This paper proposes a motion based region growing segmentation scheme for the object based video coding which segments an image into homogeneous regions characterized by a coherent motion.
But if the region has a strange shape or if a density is not homogeneous, if parts of it are heavier then you will get whatever the weighted average will be.
但如果这区域的形状很特殊，或者密度不均匀，也就是某些部分比较重，那就需要求加权平均值。
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At the low supersaturation region, experimental results deviate from the theoretical characterization of homogeneous nucleation.