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# Revision history [back]

First of all, don't mix C with C++. Include (and of course link against it) <opencv2/core/core.hpp> (guess you do that already since the compiler suggest already using cv::-prefix) and use cv::putText(). putText() is declared in the namespace cv, so either write "using namespace cv" above your class, or write the namespaces like cv:: and std:: explicitly to each command (I prefer the latter one so I always know where each command stems from).