1 /* GradientPaintContext.java --
2 Copyright (C) 2005, Free Software Foundation, Inc.
4 This file is part of GNU Classpath.
6 GNU Classpath is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 GNU Classpath is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU Classpath; see the file COPYING. If not, write to the
18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
21 Linking this library statically or dynamically with other modules is
22 making a combined work based on this library. Thus, the terms and
23 conditions of the GNU General Public License cover the whole
26 As a special exception, the copyright holders of this library give you
27 permission to link this library with independent modules to produce an
28 executable, regardless of the license terms of these independent
29 modules, and to copy and distribute the resulting executable under
30 terms of your choice, provided that you also meet, for each linked
31 independent module, the terms and conditions of the license of that
32 module. An independent module is a module which is not derived from
33 or based on this library. If you modify this library, you may extend
34 this exception to your version of the library, but you are not
35 obligated to do so. If you do not wish to do so, delete this
36 exception statement from your version. */
40 import java
.awt
.geom
.Point2D
;
41 import java
.awt
.image
.ColorModel
;
42 import java
.awt
.image
.Raster
;
43 import java
.awt
.image
.WritableRaster
;
44 import java
.awt
.PaintContext
;
45 import java
.awt
.Color
;
48 * A {@link PaintContext} used by the {@link GradientPaint} class.
50 public class GradientPaintContext
implements PaintContext
53 // This implementation follows the technique described in
54 // "Java(tm) 2D Graphics" by Jonathan Knudsen (O'Reilly 1999).
56 /** The x-coordinate of the anchor point for color 1. */
57 private final float x1
;
59 /** The y-coordinate of the anchor point for color 1. */
60 private final float y1
;
63 private final Color c1
;
65 /** The x-coordinate of the anchor point for color 2. */
66 private final float x2
;
68 /** The y-coordinate of the anchor point for color 2. */
69 private final float y2
;
72 private final Color c2
;
74 /** A flag indicating whether the gradient is cyclic or acyclic. */
75 private final boolean cyclic
;
77 /** The length of the gradient line - computed from the two anchor points. */
78 private final double length
;
81 * Creates a new instance.
83 * @param x1 the x-coordinate for the anchor point for color 1.
84 * @param y1 the y-coordinate for the anchor point for color 1.
86 * @param x2 the x-coordinate for the anchor point for color 2.
87 * @param y2 the y-coordinate for the anchor point for color 2.
89 * @param cyclic a flag that determines whether the gradient is cyclic
92 public GradientPaintContext(float x1
, float y1
, Color c1
,
93 float x2
, float y2
, Color c2
, boolean cyclic
)
101 this.cyclic
= cyclic
;
102 length
= Point2D
.distance(x1
, y1
, x2
, y2
);
106 * Return the color model of this context. It may be different from the
107 * hint specified during createContext, as not all contexts can generate
108 * color patterns in an arbitrary model.
110 * @return the context color model
112 public ColorModel
getColorModel()
114 return ColorModel
.getRGBdefault();
118 * Return a raster containing the colors for the graphics operation.
120 * @param x the x-coordinate, in device space
121 * @param y the y-coordinate, in device space
122 * @param w the width, in device space
123 * @param h the height, in device space
124 * @return a raster for the given area and color
126 public Raster
getRaster(int x
, int y
, int w
, int h
) {
127 ColorModel cm
= getColorModel();
128 WritableRaster raster
= cm
.createCompatibleWritableRaster(w
, h
);
129 int[] data
= new int[w
* h
* 4];
130 double pd2
= (x1
- x2
) * (x1
- x2
) + (y1
- y2
) * (y1
- y2
);
131 for (int r
= 0; r
< h
; r
++) {
132 for (int c
= 0; c
< w
; c
++) {
135 u
= (((x
+ c
) - x1
) * (x2
- x1
) + ((y
+ r
) - y1
) * (y2
- y1
))
137 double ratio
= u
/ length
;
139 ratio
= Math
.abs(ratio
- Math
.floor((ratio
+ 1.0) / 2.0) * 2.0);
141 ratio
= Math
.max(0.0, Math
.min(1.0, ratio
));
142 int base
= (r
* w
+ c
) * 4;
143 data
[base
] = (int) (c1
.getRed() + ratio
* (c2
.getRed() - c1
.getRed()));
145 = (int) (c1
.getGreen() + ratio
* (c2
.getGreen() - c1
.getGreen()));
147 = (int) (c1
.getBlue() + ratio
* (c2
.getBlue() - c1
.getBlue()));
149 = (int) (c1
.getAlpha() + ratio
* (c2
.getAlpha() - c1
.getAlpha()));
152 raster
.setPixels(0, 0, w
, h
, data
);
157 * Release the resources allocated for the paint (none in this
160 public void dispose() {