Abstract

We propose a locally regularized snake based on smoothing-spline filtering. The proposed algorithm associates a regularization process with a force equilibrium scheme leading the snake's deformation. In this algorithm, the regularization is implemented with a smoothing of the deformation forces. The regularization level is controlled through a unique parameter that can vary along the contour. It provides a locally regularized smoothing B-snake that offers a powerful framework to introduce prior knowledge. We illustrate the snake behavior on synthetic and real images, with global and local regularization.

Highlights

  • Active contour models are well adapted for edge detection and segmentation

  • Xu and Prince [4] defined another external force called gradient vector flow (GVF) that brings a better control on the deformation directions: they proposed to diffuse the gradient over the image according to optical flow theory

  • Where A is a pentadiagonal banded matrix built from α(k) and β(k) function values, where vectors x and y contain the point coordinates of the discrete version g(k) of the curve g(s), and where vectors fx and fy constitute the external forces computed at the kth point of the snake as follows: f (k) =

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Summary

INTRODUCTION

Active contour models (or snakes) are well adapted for edge detection and segmentation. Xu and Prince [4] defined another external force called gradient vector flow (GVF) that brings a better control on the deformation directions: they proposed to diffuse the gradient over the image according to optical flow theory Beside these works, the multiresolution frameworks were integrated within the active contours. Precioso et al [8] proposed a region-based active contour that achieves real-time computation adapted to video segmentation. They extended their model by applying a smoothing B-spline filter [9, 10] on the contour.

SNAKES AND B-SPLINES
Snakes: active contour model
B-splines for B-snakes
Smoothing B-splines
Smoothing B-splines and snakes
LOCALLY REGULARIZED SMOOTHING B-SNAKE
Deformation forces computation
Global regularization process through deformation forces smoothing
Local regularization process
Resampling
Open and closed contours
RESULTS
Global regularization
Local regularization
CONCLUSIONS
Smoothing B-spline filter pole analysis
Smoothing B-spline filter implementation
Full Text
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