hough.java

java代码

/*
 **************************************************************************
 *
 *    Hough Transform
 *
 *    1. Hough array: hough[nrho][271]
 *    2  Take a sharpened image
 *    3. From rho = x*cos(theta) + y*sin(theta);
 *       - Vary the theta form -90 to 180 degrees to find a solution to rho;
 *       - If (rho>=0 && rho<nrho) then the line exists.
 *
 **************************************************************************
 */
import java.io.*;

public class Hough {

  public static void main(String[] args) {
    int  in_img[][], out_img[][], hough_img[][];
    int  nrows, ncols, nrho, ntheta, x, y;
    double  hough[][], thresh, theta, rho, rad, max, alpha;

    if (args.length != 5) {
      System.out.println(
        "Usage: Hough <nrows> <ncols> <thresh> <in_img> <out_img>");
      System.exit(0);
    }
    nrows = Integer.parseInt(args[0]);
    ncols = Integer.parseInt(args[1]);
    nrho = (int)Math.sqrt(nrows*nrows+ncols*ncols) + 1;
    ntheta = 271;    // -90 ~ 180
    thresh = Double.parseDouble(args[2]);
    rad = Math.PI/180;
    max = 0;

    in_img = new int[nrows][ncols];
    ArrayIO.readByteArray(args[3], in_img, nrows, ncols);
    hough = new double[nrho][ntheta];
    hough_img = new int[nrho][ntheta];
    out_img = new int[nrows][ncols];

    // Initialize Hough array
    for (x=0; x<nrho; x++)
      for (y=0; y<ntheta; y++)
        hough[x][y] = 0;

    for (x=0; x<nrows; x++)
      for (y=0; y<ncols; y++)
        if (in_img[x][y] == 255)
          for (theta= -90; theta<=180; theta++) {
	    rho = x*Math.cos(theta*rad) + y*Math.sin(theta*rad);
	    if (rho>0 && rho<nrho) {   // Solution of rho found.
              hough[(int)rho][(int)(theta+90)]++;
	      if (max < hough[(int)rho][(int)(theta+90)])
                max = hough[(int)rho][(int)(theta+90)];
            }
	  }

    // Normalize to the range of [0, 255]
    alpha = 255/max;
    for (x=0; x<nrho; x++)
      for (y=0; y<ntheta; y++)
        hough_img[x][y] = (int)(alpha*hough[x][y]);
    ArrayIO.writeByteArray("Hough.raw", hough_img, nrho, ntheta);
    System.out.println("'Hough.raw' (" + nrho + " x 271) created");

    for (x=0; x<nrows; x++)
      for (y=0; y<ncols; y++) {
        out_img[x][y] = 0;
        // The following 'if' statement can be commented to see straight lines
        // if (in_img[x][y] != 255)
          // continue;
        for (theta=-90; theta<180; theta++) {
	  rho = x*Math.cos(theta*rad) + y*Math.sin(theta*rad);
	  if (rho>0 && rho<nrho && hough[(int)rho][(int)(theta+90)]>thresh)
            out_img[x][y] = 255;
        }
      }

    ArrayIO.writeByteArray(args[4], out_img, nrows, ncols);
  }

}