Abstract
We can apply the technique of the digital curve in 2-dimensional space to the analyzing of object-shape in 3-dimensional space by using the contour lines. Those contour lines are 2-dimensional digital curves. The shape of digital curve on the plane is analyzed by using correlation of the complex valued functions. The complex valued function represents a curved line on the complex plane which is the same as the digital curve in the 2-dimensional space. The similarity defined by cross correlation of two digital curves in the 2-dimensional space is invariant to size and rotation.
