point가 다각형 안에 위치하는지 확인하는 코드

http://stackoverflow.com/questions/7044838/finding-points-contained-in-a-path-in-android

/**

 * Minimum Polygon class for Android.

 */

public class Polygon

{

    // Polygon coodinates.

    private int[] polyY, polyX;

    // Number of sides in the polygon.

    private int polySides;

    /**

     * Default constructor.

     * @param px Polygon y coods.

     * @param py Polygon x coods.

     * @param ps Polygon sides count.

     */

    public Polygon( int[] px, int[] py, int ps )

    {

        polyX = px;

        polyY = py;

        polySides = ps;

    }

    /**

     * Checks if the Polygon contains a point.

     * @see "http://alienryderflex.com/polygon/"

     * @param x Point horizontal pos.

     * @param y Point vertical pos.

     * @return Point is in Poly flag.

     */

    public boolean contains( int x, int y )

    {

        boolean oddTransitions = false;

        for( int i = 0, j = polySides -1; i < polySides; 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;

    }  

}