CH8 编译运行时候出错，对应书中210页实践LK光流。详细见下

[SangTaoQAQ]

（1）使用pkg-config --modversion opencv 查看opencv版本：
3.1.0
（2）cmake..后正常
（3）make后出现下述问题：猜想有可能是OpenCV版本问题，望高博解答如何修改该函数的初始化。
/home/sangtao/Desktop/ch8/optical_flow.cpp: In function ‘void OpticalFlowSingleLevel(const cv::Mat&, const cv::Mat&, const std::vectorcv::KeyPoint&, std::vectorcv::KeyPoint&, std::vector&, bool, bool)’:
/home/sangtao/Desktop/ch8/optical_flow.cpp:188:28: error: invalid initialization of reference of type ‘const cv::ParallelLoopBody&’ from expression of type ‘std::_Bind_helper<false, void (OpticalFlowTracker::)(const cv::Range&), OpticalFlowTracker, const std::_Placeholder<1>&>::type {aka std::_Bind<void (OpticalFlowTracker::(OpticalFlowTracker, std::Placeholder<1>))(const cv::Range&)>}’
std::bind(&OpticalFlowTracker::calculateOpticalFlow, &tracker, placeholders::1));
~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/local/include/opencv2/core.hpp:3165:0,
from /usr/local/include/opencv2/opencv.hpp:46,
from /home/sangtao/Desktop/ch8/optical_flow.cpp:5:
/usr/local/include/opencv2/core/utility.hpp:356:17: note: in passing argument 2 of ‘void cv::parallel_for(const cv::Range&, const cv::ParallelLoopBody&, double)’
CV_EXPORTS void parallel_for(const Range& range, const ParallelLoopBody& body, double nstripes=-1.);
^~~~~~~~~~~~~
CMakeFiles/optical_flow.dir/build.make:62: recipe for target 'CMakeFiles/optical_flow.dir/optical_flow.cpp.o' failed
make[2]: *** [CMakeFiles/optical_flow.dir/optical_flow.cpp.o] Error 1
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/optical_flow.dir/all' failed
make[1]: *** [CMakeFiles/optical_flow.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2

[gaoxiang12]

parallel_for需要opencv 4以上，写书的时候忘提这件事了，后来在勘误里加上了。
可以自己安装opencv 4，或者自行改写下parallel_for函数。

[SangTaoQAQ]

谢谢～