Java旋轉Polgon使其變形-有解無憂

我寫了一個方法，它隨機生成多邊形形狀，然后在螢屏上旋轉和移動。因為我想檢測與這些形狀的碰撞，所以我沒有使用 Graphics2D 旋轉它們，而是使用 AffineTransform 來旋轉它們。但出于某種原因，某些形狀因旋轉而變得混亂，而其他形狀則不受影響。以下是導致問題的形狀之一的示例。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Polygon;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.Timer;

public class Test extends JLabel{

    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

    private static final long serialVersionUID = 1L;

    Polygon poly;

    Point center;
    Point source[];
    Point dest[];

    JFrame jf;

    public Test() {

        init();
        createPolygon();

        Timer timer = new Timer(20, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                rotatePoly();
                repaint();
            }});
        timer.start();
    }
    public void rotatePoly() {

        AffineTransform transf = AffineTransform.getRotateInstance(Math.toRadians(2), center.x, center.y);
        transf.transform(source, 0, dest, 0, source.length);

        poly = toPolygon(dest);

    }
    public Polygon toPolygon(Point[] points) {

        Polygon polygon = new Polygon();

        for (int i = 0; i < points.length; i  ) {
            polygon.addPoint(points[i].x, points[i].y);
        }
        return polygon;
    }
    public void createPolygon() {

        Point points[] = new Point[7];

        points[0] = new Point(20, 97);
        points[1] = new Point(82, 70);
        points[2] = new Point(134, 70);
        points[3] = new Point(210, 88);
        points[4] = new Point(210, 106);
        points[5] = new Point(144, 125);
        points[6] = new Point(82, 125);

        source = points;
        dest = points;

        poly = toPolygon(points);

        center = new Point(poly.getBounds().x   poly.getBounds().width / 2, poly.getBounds().y   poly.getBounds().height / 2);

    }
    public void init() {

        setVisible(true);
        setSize(260, 260);

        jf = new JFrame();
        jf.setVisible(true);
        jf.setSize(260, 260);
        jf.setContentPane(new JLabel());
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setLocation((screenSize.width / 2) - (getWidth() / 2), (screenSize.height / 2) - (getHeight() / 2));
        jf.add(this);

    }
    @Override
    public void paintComponent(Graphics g) {

        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.RED);

        g2d.drawPolygon(poly);

    }
}

如果用以下幾行替換這些點，則形狀基本保持不變。下面的形狀當然是對稱的，但是旋轉方法確實適用于其他隨機生成的和不均勻的形狀。

points[0] = new Point(10, 130);
points[1] = new Point(100, 10);
points[2] = new Point(160, 10);
points[3] = new Point(250, 100);
points[4] = new Point(250, 160);
points[5] = new Point(160, 250);
points[6] = new Point(100, 250);

uj5u.com熱心網友回復：

這適用于您的 AffineTransform。它回傳一個變換的形狀而不是修改坐標。我也推薦：

JFrame.setLocationRelativeTo(null); 用于在螢屏上居中。
使用RenderingHints反走樣上理順圖形。
由于 Polygon 實作了 Shape，因此需要重新鍵入一些位置。

class Text extends JLabel{

    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

    private static final long serialVersionUID = 1L;

    Shape poly;

    Point center;
    Point source[];
    Point dest[];

    JFrame jf;

    public static void main(String[] args) {
        new Text();
    }
    public Text() {

        init();
        createPolygon();

        Timer timer = new Timer(20, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                rotatePoly();
                repaint();
            }});
        timer.start();
    }
    public void rotatePoly() {

        AffineTransform transf = 
        AffineTransform.getRotateInstance(Math.toRadians(2), center.x, center.y);
        poly = transf.createTransformedShape(poly);

    }
    public Shape toPolygon(Point[] points) {

        Polygon polygon = new Polygon();

        for (int i = 0; i < points.length; i  ) {
            polygon.addPoint(points[i].x, points[i].y);
        }
        return polygon;
    }
    public void createPolygon() {

        Point points[] = new Point[7];

        points[0] = new Point(20, 97);
        points[1] = new Point(82, 70);
        points[2] = new Point(134, 70);
        points[3] = new Point(210, 88);
        points[4] = new Point(210, 106);
        points[5] = new Point(144, 125);
        points[6] = new Point(82, 125);

        source = points;
        dest = points;

        poly = toPolygon(points);

        center = new Point(poly.getBounds().x   poly.getBounds().width / 2, poly.getBounds().y   poly.getBounds().height / 2);

    }
    public void init() {

        setVisible(true);
        setSize(260, 260);

        jf = new JFrame();
        jf.setVisible(true);
        jf.setSize(260, 260);
        jf.setContentPane(new JLabel());
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setLocation((screenSize.width / 2) - (getWidth() / 2), (screenSize.height / 2) - (getHeight() / 2));
        jf.add(this);

    }
    @Override
    public void paintComponent(Graphics g) {

        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.RED);

        g2d.draw(poly);

    }
}

uj5u.com熱心網友回復：

該問題主要是由對多邊形使用整數坐標引起的。
不是在多邊形本身中累積旋轉，而是使用變數來保持角度并在每次更改角度時基于原始多邊形計算新多邊形。原始多邊形不會改變。

我試圖盡可能地維護原始代碼¹：

package cfh.test.sf;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Polygon;
import java.awt.Shape;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.Timer;

public class PolygonTest extends JLabel{

    public static void main(String[] args) {
        new PolygonTest();
    }
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

    private static final long serialVersionUID = 1L;

    Polygon poly;
    Shape rotated;
    Point center;
    int angle = 0;

    JFrame jf;

    public PolygonTest() {

        init();
        createPolygon();

        Timer timer = new Timer(20, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                rotatePoly();
                repaint();
            }});
        timer.start();
    }
    public void rotatePoly() {
        angle  = 2;
        AffineTransform transf = AffineTransform.getRotateInstance(Math.toRadians(angle), center.x, center.y);
        rotated = transf.createTransformedShape(poly);
    }
    public Polygon toPolygon(Point[] points) {

        Polygon polygon = new Polygon();

        for (int i = 0; i < points.length; i  ) {
            polygon.addPoint(points[i].x, points[i].y);
        }
        return polygon;
    }
    public void createPolygon() {

        Point points[] = new Point[7];

        points[0] = new Point(20, 97);
        points[1] = new Point(82, 70);
        points[2] = new Point(134, 70);
        points[3] = new Point(210, 88);
        points[4] = new Point(210, 106);
        points[5] = new Point(144, 125);
        points[6] = new Point(82, 125);

        poly = toPolygon(points);
        rotated = poly;

        center = new Point(poly.getBounds().x   poly.getBounds().width / 2, poly.getBounds().y   poly.getBounds().height / 2);

    }
    public void init() {

        setVisible(true);
        setSize(260, 260);

        jf = new JFrame();
        jf.setVisible(true);
        jf.setSize(260, 260);
        jf.setContentPane(new JLabel());
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setLocation((screenSize.width / 2) - (getWidth() / 2), (screenSize.height / 2) - (getHeight() / 2));
        jf.add(this);

    }
    @Override
    public void paintComponent(Graphics g) {

        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.RED);

        g2d.draw(rotated);

    }
}

^{1 - 我寧愿在paintComponent. 不確定這是否與程式的其余部分沖突（例如計算交集）}

替代，未測驗：使用Point2D.Float或Point2D.Double代替Point坐標。

轉載請註明出處，本文鏈接：https://www.uj5u.com/qiye/348543.html

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