An active contour model for colour region extraction in natural scenes

Abstract

The performance of active contours depends on the proper selection of model parameters and initial contours. In natural scenes, active contours often fail to converge to the desired solution because of unconstrained environmental conditions and complex object shapes. This paper presents a new active contour model for contour extraction in natural scenes. The proposed model is able to extract fairly complex object boundaries without the need to retune model parameters and image thresholds. Specific object features and a priori knowledge of the objects’ topology are not required. Four schemes are proposed. An attraction/repulsion scheme deforms the active contour towards the object’s boundary and makes it less sensitive to initialisation. A positive/negative contour scheme allows closed active contours to change their connectivity by splitting, thereby undergoing topological changes during the deformation process. An image scale scheme and an automatic thresholding scheme dynamically adapt the active contour in natural scenes. The proposed model is found to outperform the original snake model and degrade gracefully in the presence of image blur and Gaussian noise. Object boundaries are reliably extracted from a range of natural images.