mycanvas.java

由浅入深的介绍JAVAse的基本编程思想

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){
			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;	
		image_width = bi.getWidth(this);
		image_height = bi.getHeight(this);
		double image_proportion = 1.0 * image_height / image_width;
		if(image_proportion > screen_proportion){
			image_height = screen_height;
			image_width = (int)(image_height / image_proportion);	
		}else{
			image_width = screen_width;
			image_height = (int)(image_width * image_proportion); 	
		}
		im = bi.getScaledInstance(image_width,image_height,Image.SCALE_SMOOTH);
	}
	
}