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| 1 | /* | ||
| 2 | * Copyright (c) 2005, 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 com.sun.imageio.plugins.common; | ||
| 27 | |||
| 28 | import java.awt.Point; | ||
| 29 | import java.awt.Rectangle; | ||
| 30 | import java.io.IOException; | ||
| 31 | import javax.imageio.stream.ImageInputStream; | ||
| 32 | |||
| 33 | /** | ||
| 34 | * This class contains utility methods that may be useful to ImageReader | ||
| 35 | * plugins. Ideally these methods would be in the ImageReader base class | ||
| 36 | * so that all subclasses could benefit from them, but that would be an | ||
| 37 | * addition to the existing API, and it is not yet clear whether these methods | ||
| 38 | * are universally useful, so for now we will leave them here. | ||
| 39 | */ | ||
| 40 | public class ReaderUtil { | ||
| 41 | |||
| 42 | // Helper for computeUpdatedPixels method | ||
| 43 | private static void computeUpdatedPixels(int sourceOffset, | ||
| 44 | int sourceExtent, | ||
| 45 | int destinationOffset, | ||
| 46 | int dstMin, | ||
| 47 | int dstMax, | ||
| 48 | int sourceSubsampling, | ||
| 49 | int passStart, | ||
| 50 | int passExtent, | ||
| 51 | int passPeriod, | ||
| 52 | int[] vals, | ||
| 53 | int offset) | ||
| 54 | { | ||
| 55 | // We need to satisfy the congruences: | ||
| 56 | // dst = destinationOffset + (src - sourceOffset)/sourceSubsampling | ||
| 57 | // | ||
| 58 | // src - passStart == 0 (mod passPeriod) | ||
| 59 | // src - sourceOffset == 0 (mod sourceSubsampling) | ||
| 60 | // | ||
| 61 | // subject to the inequalities: | ||
| 62 | // | ||
| 63 | // src >= passStart | ||
| 64 | // src < passStart + passExtent | ||
| 65 | // src >= sourceOffset | ||
| 66 | // src < sourceOffset + sourceExtent | ||
| 67 | // dst >= dstMin | ||
| 68 | // dst <= dstmax | ||
| 69 | // | ||
| 70 | // where | ||
| 71 | // | ||
| 72 | // dst = destinationOffset + (src - sourceOffset)/sourceSubsampling | ||
| 73 | // | ||
| 74 | // For now we use a brute-force approach although we could | ||
| 75 | // attempt to analyze the congruences. If passPeriod and | ||
| 76 | // sourceSubsamling are relatively prime, the period will be | ||
| 77 | // their product. If they share a common factor, either the | ||
| 78 | // period will be equal to the larger value, or the sequences | ||
| 79 | // will be completely disjoint, depending on the relationship | ||
| 80 | // between passStart and sourceOffset. Since we only have to do this | ||
| 81 | // twice per image (once each for X and Y), it seems cheap enough | ||
| 82 | // to do it the straightforward way. | ||
| 83 | |||
| 84 | boolean gotPixel = false; | ||
| 85 | int firstDst = -1; | ||
| 86 | int secondDst = -1; | ||
| 87 | int lastDst = -1; | ||
| 88 | |||
| 89 | for (int i = 0; i < passExtent; i++) { | ||
| 90 | int src = passStart + i*passPeriod; | ||
| 91 | if (src < sourceOffset) { | ||
| 92 | continue; | ||
| 93 | } | ||
| 94 | if ((src - sourceOffset) % sourceSubsampling != 0) { | ||
| 95 | continue; | ||
| 96 | } | ||
| 97 | if (src >= sourceOffset + sourceExtent) { | ||
| 98 | break; | ||
| 99 | } | ||
| 100 | |||
| 101 | int dst = destinationOffset + | ||
| 102 | (src - sourceOffset)/sourceSubsampling; | ||
| 103 | if (dst < dstMin) { | ||
| 104 | continue; | ||
| 105 | } | ||
| 106 | if (dst > dstMax) { | ||
| 107 | break; | ||
| 108 | } | ||
| 109 | |||
| 110 | if (!gotPixel) { | ||
| 111 | firstDst = dst; // Record smallest valid pixel | ||
| 112 | gotPixel = true; | ||
| 113 | } else if (secondDst == -1) { | ||
| 114 | secondDst = dst; // Record second smallest valid pixel | ||
| 115 | } | ||
| 116 | lastDst = dst; // Record largest valid pixel | ||
| 117 | } | ||
| 118 | |||
| 119 | vals[offset] = firstDst; | ||
| 120 | |||
| 121 | // If we never saw a valid pixel, set width to 0 | ||
| 122 | if (!gotPixel) { | ||
| 123 | vals[offset + 2] = 0; | ||
| 124 | } else { | ||
| 125 | vals[offset + 2] = lastDst - firstDst + 1; | ||
| 126 | } | ||
| 127 | |||
| 128 | // The period is given by the difference of any two adjacent pixels | ||
| 129 | vals[offset + 4] = Math.max(secondDst - firstDst, 1); | ||
| 130 | } | ||
| 131 | |||
| 132 | /** | ||
| 133 | * A utility method that computes the exact set of destination | ||
| 134 | * pixels that will be written during a particular decoding pass. | ||
| 135 | * The intent is to simplify the work done by readers in combining | ||
| 136 | * the source region, source subsampling, and destination offset | ||
| 137 | * information obtained from the <code>ImageReadParam</code> with | ||
| 138 | * the offsets and periods of a progressive or interlaced decoding | ||
| 139 | * pass. | ||
| 140 | * | ||
| 141 | * @param sourceRegion a <code>Rectangle</code> containing the | ||
| 142 | * source region being read, offset by the source subsampling | ||
| 143 | * offsets, and clipped against the source bounds, as returned by | ||
| 144 | * the <code>getSourceRegion</code> method. | ||
| 145 | * @param destinationOffset a <code>Point</code> containing the | ||
| 146 | * coordinates of the upper-left pixel to be written in the | ||
| 147 | * destination. | ||
| 148 | * @param dstMinX the smallest X coordinate (inclusive) of the | ||
| 149 | * destination <code>Raster</code>. | ||
| 150 | * @param dstMinY the smallest Y coordinate (inclusive) of the | ||
| 151 | * destination <code>Raster</code>. | ||
| 152 | * @param dstMaxX the largest X coordinate (inclusive) of the destination | ||
| 153 | * <code>Raster</code>. | ||
| 154 | * @param dstMaxY the largest Y coordinate (inclusive) of the destination | ||
| 155 | * <code>Raster</code>. | ||
| 156 | * @param sourceXSubsampling the X subsampling factor. | ||
| 157 | * @param sourceYSubsampling the Y subsampling factor. | ||
| 158 | * @param passXStart the smallest source X coordinate (inclusive) | ||
| 159 | * of the current progressive pass. | ||
| 160 | * @param passYStart the smallest source Y coordinate (inclusive) | ||
| 161 | * of the current progressive pass. | ||
| 162 | * @param passWidth the width in pixels of the current progressive | ||
| 163 | * pass. | ||
| 164 | * @param passHeight the height in pixels of the current progressive | ||
| 165 | * pass. | ||
| 166 | * @param passPeriodX the X period (horizontal spacing between | ||
| 167 | * pixels) of the current progressive pass. | ||
| 168 | * @param passPeriodY the Y period (vertical spacing between | ||
| 169 | * pixels) of the current progressive pass. | ||
| 170 | * | ||
| 171 | * @return an array of 6 <code>int</code>s containing the | ||
| 172 | * destination min X, min Y, width, height, X period and Y period | ||
| 173 | * of the region that will be updated. | ||
| 174 | */ | ||
| 175 | public static int[] computeUpdatedPixels(Rectangle sourceRegion, | ||
| 176 | Point destinationOffset, | ||
| 177 | int dstMinX, | ||
| 178 | int dstMinY, | ||
| 179 | int dstMaxX, | ||
| 180 | int dstMaxY, | ||
| 181 | int sourceXSubsampling, | ||
| 182 | int sourceYSubsampling, | ||
| 183 | int passXStart, | ||
| 184 | int passYStart, | ||
| 185 | int passWidth, | ||
| 186 | int passHeight, | ||
| 187 | int passPeriodX, | ||
| 188 | int passPeriodY) | ||
| 189 | { | ||
| 190 | int[] vals = new int[6]; | ||
| 191 | computeUpdatedPixels(sourceRegion.x, sourceRegion.width, | ||
| 192 | destinationOffset.x, | ||
| 193 | dstMinX, dstMaxX, sourceXSubsampling, | ||
| 194 | passXStart, passWidth, passPeriodX, | ||
| 195 | vals, 0); | ||
| 196 | computeUpdatedPixels(sourceRegion.y, sourceRegion.height, | ||
| 197 | destinationOffset.y, | ||
| 198 | dstMinY, dstMaxY, sourceYSubsampling, | ||
| 199 | passYStart, passHeight, passPeriodY, | ||
| 200 | vals, 1); | ||
| 201 | return vals; | ||
| 202 | } | ||
| 203 | |||
| 204 | public static int readMultiByteInteger(ImageInputStream iis) | ||
| 205 | throws IOException | ||
| 206 | { | ||
| 207 | int value = iis.readByte(); | ||
| 208 | int result = value & 0x7f; | ||
| 209 | while((value & 0x80) == 0x80) { | ||
| 210 | result <<= 7; | ||
| 211 | value = iis.readByte(); | ||
| 212 | result |= (value & 0x7f); | ||
| 213 | } | ||
| 214 | return result; | ||
| 215 | } | ||
| 216 | } | ||