java图像处理之倒角距离变换

package com.gloomyfish.image.transform; 
 
import java.awt.Color; 
import java.awt.image.BufferedImage; 
import java.util.Arrays; 
 
import com.gloomyfish.filter.study.AbstractBufferedImageOp; 
 
public class CDTFilter extends AbstractBufferedImageOp { 
  private float[] dis; // nn-distances 
  private int[] pos; // nn-positions, 32 bit index 
  private Color bakcgroundColor; 
   
  public CDTFilter(Color bgColor) 
  { 
    this.bakcgroundColor = bgColor; 
  } 
 
  @Override 
  public BufferedImage filter(BufferedImage src, BufferedImage dest) { 
    int width = src.getWidth(); 
    int height = src.getHeight(); 
 
    if (dest == null) 
      dest = createCompatibleDestImage(src, null); 
 
    int[] inPixels = new int[width * height]; 
    pos = new int[width * height]; 
    dis = new float[width * height]; 
    src.getRGB(0, 0, width, height, inPixels, 0, width); 
    // 随机生成距离变换点 
    int index = 0; 
    Arrays.fill(dis, Float.MAX_VALUE); 
    int numOfFC = 0; 
    for (int row = 0; row < height; row++) { 
      for (int col = 0; col < width; col++) { 
        index = row * width + col; 
        if (inPixels[index] != bakcgroundColor.getRGB()) { 
          dis[index] = 0; 
          pos[index] = index; 
          numOfFC++; 
        } 
      } 
    } 
    final float d1 = 1; 
    final float d2 = (float) Math.sqrt(d1 * d1 + d1 * d1); 
    System.out.println(numOfFC); 
    float nd, nd_tmp; 
    int i, in, cols, rows, nearestPixel; 
 
    // 1 2 3 
    // 0 i 4 
    // 7 6 5 
    // first pass: forward -> L->R, T-B 
    for (rows = 1; rows < height - 1; rows++) { 
      for (cols = 1; cols < width - 1; cols++) { 
        i = rows * width + cols; 
 
        nd = dis[i]; 
        nearestPixel = pos[i]; 
        if (nd != 0) { // skip background pixels 
          in = i; 
 
          in += -1; // 0 
          if ((nd_tmp = d1 + dis[in]) < nd) { 
            nd = nd_tmp; 
            nearestPixel = pos[in]; 
          } 
 
          in += -width; // 1 
          if ((nd_tmp = d2 + dis[in]) < nd) { 
            nd = nd_tmp; 
            nearestPixel = pos[in]; 
          } 
 
          in += +1; // 2 
          if ((nd_tmp = d1 + dis[in]) < nd) { 
            nd = nd_tmp; 
            nearestPixel = pos[in]; 
          } 
 
          in += +1; // 3 
          if ((nd_tmp = d2 + dis[in]) < nd) { 
            nd = nd_tmp; 
            nearestPixel = pos[in]; 
          } 
 
          dis[i] = nd; 
          pos[i] = nearestPixel; 
        } 
      } 
    } 
 
    // second pass: backwards -> R->L, B-T 
    // exactly same as first pass, just in the reverse direction 
    for (rows = height - 2; rows >= 1; rows--) { 
      for (cols = width - 2; cols >= 1; cols--) { 
        i = rows * width + cols; 
 
        nd = dis[i]; 
        nearestPixel = pos[i]; 
        if (nd != 0) { 
          in = i; 
 
          in += +1; // 4 
          if ((nd_tmp = d1 + dis[in]) < nd) { 
            nd = nd_tmp; 
            nearestPixel = pos[in]; 
          } 
 
          in += +width; // 5 
          if ((nd_tmp = d2 + dis[in]) < nd) { 
            nd = nd_tmp; 
            nearestPixel = pos[in]; 
          } 
 
          in += -1; // 6 
          if ((nd_tmp = d1 + dis[in]) < nd) { 
            nd = nd_tmp; 
            nearestPixel = pos[in]; 
          } 
 
          in += -1; // 7 
          if ((nd_tmp = d2 + dis[in]) < nd) { 
            nd = nd_tmp; 
            nearestPixel = pos[in]; 
          } 
 
          dis[i] = nd; 
          pos[i] = nearestPixel; 
 
        } 
      } 
    } 
 
    for (int row = 0; row < height; row++) { 
      for (int col = 0; col < width; col++) { 
        index = row * width + col; 
        if (Float.MAX_VALUE != dis[index]) { 
          int gray = clamp((int) (dis[index])); 
          inPixels[index] = (255 << 24) | (gray << 16) | (gray << 8) 
              | gray; 
        } 
      } 
    } 
    setRGB(dest, 0, 0, width, height, inPixels); 
    return dest; 
  } 
 
  private int clamp(int i) { 
    return i > 255 ? 255 : (i < 0 ? 0 : i); 
  } 
 
}