Suppose DoIt is a function that takes a cv::Mat as argument and suppose AMat is a cv::Mat. In openCV 2.1.0 [code lang=”cpp”] //You cannot do this DoIt(AMat*50.0); //Or this DoIt((cv::Mat)AMat*50.0); //You have to do either this: cv:Mat temp = AMat*50; DoIt(temp); //Or this DoIt((cv::Mat)(AMat*50.0)); //Or this DoIt(cv::Mat(AMat*50.0)); [/code]