fix rainyl/opencv_dart#314

Author: rainyl

dartcv/videoio/videoio.cpp

@@ -234,3 +234,11 @@ int cv_VideoWriter_fourcc(char c1, char c2, char c3, char c4) {
 char* cv_VideoWriter_getBackendName(VideoWriter self) {
     return strdup(self.ptr->getBackendName().c_str());
 }
+
+double cv_VideoWriter_get(VideoWriter self, int propId) {
+    return self.ptr->get(propId);
+}
+
+void cv_VideoWriter_set(VideoWriter self, int propId, double val) {
+    self.ptr->set(propId, val);
+}

dartcv/videoio/videoio.h

@@ -108,6 +108,8 @@ CvStatus* cv_VideoWriter_write(VideoWriter self, Mat img, CvCallback_0 callback)
 CvStatus* cv_VideoWriter_release(VideoWriter self);
 int cv_VideoWriter_fourcc(char c1, char c2, char c3, char c4);
 char* cv_VideoWriter_getBackendName(VideoWriter self);
+double cv_VideoWriter_get(VideoWriter self, int propId);
+void cv_VideoWriter_set(VideoWriter self, int propId, double val);
 
 #ifdef __cplusplus
 }