| 1 | /*
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| 2 | * MoveTo.java
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| 3 | *
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| 4 | *
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| 5 | * The Salamander Project - 2D and 3D graphics libraries in Java
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| 6 | * Copyright (C) 2004 Mark McKay
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| 7 | *
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| 8 | * This library is free software; you can redistribute it and/or
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| 9 | * modify it under the terms of the GNU Lesser General Public
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| 10 | * License as published by the Free Software Foundation; either
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| 11 | * version 2.1 of the License, or (at your option) any later version.
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| 12 | *
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| 13 | * This library is distributed in the hope that it will be useful,
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| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 16 | * Lesser General Public License for more details.
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| 17 | *
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| 18 | * You should have received a copy of the GNU Lesser General Public
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| 19 | * License along with this library; if not, write to the Free Software
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| 20 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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| 21 | *
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| 22 | * Mark McKay can be contacted at mark@kitfox.com. Salamander and other
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| 23 | * projects can be found at http://www.kitfox.com
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| 24 | *
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| 25 | * Created on January 26, 2004, 8:40 PM
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| 26 | */
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| 27 |
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| 28 | package com.kitfox.svg.pathcmd;
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| 29 |
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| 30 | //import org.apache.batik.ext.awt.geom.ExtendedGeneralPath;
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| 31 | import java.awt.*;
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| 32 | import java.awt.geom.*;
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| 33 |
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| 34 | /**
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| 35 | * This is a little used SVG function, as most editors will save curves as
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| 36 | * Beziers. To reduce the need to rely on the Batik library, this functionallity
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| 37 | * is being bypassed for the time being. In the future, it would be nice to
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| 38 | * extend the GeneralPath command to include the arcTo ability provided by Batik.
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| 39 | *
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| 40 | * @author Mark McKay
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| 41 | * @author <a href="mailto:mark@kitfox.com">Mark McKay</a>
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| 42 | */
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| 43 | public class Arc extends PathCommand
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| 44 | {
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| 45 |
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| 46 | public float rx = 0f;
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| 47 | public float ry = 0f;
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| 48 | public float xAxisRot = 0f;
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| 49 | public boolean largeArc = false;
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| 50 | public boolean sweep = false;
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| 51 | public float x = 0f;
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| 52 | public float y = 0f;
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| 53 |
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| 54 | /** Creates a new instance of MoveTo */
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| 55 | public Arc() {
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| 56 | }
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| 57 |
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| 58 | public Arc(boolean isRelative, float rx, float ry, float xAxisRot, boolean largeArc, boolean sweep, float x, float y) {
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| 59 | super(isRelative);
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| 60 | this.rx = rx;
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| 61 | this.ry = ry;
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| 62 | this.xAxisRot = xAxisRot;
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| 63 | this.largeArc = largeArc;
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| 64 | this.sweep = sweep;
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| 65 | this.x = x;
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| 66 | this.y = y;
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| 67 | }
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| 68 |
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| 69 | // public void appendPath(ExtendedGeneralPath path, BuildHistory hist)
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| 70 | public void appendPath(GeneralPath path, BuildHistory hist)
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| 71 | {
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| 72 | float offx = isRelative ? hist.history[0].x : 0f;
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| 73 | float offy = isRelative ? hist.history[0].y : 0f;
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| 74 |
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| 75 | arcTo(path, rx, ry, xAxisRot, largeArc, sweep, x + offx, y + offy, hist.history[0].x, hist.history[0].y);
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| 76 | // path.lineTo(x + offx, y + offy);
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| 77 | hist.setPoint(x + offx, y + offy);
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| 78 | }
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| 79 |
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| 80 | public int getNumKnotsAdded()
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| 81 | {
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| 82 | return 6;
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| 83 | }
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| 84 |
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| 85 | /**
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| 86 | * Adds an elliptical arc, defined by two radii, an angle from the
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| 87 | * x-axis, a flag to choose the large arc or not, a flag to
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| 88 | * indicate if we increase or decrease the angles and the final
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| 89 | * point of the arc.
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| 90 | *
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| 91 | * @param rx the x radius of the ellipse
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| 92 | * @param ry the y radius of the ellipse
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| 93 | *
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| 94 | * @param angle the angle from the x-axis of the current
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| 95 | * coordinate system to the x-axis of the ellipse in degrees.
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| 96 | *
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| 97 | * @param largeArcFlag the large arc flag. If true the arc
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| 98 | * spanning less than or equal to 180 degrees is chosen, otherwise
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| 99 | * the arc spanning greater than 180 degrees is chosen
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| 100 | *
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| 101 | * @param sweepFlag the sweep flag. If true the line joining
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| 102 | * center to arc sweeps through decreasing angles otherwise it
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| 103 | * sweeps through increasing angles
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| 104 | *
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| 105 | * @param x the absolute x coordinate of the final point of the arc.
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| 106 | * @param y the absolute y coordinate of the final point of the arc.
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| 107 | * @param x0 - The absolute x coordinate of the initial point of the arc.
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| 108 | * @param y0 - The absolute y coordinate of the initial point of the arc.
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| 109 | */
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| 110 | public void arcTo(GeneralPath path, float rx, float ry,
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| 111 | float angle,
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| 112 | boolean largeArcFlag,
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| 113 | boolean sweepFlag,
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| 114 | float x, float y, float x0, float y0)
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| 115 | {
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| 116 |
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| 117 | // Ensure radii are valid
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| 118 | if (rx == 0 || ry == 0) {
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| 119 | path.lineTo((float) x, (float) y);
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| 120 | return;
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| 121 | }
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| 122 |
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| 123 | if (x0 == x && y0 == y) {
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| 124 | // If the endpoints (x, y) and (x0, y0) are identical, then this
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| 125 | // is equivalent to omitting the elliptical arc segment entirely.
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| 126 | return;
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| 127 | }
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| 128 |
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| 129 | Arc2D arc = computeArc(x0, y0, rx, ry, angle,
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| 130 | largeArcFlag, sweepFlag, x, y);
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| 131 | if (arc == null) return;
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| 132 |
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| 133 | AffineTransform t = AffineTransform.getRotateInstance
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| 134 | (Math.toRadians(angle), arc.getCenterX(), arc.getCenterY());
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| 135 | Shape s = t.createTransformedShape(arc);
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| 136 | path.append(s, true);
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| 137 | }
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| 138 |
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| 139 |
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| 140 | /**
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| 141 | * This constructs an unrotated Arc2D from the SVG specification of an
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| 142 | * Elliptical arc. To get the final arc you need to apply a rotation
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| 143 | * transform such as:
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| 144 | *
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| 145 | * AffineTransform.getRotateInstance
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| 146 | * (angle, arc.getX()+arc.getWidth()/2, arc.getY()+arc.getHeight()/2);
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| 147 | */
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| 148 | public static Arc2D computeArc(double x0, double y0,
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| 149 | double rx, double ry,
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| 150 | double angle,
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| 151 | boolean largeArcFlag,
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| 152 | boolean sweepFlag,
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| 153 | double x, double y) {
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| 154 | //
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| 155 | // Elliptical arc implementation based on the SVG specification notes
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| 156 | //
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| 157 |
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| 158 | // Compute the half distance between the current and the final point
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| 159 | double dx2 = (x0 - x) / 2.0;
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| 160 | double dy2 = (y0 - y) / 2.0;
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| 161 | // Convert angle from degrees to radians
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| 162 | angle = Math.toRadians(angle % 360.0);
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| 163 | double cosAngle = Math.cos(angle);
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| 164 | double sinAngle = Math.sin(angle);
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| 165 |
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| 166 | //
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| 167 | // Step 1 : Compute (x1, y1)
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| 168 | //
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| 169 | double x1 = (cosAngle * dx2 + sinAngle * dy2);
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| 170 | double y1 = (-sinAngle * dx2 + cosAngle * dy2);
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| 171 | // Ensure radii are large enough
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| 172 | rx = Math.abs(rx);
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| 173 | ry = Math.abs(ry);
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| 174 | double Prx = rx * rx;
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| 175 | double Pry = ry * ry;
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| 176 | double Px1 = x1 * x1;
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| 177 | double Py1 = y1 * y1;
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| 178 | // check that radii are large enough
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| 179 | double radiiCheck = Px1/Prx + Py1/Pry;
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| 180 | if (radiiCheck > 1) {
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| 181 | rx = Math.sqrt(radiiCheck) * rx;
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| 182 | ry = Math.sqrt(radiiCheck) * ry;
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| 183 | Prx = rx * rx;
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| 184 | Pry = ry * ry;
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| 185 | }
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| 186 |
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| 187 | //
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| 188 | // Step 2 : Compute (cx1, cy1)
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| 189 | //
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| 190 | double sign = (largeArcFlag == sweepFlag) ? -1 : 1;
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| 191 | double sq = ((Prx*Pry)-(Prx*Py1)-(Pry*Px1)) / ((Prx*Py1)+(Pry*Px1));
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| 192 | sq = (sq < 0) ? 0 : sq;
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| 193 | double coef = (sign * Math.sqrt(sq));
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| 194 | double cx1 = coef * ((rx * y1) / ry);
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| 195 | double cy1 = coef * -((ry * x1) / rx);
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| 196 |
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| 197 | //
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| 198 | // Step 3 : Compute (cx, cy) from (cx1, cy1)
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| 199 | //
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| 200 | double sx2 = (x0 + x) / 2.0;
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| 201 | double sy2 = (y0 + y) / 2.0;
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| 202 | double cx = sx2 + (cosAngle * cx1 - sinAngle * cy1);
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| 203 | double cy = sy2 + (sinAngle * cx1 + cosAngle * cy1);
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| 204 |
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| 205 | //
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| 206 | // Step 4 : Compute the angleStart (angle1) and the angleExtent (dangle)
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| 207 | //
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| 208 | double ux = (x1 - cx1) / rx;
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| 209 | double uy = (y1 - cy1) / ry;
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| 210 | double vx = (-x1 - cx1) / rx;
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| 211 | double vy = (-y1 - cy1) / ry;
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| 212 | double p, n;
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| 213 | // Compute the angle start
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| 214 | n = Math.sqrt((ux * ux) + (uy * uy));
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| 215 | p = ux; // (1 * ux) + (0 * uy)
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| 216 | sign = (uy < 0) ? -1d : 1d;
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| 217 | double angleStart = Math.toDegrees(sign * Math.acos(p / n));
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| 218 |
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| 219 | // Compute the angle extent
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| 220 | n = Math.sqrt((ux * ux + uy * uy) * (vx * vx + vy * vy));
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| 221 | p = ux * vx + uy * vy;
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| 222 | sign = (ux * vy - uy * vx < 0) ? -1d : 1d;
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| 223 | double angleExtent = Math.toDegrees(sign * Math.acos(p / n));
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| 224 | if(!sweepFlag && angleExtent > 0) {
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| 225 | angleExtent -= 360f;
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| 226 | } else if (sweepFlag && angleExtent < 0) {
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| 227 | angleExtent += 360f;
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| 228 | }
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| 229 | angleExtent %= 360f;
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| 230 | angleStart %= 360f;
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| 231 |
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| 232 | //
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| 233 | // We can now build the resulting Arc2D in double precision
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| 234 | //
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| 235 | Arc2D.Double arc = new Arc2D.Double();
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| 236 | arc.x = cx - rx;
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| 237 | arc.y = cy - ry;
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| 238 | arc.width = rx * 2.0;
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| 239 | arc.height = ry * 2.0;
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| 240 | arc.start = -angleStart;
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| 241 | arc.extent = -angleExtent;
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| 242 |
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| 243 | return arc;
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| 244 | }
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| 245 | }
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