[C++知识库] windows获取精确的毫秒

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[C++知识库]windows获取精确的毫秒

试验过三种方法：

1. 方法一：? opencv自带


	double ss, ee;
	ss = (double)cv::getCPUTickCount();
    //ss = (double)cv::getTickCount();   //same result
	Sleep(10);
	cv::waitKey(5);
	this_thread::sleep_for(std::chrono::milliseconds(10));
	ee = (double)cv::getCPUTickCount();
    //ee = (double)cv::getTickCount();
	cout << "GetTickCount:" << (ee - ss)/cv::getTickFrequency()*1000 << endl;
	printf("read time: %0.2f ms\n", (ee - ss) / cv::getTickFrequency() * 1000);

result:
GetTickCount:25.xxxx
read time: 25.xx ms

2. 方法二：需要windows.h，不准确

#include <windows.h>

	DWORD ss, ee;
	ss = GetTickCount();
	Sleep(10);
	//cv::waitKey(5);
	this_thread::sleep_for(std::chrono::milliseconds(10));
	ee = GetTickCount();
	cout << "GetTickCount:" << (ee - ss)  << endl;
	printf("read time: %ld ms\n", (ee - ss));

result:

GetTickCount: 16
read time: 16 ms
//不准确

3. 方法三，需要windows.h和 winmm.lib, winmm.dll, 比较准确

	DWORD start = timeGetTime();
	Sleep(10);
	cv::waitKey(10);
	this_thread::sleep_for(std::chrono::milliseconds(10));
	DWORD end = timeGetTime();
	cout << end - start << endl;
	printf("read time: %ld ms\n", (end - start));

result:
31
read time: 31 ms


	DWORD start = timeGetTime();
	Sleep(10);
	//cv::waitKey(10);   //attention!
	this_thread::sleep_for(std::chrono::milliseconds(10));
	DWORD end = timeGetTime();
	cout << end - start << endl;
	printf("read time: %ld ms\n", (end - start));

result:
20
read time: 20 ms

参考：error LNK2001:无法解析的外部符号_imp_timeGetTime@0_草上爬的博客-CSDN博客??????

参考链接：https://msdn.microsoft.com/en-us/library/dd757629