imshow function
displays an image Mat in the specified window. This function should be followed by the WaitKey function which displays the image for specified milliseconds. Otherwise, it won't display the image.
For further details, please see: http://docs.opencv.org/master/d7/dfc/group__highgui.html#ga453d42fe4cb60e5723281a89973ee563
Implementation
void imshow(String winName, Mat img) {
final cWinName = winName.toNativeUtf8().cast<ffi.Char>();
cvRun(() => chighgui.cv_imshow(cWinName, img.ref));
calloc.free(cWinName);
}