如何在 Java 中找到沿 Arc2D 的所有坐标？

Question

我在 Java 中绘制了一个 Arc2D，我希望能够找到 Arc2D 包含的所有点。有什么办法可以做到吗？

Answer 1

您想使用 PathIterator

基本上这将允许您在构成路径的点之间进行迭代。您可以使用 flatness 参数

控制“精度”（或点之间的距离）

例如...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Arc2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.PathIterator;
import java.awt.geom.Point2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public final class Main {
    public static void main(String[] args) {
        new Main();
    }

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private Arc2D shape;
        private double flatness = 0.4;

        public TestPane() {
            shape = new Arc2D.Double(50, 50, 100, 100, 0, 180, Arc2D.OPEN);

            setLayout(new BorderLayout());
            JSlider slider = new JSlider(0, 100);
            slider.addChangeListener(new ChangeListener() {
                @Override
                public void stateChanged(ChangeEvent e) {
                    double progress = slider.getValue() / 100d;
                    flatness = 0.001 + (0.4d * progress);
                    repaint();
                }
            });
            slider.setValue(0);

            add(slider, BorderLayout.SOUTH);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.draw(shape);
            g2d.setColor(Color.RED);
            PathIterator pi = shape.getPathIterator(null, flatness);
            // Use this if you want to draw lines between the points
            Point2D lastPoint;
            while (!pi.isDone()) {
                double[] coords = new double[6];
                switch (pi.currentSegment(coords)) {
                    case PathIterator.SEG_MOVETO:
                        // Starting point of next line
                        lastPoint = new Point2D.Double(coords[0], coords[1]);
                        // You don't need this if you're drawing lines
                        g2d.fill(new Ellipse2D.Double(coords[0] - 2, coords[1] - 2, 4, 4));
                        break;
                    case PathIterator.SEG_LINETO:
                        g2d.fill(new Ellipse2D.Double(coords[0] - 2, coords[1] - 2, 4, 4));
                        // If you were drawing lines, then you'd draw a line
                        // between the last point and this point
                        lastPoint = new Point2D.Double(coords[0], coords[1]);
                        break;
                }
                pi.next();
            }
            g2d.dispose();
        }

    }
}

如何在 Java 中找到沿 Arc2D 的所有坐标？

How can I find all of the coordinates along an Arc2D in Java?

java

graphics

coordinates

graphics2d