Java图像查看器详解编程语言

MyCanvas.java

package PictureViewer; 
  
import java.awt.*; 
import java.awt.event.*; 
import java.awt.image.*; 
public class MyCanvas extends Canvas implements ComponentListener{ 
    private BufferedImage bi; 
    private Image im; 
    private int image_width; 
    private int image_height; 
    public void setImage(BufferedImage bi){ 
        this.bi = bi; 
        this.zoom(); 
    } 
    public void paint(Graphics g){ 
        g.drawImage(im,(this.getWidth()-image_width)/2,(this.getHeight()-image_height)/2,this); 
    } 
    public void componentResized(ComponentEvent e){ 
        if(bi != null){ 
            System.out.println("resize!!"); 
              
            this.zoom(); 
            this.repaint(); 
        } 
    }    
    public void componentMoved(ComponentEvent e){} 
    public void componentShown(ComponentEvent e){} 
    public void componentHidden(ComponentEvent e){} 
    public void zoom(){ 
        if(bi == null) 
            return; 
        int screen_width = this.getWidth(); 
        int screen_height = this.getHeight(); 
        double screen_proportion = 1.0 * screen_height / screen_width;   
        System.out.println("screen: w "+screen_width+" ,h "+screen_height+" ,p0 "+screen_proportion); 
          
        image_width = bi.getWidth(this); 
        image_height = bi.getHeight(this); 
        double image_proportion = 1.0 * image_height / image_width; 
        System.out.println("image: w "+image_width+" ,h "+image_height+" ,p1 "+image_proportion); 
          
        if(image_proportion > screen_proportion){ 
            image_height = screen_height; 
            image_width = (int)(image_height / image_proportion);    
            System.out.println("  p1>p0  w= "+image_width); 
        }else{ 
            image_width = screen_width; 
            image_height = (int)(image_width * image_proportion);    
            System.out.println("  p0>p1  h= "+image_height); 
        } 
        im = bi.getScaledInstance(image_width,image_height,Image.SCALE_SMOOTH); 
    } 
      
}   

MyFilter.java

package PictureViewer; 
  
import java.io.File; 
import java.io.FilenameFilter; 
  
public class MyFilter implements FilenameFilter{ 
    private String[] extension;    
    public MyFilter(){ 
        extension = new String[]{".jpg", ".JPG", ".gif", ".GIF", ".png", ".PNG", ".jpeg", ".JPEG"};  
    } 
    public MyFilter(String[] extension){ 
        this.extension = extension;  
    } 
    public boolean accept(File dir,String name){ 
        for(String s : extension){ 
            if(name.endsWith(s)){ 
                return true;     
            } 
        }    
        return  false;  
    }    
}

PictureViewer.java

package PictureViewer; 
  
import java.awt.*; 
import java.awt.event.*; 
import java.awt.image.*; 
import java.io.*; 
import javax.imageio.*; 
  
public class PictureViewer implements ActionListener{ 
    private Frame frame; 
    private MyCanvas mc ; 
    private String fpath; 
    private String fname; 
    private File[] files; 
    private int findex ; 
    private FileDialog fd_load;  
    private MyFilter filter; 
    private Button previous ; 
    private Button next ; 
    public static void main( String args[]) throws Exception { 
        new PictureViewer().init(); 
    } 
    public void init(){ 
        frame = new Frame("PictureViewer"); 
        Panel pb = new Panel(); 
        Button select = new Button("选择图片"); 
        previous = new Button("上一张"); 
        next = new Button("下一张"); 
        select.addActionListener(this); 
        previous.addActionListener(this); 
        next.addActionListener(this); 
        pb.add(select); 
        pb.add(previous); 
        pb.add(next);  
        mc = new MyCanvas(); 
        mc.setBackground(new Color(200,210,230)); 
        mc.addComponentListener(mc); 
        frame.add(pb,"North"); 
        frame.add(mc,"Center"); 
        frame.setSize(360,360); 
        frame.setLocation(400,200); 
        frame.addWindowListener(new WindowAdapter(){ 
            public void windowClosing(WindowEvent e){ 
                System.exit(0);  
            }    
        });   
        frame.setVisible(true);  
        this.validateButton(); 
        filter = new MyFilter(); 
        fd_load = new FileDialog(frame,"打开文件",FileDialog.LOAD); 
        fd_load.setFilenameFilter(filter); 
    } 
      
    public void actionPerformed(ActionEvent e){ 
        String command = e.getActionCommand(); 
        if(command.equals("选择图片")){ 
            fd_load.setVisible(true); 
            fpath = fd_load.getDirectory(); 
            fname = fd_load.getFile(); 
            if((fpath != null) && (fname != null)){ 
                this.display(new File(fpath + fname));   
                files = new File(fpath).listFiles(filter); 
                this.setIndex(); 
            }            
        }else if(command.equals("上一张")){ 
            findex--; 
            if(findex<0) 
                findex = 0; 
            this.display(files[findex]); 
        }else if(command.equals("下一张")){ 
            findex++; 
            if(findex >= files.length) 
                findex = files.length-1; 
            this.display(files[findex]); 
        } 
        this.validateButton(); 
    }    
    public void display(File f){ 
        try{ 
            BufferedImage bi = ImageIO.read(f); 
            mc.setImage(bi); 
            frame.setTitle("PictureViewer - [" +  f.getName() + "]"); 
        }catch(Exception e){ 
            e.printStackTrace();     
        } 
        mc.repaint(); 
    } 
    public void setIndex(){ 
        File current = new File(fpath + fname);  
        if(files != null){ 
            for(int i=0;i<files.length;i++){ 
                if(current.equals(files[i])){ 
                    findex = i;  
                }    
            }            
        } 
    } 
    public void validateButton(){ 
        previous.setEnabled((files!=null) && (findex > 0)); 
        next.setEnabled((files!=null) && (findex<(files.length-1)));  
    } 
}