opencv小技巧一

比直接使用ptr指针要快

	clock_t start, finish;
	start = clock();
	cv::Mat img = cv::Mat::zeros(3000, 3200, CV_32FC3);

	for (int i = 0; i < 3000; i++)
	{
		float* img_ptr = (float*)img.data + i * img.step1();
		for (int j = 0; j < 3200; j++)
		{
			//img.ptr<float>(i, j)[0] = 1;
			//img.ptr<float>(i, j)[1] = 2;
			//img.ptr<float>(i, j)[2] = 3;
			img_ptr[0] = 1;
			img_ptr[1] = 2;
			img_ptr[2] = 3;
			img_ptr+=3;
		}
	}
	finish = clock();
	qDebug() << start << finish << (double)(finish - start) / 1000;