Object Shape Postprocessing

Abstract

The object masks obtained from the spatial-temporal segmentation procedure described in Section III sometimes have irregularity in extracted boundaries such as small gulfs and isthmi due to temporal and spatial signal fluctuations. These irregular features lead to a visually annoying appearance and also increase the cost of shape coding. We adopt two boundary postprocessing techniques to handle this problem. First, we use the morphological open and close operators to remove unwanted gulfs and isthmi for object boundary smoothing, where a circular structuring element with a radius of 2 pixels is used in these morphological filters. Second, we consider the confidence level of extracted object boundaries by using boundaries of variable width, where a higher (or lower) confidence level leads to a narrower (or wider) boundary width. Consequently, we are able to adjust the shape of the segmentation mask in low confidence regions more freely to increase the shape coding efficiency.