    001/* ===========================================================
    002 * JFreeChart : a free chart library for the Java(tm) platform
    003 * ===========================================================
    004 *
    005 * (C) Copyright 2000-2011, by Object Refinery Limited and Contributors.
    006 *
    007 * Project Info:  http://www.jfree.org/jfreechart/index.html
    008 *
    009 * This library is free software; you can redistribute it and/or modify it
    010 * under the terms of the GNU Lesser General Public License as published by
    011 * the Free Software Foundation; either version 2.1 of the License, or
    012 * (at your option) any later version.
    013 *
    014 * This library is distributed in the hope that it will be useful, but
    015 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    016 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
    017 * License for more details.
    018 *
    019 * You should have received a copy of the GNU Lesser General Public
    020 * License along with this library; if not, write to the Free Software
    021 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
    022 * USA.
    023 *
    024 * [Oracle and Java are registered trademarks of Oracle and/or its affiliates.
    025 * Other names may be trademarks of their respective owners.]
    026 *
    027 * ------------------
    028 * LineUtilities.java
    029 * ------------------
    030 * (C) Copyright 2008, by Object Refinery Limited and Contributors.
    031 *
    032 * Original Author:  David Gilbert (for Object Refinery Limited);
    033 * Contributor(s):   -;
    034 *
    035 * Changes
    036 * -------
    037 * 05-Nov-2008 : Version 1 (DG);
    038 *
    039 */
    040
    041package org.jfree.chart.util;
    042
    043import java.awt.geom.Line2D;
    044import java.awt.geom.Rectangle2D;
    045
    046/**
    047 * Some utility methods for {@link Line2D} objects.
    048 *
    049 * @since 1.0.12
    050 */
    051public class LineUtilities {
    052
    053    /**
    054     * Clips the specified line to the given rectangle.
    055     *
    056     * @param line  the line (<code>null</code> not permitted).
    057     * @param rect  the clipping rectangle (<code>null</code> not permitted).
    058     *
    059     * @return <code>true</code> if the clipped line is visible, and
    060     *     <code>false</code> otherwise.
    061     */
    062    public static boolean clipLine(Line2D line, Rectangle2D rect) {
    063
    064        double x1 = line.getX1();
    065        double y1 = line.getY1();
    066        double x2 = line.getX2();
    067        double y2 = line.getY2();
    068
    069        double minX = rect.getMinX();
    070        double maxX = rect.getMaxX();
    071        double minY = rect.getMinY();
    072        double maxY = rect.getMaxY();
    073
    074        int f1 = rect.outcode(x1, y1);
    075        int f2 = rect.outcode(x2, y2);
    076
    077        while ((f1 | f2) != 0) {
    078            if ((f1 & f2) != 0) {
    079                return false;
    080            }
    081            double dx = (x2 - x1);
    082            double dy = (y2 - y1);
    083            // update (x1, y1), (x2, y2) and f1 and f2 using intersections
    084            // then recheck
    085            if (f1 != 0) {
    086                // first point is outside, so we update it against one of the
    087                // four sides then continue
    088                if ((f1 & Rectangle2D.OUT_LEFT) == Rectangle2D.OUT_LEFT
    089                        && dx != 0.0) {
    090                    y1 = y1 + (minX - x1) * dy / dx;
    091                    x1 = minX;
    092                }
    093                else if ((f1 & Rectangle2D.OUT_RIGHT) == Rectangle2D.OUT_RIGHT
    094                        && dx != 0.0) {
    095                    y1 = y1 + (maxX - x1) * dy / dx;
    096                    x1 = maxX;
    097                }
    098                else if ((f1 & Rectangle2D.OUT_BOTTOM) == Rectangle2D.OUT_BOTTOM
    099                        && dy != 0.0) {
    100                    x1 = x1 + (maxY - y1) * dx / dy;
    101                    y1 = maxY;
    102                }
    103                else if ((f1 & Rectangle2D.OUT_TOP) == Rectangle2D.OUT_TOP
    104                        && dy != 0.0) {
    105                    x1 = x1 + (minY - y1) * dx / dy;
    106                    y1 = minY;
    107                }
    108                f1 = rect.outcode(x1, y1);
    109            }
    110            else if (f2 != 0) {
    111                // second point is outside, so we update it against one of the
    112                // four sides then continue
    113                if ((f2 & Rectangle2D.OUT_LEFT) == Rectangle2D.OUT_LEFT
    114                        && dx != 0.0) {
    115                    y2 = y2 + (minX - x2) * dy / dx;
    116                    x2 = minX;
    117                }
    118                else if ((f2 & Rectangle2D.OUT_RIGHT) == Rectangle2D.OUT_RIGHT
    119                        && dx != 0.0) {
    120                    y2 = y2 + (maxX - x2) * dy / dx;
    121                    x2 = maxX;
    122                }
    123                else if ((f2 & Rectangle2D.OUT_BOTTOM) == Rectangle2D.OUT_BOTTOM
    124                        && dy != 0.0) {
    125                    x2 = x2 + (maxY - y2) * dx / dy;
    126                    y2 = maxY;
    127                }
    128                else if ((f2 & Rectangle2D.OUT_TOP) == Rectangle2D.OUT_TOP
    129                        && dy != 0.0) {
    130                    x2 = x2 + (minY - y2) * dx / dy;
    131                    y2 = minY;
    132                }
    133                f2 = rect.outcode(x2, y2);
    134            }
    135        }
    136
    137        line.setLine(x1, y1, x2, y2);
    138        return true;  // the line is visible - if it wasn't, we'd have
    139                      // returned false from within the while loop above
    140
    141    }
    142}