Languages: C/C++
Categories: 图形图像处理
gistfile1.txt
#include <iostream>
#include <g2o/core/base_vertex.h>
#include <g2o/core/base_unary_edge.h>
#include <g2o/core/block_solver.h>
#include <g2o/core/optimization_algorithm_levenberg.h>
#include <g2o/core/optimization_algorithm_gauss_newton.h>
#include <g2o/core/optimization_algorithm_dogleg.h>
#include <g2o/solvers/dense/linear_solver_dense.h>
#include <Eigen/Core>
#include <opencv2/core/core.hpp>
#include <cmath>
#include <chrono>
using namespace std;

// 曲线模型的顶点，模板参数：优化变量维度和数据类型
class CurveFittingVertex : public g2o::BaseVertex<3, Eigen::Vector3d>
{
public:
EIGEN_MAKE_ALIGNED_OPERATOR_NEW
virtual void setToOriginImpl() // 重置
{
_estimate << 0, 0, 0;
}

virtual void oplusImpl(const double* update) // 更新
{
_estimate += Eigen::Vector3d(update);
}
// 存盘和读盘：留空
virtual bool read(istream& in) { return false; }
virtual bool write(ostream& out) const { return false; }
};

// 误差模型 模板参数：观测值维度，类型，连接顶点类型
class CurveFittingEdge : public g2o::BaseUnaryEdge<1, double, CurveFittingVertex>
{
public:
EIGEN_MAKE_ALIGNED_OPERATOR_NEW
CurveFittingEdge(double x) : BaseUnaryEdge(), _x(x) {}
// 计算曲线模型误差
void computeError()
{
const CurveFittingVertex* v = static_cast<const CurveFittingVertex*> (_vertices[0]);
const Eigen::Vector3d abc = v->estimate();
_error(0, 0) = _measurement - std::exp(abc(0, 0)*_x*_x + abc(1, 0)*_x + abc(2, 0));
}
virtual bool read(istream& in) { return false; }
virtual bool write(ostream& out) const { return false; }
public:
double _x;  // x 值， y 值为 _measurement
};

int main(int argc, char** argv)
{
double a = 1.0, b = 2.0, c = 1.0;         // 真实参数值
int N = 100;                          // 数据点
double w_sigma = 1.0;                 // 噪声Sigma值
cv::RNG rng;                        // OpenCV随机数产生器
double abc[3] = { 0,0,0 };            // abc参数的估计值

vector<double> x_data, y_data;      // 数据

cout << "generating data: " << endl;
for (int i = 0; i < N; i++)
{
double x = i / 100.0;
x_data.push_back(x);
y_data.push_back(
exp(a*x*x + b * x + c) + rng.gaussian(w_sigma)
);
cout << x_data[i] << " " << y_data[i] << endl;
}

// 构建图优化，先设定g2o
typedef g2o::BlockSolver< g2o::BlockSolverTraits<3, 1> > Block;// 每个误差项优化变量维度为3，误差值维度为1
Block::LinearSolverType* linearSolver = new g2o::LinearSolverDense<Block::PoseMatrixType>();// 线性方程求解器
Block* solver_ptr = new Block(std::unique_ptr<Block::LinearSolverType>(linearSolver));// 矩阵块求解器
g2o::OptimizationAlgorithmLevenberg* solver = new g2o::OptimizationAlgorithmLevenberg(std::unique_ptr<Block>(solver_ptr));
// 梯度下降方法，从GN, LM, DogLeg 中选
// g2o::OptimizationAlgorithmGaussNewton* solver = new g2o::OptimizationAlgorithmGaussNewton( solver_ptr );
// g2o::OptimizationAlgorithmDogleg* solver = new g2o::OptimizationAlgorithmDogleg( solver_ptr );
g2o::SparseOptimizer optimizer;// 图模型
optimizer.setAlgorithm(solver);// 设置求解器
optimizer.setVerbose(true);// 打开调试输出

// 往图中增加顶点
CurveFittingVertex* v = new CurveFittingVertex();
v->setEstimate(Eigen::Vector3d(0, 0, 0));
v->setId(0);

// 往图中增加边
for (int i = 0; i < N; i++)
{
CurveFittingEdge* edge = new CurveFittingEdge(x_data[i]);
edge->setId(i);
edge->setVertex(0, v);                // 设置连接的顶点
edge->setMeasurement(y_data[i]);      // 观测数值
edge->setInformation(Eigen::Matrix<double, 1, 1>::Identity() * 1 / (w_sigma*w_sigma)); // 信息矩阵：协方差矩阵之逆
}

// 执行优化
cout << "start optimization" << endl;
optimizer.initializeOptimization();
optimizer.optimize(100);
chrono::duration<double> time_used = chrono::duration_cast<chrono::duration<double>>(t2 - t1);
cout << "solve time cost = " << time_used.count() << " seconds. " << endl;

// 输出优化值
Eigen::Vector3d abc_estimate = v->estimate();
cout << "estimated model: " << abc_estimate.transpose() << endl;
system("pause");
return 0;
}