threshold function
Implementation
VARP threshold(VARP src, double thresh, double maxval, int type) {
MnnAssert(
type != THRESH_MASK && type != THRESH_OTSU && type != THRESH_TRIANGLE,
"Don't support THRESH_MASK/THRESH_OTSU/THRESH_TRIANGLE.",
);
final pOut = c.mnn_cv_threshold(src.ptr, thresh, maxval, type);
final rval = VARP.fromPointer(pOut);
return rval;
}