椒盐噪声及中值滤波处理

椒盐噪声也称为脉冲噪声，是图像中经常见到的一种噪声，它是一种随机出现的白点或者黑点，可能是亮的区域有黑色像素或是在暗的区域有白色像素（或是两者皆有）。盐和胡椒噪声的成因可能是影像讯号受到突如其来的强烈干扰而产生、类比数位转换器或位元传输错误等。例如失效的感应器导致像素值为最小值，饱和的感应器导致像素值为最大值。

常用的去除这种噪声的有效手段是使用中值滤波器

带椒盐噪声的图片

均值滤波的效果如上，可以看出，椒盐噪声被处理成了小的气泡，同时图像变模糊： 

中值滤波的效果如上，可以看到，几乎完全去除了椒盐噪声。 

下面是用java实现的代码

package p01;

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.*;

public class colorfilter extends Frame{
    Image im, tmp;
    int i, iw, ih;
    int[] pixels;
    boolean flag_load = false;
    
    public colorfilter(){    
        this.setTitle("彩色图像均值中值滤波3*3");
    	Panel pdown;
    	Button load, mean, median, save, quit; 
    	addWindowListener(new WindowAdapter(){
    		public void windowClosing(WindowEvent e){
    			System.exit(0);
    		}
    	});
    	
    	pdown = new Panel();
    	pdown.setBackground(Color.lightGray);
    	//定义按钮
    	load = new Button("装载图像");    
    	mean = new Button("均值滤波3*3");
    	median = new Button("中值滤波3*3");
    	save = new Button("保存");
    	quit = new Button("退出");
    	
    	this.add(pdown, BorderLayout.SOUTH);
    	//添加按钮
    	pdown.add(load);    
    	pdown.add(mean);
    	pdown.add(median);
    	pdown.add(save);
    	pdown.add(quit);
        //按钮的动作程序  装载图像
    	load.addActionListener(new ActionListener(){    
    		public void actionPerformed(ActionEvent e){
    			try {
				jLoad_ActionPerformed(e);
				} catch (IOException e1) {
					e1.printStackTrace();
				}
    		}
    	});
    	//按钮的动作程序  均值滤波
    	mean.addActionListener(new ActionListener(){    
    		public void actionPerformed(ActionEvent e){
    			jMean_ActionPerformed(e);
    		}
    	});
    	//按钮的动作程序  中值滤波
    	median.addActionListener(new ActionListener(){    
    		public void actionPerformed(ActionEvent e){
    			jMedian_ActionPerformed(e);
    		}
    	});
    	//按钮的动作程序  保存
    	save.addActionListener(new ActionListener(){    
    		public void actionPerformed(ActionEvent e){
    			try {
				jSave_ActionPerformed(e);
				} catch (IOException e1) {
					e1.printStackTrace();
				}
    		}
    	});
    	//按钮的动作程序  退出
    	quit.addActionListener(new ActionListener(){    
    		public void actionPerformed(ActionEvent e){
    			jQuit_ActionPerformed(e);
    		}
    	});
    }
  //按钮动作的实现  加载图像
    public void jLoad_ActionPerformed(ActionEvent e) throws IOException{    
    	File inputFile = new File("E:\\f2\\sc\\lena_zaosheng08.jpg");
        BufferedImage input = ImageIO.read(inputFile);
        iw = input.getWidth(this);
        ih = input.getHeight(this);
	pixels = new int[iw*ih];
	im = input;
	tmp = input;
        flag_load = true;
        repaint();
	}
  //按钮动作的实现 均值滤波  
  	public void jMean_ActionPerformed(ActionEvent e) {    
        if(flag_load){
        	try{
  			      PixelGrabber pg = new PixelGrabber(im,0,0,iw,ih,pixels,0,iw);
  			      pg.grabPixels();
  		      }catch(InterruptedException e3){
  			    e3.printStackTrace();
  		      }
  		    BufferedImage grayImage = new BufferedImage(iw, ih, 
					  BufferedImage.TYPE_INT_RGB);
  		    
  		    ColorModel cm = ColorModel.getRGBdefault();
  		    
  		    for(int i=1;i<ih-1;i++){
  		    	for(int j=1;j<iw-1;j++){
  		    		
  		    	    int red1 = cm.getRed(pixels[(i-1)*iw+j-1]);
  		    	    int red2 = cm.getRed(pixels[(i-1)*iw+j]);
  		    	    int red3 = cm.getRed(pixels[(i-1)*iw+j+1]);
  		    	    int red4 = cm.getRed(pixels[i*iw+j-1]);
  		    	    int red6 = cm.getRed(pixels[i*iw+j+1]);
  		    	    int red7 = cm.getRed(pixels[(i+1)*iw+j-1]);
  		    	    int red8 = cm.getRed(pixels[(i+1)*iw+j]);
  		    	    int red9 = cm.getRed(pixels[(i+1)*iw+j+1]);
  		    	    int meanRed = (red1+red2+red3+red4+red6+red7+red8+red9)/8;
  		    	    
  		    	    int green1 = cm.getGreen(pixels[(i-1)*iw+j-1]);
		    	    int green2 = cm.getGreen(pixels[(i-1)*iw+j]);
		    	    int green3 = cm.getGreen(pixels[(i-1)*iw+j+1]);
		    	    int green4 = cm.getGreen(pixels[i*iw+j-1]);
		    	    int green6 = cm.getGreen(pixels[i*iw+j+1]);
		    	    int green7 = cm.getGreen(pixels[(i+1)*iw+j-1]);
		    	    int green8 = cm.getGreen(pixels[(i+1)*iw+j]);
		    	    int green9 = cm.getGreen(pixels[(i+1)*iw+j+1]);
		    	    int meanGreen = (green1+green2+green3+green4+green6+green7+green8+green9)/8;
				    
		    	   int blue1 = cm.getBlue(pixels[(i-1)*iw+j-1]);
  		    	    int blue2 = cm.getBlue(pixels[(i-1)*iw+j]);
  		    	    int blue3 = cm.getBlue(pixels[(i-1)*iw+j+1]);
  		    	    int blue4 = cm.getBlue(pixels[i*iw+j-1]);
  		    	    int blue6 = cm.getBlue(pixels[i*iw+j+1]);
  		    	    int blue7 = cm.getBlue(pixels[(i+1)*iw+j-1]);
  		    	    int blue8 = cm.getBlue(pixels[(i+1)*iw+j]);
  		    	    int blue9 = cm.getBlue(pixels[(i+1)*iw+j+1]);
  		    	    int meanBlue = (blue1+blue2+blue3+blue4+blue6+blue7+blue8+blue9)/8;
		    	    
  		    	    int rgb = 255<<24|meanRed<<16|meanGreen<<8|meanBlue; 
		    	    grayImage.setRGB(j, i, rgb);
  		    	}	
  		    }
  		    tmp = grayImage;
			repaint();
  		
  	    }else{
  		    JOptionPane.showMessageDialog(null, "先点击“装载图像”，3Q！","提示：",
  				    JOptionPane.WARNING_MESSAGE);
  		    }
  	}
  //按钮动作的实现 中值滤波  
  	public void jMedian_ActionPerformed(ActionEvent e) {    
        if(flag_load){
        	try{
  			      PixelGrabber pg = new PixelGrabber(im,0,0,iw,ih,pixels,0,iw);
  			      pg.grabPixels();
  		      }catch(InterruptedException e3){
  			    e3.printStackTrace();
  		      }
  		    BufferedImage grayImage = new BufferedImage(iw, ih, 
					  BufferedImage.TYPE_INT_RGB);
  		    
  		    ColorModel cm = ColorModel.getRGBdefault();
  		    
  		    int[] tpRed = new int[9];
  		    int[] tpGreen = new int[9];
  		    int[] tpBlue = new int[9];
  		    
  		    for(int i=1;i<ih-1;i++){
  		    	for(int j=1;j<iw-1;j++){
  		    		
  		    		tpRed[0] = cm.getRed(pixels[(i-1)*iw+j-1]);
  		    		tpRed[1] = cm.getRed(pixels[(i-1)*iw+j]);
  		    		tpRed[2] = cm.getRed(pixels[(i-1)*iw+j+1]);
  		    		tpRed[3] = cm.getRed(pixels[i*iw+j-1]);
  		    		tpRed[4] = cm.getRed(pixels[i*iw+j]);
  		    		tpRed[5] = cm.getRed(pixels[i*iw+j+1]);
  		    		tpRed[6] = cm.getRed(pixels[(i+1)*iw+j-1]);
  		    		tpRed[7] = cm.getRed(pixels[(i+1)*iw+j]);
  		    		tpRed[8] = cm.getRed(pixels[(i+1)*iw+j+1]);
  		    	        for(int rj=0; rj<8; rj++){
  		    	    	for(int ri=0; ri<8-rj; ri++){
  		    	    		if(tpRed[ri]>tpRed[ri+1]){
  		    	    			int Red_Temp = tpRed[ri];
  	  		    	    		tpRed[ri] = tpRed[ri+1];
  	  		    	    		tpRed[ri+1] = Red_Temp;
  		    	    		}
  		    	    	}
  		    	    }
  		    	    int medianRed = tpRed[4];
  		    	    
  		    	    tpGreen[0] = cm.getGreen(pixels[(i-1)*iw+j-1]);
  		    	    tpGreen[1] = cm.getGreen(pixels[(i-1)*iw+j]);
  		    	    tpGreen[2] = cm.getGreen(pixels[(i-1)*iw+j+1]);
  		    	    tpGreen[3] = cm.getGreen(pixels[i*iw+j-1]);
  		    	    tpGreen[4] = cm.getGreen(pixels[i*iw+j]);
  		    	    tpGreen[5] = cm.getGreen(pixels[i*iw+j+1]);
  		    	    tpGreen[6] = cm.getGreen(pixels[(i+1)*iw+j-1]);
  		    	    tpGreen[7] = cm.getGreen(pixels[(i+1)*iw+j]);
  		    	    tpGreen[8] = cm.getGreen(pixels[(i+1)*iw+j+1]);
  		    	    for(int rj=0; rj<8; rj++){
		    	    	for(int ri=0; ri<8-rj; ri++){
		    	    		if(tpGreen[ri]>tpGreen[ri+1]){
		    	    			int Green_Temp = tpGreen[ri];
			    	    		tpGreen[ri] = tpGreen[ri+1];
			    	    		tpGreen[ri+1] = Green_Temp;
		    	    		}
		    	    	}
		    	    }
		    	    int medianGreen = tpGreen[4];
				    
		    	    tpBlue[0] = cm.getBlue(pixels[(i-1)*iw+j-1]);
		    	    tpBlue[1] = cm.getBlue(pixels[(i-1)*iw+j]);
		    	    tpBlue[2] = cm.getBlue(pixels[(i-1)*iw+j+1]);
		    	    tpBlue[3] = cm.getBlue(pixels[i*iw+j-1]);
		    	    tpBlue[4] = cm.getBlue(pixels[i*iw+j]);
		    	    tpBlue[5] = cm.getBlue(pixels[i*iw+j+1]);
		    	    tpBlue[6] = cm.getBlue(pixels[(i+1)*iw+j-1]);
		    	    tpBlue[7] = cm.getBlue(pixels[(i+1)*iw+j]);
		    	    tpBlue[8] = cm.getBlue(pixels[(i+1)*iw+j+1]);
		    	    for(int rj=0; rj<8; rj++){
		    	    	for(int ri=0; ri<8-rj; ri++){
		    	    		if(tpBlue[ri]>tpBlue[ri+1]){
		    	    			int Blue_Temp = tpBlue[ri];
			    	    		tpBlue[ri] = tpBlue[ri+1];
			    	    		tpBlue[ri+1] = Blue_Temp;
		    	    		}
		    	    	}
		    	    }
		    	    int medianBlue = tpBlue[4];
		    	    
  		    	    int rgb = 255<<24|medianRed<<16|medianGreen<<8|medianBlue; 
		    	    grayImage.setRGB(j, i, rgb);
  		    	}	
  		    }
  		    tmp = grayImage;
			repaint();
  		
  	    }else{
  		    JOptionPane.showMessageDialog(null, "先点击“装载图像”，3Q！","提示：",
  				    JOptionPane.WARNING_MESSAGE);
  		    }
  	}
  	//按钮动作的实现  save
  	public void jSave_ActionPerformed(ActionEvent e) throws IOException{    
        if(flag_load){
        	
    		BufferedImage bi = new BufferedImage(tmp.getWidth(null),tmp.getHeight(null), 
    				BufferedImage.TYPE_INT_RGB);
            Graphics g = bi.getGraphics();
            g.drawImage(tmp,0, 0,null);
            g.dispose();
    		
  		    File save_path=new File("E:\\f2\\sc\\save.jpg");
            ImageIO.write(bi, "JPG", save_path);

  	}else{
  		JOptionPane.showMessageDialog(null, "先点击“装载图像”，3Q！","提示：",
  				JOptionPane.WARNING_MESSAGE);
  		}
  	}
  	//按钮动作的实现  退出
  	public void jQuit_ActionPerformed(ActionEvent e){
  		System.exit(0);
  	}
  //绘图函数
  	public void paint(Graphics g){
  		if(flag_load){
  			g.drawImage(tmp,50,50,this);
  		}else{}
  	}
  	
	public static void main(String[] args) {
		colorfilter ti = new colorfilter();
		ti.setSize(1000,860);
		ti.setVisible(true);
	}
}