BresenhamsLine.java

package vooga.towerdefense.model.AStar;

import java.awt.Point;
import java.util.ArrayList;

public class BresenhamsLine {
        public static ArrayList<Point> getPointsOnLine(Point p1, Point p2) {
               
                Point a = (Point) p1.clone();
                Point b = (Point) p2.clone();
               
                ArrayList<Point> pointsOnLine = new ArrayList<Point>();
               
                boolean steep = Math.abs(b.y - a.y) > Math.abs(b.x - a.x);
               
                if(steep) {
                        // swap(a.x, a.y)
                        int temp;
                        temp = a.x;
                        a.x = a.y;
                        a.y = temp;
                        // swap(b.x, b.y)
                        temp = a.x;
                        b.x = b.y;
                        b.y = temp;
                }
                if(a.x > b.x) {
                        // swap(a.x, b.x)
                        int temp;
                        temp = a.x;
                        a.x = b.x;
                        b.x = temp;
                        // swap(a.y, b.y)
                        temp = a.y;
                        a.y = b.y;
                        b.y = temp;
                }
               
                int deltaX = b.x - a.x;
                int deltaY = Math.abs(b.y - a.y);
                int error = deltaX/2;
               
                int yStep;
                int y = a.y;
                if (a.y < b.y)
                        yStep = 1;
                else
                        yStep = -1;
               
                for(int x=a.x; x<=b.x; x++) {
                        if(steep)
                                pointsOnLine.add(new Point(y,x));
                        else
                                pointsOnLine.add(new Point(x,y));
                        error = error - deltaY;
                        if(error<0) {
                                y = y + yStep;
                                error = error + deltaX;
                        }
                }
                                       
                return pointsOnLine;
               
//              function line(x0, x1, y0, y1)
//           boolean steep := abs(y1 - y0) > abs(x1 - a.x)
//           if steep then
//               swap(a.x, y0)
//               swap(x1, y1)
//           if a.x > x1 then
//               swap(a.x, x1)
//               swap(y0, y1)
//           int deltax := x1 - a.x
//           int deltay := abs(y1 - y0)
//           int error := deltax / 2
//           int ystep
//           int y := y0
//           if y0 < y1 then ystep := 1 else ystep := -1
//           for x from a.x to b.x
//               if steep then plot(y,x) else plot(x,y)
//               error := error - deltay
//               if error < 0 then
//                   y := y + ystep
//                   error := error + deltax

        }
       
}