We present an edge-based active contour model, which is an extension of our MAC model to deal with the initialization dependency problem that commonly appears in edge-based approaches. Its dynamic force field, unique bidirectionality, and constrained diffusion-based level set evolution provide great freedom in contour initialization and show significant improvements in initialization independency compared to other edge-based techniques. It can handle more sophisticated topological changes than splitting and merging. It provides new potentials for edge-based active contour methods, particularly when detecting and localizing objects with unknown location, geometry, and topology.

Example results - recovering objects with internal holes and inhomogeneous intensity

   Initial Contour  Evolving ContoursStabilized Contour
Proposed method

Example results - bidirectionality (initialization on both sides of an object boundary)

Proposed method

Example results - initialization inside an object boundary

Basic MAC
Proposed method (lambda=1)
Proposed method (lambda=2)

Example results - recovering weak/broken edges using proposed method

Weak/Broken EdgesInitial ShapeEvolving ShapesStabilized Shape

Example results - initialization flexibility using proposed method

Random initialization
Cross-boundary initialization
Single inside initialization
No initialization (lambda=1)
No initialization (lambda=2)

Example results - recovering noisy complex shape using proposed method

Complex shape with 50% Gaussian noise and its recovery result using force diffusion
Weak/broken edges after heavy edge thresholding and its recovery result without force diffusion

Example results - segmentation of a bone CT image

Proposed method (no initialization)
Proposed method (cross-boundary initialization)
Proposed method (horizontal-line initialization)

Example results - segmentation of color images using proposed method

 Skin lesion image with weak edges & noiseHorse image with large color variations & weak edgesBlood vessel image with complex shape & topology, varying intensity, & weak edgesFish swarm image with inhomogeneous color distribution, complex topology, & weak edges
No initialization
Horizontal-line initialization