LineIterator.java

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package robotinterface.util;

import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * Bresenham's algorithm to find all pixels on a Line2D.
 *
 * @author nes
 *
 */
public class LineIterator implements Iterator<Point2D> {

    final static double DEFAULT_PRECISION = 1.0;
    final Line2D line;
    final double precision;
    final double sx, sy;
    final double dx, dy;
    double x, y, error;

    public LineIterator(Line2D line, double precision) {
        this.line = line;
        this.precision = precision;

        sx = line.getX1() < line.getX2() ? precision : -1 * precision;
        sy = line.getY1() < line.getY2() ? precision : -1 * precision;

        dx = Math.abs(line.getX2() - line.getX1());
        dy = Math.abs(line.getY2() - line.getY1());

        error = dx - dy;

        y = line.getY1();
        x = line.getX1();
    }

    public LineIterator(Line2D line) {
        this(line, DEFAULT_PRECISION);
    }

    @Override
    public boolean hasNext() {
        return Math.abs(x - line.getX2()) > 0.9 || (Math.abs(y - line.getY2()) > 0.9);
    }

    @Override
    public Point2D next() {
        Point2D ret = new Point2D.Double(x, y);

        double e2 = 2 * error;
        if (e2 > -dy) {
            error -= dy;
            x += sx;
        }
        if (e2 < dx) {
            error += dx;
            y += sy;
        }

        return ret;
    }

    @Override
    public void remove() {
        throw new AssertionError();
    }
}