java - Java 中的形状和线段

Question

我有一个形状。我基本上是在尝试使用线段作为二等分将一个区域分成两个区域。

public Shape divide(Shape a, Point2D p1, Point2D p2)  {    

        Shape str = new BasicStroke().createStrokedShape(new Line2D.Double(p1,p2));    
        Shape line = new Shape(str); 
        Shape temp = a;    
        line.intersect(temp);    
        temp.exclusiveOr(line);
        // temp is the shape with the line intersecting it

        AffineTransform t = new AffineTransform(); 
        double angle = Math.atan2(p2.getY() - p1.getY(), p2.getX() - p1.getX()); 

        t.rotate(angle, p1.getX(), p1.getY());          
        temp = temp.createTransformedArea(t);       

        return Shape ;

     }

我想使用线段将形状一分为二，但不确定如何去做，我正在查看相交方法: http://docs.oracle.com/javase/7/docs/api/java/awt/geom/Area.html但仍然不确定如何从一个区域获得两个区域。我希望返回类似的内容:

return  firstHalf secondHalf;

Answer 1

我会这样做。请注意，当从右下角开始的点结束到左上角点的左侧时，代码有一个错误。留给用户作为练习。

import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import javax.swing.*;

class SplitArea {

    int s = 100;
    JPanel gui = new JPanel(new BorderLayout());
    BufferedImage[] images = new BufferedImage[4];
    Point p1 = new Point(s / 4, s / 4);
    Point p2 = new Point(s * 3 / 4, s * 3 / 4);
    Ellipse2D ellipse = new Ellipse2D.Float(
            s / 5, s / 5, s * 3 / 5, s * 3 / 5);
    Rectangle2D bg = new Rectangle2D.Float(0, 0, s, s);

    SplitArea() {
        JToolBar tb = new JToolBar();
        gui.add(tb, BorderLayout.PAGE_START);
        final JToggleButton tob = new JToggleButton("Primary Point");
        tb.add(tob);

        JPanel view = new JPanel(new GridLayout(1, 0, 4, 4));
        gui.add(view, BorderLayout.CENTER);
        for (int ii = 0; ii < images.length; ii++) {
            BufferedImage bi = new BufferedImage(
                    s, s, BufferedImage.TYPE_INT_RGB);
            images[ii] = bi;
            JLabel l = new JLabel(new ImageIcon(bi));
            if (ii == 0) {
                l.addMouseListener(new MouseAdapter() {

                    @Override
                    public void mouseClicked(MouseEvent e) {
                        if (tob.isSelected()) {
                            p1 = e.getPoint();
                        } else {
                            p2 = e.getPoint();
                        }
                        drawImages();
                    }
                });
            }
            view.add(l);
        }

        drawImages();
    }

    public final void drawImages() {
        Graphics2D g;

        // image 0
        g = images[0].createGraphics();
        g.setColor(Color.BLACK);
        g.fill(bg);

        g.setColor(Color.CYAN);
        g.fill(ellipse);
        g.setColor(Color.WHITE);
        g.draw(ellipse);

        g.setColor(Color.red);
        drawPoint(g, p1);
        drawPoint(g, p2);

        g.dispose();

        int xDiff = p1.x - p2.x;
        int yDiff = p1.y - p2.y;
        Point2D xAxis;
        Point2D xSAxis;
        if (xDiff == 0) {
            xAxis = new Point2D.Double(p1.x, 0);
            xSAxis = new Point2D.Double(p1.x, s);
        } else if (yDiff == 0) {
            xAxis = new Point2D.Double(0, p1.y);
            xSAxis = new Point2D.Double(s, p1.y);
        } else {
            System.out.println("Not vertical or horizontal!");
            // will throw a NaN if line is vertical
            double m = (double) yDiff / (double) xDiff;
            System.out.println("m: " + m);

            double b = (double) p1.y - (m * (double) p1.x);
            System.out.println("b: " + b);

            // crosses x axis at.. 
            xAxis = new Point2D.Double(0d, b);
            double pointS = (s - b) / m;
            xSAxis = new Point2D.Double(pointS, s);
        }

        // image 1
        g = images[1].createGraphics();
        g.setColor(Color.BLACK);
        g.fill(bg);

        g.setColor(Color.CYAN);
        g.fill(ellipse);
        g.setColor(Color.WHITE);
        g.draw(ellipse);

        g.setColor(Color.YELLOW);
        System.out.println(xAxis);
        System.out.println(xSAxis);
        g.drawLine(
                (int) xAxis.getX(), (int) xAxis.getY(),
                (int) xSAxis.getX(), (int) xSAxis.getY());

        g.setColor(Color.red);
        drawPoint(g, p1);
        drawPoint(g, p2);

        g.dispose();

        // image 2
        g = images[1].createGraphics();
        g.setColor(Color.BLACK);
        g.fill(bg);

        g.setColor(Color.CYAN);
        g.fill(ellipse);
        g.setColor(Color.WHITE);
        g.draw(ellipse);

        g.setColor(Color.YELLOW);
        System.out.println(xAxis);
        System.out.println(xSAxis);
        g.drawLine(
                (int) xAxis.getX(), (int) xAxis.getY(),
                (int) xSAxis.getX(), (int) xSAxis.getY());

        g.setColor(Color.red);
        drawPoint(g, p1);
        drawPoint(g, p2);

        g.dispose();

        // split the regions
        Rectangle2D.Double all = new Rectangle2D.Double(0, 0, s, s);
        Area a1 = new Area(all);
        Area a2 = new Area(all);
        GeneralPath aPart = new GeneralPath();
        aPart.moveTo(0, 0);
        aPart.lineTo(0, s);
        aPart.lineTo(xSAxis.getX(), xSAxis.getY());
        aPart.lineTo(xAxis.getX(), xAxis.getY());
        aPart.closePath();
        a1.subtract(new Area(aPart));
        a2.subtract(a1);

        Area ellipsePartA = new Area(ellipse);
        ellipsePartA.subtract(a1);
        Area ellipsePartB = new Area(ellipse);
        ellipsePartB.subtract(a2);

        // image 3
        g = images[2].createGraphics();
        g.setColor(Color.BLACK);
        g.fill(bg);

        g.setColor(Color.CYAN);
        g.fill(ellipsePartA);
        g.setColor(Color.WHITE);
        g.draw(ellipsePartA);

        g.setColor(Color.red);
        drawPoint(g, p1);
        drawPoint(g, p2);

        g.dispose();

        // image 4
        g = images[3].createGraphics();
        g.setColor(Color.BLACK);
        g.fill(bg);

        g.setColor(Color.CYAN);
        g.fill(ellipsePartB);
        g.setColor(Color.WHITE);
        g.draw(ellipsePartB);

        g.setColor(Color.red);
        drawPoint(g, p1);
        drawPoint(g, p2);

        g.dispose();

        gui.repaint();
    }

    public final void drawPoint(Graphics g, Point2D p) {
        g.setColor(new Color(255, 0, 0, 128));
        int x = (int) p.getX();
        int y = (int) p.getY();
        g.drawLine(x - 1, y, x - 5, y);
        g.drawLine(x + 1, y, x + 5, y);
        g.drawLine(x, y - 1, x, y - 5);
        g.drawLine(x, y + 1, x, y + 5);
    }

    public Area[] split(Area a, Point2D p1, Point2D p2) {

        Shape str = new BasicStroke().createStrokedShape(new Line2D.Double(p1, p2));
        Area line = new Area(str);
        Area temp = a;
        line.intersect(temp);
        temp.exclusiveOr(line);
        // temp is the shape with the line intersecting it          

        Area[] areas = {new Area(temp)};

        return areas;
    }

    public JComponent getGui() {
        return gui;
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {

            @Override
            public void run() {
                SplitArea sa = new SplitArea();
                JOptionPane.showMessageDialog(null, sa.getGui());
            }
        };
        // Swing GUIs should be created and updated on the EDT
        // http://docs.oracle.com/javase/tutorial/uiswing/concurrency
        SwingUtilities.invokeLater(r);
    }
}