Исходный текст программы GrayFilter.java

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// ==========================================
// GrayFilter.java
//(C) Alexandr Frolov, 1998
// E-mail: frolov@glasnet.ru
// Web:    http://www.glasnet.ru/~frolov 
// ==========================================

import java.applet.Applet;
import java.awt.*;
import java.awt.image.*;

public class GrayFilter extends Applet
{
  cButton btnRed;
  cButton btnBlue;
  cButton btnYellow;
  
  Image imgButtonUp;
  Image imgButtonDn;
  
  // ===========================================
  // init
  // ===========================================
  public void init()
  {
    setBackground(Color.yellow);
    setForeground(Color.black);
    
    imgButtonUp = 
      getImage(getCodeBase(), "btnup.gif");
      
    imgButtonDn = 
      getImage(getCodeBase(), "btndn.gif");

    MediaTracker mt = new MediaTracker(this);
    mt.addImage(imgButtonUp, 0);  
    mt.addImage(imgButtonDn, 0);  
    
    try
    {
      mt.waitForAll();
    }
    catch(InterruptedException ie)
    {
      return;
    }	
        
    btnRed =  new cButton(this, 
      imgButtonUp, imgButtonDn, "Red",
      80, 20);
    
    btnBlue =  new cButton(this, 
      imgButtonUp, imgButtonDn, "Blue",
      80, 20);
      
    btnYellow =  new cButton(this, 
      imgButtonUp, imgButtonDn, "Yellow", 
      80, 20);
      
    add(btnRed);
    add(btnBlue);
    add(btnYellow);
  }
  
  // ===========================================
  // getAppletInfo
  // ===========================================
  public String getAppletInfo()
  {
    return "Name: GrayFilter";
  }
  
  // ===========================================
  // doButtonAction
  // ===========================================
  public void doButtonAction(cButton btn)
  {
    if(btn.equals(btnRed))
      setBackground(Color.red);
      
    else if(btn.equals(btnBlue))
      setBackground(Color.blue);
      
    else if(btn.equals(btnYellow))
      setBackground(Color.yellow);
      
    repaint();
  }
}

// ===========================================
// Class cButton
// ===========================================
class cButton extends Canvas
{
  Image imgButtonUp;
  Image imgButtonDn;
  Container cont;
  int btnWidth;
  int btnHeight;
  Dimension dimMinSize;
  boolean bButtonUp = true;
  boolean bMouseEnter = false;
  
  String btnTitle;
  
  Thread threadAnimate = null;
  Color clrTitleColor = Color.black;
    
  // ===========================================
  // cButton
  // ===========================================
  public cButton(Container parent,
    Image imgUp, Image imgDn,
    String btnTitle, int width, int height)
  {
    if(imgUp == null || imgDn == null)
    {
      System.err.println("Invalid image");
      return;
    }
    
    imgButtonUp = imgUp;
    imgButtonDn = imgDn;
    cont = parent;
    
    btnWidth  = width;
    btnHeight = height;
    this.btnTitle = btnTitle;
    
    dimMinSize = new Dimension(
      btnWidth, btnHeight);
  }  
  
  // ===========================================
  // getPreferredSize
  // ===========================================
  public Dimension getPreferredSize()
  {
    return dimMinSize;
  }
  
  // ===========================================
  // getMinimumSize
  // ===========================================
  public Dimension getMinimumSize()
  {
    return dimMinSize;
  }
  
  // ===========================================
  // preferredSize
  // ===========================================
  public Dimension preferredSize()
  {
    return dimMinSize;
  }
  
  // ===========================================
  // minimumSize
  // ===========================================
  public Dimension minimumSize()
  {
    return dimMinSize;
  }
  
  // ===========================================
  // paint
  // ===========================================
  public void paint(Graphics g)
  {
    if(bButtonUp)
    {
      g.setColor(clrTitleColor);
      
      if(!bMouseEnter)
        drawButton(imgButtonUp, 0);
      else	
        drawButton(imgToGray(imgButtonUp), 0);
    }
    else
    {
      g.setColor(Color.blue);
      drawButton(imgToGray(imgButtonDn), 1);
    }
  }
  
  // ===========================================
  // mouseDown
  // ===========================================
  public boolean mouseDown(
    Event ev, int x, int y)
  {
    if(bButtonUp)
    {
      bButtonUp = false;
      repaint();
      doButtonAction();
    }  
    
    return true;
  }

  // ===========================================
  // mouseUp
  // ===========================================
  public boolean mouseUp(
    Event ev, int x, int y)
  {
    if(!bButtonUp)
    {
      bButtonUp = true;
      repaint();
    }  
    return true;
  }
  
  // ===========================================
  // mouseEnter
  // ===========================================
  public boolean mouseEnter(
    Event ev, int x, int y)
  {
    bMouseEnter = true;
    drawButton(imgToGray(imgButtonUp), 0);
    return true;
  }
  
  // ===========================================
  // mouseExit
  // ===========================================
  public boolean mouseExit(
    Event ev, int x, int y)
  {
    bMouseEnter = false;
    drawButton(imgButtonUp, 0);
    return true;
  }
  
  // ===========================================
  // doButtonAction
  // ===========================================
  public void doButtonAction()
  {
    ((GrayFilter)cont).doButtonAction(this);
  }
  
  // ===========================================
  // drawButton
  // ===========================================
  void drawButton(Image imgSrc, int offset)
  {
    Graphics g = getGraphics();
    g.drawImage(imgSrc, 0, 0, this);
    drawTitle(g, offset);
  }
  
  // ===========================================
  // drawTitle
  // ===========================================
  void drawTitle(Graphics g, int offset)
  {
    FontMetrics fm = g.getFontMetrics();
    int nTitileWidth = fm.stringWidth(btnTitle);
    int nTitleHeight = fm.getAscent() - 
      fm.getLeading() - fm.getDescent();
    
    int x0 = (btnWidth - nTitileWidth) / 2;
    int y0 = ((btnHeight - nTitleHeight) / 2) +
       nTitleHeight;
       
    g.drawString(btnTitle, 
      x0 - offset, y0 - offset);
  }
  
  // ===========================================
  // imgToGray
  // ===========================================
  Image imgToGray(Image imgSrc)
  {
    GrayImageFilter grFilter = 
      new GrayImageFilter();
      
    ImageProducer ip = new FilteredImageSource(
      imgSrc.getSource(), grFilter);
    
    Image imGrayed = createImage(ip);    
    
    MediaTracker mt = new MediaTracker(this);
    mt.addImage(imGrayed, 0);  
    
    try
    {
      mt.waitForAll();
    }
    catch(InterruptedException ie)
    {
      return null;
    }	
    
    return imGrayed;
  }
}

// ===========================================
// Class GrayImageFilter
// ===========================================
class GrayImageFilter extends RGBImageFilter
{
  // ===========================================
  // filterRGB
  // ===========================================
  public int filterRGB(int x, int y, int nRGB)
  {
    int nR = (nRGB >> 16) & 0xff;
    int nG = (nRGB >> 8) & 0xff;
    int nB = nRGB & 0xff;
    
    int nGray = (int)(0.56 * nG + 0.33 * nR + 
      0.11 * nB);
    
    return (0xff000000 | nGray << 16 | 
      nGray << 8 | nGray);
  }
}

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