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annotate dwt/internal/image/PngDecodingDataStream.d @ 213:36f5cb12e1a2

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Update to SWT 3.4M7
author Frank Benoit <benoit@tionex.de>
date Sat, 17 May 2008 17:34:28 +0200
parents 9a64a7781bab
children
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1 /*******************************************************************************
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2 * Copyright (c) 2000, 2006 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM Corporation - initial API and implementation
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10 * Port to the D programming language:
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11 * Frank Benoit <benoit@tionex.de>
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12 *******************************************************************************/
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13 module dwt.internal.image.PngDecodingDataStream;
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14
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15
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16 import dwt.dwthelper.InputStream;
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17
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18 import dwt.DWT;
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19 import dwt.internal.image.PngLzBlockReader;
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20
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21 public class PngDecodingDataStream : InputStream {
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22
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23 alias InputStream.read read;
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24
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25 InputStream stream;
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26 byte currentByte;
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27 int nextBitIndex;
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28
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29 PngLzBlockReader lzBlockReader;
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30 int adlerValue;
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31
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32 static final int PRIME = 65521;
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33 static final int MAX_BIT = 7;
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34
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35 this(InputStream stream) {
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36 super();
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37 this.stream = stream;
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38 nextBitIndex = MAX_BIT + 1;
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39 adlerValue = 1;
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40 lzBlockReader = new PngLzBlockReader(this);
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41 readCompressedDataHeader();
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42 lzBlockReader.readNextBlockHeader();
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43 }
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44
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45 /**
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46 * This method should be called when the image decoder thinks
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47 * that all of the compressed image data has been read. This
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48 * method will ensure that the next data value is an end of
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49 * block marker. If there are more blocks after this one,
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50 * the method will read them and ensure that they are empty.
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51 */
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52 void assertImageDataAtEnd() {
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53 lzBlockReader.assertCompressedDataAtEnd();
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54 }
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55
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56 public override void close() {
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57 assertImageDataAtEnd();
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58 checkAdler();
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59 }
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60
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61 int getNextIdatBits(int length) {
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62 int value = 0;
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63 for (int i = 0; i < length; i++) {
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64 value |= (getNextIdatBit() << i);
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65 }
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66 return value;
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67 }
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68
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69 int getNextIdatBit() {
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70 if (nextBitIndex > MAX_BIT) {
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71 currentByte = getNextIdatByte();
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72 nextBitIndex = 0;
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73 }
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74 return (currentByte & (1 << nextBitIndex)) >> nextBitIndex++;
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75 }
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77 byte getNextIdatByte() {
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78 byte nextByte = cast(byte)stream.read();
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79 nextBitIndex = MAX_BIT + 1;
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80 return nextByte;
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81 }
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82
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83 void updateAdler(byte value) {
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84 int low = adlerValue & 0xFFFF;
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85 int high = (adlerValue >> 16) & 0xFFFF;
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86 int valueInt = value & 0xFF;
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87 low = (low + valueInt) % PRIME;
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88 high = (low + high) % PRIME;
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89 adlerValue = (high << 16) | low;
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90 }
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91
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92 public override int read() {
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93 byte nextDecodedByte = lzBlockReader.getNextByte();
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94 updateAdler(nextDecodedByte);
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95 return nextDecodedByte & 0xFF;
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96 }
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97
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98 public override int read(byte[] buffer, int off, int len) {
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99 for (int i = 0; i < len; i++) {
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100 int b = read();
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101 if (b is -1) return i;
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102 buffer[off + i] = cast(byte)b;
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103 }
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104 return len;
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105 }
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106
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107 void error() {
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108 DWT.error(DWT.ERROR_INVALID_IMAGE);
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109 }
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110
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111 private void readCompressedDataHeader() {
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112 byte headerByte1 = getNextIdatByte();
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113 byte headerByte2 = getNextIdatByte();
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114
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115 int number = ((headerByte1 & 0xFF) << 8) | (headerByte2 & 0xFF);
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116 if (number % 31 !is 0) error();
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117
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118 int compressionMethod = headerByte1 & 0x0F;
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119 if (compressionMethod !is 8) error();
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120
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121 int windowSizeHint = (headerByte1 & 0xF0) >> 4;
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122 if (windowSizeHint > 7) error();
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123 int windowSize = (1 << (windowSizeHint + 8));
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124 lzBlockReader.setWindowSize(windowSize);
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125
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126 int dictionary = (headerByte2 & (1 << 5));
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127 if (dictionary !is 0) error();
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128
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129 // int compressionLevel = (headerByte2 & 0xC0) >> 6;
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130 }
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131
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132 void checkAdler() {
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133 int storedAdler = 0;
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134 storedAdler |= ((getNextIdatByte() & 0xFF) << 24);
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135 storedAdler |= ((getNextIdatByte() & 0xFF) << 16);
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136 storedAdler |= ((getNextIdatByte() & 0xFF) << 8);
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137 storedAdler |= (getNextIdatByte() & 0xFF);
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138 if (storedAdler !is adlerValue) error();
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139 }
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140
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141 }