Meaningful Object Segmentation From SAR Images via a Multiscale Nonlocal Active Contour Model

The segmentation of synthetic aperture radar (SAR) images is a long-standing yet challenging task, not only because of the presence of speckle but also due to the variations of surface backscattering properties in the images. Tremendous investigations have been made to suppress the speckle effects for the segmentation of SAR images, whereas few works are devoted to dealing with the variations of backscattering intensities in the images. To overcome the two difficulties, this paper presents a novel SAR image segmentation method by exploiting a multiscale active contour model based on the nonlocal processing principle. More precisely, we first formulize the SAR segmentation problem with an active contour model by integrating the nonlocal interactions between pairs of patches inside and outside the segmented regions. Second, a multiscale strategy is proposed to speed up the nonlocal active contour segmentation procedure and to avoid falling into a local minimum for achieving more accurate segmentation results. Experimental results on simulated and real SAR images demonstrate the efficiency and feasibility of the proposed method: It can not only achieve precise segmentations for images with heavy speckle and nonlocal intensity variations but also be used for SAR images from different types of sensors.