source: josm/trunk/src/com/kitfox/svg/pathcmd/Arc.java@ 17333

Last change on this file since 17333 was 17333, checked in by Don-vip, 4 years ago

see #20129 - Fix typos and misspellings in the code (patch by gaben)

  • Property svn:eol-style set to native
File size: 9.8 KB
Line 
1/*
2 * SVG Salamander
3 * Copyright (c) 2004, Mark McKay
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or
7 * without modification, are permitted provided that the following
8 * conditions are met:
9 *
10 * - Redistributions of source code must retain the above
11 * copyright notice, this list of conditions and the following
12 * disclaimer.
13 * - Redistributions in binary form must reproduce the above
14 * copyright notice, this list of conditions and the following
15 * disclaimer in the documentation and/or other materials
16 * provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
21 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
22 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
23 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
24 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
25 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
27 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
29 * OF THE POSSIBILITY OF SUCH DAMAGE.
30 *
31 * Mark McKay can be contacted at mark@kitfox.com. Salamander and other
32 * projects can be found at http://www.kitfox.com
33 *
34 * Created on January 26, 2004, 8:40 PM
35 */
36
37package com.kitfox.svg.pathcmd;
38
39//import org.apache.batik.ext.awt.geom.ExtendedGeneralPath;
40import java.awt.*;
41import java.awt.geom.*;
42
43/**
44 * This is a little used SVG function, as most editors will save curves as
45 * Beziers. To reduce the need to rely on the Batik library, this functionality
46 * is being bypassed for the time being. In the future, it would be nice to
47 * extend the GeneralPath command to include the arcTo ability provided by Batik.
48 *
49 * @author Mark McKay
50 * @author <a href="mailto:mark@kitfox.com">Mark McKay</a>
51 */
52public class Arc extends PathCommand
53{
54
55 public float rx = 0f;
56 public float ry = 0f;
57 public float xAxisRot = 0f;
58 public boolean largeArc = false;
59 public boolean sweep = false;
60 public float x = 0f;
61 public float y = 0f;
62
63 /** Creates a new instance of MoveTo */
64 public Arc() {
65 }
66
67 public Arc(boolean isRelative, float rx, float ry, float xAxisRot, boolean largeArc, boolean sweep, float x, float y) {
68 super(isRelative);
69 this.rx = rx;
70 this.ry = ry;
71 this.xAxisRot = xAxisRot;
72 this.largeArc = largeArc;
73 this.sweep = sweep;
74 this.x = x;
75 this.y = y;
76 }
77
78// public void appendPath(ExtendedGeneralPath path, BuildHistory hist)
79 @Override
80 public void appendPath(GeneralPath path, BuildHistory hist)
81 {
82 float offx = isRelative ? hist.lastPoint.x : 0f;
83 float offy = isRelative ? hist.lastPoint.y : 0f;
84
85 arcTo(path, rx, ry, xAxisRot, largeArc, sweep,
86 x + offx, y + offy,
87 hist.lastPoint.x, hist.lastPoint.y);
88// path.lineTo(x + offx, y + offy);
89// hist.setPoint(x + offx, y + offy);
90 hist.setLastPoint(x + offx, y + offy);
91 hist.setLastKnot(x + offx, y + offy);
92 }
93
94 @Override
95 public int getNumKnotsAdded()
96 {
97 return 6;
98 }
99
100 /**
101 * Adds an elliptical arc, defined by two radii, an angle from the
102 * x-axis, a flag to choose the large arc or not, a flag to
103 * indicate if we increase or decrease the angles and the final
104 * point of the arc.
105 *
106 * @param path The path that the arc will be appended to.
107 *
108 * @param rx the x radius of the ellipse
109 * @param ry the y radius of the ellipse
110 *
111 * @param angle the angle from the x-axis of the current
112 * coordinate system to the x-axis of the ellipse in degrees.
113 *
114 * @param largeArcFlag the large arc flag. If true the arc
115 * spanning less than or equal to 180 degrees is chosen, otherwise
116 * the arc spanning greater than 180 degrees is chosen
117 *
118 * @param sweepFlag the sweep flag. If true the line joining
119 * center to arc sweeps through decreasing angles otherwise it
120 * sweeps through increasing angles
121 *
122 * @param x the absolute x coordinate of the final point of the arc.
123 * @param y the absolute y coordinate of the final point of the arc.
124 * @param x0 - The absolute x coordinate of the initial point of the arc.
125 * @param y0 - The absolute y coordinate of the initial point of the arc.
126 */
127 public void arcTo(GeneralPath path, float rx, float ry,
128 float angle,
129 boolean largeArcFlag,
130 boolean sweepFlag,
131 float x, float y, float x0, float y0)
132 {
133
134 // Ensure radii are valid
135 if (rx == 0 || ry == 0) {
136 path.lineTo((float) x, (float) y);
137 return;
138 }
139
140 if (x0 == x && y0 == y) {
141 // If the endpoints (x, y) and (x0, y0) are identical, then this
142 // is equivalent to omitting the elliptical arc segment entirely.
143 return;
144 }
145
146 Arc2D arc = computeArc(x0, y0, rx, ry, angle,
147 largeArcFlag, sweepFlag, x, y);
148 if (arc == null) return;
149
150 AffineTransform t = AffineTransform.getRotateInstance
151 (Math.toRadians(angle), arc.getCenterX(), arc.getCenterY());
152 Shape s = t.createTransformedShape(arc);
153 path.append(s, true);
154 }
155
156
157 /**
158 * This constructs an unrotated Arc2D from the SVG specification of an
159 * Elliptical arc. To get the final arc you need to apply a rotation
160 * transform such as:
161 *
162 * AffineTransform.getRotateInstance
163 * (angle, arc.getX()+arc.getWidth()/2, arc.getY()+arc.getHeight()/2);
164 *
165 * @param x0 origin of arc in x
166 * @param y0 origin of arc in y
167 * @param rx radius of arc in x
168 * @param ry radius of arc in y
169 * @param angle number of radians in arc
170 * @param largeArcFlag
171 * @param sweepFlag
172 * @param x ending coordinate of arc in x
173 * @param y ending coordinate of arc in y
174 * @return arc shape
175 *
176 */
177 public static Arc2D computeArc(double x0, double y0,
178 double rx, double ry,
179 double angle,
180 boolean largeArcFlag,
181 boolean sweepFlag,
182 double x, double y) {
183 //
184 // Elliptical arc implementation based on the SVG specification notes
185 //
186
187 // Compute the half distance between the current and the final point
188 double dx2 = (x0 - x) / 2.0;
189 double dy2 = (y0 - y) / 2.0;
190 // Convert angle from degrees to radians
191 angle = Math.toRadians(angle % 360.0);
192 double cosAngle = Math.cos(angle);
193 double sinAngle = Math.sin(angle);
194
195 //
196 // Step 1 : Compute (x1, y1)
197 //
198 double x1 = (cosAngle * dx2 + sinAngle * dy2);
199 double y1 = (-sinAngle * dx2 + cosAngle * dy2);
200 // Ensure radii are large enough
201 rx = Math.abs(rx);
202 ry = Math.abs(ry);
203 double Prx = rx * rx;
204 double Pry = ry * ry;
205 double Px1 = x1 * x1;
206 double Py1 = y1 * y1;
207 // check that radii are large enough
208 double radiiCheck = Px1/Prx + Py1/Pry;
209 if (radiiCheck > 1) {
210 rx = Math.sqrt(radiiCheck) * rx;
211 ry = Math.sqrt(radiiCheck) * ry;
212 Prx = rx * rx;
213 Pry = ry * ry;
214 }
215
216 //
217 // Step 2 : Compute (cx1, cy1)
218 //
219 double sign = (largeArcFlag == sweepFlag) ? -1 : 1;
220 double sq = ((Prx*Pry)-(Prx*Py1)-(Pry*Px1)) / ((Prx*Py1)+(Pry*Px1));
221 sq = (sq < 0) ? 0 : sq;
222 double coef = (sign * Math.sqrt(sq));
223 double cx1 = coef * ((rx * y1) / ry);
224 double cy1 = coef * -((ry * x1) / rx);
225
226 //
227 // Step 3 : Compute (cx, cy) from (cx1, cy1)
228 //
229 double sx2 = (x0 + x) / 2.0;
230 double sy2 = (y0 + y) / 2.0;
231 double cx = sx2 + (cosAngle * cx1 - sinAngle * cy1);
232 double cy = sy2 + (sinAngle * cx1 + cosAngle * cy1);
233
234 //
235 // Step 4 : Compute the angleStart (angle1) and the angleExtent (dangle)
236 //
237 double ux = (x1 - cx1) / rx;
238 double uy = (y1 - cy1) / ry;
239 double vx = (-x1 - cx1) / rx;
240 double vy = (-y1 - cy1) / ry;
241 double p, n;
242 // Compute the angle start
243 n = Math.sqrt((ux * ux) + (uy * uy));
244 p = ux; // (1 * ux) + (0 * uy)
245 sign = (uy < 0) ? -1d : 1d;
246 double angleStart = Math.toDegrees(sign * Math.acos(p / n));
247
248 // Compute the angle extent
249 n = Math.sqrt((ux * ux + uy * uy) * (vx * vx + vy * vy));
250 p = ux * vx + uy * vy;
251 sign = (ux * vy - uy * vx < 0) ? -1d : 1d;
252 double angleExtent = Math.toDegrees(sign * Math.acos(p / n));
253 if(!sweepFlag && angleExtent > 0) {
254 angleExtent -= 360f;
255 } else if (sweepFlag && angleExtent < 0) {
256 angleExtent += 360f;
257 }
258 angleExtent %= 360f;
259 angleStart %= 360f;
260
261 //
262 // We can now build the resulting Arc2D in double precision
263 //
264 Arc2D.Double arc = new Arc2D.Double();
265 arc.x = cx - rx;
266 arc.y = cy - ry;
267 arc.width = rx * 2.0;
268 arc.height = ry * 2.0;
269 arc.start = -angleStart;
270 arc.extent = -angleExtent;
271
272 return arc;
273 }
274
275 @Override
276 public String toString()
277 {
278 return "A " + rx + " " + ry
279 + " " + xAxisRot + " " + largeArc
280 + " " + sweep
281 + " " + x + " " + y;
282 }
283}
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