/*******************************************************************************
* Copyright 2011 See AUTHORS file.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
******************************************************************************/
package com.badlogic.gdx.math;
import com.badlogic.gdx.utils.Array;
import com.badlogic.gdx.utils.Pool;
/** Returns a list of points at integer coordinates for a line on a 2D grid, using the Bresenham algorithm.
* <p>
*
* Instances of this class own the returned array of points and the points themselves to avoid garbage collection as much as
* possible. Calling any of the methods will result in the reuse of the previously returned array and vectors, expect
* @author badlogic */
public class Bresenham2 {
private final Array<GridPoint2> points = new Array<GridPoint2>();
private final Pool<GridPoint2> pool = new Pool<GridPoint2>() {
@Override
protected GridPoint2 newObject () {
return new GridPoint2();
}
};
/** Returns a list of {@link GridPoint2} instances along the given line, at integer coordinates.
* @param start the start of the line
* @param end the end of the line
* @return the list of points on the line at integer coordinates */
public Array<GridPoint2> line (GridPoint2 start, GridPoint2 end) {
return line(start.x, start.y, end.x, end.y);
}
/** Returns a list of {@link GridPoint2} instances along the given line, at integer coordinates.
* @param startX the start x coordinate of the line
* @param startY the start y coordinate of the line
* @param endX the end x coordinate of the line
* @param endY the end y coordinate of the line
* @return the list of points on the line at integer coordinates */
public Array<GridPoint2> line (int startX, int startY, int endX, int endY) {
pool.freeAll(points);
points.clear();
return line(startX, startY, endX, endY, pool, points);
}
/** Returns a list of {@link GridPoint2} instances along the given line, at integer coordinates.
* @param startX the start x coordinate of the line
* @param startY the start y coordinate of the line
* @param endX the end x coordinate of the line
* @param endY the end y coordinate of the line
* @param pool the pool from which GridPoint2 instances are fetched
* @param output the output array, will be cleared in this method
* @return the list of points on the line at integer coordinates */
public Array<GridPoint2> line (int startX, int startY, int endX, int endY, Pool<GridPoint2> pool, Array<GridPoint2> output) {
int w = endX - startX;
int h = endY - startY;
int dx1 = 0, dy1 = 0, dx2 = 0, dy2 = 0;
if (w < 0) {
dx1 = -1;
dx2 = -1;
} else if (w > 0) {
dx1 = 1;
dx2 = 1;
}
if (h < 0)
dy1 = -1;
else if (h > 0) dy1 = 1;
int longest = Math.abs(w);
int shortest = Math.abs(h);
if (longest <= shortest) {
longest = Math.abs(h);
shortest = Math.abs(w);
if (h < 0)
dy2 = -1;
else if (h > 0) dy2 = 1;
dx2 = 0;
}
int numerator = longest >> 1;
for (int i = 0; i <= longest; i++) {
GridPoint2 point = pool.obtain();
point.set(startX, startY);
output.add(point);
numerator += shortest;
if (numerator > longest) {
numerator -= longest;
startX += dx1;
startY += dy1;
} else {
startX += dx2;
startY += dy2;
}
}
return output;
}
}