package com.whyc.util;
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import com.whyc.dto.Point;
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public class PointUtil {
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public static void main(String[] args) {
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/*double a1 = 1, b1 = 2;
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double a2 = 3, b2 = 4;
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double x0 = 9, y0 = 9;
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Point p1 = new Point(1, 2);
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Point p2 = new Point(3, 4);
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Point p0 = new Point(9, 9);
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Point p = findIntersection2(p1, p2, p0);
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System.out.println(p);
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double[] p3 = findIntersection(a1, b1, a2, b2, x0, y0);
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System.out.println("Intersection Point P3: (" + p3[0] + ", " + p3[1] + ")");
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String position = determinePosition(a1, b1, a2, b2, x0, y0);
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System.out.println("Point P is on the " + position + " of the line P1P2.");*/
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double x0 = 5, y0 = 5;
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double x1 = 0, y1 = 0;
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double x2 = 2, y2 = 2;
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double proportion = calculateProportion(x0, y0, x1, y1, x2, y2);
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if (proportion >= 0) {
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System.out.println("垂足到mstPointStart的距离占整条线段长度的比例是: " + proportion);
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} else {
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System.out.println("垂足不在线段上");
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}
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}
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public static double[] findIntersection(double a1, double b1, double a2, double b2, double x0, double y0) {
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// 检查 p1p2 是否为垂直线
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if (a2 == a1) {
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return new double[]{a1, y0};
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}
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// 检查 p1p2 是否为水平线
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if (b2 == b1) {
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return new double[]{x0, b1};
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}
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double m = (b2 - b1) / (a2 - a1);
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double mPerpendicular = (a1 - a2) / (b2 - b1);
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double x = ((b1 - m * a1) - (y0 - mPerpendicular * x0)) / (mPerpendicular - m);
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double y = m * x + (b1 - m * a1);
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return new double[]{x, y};
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}
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public static Point findIntersection2(Point p1, Point p2, Point p0) {
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// 检查 p1p2 是否为垂直线
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int a1 = p1.getX();
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int b1 = p1.getY();
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int a2 = p2.getX();
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int b2 = p2.getY();
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int x0 = p0.getX();
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int y0 = p0.getY();
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if (a2 == a1) {
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return new Point(a1, y0);
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}
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// 检查 p1p2 是否为水平线
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if (b2 == b1) {
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return new Point(x0, b1);
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}
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double m = (b2 - b1) / (a2 - a1);
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double mPerpendicular = (a1 - a2) / (b2 - b1);
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double x = ((b1 - m * a1) - (y0 - mPerpendicular * x0)) / (mPerpendicular - m);
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double y = m * x + (b1 - m * a1);
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return new Point((int) x, (int) y);
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}
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public static String determinePosition(double a1, double b1, double a2, double b2, double x0, double y0) {
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double cross = (a2 - a1) * (y0 - b1) - (x0 - a1) * (b2 - b1);
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if (cross > 0) {
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return "left";
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} else if (cross < 0) {
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return "right";
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} else {
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return "line";
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}
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}
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/**
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* 计算点到线段的距离占线段长度的比例
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* @param x0 垂足x点
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* @param y0 垂足y点
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* @param x1 起点x点
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* @param y1 起点y点
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* @param x2 终点x点
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* @param y2 终点y点
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* @return
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*/
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public static double calculateProportion(double x0, double y0, double x1, double y1, double x2, double y2) {
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// 向量 AB
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double ABx = x2 - x1;
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double ABy = y2 - y1;
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// 向量 AP
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double APx = x0 - x1;
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double APy = y0 - y1;
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// 向量积 AB × AP
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double crossProduct = ABx * APy - APx * ABy;
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if (crossProduct == 0) {
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// 点在直线上，判断是否在线段上
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double dotProduct = APx * ABx + APy * ABy;
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double squaredLengthAB = ABx * ABx + ABy * ABy;
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double t = dotProduct / squaredLengthAB;
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if (t >= 0 && t <= 1) {
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return t; // 垂足到mstPointStart的距离占整条线段长度的比例
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} else if (t < 0) {
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//点在mstPointStart的延长线上
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return 0;
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} else {
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//点在mstPointEnd的延长线上
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return 1;
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}
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} else {
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return -1; // 点不在直线上
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}
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}
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}
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