J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2006 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package java.awt; |
| 27 | |
| 28 | import java.awt.MultipleGradientPaint.CycleMethod; |
| 29 | import java.awt.MultipleGradientPaint.ColorSpaceType; |
| 30 | import java.awt.geom.AffineTransform; |
| 31 | import java.awt.geom.Point2D; |
| 32 | import java.awt.geom.Rectangle2D; |
| 33 | import java.awt.image.ColorModel; |
| 34 | |
| 35 | /** |
| 36 | * Provides the actual implementation for the LinearGradientPaint. |
| 37 | * This is where the pixel processing is done. |
| 38 | * |
| 39 | * @see java.awt.LinearGradientPaint |
| 40 | * @see java.awt.PaintContext |
| 41 | * @see java.awt.Paint |
| 42 | * @author Nicholas Talian, Vincent Hardy, Jim Graham, Jerry Evans |
| 43 | */ |
| 44 | final class LinearGradientPaintContext extends MultipleGradientPaintContext { |
| 45 | |
| 46 | /** |
| 47 | * The following invariants are used to process the gradient value from |
| 48 | * a device space coordinate, (X, Y): |
| 49 | * g(X, Y) = dgdX*X + dgdY*Y + gc |
| 50 | */ |
| 51 | private float dgdX, dgdY, gc; |
| 52 | |
| 53 | /** |
| 54 | * Constructor for LinearGradientPaintContext. |
| 55 | * |
| 56 | * @param paint the {@code LinearGradientPaint} from which this context |
| 57 | * is created |
| 58 | * @param cm {@code ColorModel} that receives |
| 59 | * the <code>Paint</code> data. This is used only as a hint. |
| 60 | * @param deviceBounds the device space bounding box of the |
| 61 | * graphics primitive being rendered |
| 62 | * @param userBounds the user space bounding box of the |
| 63 | * graphics primitive being rendered |
| 64 | * @param t the {@code AffineTransform} from user |
| 65 | * space into device space (gradientTransform should be |
| 66 | * concatenated with this) |
| 67 | * @param hints the hints that the context object uses to choose |
| 68 | * between rendering alternatives |
| 69 | * @param dStart gradient start point, in user space |
| 70 | * @param dEnd gradient end point, in user space |
| 71 | * @param fractions the fractions specifying the gradient distribution |
| 72 | * @param colors the gradient colors |
| 73 | * @param cycleMethod either NO_CYCLE, REFLECT, or REPEAT |
| 74 | * @param colorSpace which colorspace to use for interpolation, |
| 75 | * either SRGB or LINEAR_RGB |
| 76 | */ |
| 77 | LinearGradientPaintContext(LinearGradientPaint paint, |
| 78 | ColorModel cm, |
| 79 | Rectangle deviceBounds, |
| 80 | Rectangle2D userBounds, |
| 81 | AffineTransform t, |
| 82 | RenderingHints hints, |
| 83 | Point2D start, |
| 84 | Point2D end, |
| 85 | float[] fractions, |
| 86 | Color[] colors, |
| 87 | CycleMethod cycleMethod, |
| 88 | ColorSpaceType colorSpace) |
| 89 | { |
| 90 | super(paint, cm, deviceBounds, userBounds, t, hints, fractions, |
| 91 | colors, cycleMethod, colorSpace); |
| 92 | |
| 93 | // A given point in the raster should take on the same color as its |
| 94 | // projection onto the gradient vector. |
| 95 | // Thus, we want the projection of the current position vector |
| 96 | // onto the gradient vector, then normalized with respect to the |
| 97 | // length of the gradient vector, giving a value which can be mapped |
| 98 | // into the range 0-1. |
| 99 | // projection = |
| 100 | // currentVector dot gradientVector / length(gradientVector) |
| 101 | // normalized = projection / length(gradientVector) |
| 102 | |
| 103 | float startx = (float)start.getX(); |
| 104 | float starty = (float)start.getY(); |
| 105 | float endx = (float)end.getX(); |
| 106 | float endy = (float)end.getY(); |
| 107 | |
| 108 | float dx = endx - startx; // change in x from start to end |
| 109 | float dy = endy - starty; // change in y from start to end |
| 110 | float dSq = dx*dx + dy*dy; // total distance squared |
| 111 | |
| 112 | // avoid repeated calculations by doing these divides once |
| 113 | float constX = dx/dSq; |
| 114 | float constY = dy/dSq; |
| 115 | |
| 116 | // incremental change along gradient for +x |
| 117 | dgdX = a00*constX + a10*constY; |
| 118 | // incremental change along gradient for +y |
| 119 | dgdY = a01*constX + a11*constY; |
| 120 | |
| 121 | // constant, incorporates the translation components from the matrix |
| 122 | gc = (a02-startx)*constX + (a12-starty)*constY; |
| 123 | } |
| 124 | |
| 125 | /** |
| 126 | * Return a Raster containing the colors generated for the graphics |
| 127 | * operation. This is where the area is filled with colors distributed |
| 128 | * linearly. |
| 129 | * |
| 130 | * @param x,y,w,h the area in device space for which colors are |
| 131 | * generated. |
| 132 | */ |
| 133 | protected void fillRaster(int[] pixels, int off, int adjust, |
| 134 | int x, int y, int w, int h) |
| 135 | { |
| 136 | // current value for row gradients |
| 137 | float g = 0; |
| 138 | |
| 139 | // used to end iteration on rows |
| 140 | int rowLimit = off + w; |
| 141 | |
| 142 | // constant which can be pulled out of the inner loop |
| 143 | float initConst = (dgdX*x) + gc; |
| 144 | |
| 145 | for (int i = 0; i < h; i++) { // for every row |
| 146 | |
| 147 | // initialize current value to be start |
| 148 | g = initConst + dgdY*(y+i); |
| 149 | |
| 150 | while (off < rowLimit) { // for every pixel in this row |
| 151 | // get the color |
| 152 | pixels[off++] = indexIntoGradientsArrays(g); |
| 153 | |
| 154 | // incremental change in g |
| 155 | g += dgdX; |
| 156 | } |
| 157 | |
| 158 | // change in off from row to row |
| 159 | off += adjust; |
| 160 | |
| 161 | //rowlimit is width + offset |
| 162 | rowLimit = off + w; |
| 163 | } |
| 164 | } |
| 165 | } |