arcLength 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
double arcLength(VecPoint curve, bool closed) {
final p = calloc<ffi.Double>();
cvRun(() => cimgproc.cv_arcLength(curve.ref, closed, p, ffi.nullptr));
final rval = p.value;
calloc.free(p);
return rval;
}