13_OpenCV计算矩阵中非0元素的个数

cv::countNonZero()函数返回矩阵中的非0像素数。使用时需要注意输入矩阵必须是单通道矩阵，否则会抛出异常。

函数原型：

int cv::countNonZero(
	cv::InputArray mtx
);

 

使用示例：

    try
	{
		std::string strFilename = "Test.bmp";
		cv::Mat img = cv::imread(strFilename);
		cv::Mat gray;
		cv::cvtColor(img, gray, cv::COLOR_RGB2GRAY);
		int nCount = cv::countNonZero(gray);
		std::cout << "count = " << nCount << std::endl;
	}
	catch(cv::Exception excep)
	{
		std::cout << std::endl;
		std::cout << "exp_msg = " << excep.msg.c_str() << std::endl;
		std::cout << "exp_code = " << excep.code << std::endl;
		std::cout << "exp_err = " << excep.err.c_str() << std::endl;
		std::cout << "exp_func = " << excep.func.c_str() << std::endl;
		std::cout << "exp_file = " << excep.file.c_str() << std::endl;
		std::cout << "exp_line = " << excep.line << std::endl;

	}
	catch (...){
		std::cout << "ERROR: 出现异常，请检查代码" << std::endl;
	}