图像分析之直方图分析

 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.length; i++) {
          intensity[i] = 0;
        }
        getRGB( srcImage, 0, 0, srcImage.getWidth(), srcImage.getHeight(), inPixels );
        int index = 0;
        for(int row=0; row<srcImage.getHeight(); row++) {
          int ta = 0, tr = 0, tg = 0, tb = 0;
          for(int col=0; col<srcImage.getWidth(); 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<intensity.length; 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<intensity.length; 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 );
    }
 
}