Polygon.java

/*
 * Copyright 2013 MicaByte Systems
 * 
 * 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.micabytes.math;

/**
 * Minimal Polygon class for Android. <p/> Basic polygon wrapper to handle simple point in polygon
 * problems.
 */
@SuppressWarnings({"unused", "ClassIndependentOfModule", "ClassUnconnectedToPackage"})
public class Polygon {
  // Polygon coordinates.
  private final int[] polyX;
  private final int[] polyY;
  // Number of sides in the polygon.
  private final int polyN;

  public Polygon(int[] px, int[] py, int ps) {
    polyX = new int[px.length];
    System.arraycopy(px, 0, polyX, 0, px.length);
    polyY = new int[py.length];
    System.arraycopy(py, 0, polyY, 0, py.length);
    polyN = ps;
  }

  /**
   * Checks if the Polygon contains the point x, y
   */
  @SuppressWarnings({"ValueOfIncrementOrDecrementUsed", "OverlyComplexArithmeticExpression", "OverlyComplexBooleanExpression"})
  public boolean contains(int x, int y) {
    boolean oddTransitions = false;
    for (int i = 0, j = polyN - 1; i < polyN; j = i++) {
      if (((polyY[i] < y) && (polyY[j] >= y)) || ((polyY[j] < y) && (polyY[i] >= y))) {
        if ((polyX[i] + (((y - polyY[i]) / (polyY[j] - polyY[i])) * (polyX[j] - polyX[i]))) < x) {
          oddTransitions = !oddTransitions;
        }
      }
    }
    return oddTransitions;
  }

}