arcLengthAsync function
ArcLength calculates a contour perimeter or a curve length.
For further details, please see:
https:///docs.opencv.org/master/d3/dc0/group__imgproc__shape.html#ga8d26483c636be6b35c3ec6335798a47c
Implementation
Future<double> arcLengthAsync(VecPoint curve, bool closed) async =>
cvRunAsync((callback) => cimgproc.ArcLength_Async(curve.ref, closed, callback), doubleCompleter);