main.java

JAVA 繪圖功能 以繪製出可以調整的弦波

/*
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 * and open the template in the editor.
 */

package graphic;

/**
 *
 * @author spider
 */
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
import javax.swing.event.*;
 
public class Main extends JComponent {
    public static void main(String[] args) {
        JFrame f = new JFrame("QuadVadis");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final Main app = (Main) f.getContentPane().add(new Main());
        JPanel ui = new JPanel();
        f.getContentPane().add(ui, BorderLayout.SOUTH);
        final JLabel label = (JLabel) ui.add(new JLabel("N="+app.N+":"));
        final JSlider size = (JSlider) ui.add(new JSlider(8,100,app.N));
        size.addChangeListener(new ChangeListener(){
            public void stateChanged(ChangeEvent e) {
                if (!size.getValueIsAdjusting()) {
                    app.N = size.getValue();
                    app.repaint();
                }
                label.setText("N="+size.getValue()+":");
            }
        });
        final JCheckBox samples = (JCheckBox) ui.add(new JCheckBox("samples", true));
        final JCheckBox tangents = (JCheckBox) ui.add(new JCheckBox("tangents", true));
        ActionListener al = new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                app.showTangents = tangents.isSelected();
                app.showSamples = samples.isSelected();
                app.repaint();
            }
        };
        samples.addActionListener(al);
        tangents.addActionListener(al);
        f.setSize(450,450);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }
 
    int N = 32;
    GeneralPath path=new GeneralPath(), tangents=new GeneralPath(), samples=new GeneralPath();
    boolean showSamples=true, showTangents=true;
 
    float  x(float t) {return (float) Math.cos(3.0*t);}
    float  y(float t) {return (float) Math.sin(5.0*t);}
    float dx(float t) {return (float) (-3.0 * Math.sin(3.0*t));}
    float dy(float t) {return (float) (5.0* Math.cos(5.0*t));}
 
    void calculate() {
        float x1=x(0), y1=y(0), dx1=dx(0), dy1=dy(0), side=0.05f, t, x2, y2, dx2, dy2;
        path.reset(); tangents.reset(); samples.reset();
        path.moveTo(x1, y1); tangents.moveTo(x1, y1);
        for(int i=0; i<N; ++i, x1=x2, y1=y2, dx1=dx2, dy1=dy2) {
            t=(i+1)*2*(float)Math.PI/N; x2=x(t); y2=y(t); dx2=dx(t); dy2=dy(t);
            samples.moveTo(x2-side/2, y2); samples.lineTo(x2+side/2,y2);
            samples.moveTo(x2, y2-side/2); samples.lineTo(x2,y2+side/2);
            float desc = dx1*dy2 - dx2*dy1;
            if (Math.abs(desc) < 0.1f) {
                path.lineTo(x2, y2);
                tangents.moveTo(x2, y2);
            } else {
                float ctrlx = (x2*dx1*dy2 - x1*dx2*dy1 + dx1*dx2*y1 - dx1*dx2*y2)/desc;
                float ctrly = (x2*dy1*dy2 - x1*dy1*dy2 + dx1*y1*dy2 - dx2*y2*dy1)/desc;
                path.quadTo(ctrlx, ctrly, x2, y2);
                tangents.lineTo(ctrlx, ctrly); tangents.lineTo(x2, y2);
            }
        }
    }
 
    protected void paintComponent(Graphics g) {
        calculate();
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        float scale = 0.45f * Math.min(getWidth(),getHeight());
        AffineTransform xform = new AffineTransform(scale,0,0,scale,getWidth()/2,getHeight()/2);
        g2.setPaint(Color.RED);
        if (showTangents)
            g2.draw(tangents.createTransformedShape(xform));
        g2.setPaint(Color.BLUE);
        g2.setStroke(new BasicStroke(2));
        g2.draw(path.createTransformedShape(xform));
        g2.setPaint(Color.BLACK);
        if (showSamples)
            g2.draw(samples.createTransformedShape(xform));
    }
}