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My first initial commit with all of mine experimental changes.

Dmitry Kabak (userdima committed 13 years ago

Commit d37b88d1 parent 3f5b46618352 files · +2598093 −-8690Browse files

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java/pkg/java/awt/geom/ArcIterator.java+312−0
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1+/*
2+ * Copyright (c) 1997, 2003, Oracle and/or its affiliates. All rights reserved.
3+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4+ *
5+ * This code is free software; you can redistribute it and/or modify it
6+ * under the terms of the GNU General Public License version 2 only, as
7+ * published by the Free Software Foundation. Oracle designates this
8+ * particular file as subject to the "Classpath" exception as provided
9+ * by Oracle in the LICENSE file that accompanied this code.
10+ *
11+ * This code is distributed in the hope that it will be useful, but WITHOUT
12+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14+ * version 2 for more details (a copy is included in the LICENSE file that
15+ * accompanied this code).
16+ *
17+ * You should have received a copy of the GNU General Public License version
18+ * 2 along with this work; if not, write to the Free Software Foundation,
19+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20+ *
21+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22+ * or visit www.oracle.com if you need additional information or have any
23+ * questions.
24+ */
25+
26+package java.awt.geom;
27+
28+import java.util.*;
29+
30+/**
31+ * A utility class to iterate over the path segments of an arc
32+ * through the PathIterator interface.
33+ *
34+ * @author Jim Graham
35+ */
36+class ArcIterator implements PathIterator {
37+ double x, y, w, h, angStRad, increment, cv;
38+ AffineTransform affine;
39+ int index;
40+ int arcSegs;
41+ int lineSegs;
42+
43+ ArcIterator(Arc2D a, AffineTransform at) {
44+ this.w = a.getWidth() / 2;
45+ this.h = a.getHeight() / 2;
46+ this.x = a.getX() + w;
47+ this.y = a.getY() + h;
48+ this.angStRad = -Math.toRadians(a.getAngleStart());
49+ this.affine = at;
50+ double ext = -a.getAngleExtent();
51+ if (ext >= 360.0 || ext <= -360) {
52+ arcSegs = 4;
53+ this.increment = Math.PI / 2;
54+ // btan(Math.PI / 2);
55+ this.cv = 0.5522847498307933;
56+ if (ext < 0) {
57+ increment = -increment;
58+ cv = -cv;
59+ }
60+ } else {
61+ arcSegs = (int) Math.ceil(Math.abs(ext) / 90.0);
62+ this.increment = Math.toRadians(ext / arcSegs);
63+ this.cv = btan(increment);
64+ if (cv == 0) {
65+ arcSegs = 0;
66+ }
67+ }
68+ switch (a.getArcType()) {
69+ case Arc2D.OPEN:
70+ lineSegs = 0;
71+ break;
72+ case Arc2D.CHORD:
73+ lineSegs = 1;
74+ break;
75+ case Arc2D.PIE:
76+ lineSegs = 2;
77+ break;
78+ }
79+ if (w < 0 || h < 0) {
80+ arcSegs = lineSegs = -1;
81+ }
82+ }
83+
84+ /**
85+ * Return the winding rule for determining the insideness of the
86+ * path.
87+ * @see #WIND_EVEN_ODD
88+ * @see #WIND_NON_ZERO
89+ */
90+ public int getWindingRule() {
91+ return WIND_NON_ZERO;
92+ }
93+
94+ /**
95+ * Tests if there are more points to read.
96+ * @return true if there are more points to read
97+ */
98+ public boolean isDone() {
99+ return index > arcSegs + lineSegs;
100+ }
101+
102+ /**
103+ * Moves the iterator to the next segment of the path forwards
104+ * along the primary direction of traversal as long as there are
105+ * more points in that direction.
106+ */
107+ public void next() {
108+ index++;
109+ }
110+
111+ /*
112+ * btan computes the length (k) of the control segments at
113+ * the beginning and end of a cubic bezier that approximates
114+ * a segment of an arc with extent less than or equal to
115+ * 90 degrees. This length (k) will be used to generate the
116+ * 2 bezier control points for such a segment.
117+ *
118+ * Assumptions:
119+ * a) arc is centered on 0,0 with radius of 1.0
120+ * b) arc extent is less than 90 degrees
121+ * c) control points should preserve tangent
122+ * d) control segments should have equal length
123+ *
124+ * Initial data:
125+ * start angle: ang1
126+ * end angle: ang2 = ang1 + extent
127+ * start point: P1 = (x1, y1) = (cos(ang1), sin(ang1))
128+ * end point: P4 = (x4, y4) = (cos(ang2), sin(ang2))
129+ *
130+ * Control points:
131+ * P2 = (x2, y2)
132+ * | x2 = x1 - k * sin(ang1) = cos(ang1) - k * sin(ang1)
133+ * | y2 = y1 + k * cos(ang1) = sin(ang1) + k * cos(ang1)
134+ *
135+ * P3 = (x3, y3)
136+ * | x3 = x4 + k * sin(ang2) = cos(ang2) + k * sin(ang2)
137+ * | y3 = y4 - k * cos(ang2) = sin(ang2) - k * cos(ang2)
138+ *
139+ * The formula for this length (k) can be found using the
140+ * following derivations:
141+ *
142+ * Midpoints:
143+ * a) bezier (t = 1/2)
144+ * bPm = P1 * (1-t)^3 +
145+ * 3 * P2 * t * (1-t)^2 +
146+ * 3 * P3 * t^2 * (1-t) +
147+ * P4 * t^3 =
148+ * = (P1 + 3P2 + 3P3 + P4)/8
149+ *
150+ * b) arc
151+ * aPm = (cos((ang1 + ang2)/2), sin((ang1 + ang2)/2))
152+ *
153+ * Let angb = (ang2 - ang1)/2; angb is half of the angle
154+ * between ang1 and ang2.
155+ *
156+ * Solve the equation bPm == aPm
157+ *
158+ * a) For xm coord:
159+ * x1 + 3*x2 + 3*x3 + x4 = 8*cos((ang1 + ang2)/2)
160+ *
161+ * cos(ang1) + 3*cos(ang1) - 3*k*sin(ang1) +
162+ * 3*cos(ang2) + 3*k*sin(ang2) + cos(ang2) =
163+ * = 8*cos((ang1 + ang2)/2)
164+ *
165+ * 4*cos(ang1) + 4*cos(ang2) + 3*k*(sin(ang2) - sin(ang1)) =
166+ * = 8*cos((ang1 + ang2)/2)
167+ *
168+ * 8*cos((ang1 + ang2)/2)*cos((ang2 - ang1)/2) +
169+ * 6*k*sin((ang2 - ang1)/2)*cos((ang1 + ang2)/2) =
170+ * = 8*cos((ang1 + ang2)/2)
171+ *
172+ * 4*cos(angb) + 3*k*sin(angb) = 4
173+ *
174+ * k = 4 / 3 * (1 - cos(angb)) / sin(angb)
175+ *
176+ * b) For ym coord we derive the same formula.
177+ *
178+ * Since this formula can generate "NaN" values for small
179+ * angles, we will derive a safer form that does not involve
180+ * dividing by very small values:
181+ * (1 - cos(angb)) / sin(angb) =
182+ * = (1 - cos(angb))*(1 + cos(angb)) / sin(angb)*(1 + cos(angb)) =
183+ * = (1 - cos(angb)^2) / sin(angb)*(1 + cos(angb)) =
184+ * = sin(angb)^2 / sin(angb)*(1 + cos(angb)) =
185+ * = sin(angb) / (1 + cos(angb))
186+ *
187+ */
188+ private static double btan(double increment) {
189+ increment /= 2.0;
190+ return 4.0 / 3.0 * Math.sin(increment) / (1.0 + Math.cos(increment));
191+ }
192+
193+ /**
194+ * Returns the coordinates and type of the current path segment in
195+ * the iteration.
196+ * The return value is the path segment type:
197+ * SEG_MOVETO, SEG_LINETO, SEG_QUADTO, SEG_CUBICTO, or SEG_CLOSE.
198+ * A float array of length 6 must be passed in and may be used to
199+ * store the coordinates of the point(s).
200+ * Each point is stored as a pair of float x,y coordinates.
201+ * SEG_MOVETO and SEG_LINETO types will return one point,
202+ * SEG_QUADTO will return two points,
203+ * SEG_CUBICTO will return 3 points
204+ * and SEG_CLOSE will not return any points.
205+ * @see #SEG_MOVETO
206+ * @see #SEG_LINETO
207+ * @see #SEG_QUADTO
208+ * @see #SEG_CUBICTO
209+ * @see #SEG_CLOSE
210+ */
211+ public int currentSegment(float[] coords) {
212+ if (isDone()) {
213+ throw new NoSuchElementException("arc iterator out of bounds");
214+ }
215+ double angle = angStRad;
216+ if (index == 0) {
217+ coords[0] = (float) (x + Math.cos(angle) * w);
218+ coords[1] = (float) (y + Math.sin(angle) * h);
219+ if (affine != null) {
220+ affine.transform(coords, 0, coords, 0, 1);
221+ }
222+ return SEG_MOVETO;
223+ }
224+ if (index > arcSegs) {
225+ if (index == arcSegs + lineSegs) {
226+ return SEG_CLOSE;
227+ }
228+ coords[0] = (float) x;
229+ coords[1] = (float) y;
230+ if (affine != null) {
231+ affine.transform(coords, 0, coords, 0, 1);
232+ }
233+ return SEG_LINETO;
234+ }
235+ angle += increment * (index - 1);
236+ double relx = Math.cos(angle);
237+ double rely = Math.sin(angle);
238+ coords[0] = (float) (x + (relx - cv * rely) * w);
239+ coords[1] = (float) (y + (rely + cv * relx) * h);
240+ angle += increment;
241+ relx = Math.cos(angle);
242+ rely = Math.sin(angle);
243+ coords[2] = (float) (x + (relx + cv * rely) * w);
244+ coords[3] = (float) (y + (rely - cv * relx) * h);
245+ coords[4] = (float) (x + relx * w);
246+ coords[5] = (float) (y + rely * h);
247+ if (affine != null) {
248+ affine.transform(coords, 0, coords, 0, 3);
249+ }
250+ return SEG_CUBICTO;
251+ }
252+
253+ /**
254+ * Returns the coordinates and type of the current path segment in
255+ * the iteration.
256+ * The return value is the path segment type:
257+ * SEG_MOVETO, SEG_LINETO, SEG_QUADTO, SEG_CUBICTO, or SEG_CLOSE.
258+ * A double array of length 6 must be passed in and may be used to
259+ * store the coordinates of the point(s).
260+ * Each point is stored as a pair of double x,y coordinates.
261+ * SEG_MOVETO and SEG_LINETO types will return one point,
262+ * SEG_QUADTO will return two points,
263+ * SEG_CUBICTO will return 3 points
264+ * and SEG_CLOSE will not return any points.
265+ * @see #SEG_MOVETO
266+ * @see #SEG_LINETO
267+ * @see #SEG_QUADTO
268+ * @see #SEG_CUBICTO
269+ * @see #SEG_CLOSE
270+ */
271+ public int currentSegment(double[] coords) {
272+ if (isDone()) {
273+ throw new NoSuchElementException("arc iterator out of bounds");
274+ }
275+ double angle = angStRad;
276+ if (index == 0) {
277+ coords[0] = x + Math.cos(angle) * w;
278+ coords[1] = y + Math.sin(angle) * h;
279+ if (affine != null) {
280+ affine.transform(coords, 0, coords, 0, 1);
281+ }
282+ return SEG_MOVETO;
283+ }
284+ if (index > arcSegs) {
285+ if (index == arcSegs + lineSegs) {
286+ return SEG_CLOSE;
287+ }
288+ coords[0] = x;
289+ coords[1] = y;
290+ if (affine != null) {
291+ affine.transform(coords, 0, coords, 0, 1);
292+ }
293+ return SEG_LINETO;
294+ }
295+ angle += increment * (index - 1);
296+ double relx = Math.cos(angle);
297+ double rely = Math.sin(angle);
298+ coords[0] = x + (relx - cv * rely) * w;
299+ coords[1] = y + (rely + cv * relx) * h;
300+ angle += increment;
301+ relx = Math.cos(angle);
302+ rely = Math.sin(angle);
303+ coords[2] = x + (relx + cv * rely) * w;
304+ coords[3] = y + (rely - cv * relx) * h;
305+ coords[4] = x + relx * w;
306+ coords[5] = y + rely * h;
307+ if (affine != null) {
308+ affine.transform(coords, 0, coords, 0, 3);
309+ }
310+ return SEG_CUBICTO;
311+ }
312+}