int pnpoly(int nvert, float *vertx, float *verty, float testx, float testy)
{
  int i, j, c = 0;
  for (i = 0, j = nvert-1; i < nvert; j = i++) 
  {
    if ( ((verty[i]>testy) != (verty[j]>testy)) &&
     (testx < (vertx[j]-vertx[i]) * (testy-verty[i]) / (verty[j]-verty[i]) + vertx[i]) )
       c = !c;
  }
  return c;
}

clc;
close;


%% poly points 设定的多边形顶点
% poly_point_x = [1 1 10 14 7];
% poly_point_y = [0 12 13 2 4];
poly_point_x = [0 0 9];
poly_point_y = [1 12 1];

%% actual points 待测试顶点
test_x = 6;
test_y = 0;

c=0;
m=0;
%% return test point in poly or not 判断测试点是否在多边形内
hold on;
plot(poly_point_x,poly_point_y,'*')
plot(test_x,test_y,'.')
n = 4;%n=顶点数+1
for i = 1: n-1
    if i == 1
        j = n - 1;
    else
        j = i - 1;
    end
    y = ((poly_point_y(:,i) > test_y) ~= (poly_point_y(:,j) > test_y));
    x = ((poly_point_x(:,j) - poly_point_x(:,i))*(test_y - poly_point_y(:,i))/(poly_point_y(:,j) - poly_point_y(:,i)) + poly_point_x(:,i))>test_x;
    
    if y&&x
        c = ~c;
    end
end
c