1、主要實現點到線段的最短距離計算。

2、具體實現程式碼如下：

double patch_line_point(double x , double y , double line_x1 , double line_y1 , double line_x2 , double line_y2)
{
   double x1 = line_x1, y1 = line_y1, x2 = line_x2, y2 = line_y2, x3 = x, y3 = y;   
    double px = x2 - x1;
    double py = y2 - y1;
    double som = px * px + py * py;
    double u =  ((x3 - x1) * px + (y3 - y1) * py) / som;
    if (u > 1) u = 1;
    if (u < 0) u = 0;
    double xx = x1 + u * px;
    double yy = y1 + u * py;
    double dx = xx - x3;
    double dy = yy - y3;     
    double dist = sqrt(dx*dx + dy*dy);
    return dist;
}