灰度图像的直方图

主要代码如下：
package chapter6;

import java.awt.*;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;

/**

• Created by LENOVO on 18-2-1.
  */
  public class Histogram extends AbstractBufferedImageOp {

  public BufferedImage filter(BufferedImage src,BufferedImage dest){
  int[] histogram = new int[256];
  int width = src.getWidth();
  int height = src.getHeight();
  if(dest == null){
  dest = creatCompatibleDestImage(src,null);
  }
  int[] inPixels = new int[width*height];
  getRGB(src,0,0,width,height,inPixels);

   //获取直方图数据
   for(int i=0;i<histogram.length;i++){
       histogram[i] = 0;
   }
   int index = 0;
   for(int row=0;row<height;row++){
       int tr = 0;
       for(int col=0;col<width;col++){
           index = row*width+col;
           tr = (inPixels[index] >> 16) & 0xff;
           histogram[tr] ++;
       }
   }
   double maxFrequency = 0;//计算像素出现的最大频率值
   for(int i=0;i<histogram.length;i++){
       maxFrequency = Math.max(histogram[i],maxFrequency);
   }
   //绘制直方图
   Graphics2D g2d = dest.createGraphics();
   g2d.setPaint(Color.LIGHT_GRAY);
   g2d.fillRect(0,0,width,height);
  
   //绘制XY轴
   g2d.setPaint(Color.black);
   g2d.drawLine(50,50,50,height-50);
   g2d.drawLine(50,height-50,width-50,height-50);
   //绘制XY轴标题
   g2d.drawString("0",50,height-30);
   g2d.drawString("255",width-50,height-30);
   g2d.drawString("0",20,height-50);
   g2d.drawString(""+maxFrequency,20,50);
   //绘制坐标轴刻度
   double xunit = (width-100)/255;
   double yunit = (height-100)/maxFrequency;
   for(int i=0;i<histogram.length;i++){
       double xp = 50+xunit*i;
       double yp = yunit*histogram[i];
       Rectangle2D rect2d = new Rectangle2D.Double(xp,height-50-yp,xunit,yp);
       g2d.fill(rect2d);
   }
   System.out.print(maxFrequency);
   return dest;
  

  }

}
测试代码同上