extractChannelAsync function
ExtractChannel extracts a single channel from src (coi is 0-based index).
For further details, please see: https://docs.opencv.org/master/d2/de8/group__core__array.html#gacc6158574aa1f0281878c955bcf35642
Implementation
Future<Mat> extractChannelAsync(InputArray src, int coi) async =>
cvRunAsync((callback) => cffi.core_ExtractChannel_Async(src.ref, coi, callback), matCompleter);