grab method
Grabs the next frame from video file or capturing device.
https://docs.opencv.org/4.x/d8/dfe/classcv_1_1VideoCapture.html#aa6480e6972ef4c00d74814ec841a2939
Implementation
void grab({int skip = 0}) {
cvRun(() => cffi.VideoCapture_Grab(ref, skip));
}