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:
- private BufferedImage pyramidReduce(BufferedImage src) {
- int width = src.getWidth();
- int height = src.getHeight();
- BufferedImage dest = createSubCompatibleDestImage(src, null);
- int[] inPixels = new int[width*height];
- int ow = width/2;
- int oh = height/2;
- int[] outPixels = new int[ow*oh];
- getRGB(src, 0, 0, width, height, inPixels );
- int inRow=0, inCol = 0, index = 0, oudex =0, ta = 0;
- float[][] keneralData = this.getHVGaussianKeneral();
- for(int row=0; row<oh; row++) {
- for(int col=0; col<ow; col++) {
- inRow = 2* row;
- inCol = 2* col;
- if(inRow >= height) {
- inRow = 0;
- }
- if(inCol >= width) {
- inCol = 0;
- }
- float sumRed = 0, sumGreen = 0, sumBlue = 0;
- for(int subRow = -2; subRow <= 2; subRow++) {
- int inRowOff = inRow + subRow;
- if(inRowOff >= height || inRowOff < 0) {
- inRowOff = 0;
- }
- for(int subCol = -2; subCol <= 2; subCol++) {
- int inColOff = inCol + subCol;
- if(inColOff >= width || inColOff < 0) {
- inColOff = 0;
- }
- index = inRowOff * width + inColOff;
- ta = (inPixels[index] >> 24) & 0xff;
- int red = (inPixels[index] >> 16) & 0xff;
- int green = (inPixels[index] >> 8) & 0xff;
- int blue = inPixels[index] & 0xff;
- sumRed += keneralData[subRow + 2][subCol + 2] * red;
- sumGreen += keneralData[subRow + 2][subCol + 2] * green;
- sumBlue += keneralData[subRow + 2][subCol + 2] * blue;
- }
- }
- oudex = row * ow + col;
- outPixels[oudex] = (ta << 24) | (clamp(sumRed) << 16) | (clamp(sumGreen) << 8) | clamp(sumBlue);
- }
- }
- setRGB( dest, 0, 0, ow, oh, outPixels );
- return dest;
- }
- public BufferedImage pyramidExpand(BufferedImage src) {
- int width = src.getWidth();
- int height = src.getHeight();
- int[] inPixels = new int[width*height];
- getRGB(src, 0, 0, width, height, inPixels );
- int ow = 2*width;
- int oh =2*height;
- int[] outPixels = new int[ow * oh];
- int index = 0, outdex = 0, ta = 0;
- float[][] keneralData = this.getHVGaussianKeneral();
- BufferedImage dest = createTwiceCompatibleDestImage(src, null);
- for(int row=0; row<oh; row++) {
- for(int col=0; col<ow; col++) {
- float sumRed = 0, sumGreen = 0, sumBlue = 0;
- for(int subRow = -2; subRow <= 2; subRow++) {
- double srcRow = (row + subRow)/2.0;
- double j = Math.floor(srcRow);
- double t = srcRow - j;
- if(t > 0) {
- continue;
- }
- if(srcRow >= height || srcRow < 0) {
- srcRow = 0;
- }
- for(int subCol = -2; subCol <= 2; subCol++) {
- double srcColOff = (col + subCol)/2.0;
- j = Math.floor(srcColOff);
- t = srcColOff - j;
- if(t > 0) {
- continue;
- }
- if(srcColOff >= width || srcColOff < 0) {
- srcColOff = 0;
- }
- index = (int)(srcRow * width + srcColOff);
- ta = (inPixels[index] >> 24) & 0xff;
- int red = (inPixels[index] >> 16) & 0xff;
- int green = (inPixels[index] >> 8) & 0xff;
- int blue = inPixels[index] & 0xff;
- sumRed += keneralData[subRow + 2][subCol + 2] * red;
- sumGreen += keneralData[subRow + 2][subCol + 2] * green;
- sumBlue += keneralData[subRow + 2][subCol + 2] * blue;
- }
- }
- outdex = row * ow + col;
- outPixels[outdex] = (ta << 24) | (clamp(4.0f * sumRed) << 16) | (clamp(4.0f * sumGreen) << 8) | clamp(4.0f * sumBlue);
- // outPixels[outdex] = (ta << 24) | (clamp(sumRed) << 16) | (clamp(sumGreen) << 8) | clamp(sumBlue);
- }
- }
- setRGB( dest, 0, 0, ow, oh, outPixels );
- return dest;
- }
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:
- package com.gloomyfish.image.pyramid;
- import java.awt.image.BufferedImage;
- import java.awt.image.ColorModel;
- public class PyramidAlgorithm extends GaussianFilter {
- private float a;
- public PyramidAlgorithm() {
- a = 0.4f;
- }
- public void setParameter(float p) {
- this.a = p;
- }
- public BufferedImage[] pyramidDown(BufferedImage src, int level) {
- BufferedImage[] imagePyramids = new BufferedImage[level + 1];
- imagePyramids[0] = src;
- for(int i=1; i<imagePyramids.length; i++) {
- imagePyramids[i] = pyramidReduce(imagePyramids[i-1]);
- }
- return imagePyramids;
- }
- public BufferedImage[] pyramidUp(BufferedImage[] srcImage) {
- BufferedImage[] imagePyramids = new BufferedImage[srcImage.length];
- for(int i=0; i<srcImage.length; i++) {
- imagePyramids[i] = pyramidExpand(srcImage[i]);
- }
- return imagePyramids;
- }
- /***
- * l1 = g1 - expand(g2)
- * l2 = g2 - expand(g3)
- * l0 = g0 - expand(g1)
- * @param reduceImages
- * @param expandImages
- * @return
- */
- public BufferedImage[] getLaplacianPyramid(BufferedImage[] reduceImages) {
- BufferedImage[] laplaciImages = new BufferedImage[reduceImages.length -1];
- for(int i=1; i<reduceImages.length; i++) {
- BufferedImage expandImage = pyramidExpand(reduceImages[i]);
- laplaciImages[i-1] = createCompatibleDestImage(expandImage, null);
- int width = reduceImages[i-1].getWidth();
- int height = reduceImages[i-1].getHeight();
- int ewidth = expandImage.getWidth();
- width = (width > ewidth) ? ewidth : width;
- height = (height > expandImage.getHeight()) ? expandImage.getHeight():height;
- System.out.println(" width = " + width + " expand width = " + ewidth);
- int[] reducePixels = new int[width*height];
- int[] expandPixels = new int[width*height];
- int[] laPixels = new int[width*height];
- getRGB( reduceImages[i-1], 0, 0, width, height, reducePixels);
- getRGB( expandImage, 0, 0, width, height, expandPixels );
- int index = 0;
- int er = 0, eg = 0, eb = 0;
- for(int row=0; row<height; row++) {
- int ta = 0, tr = 0, tg = 0, tb = 0;
- for(int col=0; col<width; col++) {
- index = row * width + col;
- ta = (reducePixels[index] >> 24) & 0xff;
- tr = (reducePixels[index] >> 16) & 0xff;
- tg = (reducePixels[index] >> 8) & 0xff;
- tb = reducePixels[index] & 0xff;
- ta = (expandPixels[index] >> 24) & 0xff;
- er = (expandPixels[index] >> 16) & 0xff;
- eg = (expandPixels[index] >> 8) & 0xff;
- eb = expandPixels[index] & 0xff;
- tr = tr - er;
- tg = tg - eg;
- tb = tb - eb;
- laPixels[index] = (ta << 24) | (clamp(tr) << 16) | (clamp(tg) << 8) | clamp(tb);
- }
- }
- setRGB( laplaciImages[i-1], 0, 0, width, height, laPixels );
- }
- return laplaciImages;
- }
- private BufferedImage pyramidReduce(BufferedImage src) {
- int width = src.getWidth();
- int height = src.getHeight();
- BufferedImage dest = createSubCompatibleDestImage(src, null);
- int[] inPixels = new int[width*height];
- int ow = width/2;
- int oh = height/2;
- int[] outPixels = new int[ow*oh];
- getRGB(src, 0, 0, width, height, inPixels );
- int inRow=0, inCol = 0, index = 0, oudex =0, ta = 0;
- float[][] keneralData = this.getHVGaussianKeneral();
- for(int row=0; row<oh; row++) {
- for(int col=0; col<ow; col++) {
- inRow = 2* row;
- inCol = 2* col;
- if(inRow >= height) {
- inRow = 0;
- }
- if(inCol >= width) {
- inCol = 0;
- }
- float sumRed = 0, sumGreen = 0, sumBlue = 0;
- for(int subRow = -2; subRow <= 2; subRow++) {
- int inRowOff = inRow + subRow;
- if(inRowOff >= height || inRowOff < 0) {
- inRowOff = 0;
- }
- for(int subCol = -2; subCol <= 2; subCol++) {
- int inColOff = inCol + subCol;
- if(inColOff >= width || inColOff < 0) {
- inColOff = 0;
- }
- index = inRowOff * width + inColOff;
- ta = (inPixels[index] >> 24) & 0xff;
- int red = (inPixels[index] >> 16) & 0xff;
- int green = (inPixels[index] >> 8) & 0xff;
- int blue = inPixels[index] & 0xff;
- sumRed += keneralData[subRow + 2][subCol + 2] * red;
- sumGreen += keneralData[subRow + 2][subCol + 2] * green;
- sumBlue += keneralData[subRow + 2][subCol + 2] * blue;
- }
- }
- oudex = row * ow + col;
- outPixels[oudex] = (ta << 24) | (clamp(sumRed) << 16) | (clamp(sumGreen) << 8) | clamp(sumBlue);
- }
- }
- setRGB( dest, 0, 0, ow, oh, outPixels );
- return dest;
- }
- public BufferedImage createSubCompatibleDestImage(BufferedImage src, ColorModel dstCM) {
- if ( dstCM == null )
- dstCM = src.getColorModel();
- return new BufferedImage(dstCM, dstCM.createCompatibleWritableRaster(src.getWidth()/2, src.getHeight()/2), dstCM.isAlphaPremultiplied(), null);
- }
- public BufferedImage createTwiceCompatibleDestImage(BufferedImage src, ColorModel dstCM) {
- if ( dstCM == null )
- dstCM = src.getColorModel();
- return new BufferedImage(dstCM, dstCM.createCompatibleWritableRaster(src.getWidth()*2, src.getHeight()*2), dstCM.isAlphaPremultiplied(), null);
- }
- public BufferedImage pyramidExpand(BufferedImage src) {
- int width = src.getWidth();
- int height = src.getHeight();
- int[] inPixels = new int[width*height];
- getRGB(src, 0, 0, width, height, inPixels );
- int ow = 2*width;
- int oh =2*height;
- int[] outPixels = new int[ow * oh];
- int index = 0, outdex = 0, ta = 0;
- float[][] keneralData = this.getHVGaussianKeneral();
- BufferedImage dest = createTwiceCompatibleDestImage(src, null);
- for(int row=0; row<oh; row++) {
- for(int col=0; col<ow; col++) {
- float sumRed = 0, sumGreen = 0, sumBlue = 0;
- for(int subRow = -2; subRow <= 2; subRow++) {
- double srcRow = (row + subRow)/2.0;
- double j = Math.floor(srcRow);
- double t = srcRow - j;
- if(t > 0) {
- continue;
- }
- if(srcRow >= height || srcRow < 0) {
- srcRow = 0;
- }
- for(int subCol = -2; subCol <= 2; subCol++) {
- double srcColOff = (col + subCol)/2.0;
- j = Math.floor(srcColOff);
- t = srcColOff - j;
- if(t > 0) {
- continue;
- }
- if(srcColOff >= width || srcColOff < 0) {
- srcColOff = 0;
- }
- index = (int)(srcRow * width + srcColOff);
- ta = (inPixels[index] >> 24) & 0xff;
- int red = (inPixels[index] >> 16) & 0xff;
- int green = (inPixels[index] >> 8) & 0xff;
- int blue = inPixels[index] & 0xff;
- sumRed += keneralData[subRow + 2][subCol + 2] * red;
- sumGreen += keneralData[subRow + 2][subCol + 2] * green;
- sumBlue += keneralData[subRow + 2][subCol + 2] * blue;
- }
- }
- outdex = row * ow + col;
- outPixels[outdex] = (ta << 24) | (clamp(4.0f * sumRed) << 16) | (clamp(4.0f * sumGreen) << 8) | clamp(4.0f * sumBlue);
- // outPixels[outdex] = (ta << 24) | (clamp(sumRed) << 16) | (clamp(sumGreen) << 8) | clamp(sumBlue);
- }
- }
- setRGB( dest, 0, 0, ow, oh, outPixels );
- return dest;
- }
- }
会有问题,使用时请自己处理吧。
UI实现源代码如下:
- package com.gloomyfish.image.pyramid;
- import java.awt.BorderLayout;
- import java.awt.Dimension;
- import java.awt.FlowLayout;
- import java.awt.Graphics;
- import java.awt.MediaTracker;
- import java.awt.event.ActionEvent;
- import java.awt.event.ActionListener;
- import java.awt.image.BufferedImage;
- import java.io.File;
- import java.io.IOException;
- import javax.imageio.ImageIO;
- import javax.swing.JButton;
- import javax.swing.JComponent;
- import javax.swing.JFileChooser;
- import javax.swing.JFrame;
- import javax.swing.JPanel;
- public class PyramidDemoUI extends JComponent implements ActionListener {
- /**
- *
- */
- private static final long serialVersionUID = 1L;
- private JButton upButton;
- private JButton downButton;
- private BufferedImage[] reduceImages;
- private BufferedImage[] expandImages;
- private BufferedImage sourceImage;
- private Dimension mySize;
- private MediaTracker tracker;
- public PyramidDemoUI(File f)
- {
- initComponents(f);
- }
- private void initComponents(File f)
- {
- // TODO Auto-generated method stub
- try {
- sourceImage = ImageIO.read(f);
- } catch (IOException e1) {
- e1.printStackTrace();
- }
- tracker = new MediaTracker(this);
- tracker.addImage(sourceImage, 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
- JPanel btnPanel = new JPanel();
- btnPanel.setLayout(new FlowLayout(FlowLayout.RIGHT));
- upButton = new JButton("Laplacian Pyramid");
- downButton = new JButton("Pyramid Down");
- upButton.addActionListener(this);
- downButton.addActionListener(this);
- btnPanel.add(upButton);
- btnPanel.add(downButton);
- mySize = new Dimension(800, 800);
- JFrame mainFrame = new JFrame("Pyramid Demo - Gloomyfish");
- mainFrame.getContentPane().setLayout(new BorderLayout());
- mainFrame.getContentPane().add(this, BorderLayout.CENTER);
- mainFrame.getContentPane().add(btnPanel, BorderLayout.SOUTH);
- mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
- mainFrame.pack();
- mainFrame.setVisible(true);
- }
- @Override
- public Dimension getPreferredSize() {
- return mySize;
- }
- @Override
- protected void paintComponent(Graphics g)
- {
- // g.drawImage(sourceImage, 10, 10, sourceImage.getWidth(), sourceImage.getHeight(), null);
- int width = 10;
- // if(reduceImages != null) {
- // for(int i=1; i<reduceImages.length; i++) {
- // width += (10 + reduceImages[i-1].getWidth());
- // g.drawImage(reduceImages[i], width, 10, reduceImages[i].getWidth(), reduceImages[i].getHeight(), null);
- // }
- // }
- width = 10;
- if(expandImages != null) {
- for(int i=0; i<expandImages.length; i++) {
- g.drawImage(expandImages[i], width, 15, expandImages[i].getWidth(), expandImages[i].getHeight(), null);
- // g.drawImage(expandImages[i], width, 15 + sourceImage.getHeight(), expandImages[i].getWidth(), expandImages[i].getHeight(), null);
- width += (10 + expandImages[i].getWidth());
- }
- }
- super.paintComponent(g);
- }
- public static void main(String[] args) {
- JFileChooser chooser = new JFileChooser();
- chooser.showOpenDialog(null);
- File f = chooser.getSelectedFile();
- new PyramidDemoUI(f);
- }
- @Override
- public void actionPerformed(ActionEvent event) {
- if(event.getActionCommand().equals("Laplacian Pyramid")) {
- if(reduceImages != null) {
- // int size = reduceImages.length;
- PyramidAlgorithm pyramid = new PyramidAlgorithm();
- expandImages = pyramid.getLaplacianPyramid(reduceImages);
- // expandImages = pyramid.pyramidUp(reduceImages);
- repaint();
- } else {
- }
- } else if(event.getActionCommand().equals("Pyramid Down")) {
- // 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]
- // b.Sub sample the image by half - 选择偶数行与列
- // c.If reached desired size stop, else send the result to step 1
- PyramidAlgorithm pyramid = new PyramidAlgorithm();
- reduceImages = pyramid.pyramidDown(sourceImage, 3);
- repaint();
- } else {
- // do nothing
- }
- }
- }