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。