contourAreaAsync function
ContourArea calculates a contour area.
For further details, please see: https:///docs.opencv.org/3.3.0/d3/dc0/group__imgproc__shape.html#ga2c759ed9f497d4a618048a2f56dc97f1
Implementation
Future<double> contourAreaAsync(VecPoint contour) async =>
cvRunAsync((callback) => cimgproc.ContourArea_Async(contour.ref, callback), doubleCompleter);