects even when they are located near more dominant structures. The representation of the midlines is realised as curves in the image plane, consisting of equidistant sample points. At each sample point the tangential direction of the curve is computed directly with the smoothed gradient vector field.