图像分析之强度直方图分析

2012-6-3 17:08| 发布者: gbs| 查看: 8601| 评论: 0

摘要: 图像分析之强度直方图分析直方图介绍强度直方图图形化显示不同的像素值在不同的强度值上的出现频率，对于灰度图像来说强度范围为之间，对于RGB的彩色图像可以独立显示三种颜色的强度直方图。强度直方图是用来寻找灰 ...

图像分析之强度直方图分析

直方图介绍

强度直方图图形化显示不同的像素值在不同的强度值上的出现频率，对于灰度图像来说强度

范围为[0~255]之间，对于RGB的彩色图像可以独立显示三种颜色的强度直方图。强度直方

图是用来寻找灰度图像二值化阈值常用而且是有效的手段之一，如果一幅灰度图像的直方图

显示为两个波峰，则二值化阈值应该是这两个波峰之间的某个灰度值。同时强度直方图是调

整图像对比度的重要依据

直方图实现方法：

对一幅灰度图像从上到下，从左到右扫描每个像素值，在每个灰度值上计算像素数目，以这

些数据为基础完成图像直方图的绘制。

运行效果如下：

程序实现：

1. 首先对一幅RGB图像完成灰度转换，转换代码如下：

2. 初始化直方图数据数组int[256] 因为灰度值的范围为0～255

3. 扫描灰度图像，完成强度数据计算。

4. 使用Java 2D绘制直方图

直方图实现源代码：

package com.gloomyfish.image.analysis;

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;

public class HistogramAnalysisAlg {
private BufferedImage srcImage;
private BufferedImage histogramImage;
private int size = 280;

public HistogramAnalysisAlg(BufferedImage srcImage){
histogramImage = new BufferedImage(size,size, BufferedImage.TYPE_4BYTE_ABGR);
this.srcImage = srcImage;
}

public BufferedImage getHistogram() {
int[] inPixels = new int[srcImage.getWidth()*srcImage.getHeight()];
int[] intensity = new int[256];
for(int i=0; i intensity[i] = 0;
}
getRGB( srcImage, 0, 0, srcImage.getWidth(), srcImage.getHeight(), inPixels );
int index = 0;
for(int row=0; row int ta = 0, tr = 0, tg = 0, tb = 0;
for(int col=0; col index = row * srcImage.getWidth() + col;
ta = (inPixels[index] >> 24) & 0xff;
tr = (inPixels[index] >> 16) & 0xff;
tg = (inPixels[index] >> 8) & 0xff;
tb = inPixels[index] & 0xff;
int gray = (int)(0.299 * (double)tr + 0.587 * (double)tg + 0.114 * (double)tb);
intensity[gray]++;
}
}

// draw XY Axis lines
Graphics2D g2d = histogramImage.createGraphics();
g2d.setPaint(Color.BLACK);
g2d.fillRect(0, 0, size, size);
g2d.setPaint(Color.WHITE);
g2d.drawLine(5, 250, 265, 250);
g2d.drawLine(5, 250, 5, 5);

// scale to 200
g2d.setPaint(Color.GREEN);
int max = findMaxValue(intensity);
float rate = 200.0f/((float)max);
int offset = 2;
for(int i=0; i int frequency = (int)(intensity[i] * rate);
g2d.drawLine(5 + offset + i, 250, 5 + offset + i, 250-frequency);
}

// X Axis Gray intensity
g2d.setPaint(Color.RED);
g2d.drawString("Gray Intensity", 100, 270);
return histogramImage;
}

private int findMaxValue(int[] intensity) {
int max = -1;
for(int i=0; i if(max < intensity[i]) {
max = intensity[i];
}
}
return max;
}

/**
* A convenience method for getting ARGB pixels from an image. This tries to avoid the performance
* penalty of BufferedImage.getRGB unmanaging the image.
*/
public int[] getRGB( BufferedImage image, int x, int y, int width, int height, int[] pixels ) {
int type = image.getType();
if ( type == BufferedImage.TYPE_INT_ARGB || type == BufferedImage.TYPE_INT_RGB )
return (int [])image.getRaster().getDataElements( x, y, width, height, pixels );
return image.getRGB( x, y, width, height, pixels, 0, width );
}

/**
* A convenience method for setting ARGB pixels in an image. This tries to avoid the performance
* penalty of BufferedImage.setRGB unmanaging the image.
*/
public void setRGB( BufferedImage image, int x, int y, int width, int height, int[] pixels ) {
int type = image.getType();
if ( type == BufferedImage.TYPE_INT_ARGB || type == BufferedImage.TYPE_INT_RGB )
image.getRaster().setDataElements( x, y, width, height, pixels );
else
image.setRGB( x, y, width, height, pixels, 0, width );
}

}
测试代码如下：
package com.gloomyfish.image.analysis;

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.MediaTracker;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.JComponent;
import javax.swing.JFileChooser;
import javax.swing.JFrame;

public class ImageAnalysisUI extends JComponent {
/**
*
*/
private static final long serialVersionUID = 1518574788794973574L;
private BufferedImage rawImg;
private BufferedImage modImg;
private MediaTracker tracker;
private Dimension mySize;

public ImageAnalysisUI(File f) {
try {
rawImg = ImageIO.read(f);
HistogramAnalysisAlg filter = new HistogramAnalysisAlg(rawImg);
modImg = filter.getHistogram();
} catch (IOException e1) {
e1.printStackTrace();
}

tracker = new MediaTracker(this);
tracker.addImage(rawImg, 1);

// blocked 10 seconds to load the image data
try {
if (!tracker.waitForID(1, 10000)) {
System.out.println("Load error.");
System.exit(1);
}// end if
} catch (InterruptedException e) {
e.printStackTrace();
System.exit(1);
}// end catch

mySize = new Dimension(2*rawImg.getWidth() + 20, rawImg.getHeight()*2);
JFrame imageFrame = new JFrame("Gloomyfish - Image Analysis");
imageFrame.getContentPane().add(this);
imageFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
imageFrame.pack();
imageFrame.setVisible(true);
}

public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.drawImage(rawImg, 0, 0, rawImg.getWidth(), rawImg.getHeight(), null);
g2.drawImage(modImg, rawImg.getWidth()+10, 0, modImg.getWidth(), modImg.getHeight(), null);
g2.drawString("source image", 10, rawImg.getHeight() +10);
g2.drawString("connected component labeled area", 10 + modImg.getWidth(), rawImg.getHeight() +10);
}
public Dimension getPreferredSize() {
return mySize;
}

public Dimension getMinimumSize() {
return mySize;
}

public Dimension getMaximumSize() {
return mySize;
}

public static void main(String[] args) {
JFileChooser chooser = new JFileChooser();
chooser.showOpenDialog(null);
File f = chooser.getSelectedFile();
new ImageAnalysisUI(f);
}
}

http://blog.csdn.net/jia20003/article/details/7582666

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