高翔slam14讲中ch7代码中的一些修改

章节：高翔slam14讲中ch7
使用系统：Ubuntu18.04，opencv4.1.0

问题1: opencv版本问题，编译出错。

解决方法：在CMakeLists.txt中将find_package( OpenCV3.0 REQUIRED )中的3.0改为对应版本或者直接去掉3.0

问题2: …/ch7/pose_estimation_3d2d.cpp:43:35: error: ‘CV_LOAD_IMAGE_COLOR’ was not declared in this scope

解决方法：将所有.cpp文件中出现的CV_LOAD_IMAGE_xxxx用对应的flag值代替，具体代替值如下

   CV_LOAD_IMAGE_UNCHANGED  = -1 ( = cv::IMREAD_UNCHANGED),
   CV_LOAD_IMAGE_GRAYSCALE 	= 0  ( = cv::IMREAD_GRAYSCALE),
   CV_LOAD_IMAGE_COLOR     	= 1  ( = cv::IMREAD_COLOR),
   CV_LOAD_IMAGE_ANYDEPTH   = 2  ( = cv::IMREAD_ANYDEPTH),

注：pose_estimation_2d2d.cpp；pose_estimation_3d3d.cpp中也同样修改。

问题3: 编译2d2d.cpp时， 报错：CV_FM_8POINT was not declared in this scope

解决方法：将CV_去掉再编译就可以通过。（此处Learning OpenCV3中有关于findFundamentalMat()函数中method选择的说明）

问题4: 这个是g2o库更新导致用法改变

运行pose_estimation_3d2d.cpp (3d3d同样如下)时错误如下：

error: no matching function for call to ‘g2o::BlockSolver<g2o::BlockSolverTraits<6, 1> >::BlockSolver(g2o::BlockSolver<g2o::BlockSolverTraits<6, 1> >::LinearSolverType*&)’DirectBlock* solver_ptr = new DirectBlock ( linearSolver );

error: no matching function for call to ‘g2o::OptimizationAlgorithmLevenberg::OptimizationAlgorithmLevenberg(Block*&)’

原代码：

Block* solver_ptr = new Block( linearSolver );      // 矩阵块求解器

g2o::OptimizationAlgorithmLevenberg* solver = new g2o::OptimizationAlgorithmLevenberg( solver_ptr );

修改如下：

Block* solver_ptr = new Block( unique_ptr<Block::LinearSolverType>(linearSolver) );      // 矩阵块求解器

g2o::OptimizationAlgorithmLevenberg* solver = new g2o::OptimizationAlgorithmLevenberg( unique_ptr<Block>(solver_ptr) );

主要参考：

1. https://blog.youkuaiyun.com/weixin_43988000/article/details/84856917
2. https://blog.youkuaiyun.com/unlimitedai/article/details/86546368
3. https://blog.youkuaiyun.com/robinhjwy/article/details/78084210
4. Kaehler A, et al. Learning OpenCV 3