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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 | +} | |