HoughLine.java

//Adaptation of Olly Oechsle's Hough Transform algorithm - http://vase.essex.ac.uk/software/HoughTransform/
//David Chatting - 4th March 2013
//david@davidchatting.com
//---

import java.awt.geom.Line2D;
import java.awt.image.BufferedImage;

/** 
 * Represents a linear line as detected by the hough transform. 
 * This line is represented by an angle theta and a radius from the centre. 
 * 
 * @author Olly Oechsle, University of Essex, Date: 13-Mar-2008 
 * @version 1.0 
 */
public class HoughLine extends Line2D.Float implements Comparable<HoughLine> { 
  protected double theta; 
  protected double r;
  protected int score;

  /** 
   * Initialises the hough line 
   */
  public HoughLine(double theta, double r, int width, int height, int score) { 
    this.theta = theta; 
    this.r = r;
    this.score=score;

    // During processing h_h is doubled so that -ve r values 
    int houghHeight = (int) (Math.sqrt(2) * Math.max(height, width)) / 2; 

    // Find edge points and vote in array 
    float centerX = width / 2; 
    float centerY = height / 2; 

    // Draw edges in output array 
    double tsin = Math.sin(theta); 
    double tcos = Math.cos(theta); 

    if (theta < Math.PI * 0.25 || theta > Math.PI * 0.75) { 
      int x1=0, y1=0;
      int x2=0, y2=height-1;

      x1=(int) ((((r - houghHeight) - ((y1 - centerY) * tsin)) / tcos) + centerX);
      x2=(int) ((((r - houghHeight) - ((y2 - centerY) * tsin)) / tcos) + centerX);

      setLine(x1, y1, x2, y2);
    } 
    else {
      int x1=0, y1=0;
      int x2=width-1, y2=0;

      y1=(int) ((((r - houghHeight) - ((x1 - centerX) * tcos)) / tsin) + centerY); 
      y2=(int) ((((r - houghHeight) - ((x2 - centerX) * tcos)) / tsin) + centerY); 

      setLine(x1, y1, x2, y2);
    }
  }

  public int compareTo(HoughLine o) {
    return(this.score-o.score);
  }
}