更简单的方法。取3个顶点a，b和c以及计算：顶点之间的角度/倾斜度。

std::vector<VERTEX> path;
//fill path
std::vector<int> removeList;
//Assure that the value is in the same unit as the return of angleOf function.
double maxTinyVariation = SOMETHING;

for (int i = 0; i < quantity-2; ++i) {
  double a = path[i], b = path[i + 1] , c = path[i + 2]
  double abAngle = angleOf(a, b);
  double bcAngle = angleOf(b, c);

  if (abs(ab - bc) <= maxTinyVariation) {
     //a, b and c are colinear
     //remove b later
     removeList.push_back(i+1);
  }
}
//Remove vertecies from path using removeList.