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图像处理------高斯金字塔

简介: <p style="color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; line-height: 26px;"><span style="font-size: 18px;">一:图像金字塔基本操作</span></p> <p style="color: rgb(51, 51, 51); font-family: Arial;

一:图像金字塔基本操作

对一张图像不断的模糊之后向下采样,得到不同分辨率的图像,同时每次得到的

新的图像宽与高是原来图像的1/2, 最常见就是基于高斯的模糊之后采样,得到的

一系列图像称为高斯金字塔。




高斯金字塔不同(DoG)又称为拉普拉斯金字塔,其计算公式如下:

L(i) = G(i) – expand(G(i+1))

第i层拉普拉斯金字塔是由第i层高斯金字塔减去第i+1层高斯金字塔expand之后得到。

本文得到的DoG(Difference of Gaussian)结果如下:


二:关键代码解析

金字塔reduce操作实现代码如下:

[java] view plaincopy
  1. private BufferedImage pyramidReduce(BufferedImage src) {  
  2.     int width = src.getWidth();  
  3.        int height = src.getHeight();  
  4.        BufferedImage dest = createSubCompatibleDestImage(src, null);  
  5.        int[] inPixels = new int[width*height];  
  6.        int ow = width/2;  
  7.        int oh = height/2;  
  8.        int[] outPixels = new int[ow*oh];  
  9.        getRGB(src, 00, width, height, inPixels );  
  10.        int inRow=0, inCol = 0, index = 0, oudex =0, ta = 0;  
  11.        float[][] keneralData = this.getHVGaussianKeneral();  
  12.        for(int row=0; row<oh; row++) {  
  13.         for(int col=0; col<ow; col++) {  
  14.             inRow = 2* row;  
  15.             inCol = 2* col;  
  16.             if(inRow >= height) {  
  17.                 inRow = 0;  
  18.             }  
  19.             if(inCol >= width) {  
  20.                 inCol = 0;  
  21.             }  
  22.             float sumRed = 0, sumGreen = 0, sumBlue = 0;  
  23.             for(int subRow = -2; subRow <= 2; subRow++) {  
  24.                 int inRowOff = inRow + subRow;  
  25.                 if(inRowOff >= height || inRowOff < 0) {  
  26.                     inRowOff = 0;  
  27.                 }  
  28.                 for(int subCol = -2; subCol <= 2; subCol++) {  
  29.                     int inColOff = inCol + subCol;  
  30.                     if(inColOff >= width || inColOff < 0) {  
  31.                         inColOff = 0;  
  32.                     }  
  33.                     index = inRowOff * width + inColOff;  
  34.                     ta = (inPixels[index] >> 24) & 0xff;  
  35.                     int red = (inPixels[index] >> 16) & 0xff;  
  36.                     int green = (inPixels[index] >> 8) & 0xff;  
  37.                     int blue = inPixels[index] & 0xff;  
  38.                     sumRed += keneralData[subRow + 2][subCol + 2] * red;  
  39.                     sumGreen += keneralData[subRow + 2][subCol + 2] * green;  
  40.                     sumBlue += keneralData[subRow + 2][subCol + 2] * blue;  
  41.                 }  
  42.             }  
  43.               
  44.             oudex = row * ow + col;  
  45.             outPixels[oudex] = (ta << 24) | (clamp(sumRed) << 16) | (clamp(sumGreen) << 8) | clamp(sumBlue);  
  46.         }  
  47.        }  
  48.        setRGB( dest, 00, ow, oh, outPixels );  
  49.        return dest;  
  50. }  
金字塔expand实现代码如下:

[java] view plaincopy
  1. public BufferedImage pyramidExpand(BufferedImage src) {  
  2.     int width = src.getWidth();  
  3.     int height = src.getHeight();  
  4.     int[] inPixels = new int[width*height];  
  5.     getRGB(src, 00, width, height, inPixels );  
  6.     int ow = 2*width;  
  7.     int oh =2*height;  
  8.     int[] outPixels = new int[ow * oh];  
  9.     int index = 0, outdex = 0, ta = 0;  
  10.     float[][] keneralData = this.getHVGaussianKeneral();  
  11.     BufferedImage dest = createTwiceCompatibleDestImage(src, null);  
  12.     for(int row=0; row<oh; row++) {  
  13.         for(int col=0; col<ow; col++) {  
  14.             float sumRed = 0, sumGreen = 0, sumBlue = 0;  
  15.             for(int subRow = -2; subRow <= 2; subRow++) {  
  16.                 double srcRow = (row + subRow)/2.0;  
  17.                 double j = Math.floor(srcRow);  
  18.                 double t = srcRow - j;   
  19.                 if(t > 0) {  
  20.                     continue;  
  21.                 }  
  22.                 if(srcRow >= height || srcRow < 0) {  
  23.                     srcRow = 0;  
  24.                 }  
  25.                 for(int subCol = -2; subCol <= 2; subCol++) {  
  26.                     double srcColOff = (col + subCol)/2.0;  
  27.                     j = Math.floor(srcColOff);  
  28.                     t = srcColOff - j;  
  29.                     if(t > 0) {  
  30.                         continue;  
  31.                     }  
  32.                     if(srcColOff >= width || srcColOff < 0) {  
  33.                         srcColOff = 0;  
  34.                     }  
  35.                     index = (int)(srcRow * width + srcColOff);  
  36.                     ta = (inPixels[index] >> 24) & 0xff;  
  37.                     int red = (inPixels[index] >> 16) & 0xff;  
  38.                     int green = (inPixels[index] >> 8) & 0xff;  
  39.                     int blue = inPixels[index] & 0xff;  
  40.                     sumRed += keneralData[subRow + 2][subCol + 2] * red;  
  41.                     sumGreen += keneralData[subRow + 2][subCol + 2] * green;  
  42.                     sumBlue += keneralData[subRow + 2][subCol + 2] * blue;  
  43.                 }  
  44.             }  
  45.             outdex = row * ow + col;  
  46.             outPixels[outdex] = (ta << 24) | (clamp(4.0f * sumRed) << 16) | (clamp(4.0f * sumGreen) << 8) | clamp(4.0f * sumBlue);  
  47.             // outPixels[outdex] = (ta << 24) | (clamp(sumRed) << 16) | (clamp(sumGreen) << 8) | clamp(sumBlue);  
  48.         }  
  49.     }  
  50.     setRGB( dest, 00, ow, oh, outPixels );  
  51.     return dest;  
  52. }  
图像金字塔的reduce与expand过程都是卷积采样实现。特别注意的是expand

操作不是reduce的可逆操作。

关于什么是卷积,高斯滤波请参见博客上的其它相关文章。

高斯金字塔全部算法源代码如下:

[java] view plaincopy
  1. package com.gloomyfish.image.pyramid;  
  2.   
  3. import java.awt.image.BufferedImage;  
  4. import java.awt.image.ColorModel;  
  5.   
  6. public class PyramidAlgorithm extends GaussianFilter {  
  7.     private float a;  
  8.   
  9.     public PyramidAlgorithm() {  
  10.         a = 0.4f;  
  11.     }  
  12.       
  13.     public void setParameter(float p) {  
  14.         this.a = p;  
  15.     }  
  16.   
  17.     public BufferedImage[] pyramidDown(BufferedImage src, int level) {  
  18.         BufferedImage[] imagePyramids = new BufferedImage[level + 1];  
  19.         imagePyramids[0] = src;  
  20.         for(int i=1; i<imagePyramids.length; i++) {  
  21.             imagePyramids[i] = pyramidReduce(imagePyramids[i-1]);  
  22.         }  
  23.         return imagePyramids;  
  24.     }  
  25.       
  26.     public BufferedImage[] pyramidUp(BufferedImage[] srcImage) {  
  27.         BufferedImage[] imagePyramids = new BufferedImage[srcImage.length];  
  28.         for(int i=0; i<srcImage.length; i++) {  
  29.             imagePyramids[i] = pyramidExpand(srcImage[i]);  
  30.         }  
  31.         return imagePyramids;  
  32.     }  
  33.       
  34.     /*** 
  35.      * l1 = g1 - expand(g2) 
  36.      * l2 = g2 - expand(g3) 
  37.      * l0 = g0 - expand(g1) 
  38.      * @param reduceImages 
  39.      * @param expandImages 
  40.      * @return 
  41.      */  
  42.     public BufferedImage[] getLaplacianPyramid(BufferedImage[] reduceImages) {  
  43.         BufferedImage[] laplaciImages = new BufferedImage[reduceImages.length -1];  
  44.         for(int i=1; i<reduceImages.length; i++) {  
  45.             BufferedImage expandImage = pyramidExpand(reduceImages[i]);  
  46.             laplaciImages[i-1] = createCompatibleDestImage(expandImage, null);  
  47.             int width = reduceImages[i-1].getWidth();  
  48.             int height = reduceImages[i-1].getHeight();  
  49.               
  50.             int ewidth = expandImage.getWidth();  
  51.             width = (width > ewidth) ? ewidth : width;  
  52.             height = (height > expandImage.getHeight()) ? expandImage.getHeight():height;  
  53.             System.out.println(" width = " + width + " expand width = " + ewidth);  
  54.               
  55.             int[] reducePixels = new int[width*height];  
  56.             int[] expandPixels = new int[width*height];  
  57.             int[] laPixels = new int[width*height];  
  58.             getRGB( reduceImages[i-1], 00, width, height, reducePixels);  
  59.             getRGB( expandImage, 00, width, height, expandPixels );  
  60.             int index = 0;  
  61.             int er = 0, eg = 0, eb = 0;  
  62.             for(int row=0; row<height; row++) {  
  63.                 int ta = 0, tr = 0, tg = 0, tb = 0;  
  64.                 for(int col=0; col<width; col++) {  
  65.                     index = row * width + col;  
  66.                     ta = (reducePixels[index] >> 24) & 0xff;  
  67.                     tr = (reducePixels[index] >> 16) & 0xff;  
  68.                     tg = (reducePixels[index] >> 8) & 0xff;  
  69.                     tb = reducePixels[index] & 0xff;  
  70.                       
  71.                     ta = (expandPixels[index] >> 24) & 0xff;  
  72.                     er = (expandPixels[index] >> 16) & 0xff;  
  73.                     eg = (expandPixels[index] >> 8) & 0xff;  
  74.                     eb = expandPixels[index] & 0xff;  
  75.                       
  76.                     tr = tr - er;  
  77.                     tg = tg - eg;  
  78.                     tb = tb - eb;  
  79.                       
  80.                     laPixels[index] = (ta << 24) | (clamp(tr) << 16) | (clamp(tg) << 8) | clamp(tb);  
  81.                 }  
  82.             }  
  83.             setRGB( laplaciImages[i-1], 00, width, height, laPixels );  
  84.         }  
  85.   
  86.         return laplaciImages;  
  87.     }  
  88.       
  89.     private BufferedImage pyramidReduce(BufferedImage src) {  
  90.         int width = src.getWidth();  
  91.         int height = src.getHeight();  
  92.         BufferedImage dest = createSubCompatibleDestImage(src, null);  
  93.         int[] inPixels = new int[width*height];  
  94.         int ow = width/2;  
  95.         int oh = height/2;  
  96.         int[] outPixels = new int[ow*oh];  
  97.         getRGB(src, 00, width, height, inPixels );  
  98.         int inRow=0, inCol = 0, index = 0, oudex =0, ta = 0;  
  99.         float[][] keneralData = this.getHVGaussianKeneral();  
  100.         for(int row=0; row<oh; row++) {  
  101.             for(int col=0; col<ow; col++) {  
  102.                 inRow = 2* row;  
  103.                 inCol = 2* col;  
  104.                 if(inRow >= height) {  
  105.                     inRow = 0;  
  106.                 }  
  107.                 if(inCol >= width) {  
  108.                     inCol = 0;  
  109.                 }  
  110.                 float sumRed = 0, sumGreen = 0, sumBlue = 0;  
  111.                 for(int subRow = -2; subRow <= 2; subRow++) {  
  112.                     int inRowOff = inRow + subRow;  
  113.                     if(inRowOff >= height || inRowOff < 0) {  
  114.                         inRowOff = 0;  
  115.                     }  
  116.                     for(int subCol = -2; subCol <= 2; subCol++) {  
  117.                         int inColOff = inCol + subCol;  
  118.                         if(inColOff >= width || inColOff < 0) {  
  119.                             inColOff = 0;  
  120.                         }  
  121.                         index = inRowOff * width + inColOff;  
  122.                         ta = (inPixels[index] >> 24) & 0xff;  
  123.                         int red = (inPixels[index] >> 16) & 0xff;  
  124.                         int green = (inPixels[index] >> 8) & 0xff;  
  125.                         int blue = inPixels[index] & 0xff;  
  126.                         sumRed += keneralData[subRow + 2][subCol + 2] * red;  
  127.                         sumGreen += keneralData[subRow + 2][subCol + 2] * green;  
  128.                         sumBlue += keneralData[subRow + 2][subCol + 2] * blue;  
  129.                     }  
  130.                 }  
  131.                   
  132.                 oudex = row * ow + col;  
  133.                 outPixels[oudex] = (ta << 24) | (clamp(sumRed) << 16) | (clamp(sumGreen) << 8) | clamp(sumBlue);  
  134.             }  
  135.         }  
  136.         setRGB( dest, 00, ow, oh, outPixels );  
  137.         return dest;  
  138.     }  
  139.       
  140.     public BufferedImage createSubCompatibleDestImage(BufferedImage src, ColorModel dstCM) {  
  141.         if ( dstCM == null )  
  142.             dstCM = src.getColorModel();  
  143.         return new BufferedImage(dstCM, dstCM.createCompatibleWritableRaster(src.getWidth()/2, src.getHeight()/2), dstCM.isAlphaPremultiplied(), null);  
  144.     }  
  145.       
  146.     public BufferedImage createTwiceCompatibleDestImage(BufferedImage src, ColorModel dstCM) {  
  147.         if ( dstCM == null )  
  148.             dstCM = src.getColorModel();  
  149.         return new BufferedImage(dstCM, dstCM.createCompatibleWritableRaster(src.getWidth()*2, src.getHeight()*2), dstCM.isAlphaPremultiplied(), null);  
  150.     }  
  151.       
  152.     public BufferedImage pyramidExpand(BufferedImage src) {  
  153.         int width = src.getWidth();  
  154.         int height = src.getHeight();  
  155.         int[] inPixels = new int[width*height];  
  156.         getRGB(src, 00, width, height, inPixels );  
  157.         int ow = 2*width;  
  158.         int oh =2*height;  
  159.         int[] outPixels = new int[ow * oh];  
  160.         int index = 0, outdex = 0, ta = 0;  
  161.         float[][] keneralData = this.getHVGaussianKeneral();  
  162.         BufferedImage dest = createTwiceCompatibleDestImage(src, null);  
  163.         for(int row=0; row<oh; row++) {  
  164.             for(int col=0; col<ow; col++) {  
  165.                 float sumRed = 0, sumGreen = 0, sumBlue = 0;  
  166.                 for(int subRow = -2; subRow <= 2; subRow++) {  
  167.                     double srcRow = (row + subRow)/2.0;  
  168.                     double j = Math.floor(srcRow);  
  169.                     double t = srcRow - j;   
  170.                     if(t > 0) {  
  171.                         continue;  
  172.                     }  
  173.                     if(srcRow >= height || srcRow < 0) {  
  174.                         srcRow = 0;  
  175.                     }  
  176.                     for(int subCol = -2; subCol <= 2; subCol++) {  
  177.                         double srcColOff = (col + subCol)/2.0;  
  178.                         j = Math.floor(srcColOff);  
  179.                         t = srcColOff - j;  
  180.                         if(t > 0) {  
  181.                             continue;  
  182.                         }  
  183.                         if(srcColOff >= width || srcColOff < 0) {  
  184.                             srcColOff = 0;  
  185.                         }  
  186.                         index = (int)(srcRow * width + srcColOff);  
  187.                         ta = (inPixels[index] >> 24) & 0xff;  
  188.                         int red = (inPixels[index] >> 16) & 0xff;  
  189.                         int green = (inPixels[index] >> 8) & 0xff;  
  190.                         int blue = inPixels[index] & 0xff;  
  191.                         sumRed += keneralData[subRow + 2][subCol + 2] * red;  
  192.                         sumGreen += keneralData[subRow + 2][subCol + 2] * green;  
  193.                         sumBlue += keneralData[subRow + 2][subCol + 2] * blue;  
  194.                     }  
  195.                 }  
  196.                 outdex = row * ow + col;  
  197.                 outPixels[outdex] = (ta << 24) | (clamp(4.0f * sumRed) << 16) | (clamp(4.0f * sumGreen) << 8) | clamp(4.0f * sumBlue);  
  198.                 // outPixels[outdex] = (ta << 24) | (clamp(sumRed) << 16) | (clamp(sumGreen) << 8) | clamp(sumBlue);  
  199.             }  
  200.         }  
  201.         setRGB( dest, 00, ow, oh, outPixels );  
  202.         return dest;  
  203.     }  
  204.   
  205. }  
特别注意:我没有处理像素的宽与高,如果宽与高不是偶数可能

会有问题,使用时请自己处理吧。

UI实现源代码如下:

[java] view plaincopy
  1. package com.gloomyfish.image.pyramid;  
  2.   
  3. import java.awt.BorderLayout;  
  4. import java.awt.Dimension;  
  5. import java.awt.FlowLayout;  
  6. import java.awt.Graphics;  
  7. import java.awt.MediaTracker;  
  8. import java.awt.event.ActionEvent;  
  9. import java.awt.event.ActionListener;  
  10. import java.awt.image.BufferedImage;  
  11. import java.io.File;  
  12. import java.io.IOException;  
  13.   
  14. import javax.imageio.ImageIO;  
  15. import javax.swing.JButton;  
  16. import javax.swing.JComponent;  
  17. import javax.swing.JFileChooser;  
  18. import javax.swing.JFrame;  
  19. import javax.swing.JPanel;  
  20.   
  21. public class PyramidDemoUI extends JComponent implements ActionListener {  
  22.   
  23.     /** 
  24.      *  
  25.      */  
  26.     private static final long serialVersionUID = 1L;  
  27.     private JButton upButton;  
  28.     private JButton downButton;  
  29.     private BufferedImage[] reduceImages;  
  30.     private BufferedImage[] expandImages;  
  31.     private BufferedImage sourceImage;  
  32.     private Dimension mySize;  
  33.     private MediaTracker tracker;  
  34.       
  35.     public PyramidDemoUI(File f)  
  36.     {  
  37.         initComponents(f);  
  38.     }  
  39.   
  40.     private void initComponents(File f)  
  41.     {  
  42.         // TODO Auto-generated method stub  
  43.         try {    
  44.             sourceImage = ImageIO.read(f);    
  45.         } catch (IOException e1) {    
  46.             e1.printStackTrace();    
  47.         }    
  48.             
  49.         tracker = new MediaTracker(this);    
  50.         tracker.addImage(sourceImage, 1);    
  51.             
  52.         // blocked 10 seconds to load the image data    
  53.         try {    
  54.             if (!tracker.waitForID(110000)) {    
  55.                 System.out.println("Load error.");    
  56.                 System.exit(1);    
  57.             }// end if    
  58.         } catch (InterruptedException e) {    
  59.             e.printStackTrace();    
  60.             System.exit(1);    
  61.         }// end catch    
  62.           
  63.         JPanel btnPanel = new JPanel();  
  64.         btnPanel.setLayout(new FlowLayout(FlowLayout.RIGHT));  
  65.         upButton = new JButton("Laplacian Pyramid");  
  66.         downButton = new JButton("Pyramid Down");  
  67.         upButton.addActionListener(this);  
  68.         downButton.addActionListener(this);  
  69.         btnPanel.add(upButton);  
  70.         btnPanel.add(downButton);  
  71.         mySize = new Dimension(800800);     
  72.         JFrame mainFrame = new JFrame("Pyramid Demo - Gloomyfish");  
  73.         mainFrame.getContentPane().setLayout(new BorderLayout());  
  74.         mainFrame.getContentPane().add(this, BorderLayout.CENTER);  
  75.         mainFrame.getContentPane().add(btnPanel, BorderLayout.SOUTH);  
  76.         mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    
  77.         mainFrame.pack();    
  78.         mainFrame.setVisible(true);    
  79.     }  
  80.   
  81.     @Override  
  82.     public Dimension getPreferredSize() {  
  83.         return mySize;  
  84.     }  
  85.   
  86.     @Override  
  87.     protected void paintComponent(Graphics g)   
  88.     {  
  89. //      g.drawImage(sourceImage, 10, 10, sourceImage.getWidth(), sourceImage.getHeight(), null);  
  90.         int width = 10;  
  91. //      if(reduceImages != null) {  
  92. //          for(int i=1; i<reduceImages.length; i++) {  
  93. //              width += (10 + reduceImages[i-1].getWidth());  
  94. //              g.drawImage(reduceImages[i], width, 10, reduceImages[i].getWidth(), reduceImages[i].getHeight(), null);  
  95. //          }  
  96. //      }  
  97.           
  98.         width = 10;  
  99.         if(expandImages != null) {  
  100.             for(int i=0; i<expandImages.length; i++) {  
  101.                 g.drawImage(expandImages[i], width, 15, expandImages[i].getWidth(), expandImages[i].getHeight(), null);  
  102.                 // g.drawImage(expandImages[i], width, 15 + sourceImage.getHeight(), expandImages[i].getWidth(), expandImages[i].getHeight(), null);  
  103.                 width += (10 + expandImages[i].getWidth());  
  104.             }  
  105.         }  
  106.         super.paintComponent(g);  
  107.     }  
  108.       
  109.     public static void main(String[] args) {    
  110.         JFileChooser chooser = new JFileChooser();    
  111.         chooser.showOpenDialog(null);    
  112.         File f = chooser.getSelectedFile();    
  113.         new PyramidDemoUI(f);    
  114.     }  
  115.   
  116.     @Override  
  117.     public void actionPerformed(ActionEvent event) {  
  118.         if(event.getActionCommand().equals("Laplacian Pyramid")) {  
  119.             if(reduceImages != null) {  
  120.                 // int size = reduceImages.length;  
  121.                 PyramidAlgorithm pyramid = new PyramidAlgorithm();  
  122.                 expandImages = pyramid.getLaplacianPyramid(reduceImages);  
  123.                 // expandImages = pyramid.pyramidUp(reduceImages);  
  124.                 repaint();  
  125.             } else {  
  126.                   
  127.             }  
  128.   
  129.         } else if(event.getActionCommand().equals("Pyramid Down")) {  
  130.             // a.Smooth the image with Gaussian filter 5×5(1/4-a/2, 1/4, a, 1/4, 1/4-a/2) a = [0.3,0.6]  
  131.             // b.Sub sample the image by half - 选择偶数行与列  
  132.             // c.If reached desired size stop, else send the result to step 1  
  133.             PyramidAlgorithm pyramid = new PyramidAlgorithm();  
  134.             reduceImages = pyramid.pyramidDown(sourceImage, 3);  
  135.             repaint();  
  136.         } else {  
  137.             // do nothing  
  138.         }  
  139.           
  140.     }    
  141.   
  142. }  

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