它的核心思想就是让图像暗的地方变亮，亮的地方变暗。问题是，如果图像原本的亮暗程度就非常符合人眼的观察结果，那么直方图均衡化之后的图像就变的很糟。所以该方法要依据图像数据的特点而定。
图像整体变亮，暗处的细节得到了突出：
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 chongcaiyang extends Frame{
Image im, tmp;
int iw, ih;
int[] pixels;
boolean flag_load = false;
//构造方法
public chongcaiyang(){
super("chongcaiyang");
Panel pdown;
Button load, run, 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");
run = new Button("重采样");
save = new Button("保存");
quit = new Button("退出");
this.add(pdown, BorderLayout.SOUTH);
//添加按钮 此处的顺序为案板上的左->右的顺序
pdown.add(load);
pdown.add(run);
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 重采样
run.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
try {
jRun_ActionPerformed(e);
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
});
//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("d:\\java\\sc\\lena_grey.jpg");
BufferedImage input = ImageIO.read(inputFile);
tmp = input;
flag_load = true;
repaint();
}
//按钮动作的实现 重采样
public void jRun_ActionPerformed(ActionEvent e) throws IOException{
if(flag_load){
File inputFile = new File("d:\\java\\sc\\lena_grey.jpg");
BufferedImage input = ImageIO.read(inputFile);
iw = input.getWidth(this);
ih = input.getHeight(this);
//设定N值
int N = iw;
String s = JOptionPane.showInputDialog(null,"请输入N值(512/256/128/64/32/16/8)");
if(s!= null&& !s.equals("")){
N = Integer.parseInt(s);
}
//检查输入是否正确
if((N>512)|(N<8)){
N = 512;
JOptionPane.showMessageDialog(null, "输入不正确，请重新输入！");
}
//图像重采样
BufferedImage grayImage = new BufferedImage(iw, ih,
BufferedImage.TYPE_BYTE_GRAY);
//kao!三个循环就就能搞定，不就是重采样吗？
for(int i=0; i<ih-1; i++){
for(int j=0; j<iw-1; j=j+(ih/N)){
for(int k=0; k<(ih/N); k++){
int rgb = input.getRGB(i, j);
int grey = (int) (0.3*((rgb&0xff0000)>>16)+0.59*((rgb&0xff00)>>8)+0.11*((rgb&0xff)));
rgb = 255<<24|grey<<16|grey<<8|grey;
grayImage.setRGB(i, j+k, rgb);
}
}
}
//产生图像
tmp = grayImage;
flag_load = true;
repaint();
}else{
JOptionPane.showMessageDialog(null, "先点击“装载图像”，3Q！","提示：",
JOptionPane.WARNING_MESSAGE);
}
}
//按钮动作的实现保存
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("d:\\java\\sc\\save_t01.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) {
chongcaiyang ti = new chongcaiyang();
ti.setSize(1000,860);
ti.setVisible(true);
}
}
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 hist extends Frame{
Image im, tmp;
int iw, ih;
int[] pixels;
boolean flag_load = false;
boolean flag_grey = false;
//hist的构造方法
public hist(){
this.setTitle("直方图均衡化");
Panel pdown;
Button load, grey, hist, run, save, quit;
//添加窗口监听事件
addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
System.exit(0);
}
}
);
pdown = new Panel();
pdown.setBackground(Color.LIGHT_GRAY);
//按钮名称
load = new Button("装载图像");
grey = new Button("灰度图像");
hist = new Button("直方图");
run = new Button("均衡化");
save = new Button("保存");
quit = new Button("退出");
this.add(pdown, BorderLayout.SOUTH);
//增加按钮
pdown.add(load);
pdown.add(grey);
pdown.add(hist);
pdown.add(run);
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 灰度化
grey.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
try {
jGrey_ActionPerformed(e);
} catch (IOException e1) {
e1.printStackTrace();
}
}
});
//按钮的动作程序 直方图
hist.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
jHist_ActionPerformed(e);
}
});
//按钮的动作程序 直方图均衡化
run.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
jRun_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("d:\\java\\sc\\source.jpg");
BufferedImage input = ImageIO.read(inputFile);
im = input;
tmp = input;
flag_load = true;
repaint();
}
//按钮动作的实现 灰度化
public void jGrey_ActionPerformed(ActionEvent e) throws IOException{
if(flag_load){
File inputFile = new File("d:\\java\\sc\\source.jpg");
BufferedImage input = ImageIO.read(inputFile);
iw = input.getWidth(this);
ih = input.getHeight(this);
pixels = new int[iw*ih];
BufferedImage grayImage = new BufferedImage(iw, ih,
BufferedImage.TYPE_BYTE_GRAY);
for(int i=0; i<iw; i++){
for(int j=0; j<ih; j++){
int rgb = input.getRGB(i, j);
int grey = (int) (0.3*((rgb&0xff0000 )>>16)+0.59*((rgb&0xff00 )>>8)+0.11*((rgb&0xff)));
rgb = 255<<24|grey<<16|grey<<8|grey;
grayImage.setRGB(i, j, rgb);
}
}
tmp = grayImage;
try{
PixelGrabber pg = new PixelGrabber(tmp,0,0,iw,ih,pixels,0,iw);
pg.grabPixels();
}catch(InterruptedException e3){
e3.printStackTrace();
}
flag_grey = true;
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 直方图显示 调用histshow这个类进行操作
public void jHist_ActionPerformed(ActionEvent e){
histshow h = new histshow();
h.getData(pixels, iw, ih);
h.setSize(480,350);
h.setVisible(true);
}
//按钮动作的实现 直方图均衡化
public void jRun_ActionPerformed(ActionEvent e){
if(flag_load&&flag_grey){
try{
PixelGrabber pg = new PixelGrabber(tmp,0,0,iw,ih,pixels,0,iw);
pg.grabPixels();
}catch(InterruptedException e3){
e3.printStackTrace();
}
BufferedImage greyImage = new BufferedImage(iw, ih,
BufferedImage.TYPE_BYTE_GRAY);
//获取图像的直方图
int[] histogram = new int[256];
for(int i=0; i<ih-1; i++){
for(int j=0; j<iw-1; j++){
int grey = pixels[i*iw+j]&0xff;
histogram[grey]++;
}
}
//直方图均衡化
double a = (double)255/(iw*ih);
double[] c = new double [256];
c[0] = (a*histogram[0]);
for(int i=1; i<256; i++){
c[i] = c[i-1]+(int)(a*histogram[i]);
}
for(int i=0; i<ih; i++){
for(int j=0; j<iw; j++){
int grey = pixels[i*iw+j]&0x0000ff;
int hist = (int)(c[grey]);
pixels[i*iw+j] = 255<<24|hist<<16|hist<<8|hist;
greyImage.setRGB(j, i, pixels[i*iw+j]);
}
}
tmp = greyImage;
flag_load = true;
repaint();
}else{
JOptionPane.showMessageDialog(null, "先点击“装载图像”，3Q！","提示：",
JOptionPane.WARNING_MESSAGE);
}
}
//按钮动作的实现保存
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("d:\\java\\sc\\save_t01.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) {
hist ti = new hist();
ti.setSize(900,860);
ti.setVisible(true);
}
}
import java.awt.*;
import java.awt.event.*;
import java.awt.Window;
public class histshow extends Frame{
int data[];
int histogram[] = new int[256];
public histshow(){
this.setTitle("图像的灰度直方图");
Panel pdown;
Button quit;
pdown = new Panel();
quit = new Button("关闭窗口");
this.add(pdown, BorderLayout.SOUTH);
pdown.add(quit);
quit.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
jQuit_ActionPerformed(e);
}
});
// 添加窗口监听事件
addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
histshow.this.dispose();
}
});
}
public void jQuit_ActionPerformed(ActionEvent e){
this.setVisible(false);
}
public void getData(int[] data, int iw, int ih){
this.data = data;
for (int i = 0; i < iw * ih; i++){
int grey = data[i] & 0xff;
histogram[grey]++;
}
// 找出最大的数,进行标准化.
int temp = histogram[0];
for (int i = 0; i < 256; i++){
if (temp <= histogram[i]){
temp = histogram[i];
//System.out.println(temp);
}
}
for (int i = 0; i < 256; i++){
histogram[i] = histogram[i] * 200 / temp;
//System.out.println(temp);
}
}
//画出直方图
public void paint(Graphics g){
// 画出水平和垂直的轴
g.drawLine(100, 250, 356, 250);
g.drawLine(100, 50, 100, 250);
// 画出横轴坐标
g.drawString("0", 98, 263);
g.drawString("50", 145, 263);
g.drawString("100", 193, 263);
g.drawString("150", 243, 263);
g.drawString("200", 293, 263);
g.drawString("250", 343, 263);
// 画出纵轴坐标
g.drawString("0.5", 83, 145);
g.drawString("1", 90, 60);
// 画出图像的直方图
for (int i = 0; i < 256; i++){
g.drawLine(100 + i, 250, 100 + i, 250 - histogram[i]);
}
g.drawString("该图像的灰度直方图如上所示.", 160, 280);
}
}