fftlab.java

FFT傅立叶频谱分析

package Applet小程序;
/////////////////////////////////////////////////////////////////////////////
// Fast Fourier transform laboratory.
// Dave Hale, Landmark Graphics, 01/24/96
/////////////////////////////////////////////////////////////////////////////

import java.awt.*;
import java.util.*;

public class FftLab extends java.applet.Applet {
    MainPanel mainPanel;
    ControlPanel controlPanel;
    public void init() {
        FftLabController controller = new FftLabController();
        setLayout(new BorderLayout());
        mainPanel = new MainPanel(controller.fRealView,
                                  controller.fImagView,
                                  controller.gRealView,
                                  controller.gImagView);
        add("Center",mainPanel);
        controlPanel = new ControlPanel(controller);
        add("South",controlPanel);
    }

    public void start() {
        mainPanel.enable();
  	    controlPanel.enable();
    }

    public void stop() {
        mainPanel.disable();
        controlPanel.disable();
    }

    public boolean handleEvent(Event e) {
        if (e.id==Event.WINDOW_DESTROY) {
            System.exit(0);
        }   
        return false;
    }

    public static void main(String args[]) {
        Frame frame = new Frame("FFT Laboratory");
        FftLab fftLab = new FftLab();
        fftLab.init();
        fftLab.start();
        frame.add("Center",fftLab);
        frame.resize(600,400);
        frame.show();
    }
}


/////////////////////////////////////////////////////////////////////////////
// Main panel for FftLab contains samples views.

class MainPanel extends Panel {

    public MainPanel(SamplesView fRealView, SamplesView fImagView,
                     SamplesView gRealView, SamplesView gImagView) {
        setLayout(new GridLayout(2,1,1,1));
        add(new ComplexSamplesPanel(fRealView,
                                    fImagView,
                                    "f(x)"));
        add(new ComplexSamplesPanel(gRealView,
                                    gImagView,
                                    "F(k)"));
    }

    public void paint(Graphics g) {
        Dimension d = size();
        g.setColor(Color.blue);
        g.draw3DRect(0,0,d.width-1,d.height-1,true);
    }

    public Insets insets() {
        return new Insets(1,1,1,1);
    }
}

class ComplexSamplesPanel extends Panel {

    public ComplexSamplesPanel(SamplesView realView,
                               SamplesView imagView,
                               String label) {
        setLayout(new BorderLayout());
        add("North",new Label(label,Label.CENTER));
        Panel panel = new Panel();
        panel.setLayout(new GridLayout(1,2,1,1));
        panel.add(new SamplesPanel(realView,"Real"));
        panel.add(new SamplesPanel(imagView,"Imaginary"));
        add("Center",panel);
    }

    public void paint(Graphics g) {
        Dimension d = size();
        g.setColor(Color.blue);
        g.draw3DRect(0,0,d.width-1,d.height-1,true);
    }

    public Insets insets() {
        return new Insets(1,1,1,1);
    }
}

class SamplesPanel extends Panel {

    public SamplesPanel(SamplesView view, String label) {
        setLayout(new BorderLayout());
        add("North",new Label(label,Label.CENTER));
        add("Center",view);
    }

    public void paint(Graphics g) {
        Dimension d = size();
        g.setColor(Color.blue);
        g.draw3DRect(0,0,d.width-1,d.height-1,true);
    }

    public Insets insets() {
        return new Insets(1,1,1,1);
    }
}


/////////////////////////////////////////////////////////////////////////////
// Control panel for FftLab.

class ControlPanel extends Panel {

    public ControlPanel(FftLabController c) {
        this.c = c;
        add(new Checkbox("Origin Centered"));
        length = new LabeledChoice("Length:");
        length.choice.addItem("16");
        length.choice.addItem("32");
        length.choice.addItem("128");
        length.choice.select("32");
        add(length);
        mode = new LabeledChoice("Editing:");
        mode.choice.addItem("Draw");
        mode.choice.addItem("Negate");
        mode.choice.addItem("Zero");
        mode.choice.addItem("Shift");
        mode.choice.addItem("None");
        mode.choice.select("Draw");
        add(mode);
        add(new Button("Zero All"));
    }

    public void paint(Graphics g) {
        Dimension d = size();
        g.setColor(Color.blue);
        g.draw3DRect(0,0,d.width-1,d.height-1,true);
    }

    public Insets insets() {
        return new Insets(1,1,1,1);
    }

    public boolean handleEvent(Event e) {
        if (e.target instanceof Button) {
            c.zeroAll();
            return true;
        } else if (e.target instanceof Checkbox) {
            Checkbox cb = (Checkbox)e.target;
            c.setOriginCentered(cb.getState());
            return true;
        } else if (e.target instanceof Choice) {
            if (e.target==length.choice) {
                String item = length.choice.getSelectedItem();
                c.setLength(Integer.parseInt(item));
                return true;
            } else if (e.target==mode.choice) {
                String item = mode.choice.getSelectedItem();
                if (item=="None") {
                    c.setEditMode(SamplesView.EDIT_NONE);
                } else if (item=="Draw") {
                    c.setEditMode(SamplesView.EDIT_DRAW);
                } else if (item=="Negate") {
                    c.setEditMode(SamplesView.EDIT_NEGATE);
                } else if (item=="Zero") {
                    c.setEditMode(SamplesView.EDIT_ZERO);
                } else if (item=="Shift") {
                    c.setEditMode(SamplesView.EDIT_SHIFT);
                }
                return true;
            }
        }
        return false;
    }

    private FftLabController c;
    private LabeledChoice length;
    private LabeledChoice mode;
}

class LabeledChoice extends Panel {

    public Choice choice;

    public LabeledChoice(String label) {
        add(new Label(label,Label.RIGHT));
        choice = new Choice();
        add(choice);
    }
}


/////////////////////////////////////////////////////////////////////////////
// Controller creates and keeps Samples and SamplesViews consistent.

class FftLabController implements Observer {

    public Samples fReal,fImag,gReal,gImag;
    public SamplesView fRealView,fImagView,gRealView,gImagView;
  
    public FftLabController() {

        int origin = (originCentered)?length/2:0;
        fReal = new Samples(length,origin);
        fImag = new Samples(length,origin);
        gReal = new Samples(length,origin);
        gImag = new Samples(length,origin);
        initSamples();

        fReal.addObserver(this);
        fImag.addObserver(this);
        gReal.addObserver(this);
        gImag.addObserver(this);

        fRealView = new SamplesView(fReal);
        fImagView = new SamplesView(fImag);
        gRealView = new SamplesView(gReal);
        gImagView = new SamplesView(gImag);
        updateSampleValues(fRealView,fImagView);
        updateSampleValues(gRealView,gImagView);
    }

    public int getEditMode() {
        return editMode;
    }
    public void setEditMode(int mode) {
        editMode = mode;
        fRealView.setEditMode(mode);
        fImagView.setEditMode(mode);
        gRealView.setEditMode(mode);
        gImagView.setEditMode(mode);
    }
  
    public int getLength() {
        return length;
    }
    public void setLength(int length) {
        this.length = length;
        updateLengths();
        updateOrigins();
        initSamples();
        updateSampleValues(fRealView,fImagView);
        updateSampleValues(gRealView,gImagView);
        repaintViews();
    }

    public boolean getOriginCentered() {
        return originCentered;
    }
    public void setOriginCentered(boolean centered) {
        if (centered==originCentered) return;
        originCentered = centered;
        updateOrigins();
        repaintViews();
    }

    public void zeroAll() {
        fReal.zero();
        fImag.zero();
        gReal.zero();
        gImag.zero();
        repaintViews();
    }

    public void update(Observable o, Object arg) {
        Samples s = (Samples)o;
        if (s==fReal || s==fImag) {
            transform(1,fReal,fImag,gReal,gImag);
            updateSampleValues(gRealView,gImagView);
            gRealView.repaint();
            gImagView.repaint();
        } else {
            transform(-1,gReal,gImag,fReal,fImag);
            updateSampleValues(fRealView,fImagView);
            fRealView.repaint();
            fImagView.repaint();
        }
    }

    private int editMode = SamplesView.EDIT_DRAW;
    private int length = 32;
    private boolean originCentered = false;

    private float computeSampleValue(Samples real, Samples imag) {
        float sv = 0.0f;
        float v[];
        v = real.values;
        for (int i=0; i<length; ++i) {
            float si = v[i];
            if (-si>sv) sv = -si;
            else if (si>sv) sv = si;
        }
        v = imag.values;
        for (int i=0; i<length; ++i) {
            float si = v[i];
            if (-si>sv) sv = -si;