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图像处理之基于NCC模板匹配识别
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圖像處理之基于NCC模板匹配識別
一：基本原理
NCC是一種基于統計學計算兩組樣本數據相關性的算法，其取值范圍為[-1, 1]之間，而對圖像來說，每個像素點都可以看出是RGB數值，這樣整幅圖像就可以看成是一個樣本數據的集合，如果它有一個子集與另外一個樣本數據相互匹配則它的ncc值為1，表示相關性很高，如果是-1則表示完全不相關，基于這個原理，實現圖像基于模板匹配識別算法，其中第一步就是要歸一化數據，數學公式如下：
二：實現步驟
（1）??????獲取模板像素并計算均值與標準方差、像素與均值diff數據樣本
（2）??????根據模板大小，在目標圖像上從左到右，從上到下移動窗口，計
算每移動一個像素之后窗口內像素與模板像素的ncc值，與閾值比較，大于
閾值則記錄位置
（3）??????根據得到位置信息，使用紅色矩形標記出模板匹配識別結果。
（4）??????UI顯示結果
?
三：編程實現
基于JAVA語言完成了整個算法編程實現與演示，其中第一步的代碼如下：
[java] view plaincopy
int?tw?=?template.getWidth();??int?th?=?template.getHeight();??int[]?tpixels?=?new?int[tw?*?th];??getRGB(template,?0,?0,?tw,?th,?tpixels);??for(int?i=0;?i<tpixels.length;?i++)??{??????tpixels[i]?=?(tpixels[i]?>>?16)?&?0xff;??}??double[]?meansdev?=?getPixelsMeansAndDev(tpixels);??double[]?tDiff?=?calculateDiff(tpixels,?meansdev[0]);??int?raidus_width?=?tw?/?2;??int?raidus_height?=?th?/?2;??
第二步的實現代碼如下：
[java] view plaincopy
int[]?windowPixels?=?new?int[tw?*?th];??Arrays.fill(windowPixels,?0);??for?(int?row?=?0;?row?<?height;?row++)?{??????for?(int?col?=?0;?col?<?width;?col++)?{????????????????????if(row?<??raidus_height?||?(row?+?raidus_height)?>=?height)??????????????continue;??????????if(col?<?raidus_width?||?(col?+?raidus_width)?>=?width)???????????????continue;??????????int?wrow?=?0;??????????Arrays.fill(windowPixels,?0);??????????for(int?subrow?=?-raidus_height;?subrow?<=?raidus_height;?subrow++?)??????????{??????????????int?wcol?=?0;??????????????for(int?subcol?=?-raidus_width;?subcol?<=?raidus_width;?subcol++?)??????????????{??????????????????if(wrow?>=?th?||?wcol?>=?tw)??????????????????{??????????????????????continue;??????????????????}??????????????????windowPixels[wrow?*?tw?+?wcol]?=?getPixelValue(width,?col?+?subcol,?row?+?subrow,?inPixels);??????????????????wcol++;??????????????}??????????????wrow++;??????????}????????????????????double[]?_meansDev?=?getPixelsMeansAndDev(windowPixels);??????????double[]?diff?=?calculateDiff(windowPixels,?_meansDev[0]);??????????double?ncc?=?calculateNcc(tDiff,?diff,?_meansDev[1],?meansdev[1]);??????????if(ncc?>?threhold)?{??????????????Point?mpoint?=?new?Point();??????????????mpoint.x?=?col;??????????????mpoint.y??=?row;??????????????points.add(mpoint);??????????}??????}??}??
第三步的實現代碼如下：
[java] view plaincopy
??setRGB(?dest,?0,?0,?width,?height,?inPixels?);??Graphics2D?g2d?=?dest.createGraphics();??g2d.setPaint(Color.RED);??g2d.setStroke(new?BasicStroke(4));??for(Point?p?:?points)??{??????g2d.drawRect(p.x?-?raidus_width,?p.y?-?raidus_height,?tw,?th);??}??
其中第二步用到的計算NCC的方法實現如下：
[java] view plaincopy
private?double?calculateNcc(double[]?tDiff,?double[]?diff,?double?dev1,?double?dev2)?{????????????double?sum?=?0.0d;??????double?count?=?diff.length;??????for(int?i=0;?i<diff.length;?i++)??????{??????????sum?+=?((tDiff[i]?*?diff[i])/(dev1?*?dev2));??????}??????return?(sum?/?count);??}??
UI部分完整源代碼如下：
[java] view plaincopy
package?com.gloomyfish.image.templae.match;????import?java.awt.BorderLayout;??import?java.awt.FlowLayout;??import?java.awt.Graphics;??import?java.awt.Graphics2D;??import?java.awt.event.ActionEvent;??import?java.awt.event.ActionListener;??import?java.awt.image.BufferedImage;??import?java.io.IOException;????import?javax.imageio.ImageIO;??import?javax.swing.JButton;??import?javax.swing.JComponent;??import?javax.swing.JFrame;??import?javax.swing.JPanel;????public?class?DemoUI?extends?JComponent?{????????????????????private?static?final?long?serialVersionUID?=?1L;??????private?BufferedImage?targetImage;??????private?BufferedImage?template;????????????public?DemoUI()??????{??????????super();??????????java.net.URL?imageURL?=?this.getClass().getResource("words.png");??????????java.net.URL?templateURL?=?this.getClass().getResource("template.png");????????????????????try?{??????????????template?=?ImageIO.read(templateURL);??????????????targetImage?=?ImageIO.read(imageURL);??????????}?catch?(IOException?e)?{??????????????e.printStackTrace();??????????}??????}????????????public?void?setTarget(BufferedImage?target)?{??????????this.targetImage?=?target;??????}????????@Override??????protected?void?paintComponent(Graphics?g)?{??????????Graphics2D?g2?=?(Graphics2D)?g;??????????if(targetImage?!=?null)?{??????????????g2.drawImage(targetImage,?10,?10,?targetImage.getWidth(),?targetImage.getHeight(),?null);??????????}??????????if(template?!=?null)?{??????????????g2.drawImage(template,?20+targetImage.getWidth(),?10,?template.getWidth(),?template.getHeight(),?null);??????????}??????}????????????public?static?void?main(String[]?args)?{??????????JFrame?f?=?new?JFrame("模板匹配與識別");??????????JButton?okBtn?=?new?JButton("匹配");??????????final?DemoUI?ui?=?new?DemoUI();??????????okBtn.addActionListener(new?ActionListener()?{????????????????@Override??????????????public?void?actionPerformed(ActionEvent?e)?{????????????????????????????????????ui.process();??????????????}??????????});????????????????????JPanel?btnPanel?=?new?JPanel();??????????btnPanel.setLayout(new?FlowLayout(FlowLayout.RIGHT));??????????btnPanel.add(okBtn);????????????????????f.getContentPane().add(btnPanel,?BorderLayout.SOUTH);??????????f.getContentPane().add(ui,?BorderLayout.CENTER);??????????f.setSize(500,?500);??????????f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);??????????f.setVisible(true);??????}????????protected?void?process()?{??????????NccTemplateMatchAlg?algo?=?new?NccTemplateMatchAlg(template);??????????targetImage?=?algo.filter(targetImage,?null);??????????this.repaint();??????}????}??
四：程序運行效果如下
其中左邊是目標圖像、右邊為模板圖像
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