捕捉指向一条线 [英] Snap point to a line

问题描述

我有两个GPS坐标连接在一起形成一条线。我还有一个GPS点，它靠近线路，但从未完全在线路上。我的问题是，如何找到沿给定点的最近点？

I have two GPS coordinates which link together to make a line. I also have a GPS point which is near to, but never exactly on, the line. My question is, how do I find the nearest point along the line to the given point?

推荐答案

Game Dev有一个答案，它是在C ++中但它应该很容易移植。哪个 CarlG 完成（希望他不介意我重新发布）：

Game Dev has an answer to this, it is in C++ but it should be easy to port over. Which CarlG has kindly done (hopefully he does not mind me reposting):

public static Point2D nearestPointOnLine(double ax, double ay, double bx, double by, double px, double py,
        boolean clampToSegment, Point2D dest) {
    // Thanks StackOverflow!
    // https://stackoverflow.com/questions/1459368/snap-point-to-a-line-java
    if (dest == null) {
        dest = new Point2D.Double();
    }

    double apx = px - ax;
    double apy = py - ay;
    double abx = bx - ax;
    double aby = by - ay;

    double ab2 = abx * abx + aby * aby;
    double ap_ab = apx * abx + apy * aby;
    double t = ap_ab / ab2;
    if (clampToSegment) {
        if (t < 0) {
            t = 0;
        } else if (t > 1) {
            t = 1;
        }
    }
    dest.setLocation(ax + abx * t, ay + aby * t);
    return dest;
}

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