histogramframe.java

用java实现的对位图文件读取的源程序代码。

/**
 *	file name : Histogram.java
 *	data	: 2006-12-2
 *
 *	abstract : a class that can show a histogram of a bmp file
 *	the main data is percent of bmp file, dram the histogram by 
 *	the percent data. 
 */

import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Color;

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import java.text.DecimalFormat;

public class HistogramFrame extends Frame {
	
	private float[] percent;
	private double entropy;
	
	final int GRAPHICS_WIDTH 	= 300;
	final int GRAPHICS_HEIGHT 	= 300 * 20;
	
	final int G_X0 		= 20;
	final int G_Y0	 	= 250;
	
	final int WINDOW_WIDTH 		= 300;
	final int WINDOW_HEIGHT		= 300;
	
	public HistogramFrame() {
		setSize(WINDOW_WIDTH,WINDOW_HEIGHT);
		setTitle("位图直方图");
		this.setLocation(500,170);
		// Add window listener.
        this.addWindowListener
        (
            new WindowAdapter() {
                public void windowClosing(WindowEvent e) {
                    HistogramFrame.this.windowClosed();
                }
            }
        );  
	}
	
	/**
     * Shutdown procedure when run as an application.
     */
    protected void windowClosed() {

        this.removeAll();
        this.dispose();
    }
	
	public void setPercent(float[] aPercent) {
		percent = aPercent;
	}
	
	public void setEntropy(double AnEntropy) {
		entropy = AnEntropy;
	}
	
	DecimalFormat format = new DecimalFormat("#0");
	DecimalFormat formatEntropy = new DecimalFormat("0.00000");
	
	public void paint(Graphics g) {
		if (percent == null) {
			return ;
		}
		
		int x = G_X0;
		int y = 0;
		
		int space = 0;

		for (int i=0; i<percent.length; i++) {
			y = (int)(percent[i] * GRAPHICS_HEIGHT);
			g.setColor(Color.BLACK);
			g.drawLine(x,G_Y0,x,G_Y0-y);		
			
			if (space > 15 && percent[i] > 5E-4) {
				g.setColor(Color.RED);
				g.drawString(format.format(percent[i]*1000),x-9,40);
				g.drawString(Integer.toHexString(i+1),x-5,G_Y0 + 20);				
				g.drawLine(x,G_Y0,x,G_Y0-y);
				space = 0;
			}
			
			x ++;
			space ++;
		}
		g.setColor(Color.BLACK);
		g.drawString("单位:1/1000",GRAPHICS_WIDTH-70,50);
		g.drawString("位图的熵 : "+formatEntropy.format(entropy),GRAPHICS_WIDTH/2 - 50,G_Y0 + 40);
	}
	
	public float[] getPercent() {
		float[] percent = new float[256];
		
		for (int i=0; i<percent.length; i++) {
			percent[i] = (float) Math.random();
		}
		return percent;
	}
		
	public static void main(String[] args) {
		HistogramFrame f = new HistogramFrame();
		f.setPercent(f.getPercent());
		f.setVisible(true);
	}
}