ch8 opencv 3.2.0 parallel_for_ doesn't support std::bind function

[rancheng]

compiling error looks like this:

/home/ran/Documents/Playground/slambook2/ch8/direct_method.cpp: In function ‘void DirectPoseEstimationSingleLayer(const cv::Mat&, const cv::Mat&, const VecVector2d&, std::vector<double, std::allocator<double> >, Sophus::SE3d&)’:
/home/ran/Documents/Playground/slambook2/ch8/direct_method.cpp:172:36: error: invalid initialization of reference of type ‘const cv::ParallelLoopBody&’ from expression of type ‘std::_Bind_helper<false, void (JacobianAccumulator::*)(const cv::Range&), JacobianAccumulator*, const std::_Placeholder<1>&>::type {aka std::_Bind<void (JacobianAccumulator::*(JacobianAccumulator*, std::_Placeholder<1>))(const cv::Range&)>}’
                           std::bind(&JacobianAccumulator::accumulate_jacobian, &jaco_accu, std::placeholders::_1));
                           ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/opencv2/core.hpp:3216:0,
                 from /usr/include/opencv2/opencv.hpp:52,
                 from /home/ran/Documents/Playground/slambook2/ch8/direct_method.cpp:1:
/usr/include/opencv2/core/utility.hpp:478:17: 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.);

go to opencv utility.hpp and found that the definition of parallel_for_ is like this:

CV_EXPORTS void parallel_for_(const Range& range, const ParallelLoopBody& body, double nstripes=-1.);

so, we have to modify the class JacobianAccumulator, extend it from cv::ParallelLoopBody and change accumulate_jacobian function to it's operator override: virtual void operator()(const cv::Range& range) const

I have updated the source in my folk, you can download from here

[rancheng]

and if you are using CLion, please note that the source file's data reference was in current directory like this:

string left_file = "./left.png";
string disparity_file = "./disparity.png";

this is dirty, please make sure you parameterize your file path, since the executive file will be compiled in cmake-build-debug directory

[rancheng]

The experiments are conducted in 4 scales:

[gaoxiang12]

Thanks for commit. Looks like since opencv 4 the parallel_for_ has an overloaded form that supports std::function as the second input param: here.
For the second comment, I agree with that using params or gflags would be more elegant, but it's ok to use simple global variables in small demos like this one.

[rancheng]

Thanks for your kind reply, I really appreciate your contributions!
Just ignore my jibber jabber on the second comment, yes, I compiled opencv4 and tested your code last night, that passed.
I'll close this issue, since the problem was solved, again, thanks for your great work on SLAMBOOK!