java 图像灰度化与二值化

转载：http://www.chinasb.org/archives/2013/01/5053.shtml

   1:  package org.chinasb.client;

   2:   

   3:  import java.awt.Color;

   4:  import java.awt.image.BufferedImage;

   5:  import java.io.File;

   6:  import java.io.IOException;

   7:   

   8:  import javax.imageio.ImageIO;

   9:   

  10:  public class BinaryTest {

  11:   

  12:      public static void main(String[] args) throws IOException {

  13:          BufferedImage bufferedImage = ImageIO.read(new File("D:/passCodeAction.jpg"));

  14:          int h = bufferedImage.getHeight();

  15:          int w = bufferedImage.getWidth();

  16:   

  17:          // 灰度化

  18:          int[][] gray = new int[w][h];

  19:          for (int x = 0; x < w; x++) {

  20:              for (int y = 0; y < h; y++) {

  21:                  int argb = bufferedImage.getRGB(x, y);

  22:                  int r = (argb >> 16) & 0xFF;

  23:                  int g = (argb >> 8) & 0xFF;

  24:                  int b = (argb >> 0) & 0xFF;

  25:                  int grayPixel = (int) ((b * 29 + g * 150 + r * 77 + 128) >> 8);                

  26:                  gray[x][y] = grayPixel;

  27:              }

  28:          }

  29:   

  30:          // 二值化

  31:          int threshold = ostu(gray, w, h);

  32:          BufferedImage binaryBufferedImage = new BufferedImage(w, h, BufferedImage.TYPE_BYTE_BINARY);

  33:          for (int x = 0; x < w; x++) {

  34:              for (int y = 0; y < h; y++) {

  35:                  if (gray[x][y] > threshold) {

  36:                      gray[x][y] |= 0x00FFFF;

  37:                  } else {

  38:                      gray[x][y] &= 0xFF0000;

  39:                  }

  40:                  binaryBufferedImage.setRGB(x, y, gray[x][y]);

  41:              }

  42:          }

  43:   

  44:          // 矩阵打印

  45:          for (int y = 0; y < h; y++) {

  46:              for (int x = 0; x < w; x++) {

  47:                  if (isBlack(binaryBufferedImage.getRGB(x, y))) {

  48:                      System.out.print("*");

  49:                  } else {

  50:                      System.out.print(" ");

  51:                  }

  52:              }

  53:              System.out.println();

  54:          }

  55:   

  56:          ImageIO.write(binaryBufferedImage, "jpg", new File("D:/code.jpg"));

  57:      }

  58:   

  59:      public static boolean isBlack(int colorInt) {

  60:          Color color = new Color(colorInt);

  61:          if (color.getRed() + color.getGreen() + color.getBlue() <= 300) {

  62:              return true;

  63:          }

  64:          return false;

  65:      }

  66:   

  67:      public static boolean isWhite(int colorInt) {

  68:          Color color = new Color(colorInt);

  69:          if (color.getRed() + color.getGreen() + color.getBlue() > 300) {

  70:              return true;

  71:          }

  72:          return false;

  73:      }

  74:   

  75:      public static int isBlackOrWhite(int colorInt) {

  76:          if (getColorBright(colorInt) < 30 || getColorBright(colorInt) > 730) {

  77:              return 1;

  78:          }

  79:          return 0;

  80:      }

  81:   

  82:      public static int getColorBright(int colorInt) {

  83:          Color color = new Color(colorInt);

  84:          return color.getRed() + color.getGreen() + color.getBlue();

  85:      }

  86:   

  87:      public static int ostu(int[][] gray, int w, int h) {

  88:          int[] histData = new int[w * h];

  89:          // Calculate histogram

  90:          for (int x = 0; x < w; x++) {

  91:              for (int y = 0; y < h; y++) {

  92:                  int red = 0xFF & gray[x][y];

  93:                  histData[red]++;

  94:              }

  95:          }

  96:   

  97:          // Total number of pixels

  98:          int total = w * h;

  99:   

 100:          float sum = 0;

 101:          for (int t = 0; t < 256; t++)

 102:              sum += t * histData[t];

 103:   

 104:          float sumB = 0;

 105:          int wB = 0;

 106:          int wF = 0;

 107:   

 108:          float varMax = 0;

 109:          int threshold = 0;

 110:   

 111:          for (int t = 0; t < 256; t++) {

 112:              wB += histData[t]; // Weight Background

 113:              if (wB == 0)

 114:                  continue;

 115:   

 116:              wF = total - wB; // Weight Foreground

 117:              if (wF == 0)

 118:                  break;

 119:   

 120:              sumB += (float) (t * histData[t]);

 121:   

 122:              float mB = sumB / wB; // Mean Background

 123:              float mF = (sum - sumB) / wF; // Mean Foreground

 124:   

 125:              // Calculate Between Class Variance

 126:              float varBetween = (float) wB * (float) wF * (mB - mF) * (mB - mF);

 127:   

 128:              // Check if new maximum found

 129:              if (varBetween > varMax) {

 130:                  varMax = varBetween;

 131:                  threshold = t;

 132:              }

 133:          }

 134:   

 135:          return threshold;

 136:      }

 137:  }

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效果