Hi, I've wrote a program that calculates the normalized elliptic Fourier coefficients of a closed polyline. I used it for a set of polylines and found that some of the polylines differ in orientation (one part oriented CW, other CCW).
I found NEFD of all polylines and kept them. After that I want to make all polylines oriented CCW, and calculate new set of NEFD. Will the values of NEFD of the polylines, that are previously oriented CW, changed or not?
I've made a test and found that the orientation of the source outline influences on the signs of NEFD coefficients.
On the attached images there is the same outline with two different orientation. Yellow segments indicate orientation. Bellow are NEFD corresponded to each case (starting from the 2nd harmonic). It is apparent that bn and dn change their sign.
Does obtained results mean that all compared outlines should be equally oriented?
Yes, the signs of some elliptic Fourier coefficients will change after the polyline change its direction: cv ccv
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