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1 /* |
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2 * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Sun designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Sun in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
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22 * CA 95054 USA or visit www.sun.com if you need additional information or |
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23 * have any questions. |
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24 */ |
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25 |
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26 package java.awt; |
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27 |
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28 import java.awt.image.ColorModel; |
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29 import sun.java2d.SunCompositeContext; |
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30 |
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31 /** |
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32 * The <code>AlphaComposite</code> class implements basic alpha |
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33 * compositing rules for combining source and destination colors |
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34 * to achieve blending and transparency effects with graphics and |
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35 * images. |
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36 * The specific rules implemented by this class are the basic set |
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37 * of 12 rules described in |
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38 * T. Porter and T. Duff, "Compositing Digital Images", SIGGRAPH 84, |
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39 * 253-259. |
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40 * The rest of this documentation assumes some familiarity with the |
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41 * definitions and concepts outlined in that paper. |
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42 * |
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43 * <p> |
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44 * This class extends the standard equations defined by Porter and |
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45 * Duff to include one additional factor. |
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46 * An instance of the <code>AlphaComposite</code> class can contain |
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47 * an alpha value that is used to modify the opacity or coverage of |
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48 * every source pixel before it is used in the blending equations. |
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49 * |
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50 * <p> |
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51 * It is important to note that the equations defined by the Porter |
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52 * and Duff paper are all defined to operate on color components |
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53 * that are premultiplied by their corresponding alpha components. |
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54 * Since the <code>ColorModel</code> and <code>Raster</code> classes |
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55 * allow the storage of pixel data in either premultiplied or |
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56 * non-premultiplied form, all input data must be normalized into |
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57 * premultiplied form before applying the equations and all results |
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58 * might need to be adjusted back to the form required by the destination |
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59 * before the pixel values are stored. |
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60 * |
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61 * <p> |
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62 * Also note that this class defines only the equations |
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63 * for combining color and alpha values in a purely mathematical |
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64 * sense. The accurate application of its equations depends |
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65 * on the way the data is retrieved from its sources and stored |
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66 * in its destinations. |
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67 * See <a href="#caveats">Implementation Caveats</a> |
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68 * for further information. |
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69 * |
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70 * <p> |
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71 * The following factors are used in the description of the blending |
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72 * equation in the Porter and Duff paper: |
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73 * |
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74 * <blockquote> |
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75 * <table summary="layout"> |
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76 * <tr><th align=left>Factor <th align=left>Definition |
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77 * <tr><td><em>A<sub>s</sub></em><td>the alpha component of the source pixel |
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78 * <tr><td><em>C<sub>s</sub></em><td>a color component of the source pixel in premultiplied form |
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79 * <tr><td><em>A<sub>d</sub></em><td>the alpha component of the destination pixel |
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80 * <tr><td><em>C<sub>d</sub></em><td>a color component of the destination pixel in premultiplied form |
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81 * <tr><td><em>F<sub>s</sub></em><td>the fraction of the source pixel that contributes to the output |
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82 * <tr><td><em>F<sub>d</sub></em><td>the fraction of the destination pixel that contributes |
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83 * to the output |
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84 * <tr><td><em>A<sub>r</sub></em><td>the alpha component of the result |
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85 * <tr><td><em>C<sub>r</sub></em><td>a color component of the result in premultiplied form |
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86 * </table> |
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87 * </blockquote> |
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88 * |
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89 * <p> |
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90 * Using these factors, Porter and Duff define 12 ways of choosing |
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91 * the blending factors <em>F<sub>s</sub></em> and <em>F<sub>d</sub></em> to |
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92 * produce each of 12 desirable visual effects. |
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93 * The equations for determining <em>F<sub>s</sub></em> and <em>F<sub>d</sub></em> |
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94 * are given in the descriptions of the 12 static fields |
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95 * that specify visual effects. |
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96 * For example, |
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97 * the description for |
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98 * <a href="#SRC_OVER"><code>SRC_OVER</code></a> |
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99 * specifies that <em>F<sub>s</sub></em> = 1 and <em>F<sub>d</sub></em> = (1-<em>A<sub>s</sub></em>). |
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100 * Once a set of equations for determining the blending factors is |
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101 * known they can then be applied to each pixel to produce a result |
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102 * using the following set of equations: |
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103 * |
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104 * <pre> |
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105 * <em>F<sub>s</sub></em> = <em>f</em>(<em>A<sub>d</sub></em>) |
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106 * <em>F<sub>d</sub></em> = <em>f</em>(<em>A<sub>s</sub></em>) |
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107 * <em>A<sub>r</sub></em> = <em>A<sub>s</sub></em>*<em>F<sub>s</sub></em> + <em>A<sub>d</sub></em>*<em>F<sub>d</sub></em> |
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108 * <em>C<sub>r</sub></em> = <em>C<sub>s</sub></em>*<em>F<sub>s</sub></em> + <em>C<sub>d</sub></em>*<em>F<sub>d</sub></em></pre> |
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109 * |
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110 * <p> |
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111 * The following factors will be used to discuss our extensions to |
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112 * the blending equation in the Porter and Duff paper: |
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113 * |
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114 * <blockquote> |
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115 * <table summary="layout"> |
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116 * <tr><th align=left>Factor <th align=left>Definition |
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117 * <tr><td><em>C<sub>sr</sub></em> <td>one of the raw color components of the source pixel |
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118 * <tr><td><em>C<sub>dr</sub></em> <td>one of the raw color components of the destination pixel |
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119 * <tr><td><em>A<sub>ac</sub></em> <td>the "extra" alpha component from the AlphaComposite instance |
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120 * <tr><td><em>A<sub>sr</sub></em> <td>the raw alpha component of the source pixel |
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121 * <tr><td><em>A<sub>dr</sub></em><td>the raw alpha component of the destination pixel |
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122 * <tr><td><em>A<sub>df</sub></em> <td>the final alpha component stored in the destination |
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123 * <tr><td><em>C<sub>df</sub></em> <td>the final raw color component stored in the destination |
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124 * </table> |
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125 *</blockquote> |
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126 * |
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127 * <h3>Preparing Inputs</h3> |
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128 * |
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129 * <p> |
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130 * The <code>AlphaComposite</code> class defines an additional alpha |
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131 * value that is applied to the source alpha. |
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132 * This value is applied as if an implicit SRC_IN rule were first |
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133 * applied to the source pixel against a pixel with the indicated |
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134 * alpha by multiplying both the raw source alpha and the raw |
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135 * source colors by the alpha in the <code>AlphaComposite</code>. |
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136 * This leads to the following equation for producing the alpha |
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137 * used in the Porter and Duff blending equation: |
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138 * |
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139 * <pre> |
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140 * <em>A<sub>s</sub></em> = <em>A<sub>sr</sub></em> * <em>A<sub>ac</sub></em> </pre> |
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141 * |
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142 * All of the raw source color components need to be multiplied |
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143 * by the alpha in the <code>AlphaComposite</code> instance. |
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144 * Additionally, if the source was not in premultiplied form |
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145 * then the color components also need to be multiplied by the |
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146 * source alpha. |
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147 * Thus, the equation for producing the source color components |
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148 * for the Porter and Duff equation depends on whether the source |
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149 * pixels are premultiplied or not: |
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150 * |
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151 * <pre> |
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152 * <em>C<sub>s</sub></em> = <em>C<sub>sr</sub></em> * <em>A<sub>sr</sub></em> * <em>A<sub>ac</sub></em> (if source is not premultiplied) |
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153 * <em>C<sub>s</sub></em> = <em>C<sub>sr</sub></em> * <em>A<sub>ac</sub></em> (if source is premultiplied) </pre> |
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154 * |
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155 * No adjustment needs to be made to the destination alpha: |
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156 * |
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157 * <pre> |
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158 * <em>A<sub>d</sub></em> = <em>A<sub>dr</sub></em> </pre> |
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159 * |
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160 * <p> |
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161 * The destination color components need to be adjusted only if |
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162 * they are not in premultiplied form: |
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163 * |
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164 * <pre> |
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165 * <em>C<sub>d</sub></em> = <em>C<sub>dr</sub></em> * <em>A<sub>d</sub></em> (if destination is not premultiplied) |
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166 * <em>C<sub>d</sub></em> = <em>C<sub>dr</sub></em> (if destination is premultiplied) </pre> |
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167 * |
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168 * <h3>Applying the Blending Equation</h3> |
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169 * |
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170 * <p> |
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171 * The adjusted <em>A<sub>s</sub></em>, <em>A<sub>d</sub></em>, |
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172 * <em>C<sub>s</sub></em>, and <em>C<sub>d</sub></em> are used in the standard |
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173 * Porter and Duff equations to calculate the blending factors |
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174 * <em>F<sub>s</sub></em> and <em>F<sub>d</sub></em> and then the resulting |
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175 * premultiplied components <em>A<sub>r</sub></em> and <em>C<sub>r</sub></em>. |
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176 * |
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177 * <p> |
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178 * <h3>Preparing Results</h3> |
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179 * |
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180 * <p> |
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181 * The results only need to be adjusted if they are to be stored |
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182 * back into a destination buffer that holds data that is not |
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183 * premultiplied, using the following equations: |
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184 * |
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185 * <pre> |
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186 * <em>A<sub>df</sub></em> = <em>A<sub>r</sub></em> |
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187 * <em>C<sub>df</sub></em> = <em>C<sub>r</sub></em> (if dest is premultiplied) |
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188 * <em>C<sub>df</sub></em> = <em>C<sub>r</sub></em> / <em>A<sub>r</sub></em> (if dest is not premultiplied) </pre> |
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189 * |
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190 * Note that since the division is undefined if the resulting alpha |
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191 * is zero, the division in that case is omitted to avoid the "divide |
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192 * by zero" and the color components are left as |
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193 * all zeros. |
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194 * |
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195 * <p> |
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196 * <h3>Performance Considerations</h3> |
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197 * |
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198 * <p> |
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199 * For performance reasons, it is preferrable that |
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200 * <code>Raster</code> objects passed to the <code>compose</code> |
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201 * method of a {@link CompositeContext} object created by the |
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202 * <code>AlphaComposite</code> class have premultiplied data. |
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203 * If either the source <code>Raster</code> |
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204 * or the destination <code>Raster</code> |
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205 * is not premultiplied, however, |
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206 * appropriate conversions are performed before and after the compositing |
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207 * operation. |
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208 * |
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209 * <h3><a name="caveats">Implementation Caveats</a></h3> |
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210 * |
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211 * <ul> |
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212 * <li> |
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213 * Many sources, such as some of the opaque image types listed |
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214 * in the <code>BufferedImage</code> class, do not store alpha values |
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215 * for their pixels. Such sources supply an alpha of 1.0 for |
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216 * all of their pixels. |
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217 * |
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218 * <p> |
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219 * <li> |
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220 * Many destinations also have no place to store the alpha values |
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221 * that result from the blending calculations performed by this class. |
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222 * Such destinations thus implicitly discard the resulting |
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223 * alpha values that this class produces. |
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224 * It is recommended that such destinations should treat their stored |
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225 * color values as non-premultiplied and divide the resulting color |
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226 * values by the resulting alpha value before storing the color |
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227 * values and discarding the alpha value. |
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228 * |
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229 * <p> |
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230 * <li> |
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231 * The accuracy of the results depends on the manner in which pixels |
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232 * are stored in the destination. |
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233 * An image format that provides at least 8 bits of storage per color |
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234 * and alpha component is at least adequate for use as a destination |
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235 * for a sequence of a few to a dozen compositing operations. |
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236 * An image format with fewer than 8 bits of storage per component |
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237 * is of limited use for just one or two compositing operations |
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238 * before the rounding errors dominate the results. |
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239 * An image format |
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240 * that does not separately store |
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241 * color components is not a |
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242 * good candidate for any type of translucent blending. |
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243 * For example, <code>BufferedImage.TYPE_BYTE_INDEXED</code> |
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244 * should not be used as a destination for a blending operation |
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245 * because every operation |
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246 * can introduce large errors, due to |
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247 * the need to choose a pixel from a limited palette to match the |
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248 * results of the blending equations. |
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249 * |
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250 * <p> |
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251 * <li> |
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252 * Nearly all formats store pixels as discrete integers rather than |
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253 * the floating point values used in the reference equations above. |
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254 * The implementation can either scale the integer pixel |
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255 * values into floating point values in the range 0.0 to 1.0 or |
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256 * use slightly modified versions of the equations |
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257 * that operate entirely in the integer domain and yet produce |
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258 * analogous results to the reference equations. |
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259 * |
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260 * <p> |
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261 * Typically the integer values are related to the floating point |
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262 * values in such a way that the integer 0 is equated |
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263 * to the floating point value 0.0 and the integer |
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264 * 2^<em>n</em>-1 (where <em>n</em> is the number of bits |
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265 * in the representation) is equated to 1.0. |
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266 * For 8-bit representations, this means that 0x00 |
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267 * represents 0.0 and 0xff represents |
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268 * 1.0. |
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269 * |
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270 * <p> |
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271 * <li> |
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272 * The internal implementation can approximate some of the equations |
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273 * and it can also eliminate some steps to avoid unnecessary operations. |
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274 * For example, consider a discrete integer image with non-premultiplied |
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275 * alpha values that uses 8 bits per component for storage. |
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276 * The stored values for a |
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277 * nearly transparent darkened red might be: |
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278 * |
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279 * <pre> |
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280 * (A, R, G, B) = (0x01, 0xb0, 0x00, 0x00)</pre> |
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281 * |
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282 * <p> |
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283 * If integer math were being used and this value were being |
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284 * composited in |
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285 * <a href="#SRC"><code>SRC</code></a> |
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286 * mode with no extra alpha, then the math would |
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287 * indicate that the results were (in integer format): |
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288 * |
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289 * <pre> |
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290 * (A, R, G, B) = (0x01, 0x01, 0x00, 0x00)</pre> |
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291 * |
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292 * <p> |
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293 * Note that the intermediate values, which are always in premultiplied |
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294 * form, would only allow the integer red component to be either 0x00 |
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295 * or 0x01. When we try to store this result back into a destination |
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296 * that is not premultiplied, dividing out the alpha will give us |
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297 * very few choices for the non-premultiplied red value. |
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298 * In this case an implementation that performs the math in integer |
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299 * space without shortcuts is likely to end up with the final pixel |
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300 * values of: |
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301 * |
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302 * <pre> |
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303 * (A, R, G, B) = (0x01, 0xff, 0x00, 0x00)</pre> |
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304 * |
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305 * <p> |
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306 * (Note that 0x01 divided by 0x01 gives you 1.0, which is equivalent |
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307 * to the value 0xff in an 8-bit storage format.) |
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308 * |
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309 * <p> |
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310 * Alternately, an implementation that uses floating point math |
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311 * might produce more accurate results and end up returning to the |
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312 * original pixel value with little, if any, roundoff error. |
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313 * Or, an implementation using integer math might decide that since |
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314 * the equations boil down to a virtual NOP on the color values |
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315 * if performed in a floating point space, it can transfer the |
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316 * pixel untouched to the destination and avoid all the math entirely. |
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317 * |
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318 * <p> |
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319 * These implementations all attempt to honor the |
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320 * same equations, but use different tradeoffs of integer and |
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321 * floating point math and reduced or full equations. |
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322 * To account for such differences, it is probably best to |
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323 * expect only that the premultiplied form of the results to |
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324 * match between implementations and image formats. In this |
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325 * case both answers, expressed in premultiplied form would |
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326 * equate to: |
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327 * |
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328 * <pre> |
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329 * (A, R, G, B) = (0x01, 0x01, 0x00, 0x00)</pre> |
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330 * |
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331 * <p> |
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332 * and thus they would all match. |
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333 * |
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334 * <p> |
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335 * <li> |
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336 * Because of the technique of simplifying the equations for |
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337 * calculation efficiency, some implementations might perform |
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338 * differently when encountering result alpha values of 0.0 |
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339 * on a non-premultiplied destination. |
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340 * Note that the simplification of removing the divide by alpha |
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341 * in the case of the SRC rule is technically not valid if the |
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342 * denominator (alpha) is 0. |
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343 * But, since the results should only be expected to be accurate |
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344 * when viewed in premultiplied form, a resulting alpha of 0 |
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345 * essentially renders the resulting color components irrelevant |
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346 * and so exact behavior in this case should not be expected. |
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347 * </ul> |
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348 * @see Composite |
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349 * @see CompositeContext |
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350 */ |
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351 |
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352 public final class AlphaComposite implements Composite { |
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353 /** |
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354 * Both the color and the alpha of the destination are cleared |
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355 * (Porter-Duff Clear rule). |
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356 * Neither the source nor the destination is used as input. |
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357 *<p> |
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358 * <em>F<sub>s</sub></em> = 0 and <em>F<sub>d</sub></em> = 0, thus: |
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359 *<pre> |
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360 * <em>A<sub>r</sub></em> = 0 |
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361 * <em>C<sub>r</sub></em> = 0 |
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362 *</pre> |
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363 */ |
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364 public static final int CLEAR = 1; |
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365 |
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366 /** |
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367 * The source is copied to the destination |
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368 * (Porter-Duff Source rule). |
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369 * The destination is not used as input. |
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370 *<p> |
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371 * <em>F<sub>s</sub></em> = 1 and <em>F<sub>d</sub></em> = 0, thus: |
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372 *<pre> |
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373 * <em>A<sub>r</sub></em> = <em>A<sub>s</sub></em> |
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374 * <em>C<sub>r</sub></em> = <em>C<sub>s</sub></em> |
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375 *</pre> |
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376 */ |
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377 public static final int SRC = 2; |
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378 |
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379 /** |
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380 * The destination is left untouched |
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381 * (Porter-Duff Destination rule). |
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382 *<p> |
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383 * <em>F<sub>s</sub></em> = 0 and <em>F<sub>d</sub></em> = 1, thus: |
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384 *<pre> |
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385 * <em>A<sub>r</sub></em> = <em>A<sub>d</sub></em> |
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386 * <em>C<sub>r</sub></em> = <em>C<sub>d</sub></em> |
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387 *</pre> |
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388 * @since 1.4 |
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389 */ |
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390 public static final int DST = 9; |
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391 // Note that DST was added in 1.4 so it is numbered out of order... |
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392 |
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393 /** |
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394 * The source is composited over the destination |
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395 * (Porter-Duff Source Over Destination rule). |
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396 *<p> |
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397 * <em>F<sub>s</sub></em> = 1 and <em>F<sub>d</sub></em> = (1-<em>A<sub>s</sub></em>), thus: |
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398 *<pre> |
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399 * <em>A<sub>r</sub></em> = <em>A<sub>s</sub></em> + <em>A<sub>d</sub></em>*(1-<em>A<sub>s</sub></em>) |
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400 * <em>C<sub>r</sub></em> = <em>C<sub>s</sub></em> + <em>C<sub>d</sub></em>*(1-<em>A<sub>s</sub></em>) |
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401 *</pre> |
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402 */ |
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403 public static final int SRC_OVER = 3; |
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404 |
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405 /** |
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406 * The destination is composited over the source and |
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407 * the result replaces the destination |
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408 * (Porter-Duff Destination Over Source rule). |
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409 *<p> |
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410 * <em>F<sub>s</sub></em> = (1-<em>A<sub>d</sub></em>) and <em>F<sub>d</sub></em> = 1, thus: |
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411 *<pre> |
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412 * <em>A<sub>r</sub></em> = <em>A<sub>s</sub></em>*(1-<em>A<sub>d</sub></em>) + <em>A<sub>d</sub></em> |
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413 * <em>C<sub>r</sub></em> = <em>C<sub>s</sub></em>*(1-<em>A<sub>d</sub></em>) + <em>C<sub>d</sub></em> |
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414 *</pre> |
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415 */ |
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416 public static final int DST_OVER = 4; |
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417 |
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418 /** |
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419 * The part of the source lying inside of the destination replaces |
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420 * the destination |
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421 * (Porter-Duff Source In Destination rule). |
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422 *<p> |
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423 * <em>F<sub>s</sub></em> = <em>A<sub>d</sub></em> and <em>F<sub>d</sub></em> = 0, thus: |
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424 *<pre> |
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425 * <em>A<sub>r</sub></em> = <em>A<sub>s</sub></em>*<em>A<sub>d</sub></em> |
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426 * <em>C<sub>r</sub></em> = <em>C<sub>s</sub></em>*<em>A<sub>d</sub></em> |
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427 *</pre> |
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428 */ |
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429 public static final int SRC_IN = 5; |
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430 |
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431 /** |
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432 * The part of the destination lying inside of the source |
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433 * replaces the destination |
|
434 * (Porter-Duff Destination In Source rule). |
|
435 *<p> |
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436 * <em>F<sub>s</sub></em> = 0 and <em>F<sub>d</sub></em> = <em>A<sub>s</sub></em>, thus: |
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437 *<pre> |
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438 * <em>A<sub>r</sub></em> = <em>A<sub>d</sub></em>*<em>A<sub>s</sub></em> |
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439 * <em>C<sub>r</sub></em> = <em>C<sub>d</sub></em>*<em>A<sub>s</sub></em> |
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440 *</pre> |
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441 */ |
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442 public static final int DST_IN = 6; |
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443 |
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444 /** |
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445 * The part of the source lying outside of the destination |
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446 * replaces the destination |
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447 * (Porter-Duff Source Held Out By Destination rule). |
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448 *<p> |
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449 * <em>F<sub>s</sub></em> = (1-<em>A<sub>d</sub></em>) and <em>F<sub>d</sub></em> = 0, thus: |
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450 *<pre> |
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451 * <em>A<sub>r</sub></em> = <em>A<sub>s</sub></em>*(1-<em>A<sub>d</sub></em>) |
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452 * <em>C<sub>r</sub></em> = <em>C<sub>s</sub></em>*(1-<em>A<sub>d</sub></em>) |
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453 *</pre> |
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454 */ |
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455 public static final int SRC_OUT = 7; |
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456 |
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457 /** |
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458 * The part of the destination lying outside of the source |
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459 * replaces the destination |
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460 * (Porter-Duff Destination Held Out By Source rule). |
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461 *<p> |
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462 * <em>F<sub>s</sub></em> = 0 and <em>F<sub>d</sub></em> = (1-<em>A<sub>s</sub></em>), thus: |
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463 *<pre> |
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464 * <em>A<sub>r</sub></em> = <em>A<sub>d</sub></em>*(1-<em>A<sub>s</sub></em>) |
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465 * <em>C<sub>r</sub></em> = <em>C<sub>d</sub></em>*(1-<em>A<sub>s</sub></em>) |
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466 *</pre> |
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467 */ |
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468 public static final int DST_OUT = 8; |
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469 |
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470 // Rule 9 is DST which is defined above where it fits into the |
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471 // list logically, rather than numerically |
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472 // |
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473 // public static final int DST = 9; |
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474 |
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475 /** |
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476 * The part of the source lying inside of the destination |
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477 * is composited onto the destination |
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478 * (Porter-Duff Source Atop Destination rule). |
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479 *<p> |
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480 * <em>F<sub>s</sub></em> = <em>A<sub>d</sub></em> and <em>F<sub>d</sub></em> = (1-<em>A<sub>s</sub></em>), thus: |
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481 *<pre> |
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482 * <em>A<sub>r</sub></em> = <em>A<sub>s</sub></em>*<em>A<sub>d</sub></em> + <em>A<sub>d</sub></em>*(1-<em>A<sub>s</sub></em>) = <em>A<sub>d</sub></em> |
|
483 * <em>C<sub>r</sub></em> = <em>C<sub>s</sub></em>*<em>A<sub>d</sub></em> + <em>C<sub>d</sub></em>*(1-<em>A<sub>s</sub></em>) |
|
484 *</pre> |
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485 * @since 1.4 |
|
486 */ |
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487 public static final int SRC_ATOP = 10; |
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488 |
|
489 /** |
|
490 * The part of the destination lying inside of the source |
|
491 * is composited over the source and replaces the destination |
|
492 * (Porter-Duff Destination Atop Source rule). |
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493 *<p> |
|
494 * <em>F<sub>s</sub></em> = (1-<em>A<sub>d</sub></em>) and <em>F<sub>d</sub></em> = <em>A<sub>s</sub></em>, thus: |
|
495 *<pre> |
|
496 * <em>A<sub>r</sub></em> = <em>A<sub>s</sub></em>*(1-<em>A<sub>d</sub></em>) + <em>A<sub>d</sub></em>*<em>A<sub>s</sub></em> = <em>A<sub>s</sub></em> |
|
497 * <em>C<sub>r</sub></em> = <em>C<sub>s</sub></em>*(1-<em>A<sub>d</sub></em>) + <em>C<sub>d</sub></em>*<em>A<sub>s</sub></em> |
|
498 *</pre> |
|
499 * @since 1.4 |
|
500 */ |
|
501 public static final int DST_ATOP = 11; |
|
502 |
|
503 /** |
|
504 * The part of the source that lies outside of the destination |
|
505 * is combined with the part of the destination that lies outside |
|
506 * of the source |
|
507 * (Porter-Duff Source Xor Destination rule). |
|
508 *<p> |
|
509 * <em>F<sub>s</sub></em> = (1-<em>A<sub>d</sub></em>) and <em>F<sub>d</sub></em> = (1-<em>A<sub>s</sub></em>), thus: |
|
510 *<pre> |
|
511 * <em>A<sub>r</sub></em> = <em>A<sub>s</sub></em>*(1-<em>A<sub>d</sub></em>) + <em>A<sub>d</sub></em>*(1-<em>A<sub>s</sub></em>) |
|
512 * <em>C<sub>r</sub></em> = <em>C<sub>s</sub></em>*(1-<em>A<sub>d</sub></em>) + <em>C<sub>d</sub></em>*(1-<em>A<sub>s</sub></em>) |
|
513 *</pre> |
|
514 * @since 1.4 |
|
515 */ |
|
516 public static final int XOR = 12; |
|
517 |
|
518 /** |
|
519 * <code>AlphaComposite</code> object that implements the opaque CLEAR rule |
|
520 * with an alpha of 1.0f. |
|
521 * @see #CLEAR |
|
522 */ |
|
523 public static final AlphaComposite Clear = new AlphaComposite(CLEAR); |
|
524 |
|
525 /** |
|
526 * <code>AlphaComposite</code> object that implements the opaque SRC rule |
|
527 * with an alpha of 1.0f. |
|
528 * @see #SRC |
|
529 */ |
|
530 public static final AlphaComposite Src = new AlphaComposite(SRC); |
|
531 |
|
532 /** |
|
533 * <code>AlphaComposite</code> object that implements the opaque DST rule |
|
534 * with an alpha of 1.0f. |
|
535 * @see #DST |
|
536 * @since 1.4 |
|
537 */ |
|
538 public static final AlphaComposite Dst = new AlphaComposite(DST); |
|
539 |
|
540 /** |
|
541 * <code>AlphaComposite</code> object that implements the opaque SRC_OVER rule |
|
542 * with an alpha of 1.0f. |
|
543 * @see #SRC_OVER |
|
544 */ |
|
545 public static final AlphaComposite SrcOver = new AlphaComposite(SRC_OVER); |
|
546 |
|
547 /** |
|
548 * <code>AlphaComposite</code> object that implements the opaque DST_OVER rule |
|
549 * with an alpha of 1.0f. |
|
550 * @see #DST_OVER |
|
551 */ |
|
552 public static final AlphaComposite DstOver = new AlphaComposite(DST_OVER); |
|
553 |
|
554 /** |
|
555 * <code>AlphaComposite</code> object that implements the opaque SRC_IN rule |
|
556 * with an alpha of 1.0f. |
|
557 * @see #SRC_IN |
|
558 */ |
|
559 public static final AlphaComposite SrcIn = new AlphaComposite(SRC_IN); |
|
560 |
|
561 /** |
|
562 * <code>AlphaComposite</code> object that implements the opaque DST_IN rule |
|
563 * with an alpha of 1.0f. |
|
564 * @see #DST_IN |
|
565 */ |
|
566 public static final AlphaComposite DstIn = new AlphaComposite(DST_IN); |
|
567 |
|
568 /** |
|
569 * <code>AlphaComposite</code> object that implements the opaque SRC_OUT rule |
|
570 * with an alpha of 1.0f. |
|
571 * @see #SRC_OUT |
|
572 */ |
|
573 public static final AlphaComposite SrcOut = new AlphaComposite(SRC_OUT); |
|
574 |
|
575 /** |
|
576 * <code>AlphaComposite</code> object that implements the opaque DST_OUT rule |
|
577 * with an alpha of 1.0f. |
|
578 * @see #DST_OUT |
|
579 */ |
|
580 public static final AlphaComposite DstOut = new AlphaComposite(DST_OUT); |
|
581 |
|
582 /** |
|
583 * <code>AlphaComposite</code> object that implements the opaque SRC_ATOP rule |
|
584 * with an alpha of 1.0f. |
|
585 * @see #SRC_ATOP |
|
586 * @since 1.4 |
|
587 */ |
|
588 public static final AlphaComposite SrcAtop = new AlphaComposite(SRC_ATOP); |
|
589 |
|
590 /** |
|
591 * <code>AlphaComposite</code> object that implements the opaque DST_ATOP rule |
|
592 * with an alpha of 1.0f. |
|
593 * @see #DST_ATOP |
|
594 * @since 1.4 |
|
595 */ |
|
596 public static final AlphaComposite DstAtop = new AlphaComposite(DST_ATOP); |
|
597 |
|
598 /** |
|
599 * <code>AlphaComposite</code> object that implements the opaque XOR rule |
|
600 * with an alpha of 1.0f. |
|
601 * @see #XOR |
|
602 * @since 1.4 |
|
603 */ |
|
604 public static final AlphaComposite Xor = new AlphaComposite(XOR); |
|
605 |
|
606 private static final int MIN_RULE = CLEAR; |
|
607 private static final int MAX_RULE = XOR; |
|
608 |
|
609 float extraAlpha; |
|
610 int rule; |
|
611 |
|
612 private AlphaComposite(int rule) { |
|
613 this(rule, 1.0f); |
|
614 } |
|
615 |
|
616 private AlphaComposite(int rule, float alpha) { |
|
617 if (alpha < 0.0f || alpha > 1.0f) { |
|
618 throw new IllegalArgumentException("alpha value out of range"); |
|
619 } |
|
620 if (rule < MIN_RULE || rule > MAX_RULE) { |
|
621 throw new IllegalArgumentException("unknown composite rule"); |
|
622 } |
|
623 this.rule = rule; |
|
624 this.extraAlpha = alpha; |
|
625 } |
|
626 |
|
627 /** |
|
628 * Creates an <code>AlphaComposite</code> object with the specified rule. |
|
629 * @param rule the compositing rule |
|
630 * @throws IllegalArgumentException if <code>rule</code> is not one of |
|
631 * the following: {@link #CLEAR}, {@link #SRC}, {@link #DST}, |
|
632 * {@link #SRC_OVER}, {@link #DST_OVER}, {@link #SRC_IN}, |
|
633 * {@link #DST_IN}, {@link #SRC_OUT}, {@link #DST_OUT}, |
|
634 * {@link #SRC_ATOP}, {@link #DST_ATOP}, or {@link #XOR} |
|
635 */ |
|
636 public static AlphaComposite getInstance(int rule) { |
|
637 switch (rule) { |
|
638 case CLEAR: |
|
639 return Clear; |
|
640 case SRC: |
|
641 return Src; |
|
642 case DST: |
|
643 return Dst; |
|
644 case SRC_OVER: |
|
645 return SrcOver; |
|
646 case DST_OVER: |
|
647 return DstOver; |
|
648 case SRC_IN: |
|
649 return SrcIn; |
|
650 case DST_IN: |
|
651 return DstIn; |
|
652 case SRC_OUT: |
|
653 return SrcOut; |
|
654 case DST_OUT: |
|
655 return DstOut; |
|
656 case SRC_ATOP: |
|
657 return SrcAtop; |
|
658 case DST_ATOP: |
|
659 return DstAtop; |
|
660 case XOR: |
|
661 return Xor; |
|
662 default: |
|
663 throw new IllegalArgumentException("unknown composite rule"); |
|
664 } |
|
665 } |
|
666 |
|
667 /** |
|
668 * Creates an <code>AlphaComposite</code> object with the specified rule and |
|
669 * the constant alpha to multiply with the alpha of the source. |
|
670 * The source is multiplied with the specified alpha before being composited |
|
671 * with the destination. |
|
672 * @param rule the compositing rule |
|
673 * @param alpha the constant alpha to be multiplied with the alpha of |
|
674 * the source. <code>alpha</code> must be a floating point number in the |
|
675 * inclusive range [0.0, 1.0]. |
|
676 * @throws IllegalArgumentException if |
|
677 * <code>alpha</code> is less than 0.0 or greater than 1.0, or if |
|
678 * <code>rule</code> is not one of |
|
679 * the following: {@link #CLEAR}, {@link #SRC}, {@link #DST}, |
|
680 * {@link #SRC_OVER}, {@link #DST_OVER}, {@link #SRC_IN}, |
|
681 * {@link #DST_IN}, {@link #SRC_OUT}, {@link #DST_OUT}, |
|
682 * {@link #SRC_ATOP}, {@link #DST_ATOP}, or {@link #XOR} |
|
683 */ |
|
684 public static AlphaComposite getInstance(int rule, float alpha) { |
|
685 if (alpha == 1.0f) { |
|
686 return getInstance(rule); |
|
687 } |
|
688 return new AlphaComposite(rule, alpha); |
|
689 } |
|
690 |
|
691 /** |
|
692 * Creates a context for the compositing operation. |
|
693 * The context contains state that is used in performing |
|
694 * the compositing operation. |
|
695 * @param srcColorModel the {@link ColorModel} of the source |
|
696 * @param dstColorModel the <code>ColorModel</code> of the destination |
|
697 * @return the <code>CompositeContext</code> object to be used to perform |
|
698 * compositing operations. |
|
699 */ |
|
700 public CompositeContext createContext(ColorModel srcColorModel, |
|
701 ColorModel dstColorModel, |
|
702 RenderingHints hints) { |
|
703 return new SunCompositeContext(this, srcColorModel, dstColorModel); |
|
704 } |
|
705 |
|
706 /** |
|
707 * Returns the alpha value of this <code>AlphaComposite</code>. If this |
|
708 * <code>AlphaComposite</code> does not have an alpha value, 1.0 is returned. |
|
709 * @return the alpha value of this <code>AlphaComposite</code>. |
|
710 */ |
|
711 public float getAlpha() { |
|
712 return extraAlpha; |
|
713 } |
|
714 |
|
715 /** |
|
716 * Returns the compositing rule of this <code>AlphaComposite</code>. |
|
717 * @return the compositing rule of this <code>AlphaComposite</code>. |
|
718 */ |
|
719 public int getRule() { |
|
720 return rule; |
|
721 } |
|
722 |
|
723 /** |
|
724 * Returns a similar <code>AlphaComposite</code> object that uses |
|
725 * the specified compositing rule. |
|
726 * If this object already uses the specified compositing rule, |
|
727 * this object is returned. |
|
728 * @return an <code>AlphaComposite</code> object derived from |
|
729 * this object that uses the specified compositing rule. |
|
730 * @param rule the compositing rule |
|
731 * @throws IllegalArgumentException if |
|
732 * <code>rule</code> is not one of |
|
733 * the following: {@link #CLEAR}, {@link #SRC}, {@link #DST}, |
|
734 * {@link #SRC_OVER}, {@link #DST_OVER}, {@link #SRC_IN}, |
|
735 * {@link #DST_IN}, {@link #SRC_OUT}, {@link #DST_OUT}, |
|
736 * {@link #SRC_ATOP}, {@link #DST_ATOP}, or {@link #XOR} |
|
737 * @since 1.6 |
|
738 */ |
|
739 public AlphaComposite derive(int rule) { |
|
740 return (this.rule == rule) |
|
741 ? this |
|
742 : getInstance(rule, this.extraAlpha); |
|
743 } |
|
744 |
|
745 /** |
|
746 * Returns a similar <code>AlphaComposite</code> object that uses |
|
747 * the specified alpha value. |
|
748 * If this object already has the specified alpha value, |
|
749 * this object is returned. |
|
750 * @return an <code>AlphaComposite</code> object derived from |
|
751 * this object that uses the specified alpha value. |
|
752 * @param alpha the constant alpha to be multiplied with the alpha of |
|
753 * the source. <code>alpha</code> must be a floating point number in the |
|
754 * inclusive range [0.0, 1.0]. |
|
755 * @throws IllegalArgumentException if |
|
756 * <code>alpha</code> is less than 0.0 or greater than 1.0 |
|
757 * @since 1.6 |
|
758 */ |
|
759 public AlphaComposite derive(float alpha) { |
|
760 return (this.extraAlpha == alpha) |
|
761 ? this |
|
762 : getInstance(this.rule, alpha); |
|
763 } |
|
764 |
|
765 /** |
|
766 * Returns the hashcode for this composite. |
|
767 * @return a hash code for this composite. |
|
768 */ |
|
769 public int hashCode() { |
|
770 return (Float.floatToIntBits(extraAlpha) * 31 + rule); |
|
771 } |
|
772 |
|
773 /** |
|
774 * Determines whether the specified object is equal to this |
|
775 * <code>AlphaComposite</code>. |
|
776 * <p> |
|
777 * The result is <code>true</code> if and only if |
|
778 * the argument is not <code>null</code> and is an |
|
779 * <code>AlphaComposite</code> object that has the same |
|
780 * compositing rule and alpha value as this object. |
|
781 * |
|
782 * @param obj the <code>Object</code> to test for equality |
|
783 * @return <code>true</code> if <code>obj</code> equals this |
|
784 * <code>AlphaComposite</code>; <code>false</code> otherwise. |
|
785 */ |
|
786 public boolean equals(Object obj) { |
|
787 if (!(obj instanceof AlphaComposite)) { |
|
788 return false; |
|
789 } |
|
790 |
|
791 AlphaComposite ac = (AlphaComposite) obj; |
|
792 |
|
793 if (rule != ac.rule) { |
|
794 return false; |
|
795 } |
|
796 |
|
797 if (extraAlpha != ac.extraAlpha) { |
|
798 return false; |
|
799 } |
|
800 |
|
801 return true; |
|
802 } |
|
803 |
|
804 } |