Source code: org/apache/batik/ext/awt/LinearGradientPaint.java
1 /*
2
3 Copyright 2001-2003 The Apache Software Foundation
4
5 Licensed under the Apache License, Version 2.0 (the "License");
6 you may not use this file except in compliance with the License.
7 You may obtain a copy of the License at
8
9 http://www.apache.org/licenses/LICENSE-2.0
10
11 Unless required by applicable law or agreed to in writing, software
12 distributed under the License is distributed on an "AS IS" BASIS,
13 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 See the License for the specific language governing permissions and
15 limitations under the License.
16
17 */
18 package org.apache.batik.ext.awt;
19
20 import java.awt.Color;
21 import java.awt.PaintContext;
22 import java.awt.Rectangle;
23 import java.awt.RenderingHints;
24 import java.awt.geom.AffineTransform;
25 import java.awt.geom.NoninvertibleTransformException;
26 import java.awt.geom.Point2D;
27 import java.awt.geom.Rectangle2D;
28 import java.awt.image.ColorModel;
29
30 /**
31 * The <code>LinearGradientPaint</code> class provides a way to fill
32 * a {@link java.awt.Shape} with a linear color gradient pattern. The user may
33 * specify 2 or more gradient colors, and this paint will provide an
34 * interpolation between each color. The user also specifies start and end
35 * points which define where in user space the color gradient should begin
36 * and end.
37 * <p>
38 * The user must provide an array of floats specifying how to distribute the
39 * colors along the gradient. These values should range from 0.0 to 1.0 and
40 * act like keyframes along the gradient (they mark where the gradient should
41 * be exactly a particular color).
42 * <p>
43 * For example:
44 * <br>
45 * <code>
46 * <p>
47 * Point2D start = new Point2D.Float(0, 0);<br>
48 * Point2D end = new Point2D.Float(100,100);<br>
49 * float[] dist = {0.0, 0.2, 1.0};<br>
50 * Color[] colors = {Color.red, Color.white, Color.blue};<br>
51 * LinearGradientPaint p = new LinearGradientPaint(start, end, dist, colors);
52 * </code>
53 *<p>
54 * This code will create a LinearGradientPaint which interpolates between
55 * red and white for the first 20% of the gradient and between white and blue
56 * for the remaining 80%.
57 *
58 * <p> In the event that the user does not set the first keyframe value equal
59 * to 0 and the last keyframe value equal to 1, keyframes will be created at
60 * these positions and the first and last colors will be replicated there.
61 * So, if a user specifies the following arrays to construct a gradient:<br>
62 * {Color.blue, Color.red}, {.3, .7}<br>
63 * this will be converted to a gradient with the following keyframes:
64 * {Color.blue, Color.blue, Color.red, Color.red}, {0, .3, .7, 1}
65 *
66 * <p>
67 * The user may also select what action the LinearGradientPaint should take
68 * when filling color outside the start and end points. If no cycle method is
69 * specified, NO_CYCLE will be chosen by default, so the endpoint colors
70 * will be used to fill the remaining area.
71 *
72 * <p> The following image demonstrates the options NO_CYCLE and REFLECT.
73 *
74 * <p>
75 * <img src = "cyclic.jpg">
76 *
77 * <p> The colorSpace parameter allows the user to specify in which colorspace
78 * the interpolation should be performed, default sRGB or linearized RGB.
79 *
80 *
81 * @author Nicholas Talian, Vincent Hardy, Jim Graham, Jerry Evans
82 * @author <a href="mailto:vincent.hardy@eng.sun.com">Vincent Hardy</a>
83 * @version $Id: LinearGradientPaint.java,v 1.6 2005/03/27 08:58:32 cam Exp $
84 * @see java.awt.Paint
85 * @see java.awt.Graphics2D#setPaint
86 *
87 */
88 public final class LinearGradientPaint extends MultipleGradientPaint {
89
90 /** Gradient start and end points. */
91 private Point2D start, end;
92
93 /**<p>
94 * Constructs an <code>LinearGradientPaint</code> with the default
95 * NO_CYCLE repeating method and SRGB colorspace.
96 *
97 * @param startX the x coordinate of the gradient axis start point
98 * in user space
99 *
100 * @param startY the y coordinate of the gradient axis start point
101 * in user space
102 *
103 * @param endX the x coordinate of the gradient axis end point
104 * in user space
105 *
106 * @param endY the y coordinate of the gradient axis end point
107 * in user space
108 *
109 * @param fractions numbers ranging from 0.0 to 1.0 specifying the
110 * distribution of colors along the gradient
111 *
112 * @param colors array of colors corresponding to each fractional value
113 *
114 *
115 * @throws IllegalArgumentException if start and end points are the
116 * same points, or if fractions.length != colors.length, or if colors
117 * is less than 2 in size.
118 *
119 */
120 public LinearGradientPaint(float startX, float startY,
121 float endX, float endY,
122 float[] fractions, Color[] colors) {
123
124 this(new Point2D.Float(startX, startY),
125 new Point2D.Float(endX, endY),
126 fractions,
127 colors,
128 NO_CYCLE,
129 SRGB);
130 }
131
132 /**<p>
133 * Constructs an <code>LinearGradientPaint</code> with default SRGB
134 * colorspace.
135 *
136 * @param startX the x coordinate of the gradient axis start point
137 * in user space
138 *
139 * @param startY the y coordinate of the gradient axis start point
140 * in user space
141 *
142 * @param endX the x coordinate of the gradient axis end point
143 * in user space
144 *
145 * @param endY the y coordinate of the gradient axis end point
146 * in user space
147 *
148 * @param fractions numbers ranging from 0.0 to 1.0 specifying the
149 * distribution of colors along the gradient
150 *
151 * @param colors array of colors corresponding to each fractional value
152 *
153 * @param cycleMethod either NO_CYCLE, REFLECT, or REPEAT
154 *
155 * @throws IllegalArgumentException if start and end points are the
156 * same points, or if fractions.length != colors.length, or if colors
157 * is less than 2 in size.
158 *
159 */
160 public LinearGradientPaint(float startX, float startY,
161 float endX, float endY,
162 float[] fractions, Color[] colors,
163 CycleMethodEnum cycleMethod) {
164 this(new Point2D.Float(startX, startY),
165 new Point2D.Float(endX, endY),
166 fractions,
167 colors,
168 cycleMethod,
169 SRGB);
170 }
171
172 /**<p>
173 * Constructs a <code>LinearGradientPaint</code> with the default
174 * NO_CYCLE repeating method and SRGB colorspace.
175 *
176 * @param start the gradient axis start <code>Point</code> in user space
177 *
178 * @param end the gradient axis end <code>Point</code> in user space
179 *
180 * @param fractions numbers ranging from 0.0 to 1.0 specifying the
181 * distribution of colors along the gradient
182 *
183 * @param colors array of colors corresponding to each fractional value
184 *
185 * @throws NullPointerException if one of the points is null
186 *
187 * @throws IllegalArgumentException if start and end points are the
188 * same points, or if fractions.length != colors.length, or if colors
189 * is less than 2 in size.
190 *
191 */
192 public LinearGradientPaint(Point2D start, Point2D end, float[] fractions,
193 Color[] colors) {
194
195 this(start, end, fractions, colors, NO_CYCLE, SRGB);
196 }
197
198 /**<p>
199 * Constructs a <code>LinearGradientPaint</code>.
200 *
201 * @param start the gradient axis start <code>Point</code> in user space
202 *
203 * @param end the gradient axis end <code>Point</code> in user space
204 *
205 * @param fractions numbers ranging from 0.0 to 1.0 specifying the
206 * distribution of colors along the gradient
207 *
208 * @param colors array of colors corresponding to each fractional value
209 *
210 * @param cycleMethod either NO_CYCLE, REFLECT, or REPEAT
211 *
212 * @param colorSpace which colorspace to use for interpolation,
213 * either SRGB or LINEAR_RGB
214 *
215 * @throws NullPointerException if one of the points is null
216 *
217 * @throws IllegalArgumentException if start and end points are the
218 * same points, or if fractions.length != colors.length, or if colors
219 * is less than 2 in size.
220 *
221 */
222 public LinearGradientPaint(Point2D start, Point2D end, float[] fractions,
223 Color[] colors,
224 CycleMethodEnum cycleMethod,
225 ColorSpaceEnum colorSpace) {
226
227 this(start, end, fractions, colors, cycleMethod, colorSpace,
228 new AffineTransform());
229
230 }
231
232 /**<p>
233 * Constructs a <code>LinearGradientPaint</code>.
234 *
235 * @param start the gradient axis start <code>Point</code> in user space
236 *
237 * @param end the gradient axis end <code>Point</code> in user space
238 *
239 * @param fractions numbers ranging from 0.0 to 1.0 specifying the
240 * distribution of colors along the gradient
241 *
242 * @param colors array of colors corresponding to each fractional value
243 *
244 * @param cycleMethod either NO_CYCLE, REFLECT, or REPEAT
245 *
246 * @param colorSpace which colorspace to use for interpolation,
247 * either SRGB or LINEAR_RGB
248 *
249 * @param gradientTransform transform to apply to the gradient
250 *
251 * @throws NullPointerException if one of the points is null,
252 * or gradientTransform is null
253 *
254 * @throws IllegalArgumentException if start and end points are the
255 * same points, or if fractions.length != colors.length, or if colors
256 * is less than 2 in size.
257 *
258 */
259 public LinearGradientPaint(Point2D start, Point2D end, float[] fractions,
260 Color[] colors,
261 CycleMethodEnum cycleMethod,
262 ColorSpaceEnum colorSpace,
263 AffineTransform gradientTransform) {
264 super(fractions, colors, cycleMethod, colorSpace, gradientTransform);
265
266 //
267 // Check input parameters
268 //
269 if (start == null || end == null) {
270 throw new NullPointerException("Start and end points must be" +
271 "non-null");
272 }
273
274 if (start.equals(end)) {
275 throw new IllegalArgumentException("Start point cannot equal" +
276 "endpoint");
277 }
278
279 //copy the points...
280 this.start = (Point2D)start.clone();
281
282 this.end = (Point2D)end.clone();
283
284 }
285
286 /**
287 * Creates and returns a PaintContext used to generate the color pattern,
288 * for use by the internal rendering engine.
289 *
290 * @param cm {@link ColorModel} that receives
291 * the <code>Paint</code> data. This is used only as a hint.
292 *
293 * @param deviceBounds the device space bounding box of the
294 * graphics primitive being rendered
295 *
296 * @param userBounds the user space bounding box of the
297 * graphics primitive being rendered
298 *
299 * @param transform the {@link AffineTransform} from user
300 * space into device space
301 *
302 * @param hints the hints that the context object uses to choose
303 * between rendering alternatives
304 *
305 * @return the {@link PaintContext} that generates color patterns.
306 *
307 * @see PaintContext
308 */
309 public PaintContext createContext(ColorModel cm,
310 Rectangle deviceBounds,
311 Rectangle2D userBounds,
312 AffineTransform transform,
313 RenderingHints hints) {
314
315 // Can't modify the transform passed in...
316 transform = new AffineTransform(transform);
317 //incorporate the gradient transform
318 transform.concatenate(gradientTransform);
319
320 try {
321 return new LinearGradientPaintContext(cm,
322 deviceBounds,
323 userBounds,
324 transform,
325 hints,
326 start,
327 end,
328 fractions,
329 this.getColors(),
330 cycleMethod,
331 colorSpace);
332 }
333
334 catch(NoninvertibleTransformException e) {
335 e.printStackTrace();
336 throw new IllegalArgumentException("transform should be" +
337 "invertible");
338 }
339 }
340
341 /**
342 * Returns a copy of the start point of the gradient axis
343 * @return a {@link Point2D} object that is a copy of the point
344 * that anchors the first color of this
345 * <code>LinearGradientPaint</code>.
346 */
347 public Point2D getStartPoint() {
348 return new Point2D.Double(start.getX(), start.getY());
349 }
350
351 /** Returns a copy of the end point of the gradient axis
352 * @return a {@link Point2D} object that is a copy of the point
353 * that anchors the last color of this
354 * <code>LinearGradientPaint</code>.
355 */
356 public Point2D getEndPoint() {
357 return new Point2D.Double(end.getX(), end.getY());
358 }
359
360 }
361
362