为什么matlab的regionprops3 求出的ConvexVolume比Image要小，维度大小不对，凸包没有完全包住区域？

status=regionprops3(l,'Volume','EquivDiameter','SurfaceArea','BoundingBox','PrincipalAxisLength','Image','ConvexVolume','ConvexImage','ConvexHull','Solidity');
image=status.Image{index};
conveximage=status.ConvexImage{index};

为什么conveximage没有完全包住image？

https://blog.csdn.net/langb2014/article/details/49886787