本文实例讲述了Java实现的图像查看器。分享给大家供大家参考。具体如下：

1. 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); } }

2. 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; } }

3. 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))); } }

希望本文所述对大家的java程序设计有所帮助。