OpenCV 利用getTickCount()与getTickFrequency()计算执行时间

double t1 = (double)getTickCount();
.
.
.
double t2 = (double)getTickCount();
cout<<"time:"<<(t2-t1)*1000/getTickFrequency()<<endl;

//! Returns the number of ticks.

/*!
  The function returns the number of ticks since the certain event (e.g. when the machine was turned on).
  It can be used to initialize cv::RNG or to measure a function execution time by reading the tick count
  before and after the function call. The granularity of ticks depends on the hardware and OS used. Use
  cv::getTickFrequency() to convert ticks to seconds.
*/
CV_EXPORTS_W int64 getTickCount();

/*!
  Returns the number of ticks per seconds.

  The function returns the number of ticks (as returned by cv::getTickCount()) per second.
  The following code computes the execution time in milliseconds:

  \code
  double exec_time = (double)getTickCount();
  // do something ...
  exec_time = ((double)getTickCount() - exec_time)*1000./getTickFrequency();
  \endcode
*/
CV_EXPORTS_W double getTickFrequency();

/*!
  Returns the number of CPU ticks.

  On platforms where the feature is available, the function returns the number of CPU ticks
  since the certain event (normally, the system power-on moment). Using this function
  one can accurately measure the execution time of very small code fragments,
  for which cv::getTickCount() granularity is not enough.
*/
CV_EXPORTS_W int64 getCPUTickCount();