feature method
Extracts face feature from aligned image.
alignedImg input aligned image
clone the default implementation of opencv won't clone the returned Mat
set clone to true will return a clone of returned Mat
Implementation
Mat feature(Mat alignedImg, {bool clone = false}) {
final p = calloc<cvg.Mat>();
cvRun(() => cffi.FaceRecognizerSF_Feature(ref, alignedImg.ref, clone, p));
return Mat.fromPointer(p);
}