1 package tim.prune.jpeg.drew;
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4 import java.util.HashMap;
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6 import tim.prune.jpeg.JpegData;
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9 * Extracts Exif data from a JPEG header segment
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10 * Based on Drew Noakes' Metadata extractor at http://drewnoakes.com
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11 * which in turn is based on code from Jhead http://www.sentex.net/~mwandel/jhead/
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13 public class ExifReader
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15 /** The JPEG segment as an array of bytes */
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16 private final byte[] _data;
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19 * Represents the native byte ordering used in the JPEG segment. If true,
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20 * then we're using Motorola ordering (Big endian), else we're using Intel
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21 * ordering (Little endian).
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23 private boolean _isMotorolaByteOrder;
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25 /** Thumbnail offset */
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26 private int _thumbnailOffset = -1;
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27 /** Thumbnail length */
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28 private int _thumbnailLength = -1;
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30 /** The number of bytes used per format descriptor */
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31 private static final int[] BYTES_PER_FORMAT = {0, 1, 1, 2, 4, 8, 1, 1, 2, 4, 8, 4, 8};
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33 /** The number of formats known */
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34 private static final int MAX_FORMAT_CODE = 12;
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37 // Note: Cannot use the DataFormat enumeration in the case statement that uses these tags.
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38 // Is there a better way?
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39 //private static final int FMT_BYTE = 1;
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40 private static final int FMT_STRING = 2;
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41 //private static final int FMT_USHORT = 3;
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42 //private static final int FMT_ULONG = 4;
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43 private static final int FMT_URATIONAL = 5;
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44 //private static final int FMT_SBYTE = 6;
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45 //private static final int FMT_UNDEFINED = 7;
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46 //private static final int FMT_SSHORT = 8;
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47 //private static final int FMT_SLONG = 9;
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48 private static final int FMT_SRATIONAL = 10;
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49 //private static final int FMT_SINGLE = 11;
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50 //private static final int FMT_DOUBLE = 12;
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52 public static final int TAG_EXIF_OFFSET = 0x8769;
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53 public static final int TAG_INTEROP_OFFSET = 0xA005;
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54 public static final int TAG_GPS_INFO_OFFSET = 0x8825;
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55 public static final int TAG_MAKER_NOTE = 0x927C;
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57 public static final int TIFF_HEADER_START_OFFSET = 6;
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59 /** GPS tag version GPSVersionID 0 0 BYTE 4 */
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60 public static final int TAG_GPS_VERSION_ID = 0x0000;
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61 /** North or South Latitude GPSLatitudeRef 1 1 ASCII 2 */
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62 public static final int TAG_GPS_LATITUDE_REF = 0x0001;
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63 /** Latitude GPSLatitude 2 2 RATIONAL 3 */
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64 public static final int TAG_GPS_LATITUDE = 0x0002;
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65 /** East or West Longitude GPSLongitudeRef 3 3 ASCII 2 */
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66 public static final int TAG_GPS_LONGITUDE_REF = 0x0003;
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67 /** Longitude GPSLongitude 4 4 RATIONAL 3 */
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68 public static final int TAG_GPS_LONGITUDE = 0x0004;
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69 /** Altitude reference GPSAltitudeRef 5 5 BYTE 1 */
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70 public static final int TAG_GPS_ALTITUDE_REF = 0x0005;
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71 /** Altitude GPSAltitude 6 6 RATIONAL 1 */
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72 public static final int TAG_GPS_ALTITUDE = 0x0006;
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73 /** GPS time (atomic clock) GPSTimeStamp 7 7 RATIONAL 3 */
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74 public static final int TAG_GPS_TIMESTAMP = 0x0007;
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75 /** GPS date (atomic clock) GPSDateStamp 23 1d RATIONAL 3 */
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76 public static final int TAG_GPS_DATESTAMP = 0x001d;
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77 /** "Original" Exif timestamp */
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78 public static final int TAG_DATETIME_ORIGINAL = 0x9003;
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79 /** "Creation" or "Digitized" timestamp */
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80 public static final int TAG_DATETIME_DIGITIZED = 0x9004;
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81 /** Thumbnail offset */
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82 private static final int TAG_THUMBNAIL_OFFSET = 0x0201;
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83 /** Thumbnail length */
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84 private static final int TAG_THUMBNAIL_LENGTH = 0x0202;
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85 /** Orientation of image */
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86 private static final int TAG_ORIENTATION = 0x0112;
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90 * Creates an ExifReader for a Jpeg file
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91 * @param inFile File object to attempt to read from
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92 * @throws JpegException on failure
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94 public ExifReader(File inFile) throws JpegException
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96 JpegSegmentData segments = JpegSegmentReader.readSegments(inFile);
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97 _data = segments.getSegment(JpegSegmentReader.SEGMENT_APP1);
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101 * Performs the Exif data extraction
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102 * @return the GPS data found in the file
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104 public JpegData extract()
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106 JpegData metadata = new JpegData();
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110 // check for the header length
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111 if (_data.length<=14)
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113 metadata.addError("Exif data segment must contain at least 14 bytes");
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117 // check for the header preamble
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118 if (!"Exif\0\0".equals(new String(_data, 0, 6)))
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120 metadata.addError("Exif data segment doesn't begin with 'Exif'");
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124 // this should be either "MM" or "II"
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125 String byteOrderIdentifier = new String(_data, 6, 2);
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126 if (!setByteOrder(byteOrderIdentifier))
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128 metadata.addError("Unclear distinction between Motorola/Intel byte ordering: " + byteOrderIdentifier);
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132 // Check the next two values are 0x2A as expected
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133 if (get16Bits(8)!=0x2a)
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135 metadata.addError("Invalid Exif start - should have 0x2A at offset 8 in Exif header");
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139 int firstDirectoryOffset = get32Bits(10) + TIFF_HEADER_START_OFFSET;
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141 // Check that offset is within range
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142 if (firstDirectoryOffset>=_data.length - 1)
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144 metadata.addError("First exif directory offset is beyond end of Exif data segment");
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145 // First directory normally starts 14 bytes in -- try it here and catch another error in the worst case
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146 firstDirectoryOffset = 14;
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149 HashMap<Integer, String> processedDirectoryOffsets = new HashMap<Integer, String>();
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151 // 0th IFD (we merge with Exif IFD)
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152 processDirectory(metadata, false, processedDirectoryOffsets, firstDirectoryOffset, TIFF_HEADER_START_OFFSET);
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159 * Set the byte order identifier
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160 * @param byteOrderIdentifier String from exif
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161 * @return true if recognised, false otherwise
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163 private boolean setByteOrder(String byteOrderIdentifier)
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165 if ("MM".equals(byteOrderIdentifier)) {
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166 _isMotorolaByteOrder = true;
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167 } else if ("II".equals(byteOrderIdentifier)) {
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168 _isMotorolaByteOrder = false;
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177 * Recursive call to process one of the nested Tiff IFD directories.
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178 * 2 bytes: number of tags
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180 * 2 bytes: tag type
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181 * 2 bytes: format code
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182 * 4 bytes: component count
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184 private void processDirectory(JpegData inMetadata, boolean inIsGPS, HashMap<Integer, String> inDirectoryOffsets,
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185 int inDirOffset, int inTiffHeaderOffset)
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187 // check for directories we've already visited to avoid stack overflows when recursive/cyclic directory structures exist
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188 if (inDirectoryOffsets.containsKey(Integer.valueOf(inDirOffset)))
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191 // remember that we've visited this directory so that we don't visit it again later
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192 inDirectoryOffsets.put(Integer.valueOf(inDirOffset), "processed");
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194 if (inDirOffset >= _data.length || inDirOffset < 0)
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196 inMetadata.addError("Ignored directory marked to start outside data segment");
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200 // First two bytes in the IFD are the number of tags in this directory
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201 int dirTagCount = get16Bits(inDirOffset);
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202 // If no tags, exit without complaint
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203 if (dirTagCount == 0) return;
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205 if (!isDirectoryLengthValid(inDirOffset, inTiffHeaderOffset))
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207 inMetadata.addError("Directory length is not valid");
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211 inMetadata.setExifDataPresent();
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212 // Handle each tag in this directory
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213 for (int tagNumber = 0; tagNumber<dirTagCount; tagNumber++)
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215 final int tagOffset = calculateTagOffset(inDirOffset, tagNumber);
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217 // 2 bytes for the tag type
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218 final int tagType = get16Bits(tagOffset);
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220 // 2 bytes for the format code
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221 final int formatCode = get16Bits(tagOffset + 2);
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222 if (formatCode < 1 || formatCode > MAX_FORMAT_CODE)
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224 inMetadata.addError("Invalid format code: " + formatCode);
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228 // 4 bytes dictate the number of components in this tag's data
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229 final int componentCount = get32Bits(tagOffset + 4);
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230 if (componentCount < 0)
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232 inMetadata.addError("Negative component count in EXIF");
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235 // each component may have more than one byte... calculate the total number of bytes
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236 final int byteCount = componentCount * BYTES_PER_FORMAT[formatCode];
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237 final int tagValueOffset = calculateTagValueOffset(byteCount, tagOffset, inTiffHeaderOffset);
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238 if (tagValueOffset < 0 || tagValueOffset > _data.length)
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240 inMetadata.addError("Illegal pointer offset value in EXIF");
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244 // Check that this tag isn't going to allocate outside the bounds of the data array.
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245 // This addresses an uncommon OutOfMemoryError.
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246 if (byteCount < 0 || tagValueOffset + byteCount > _data.length)
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248 inMetadata.addError("Illegal number of bytes: " + byteCount);
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252 // Calculate the value as an offset for cases where the tag represents a directory
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253 final int subdirOffset = inTiffHeaderOffset + get32Bits(tagValueOffset);
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255 // Look in both basic Exif tags (for timestamp, thumbnail) and Gps tags (for lat, long, altitude, timestamp)
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258 case TAG_EXIF_OFFSET:
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259 processDirectory(inMetadata, false, inDirectoryOffsets, subdirOffset, inTiffHeaderOffset);
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261 case TAG_INTEROP_OFFSET:
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264 case TAG_GPS_INFO_OFFSET:
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265 processDirectory(inMetadata, true, inDirectoryOffsets, subdirOffset, inTiffHeaderOffset);
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267 case TAG_MAKER_NOTE:
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271 // not a known directory, so must just be a normal tag
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274 processGpsTag(inMetadata, tagType, tagValueOffset, componentCount, formatCode);
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278 processExifTag(inMetadata, tagType, tagValueOffset, componentCount, formatCode);
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284 // at the end of each IFD is an optional link to the next IFD
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285 final int finalTagOffset = calculateTagOffset(inDirOffset, dirTagCount);
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286 int nextDirectoryOffset = get32Bits(finalTagOffset);
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287 if (nextDirectoryOffset != 0)
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289 nextDirectoryOffset += inTiffHeaderOffset;
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290 if (nextDirectoryOffset>=_data.length)
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292 // Last 4 bytes of IFD reference another IFD with an address that is out of bounds
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295 else if (nextDirectoryOffset < inDirOffset)
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297 // Last 4 bytes of IFD reference another IFD with an address before the start of this directory
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300 // the next directory is of same type as this one
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301 processDirectory(inMetadata, false, inDirectoryOffsets, nextDirectoryOffset, inTiffHeaderOffset);
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307 * Check if the directory length is valid
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308 * @param dirStartOffset start offset for directory
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309 * @param tiffHeaderOffset Tiff header offeset
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310 * @return true if length is valid
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312 private boolean isDirectoryLengthValid(int inDirStartOffset, int inTiffHeaderOffset)
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314 int dirTagCount = get16Bits(inDirStartOffset);
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315 int dirLength = (2 + (12 * dirTagCount) + 4);
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316 if (dirLength + inDirStartOffset + inTiffHeaderOffset >= _data.length)
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318 // Note: Files that had thumbnails trimmed with jhead 1.3 or earlier might trigger this
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326 * Process a GPS tag and put the contents in the given metadata
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327 * @param inMetadata metadata holding extracted values
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328 * @param inTagType tag type (eg latitude)
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329 * @param inTagValueOffset start offset in data array
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330 * @param inComponentCount component count for tag
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331 * @param inFormatCode format code, eg byte
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333 private void processGpsTag(JpegData inMetadata, int inTagType, int inTagValueOffset,
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334 int inComponentCount, int inFormatCode)
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338 // Only interested in tags latref, lat, longref, lon, altref, alt and gps timestamp
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341 case TAG_GPS_LATITUDE_REF:
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342 inMetadata.setLatitudeRef(readString(inTagValueOffset, inFormatCode, inComponentCount));
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344 case TAG_GPS_LATITUDE:
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345 Rational[] latitudes = readRationalArray(inTagValueOffset, inFormatCode, inComponentCount);
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346 inMetadata.setLatitude(new double[] {latitudes[0].doubleValue(), latitudes[1].doubleValue(), latitudes[2].doubleValue()});
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348 case TAG_GPS_LONGITUDE_REF:
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349 inMetadata.setLongitudeRef(readString(inTagValueOffset, inFormatCode, inComponentCount));
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351 case TAG_GPS_LONGITUDE:
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352 Rational[] longitudes = readRationalArray(inTagValueOffset, inFormatCode, inComponentCount);
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353 inMetadata.setLongitude(new double[] {longitudes[0].doubleValue(), longitudes[1].doubleValue(), longitudes[2].doubleValue()});
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355 case TAG_GPS_ALTITUDE_REF:
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356 inMetadata.setAltitudeRef(_data[inTagValueOffset]);
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358 case TAG_GPS_ALTITUDE:
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359 inMetadata.setAltitude(readRational(inTagValueOffset, inFormatCode, inComponentCount).intValue());
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361 case TAG_GPS_TIMESTAMP:
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362 Rational[] times = readRationalArray(inTagValueOffset, inFormatCode, inComponentCount);
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363 inMetadata.setGpsTimestamp(new int[] {times[0].intValue(), times[1].intValue(), times[2].intValue()});
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365 case TAG_GPS_DATESTAMP:
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366 Rational[] dates = readRationalArray(inTagValueOffset, inFormatCode, inComponentCount);
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367 if (dates != null) {
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368 inMetadata.setGpsDatestamp(new int[] {dates[0].intValue(), dates[1].intValue(), dates[2].intValue()});
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371 // Not in rational array format, but maybe as String?
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372 String date = readString(inTagValueOffset, inFormatCode, inComponentCount);
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373 if (date != null && date.length() == 10) {
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374 inMetadata.setGpsDatestamp(new int[] {Integer.parseInt(date.substring(0, 4)),
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375 Integer.parseInt(date.substring(5, 7)), Integer.parseInt(date.substring(8))});
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379 default: // ignore all other tags
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382 catch (Exception e) {} // ignore and continue
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387 * Process a general Exif tag
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388 * @param inMetadata metadata holding extracted values
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389 * @param inTagType tag type (eg latitude)
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390 * @param inTagValueOffset start offset in data array
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391 * @param inComponentCount component count for tag
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392 * @param inFormatCode format code, eg byte
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394 private void processExifTag(JpegData inMetadata, int inTagType, int inTagValueOffset,
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395 int inComponentCount, int inFormatCode)
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397 // Only interested in original timestamp, thumbnail offset and thumbnail length
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398 if (inTagType == TAG_DATETIME_ORIGINAL) {
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399 inMetadata.setOriginalTimestamp(readString(inTagValueOffset, inFormatCode, inComponentCount));
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401 else if (inTagType == TAG_DATETIME_DIGITIZED) {
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402 inMetadata.setDigitizedTimestamp(readString(inTagValueOffset, inFormatCode, inComponentCount));
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404 else if (inTagType == TAG_THUMBNAIL_OFFSET) {
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405 _thumbnailOffset = TIFF_HEADER_START_OFFSET + get16Bits(inTagValueOffset);
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406 extractThumbnail(inMetadata);
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408 else if (inTagType == TAG_THUMBNAIL_LENGTH) {
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409 _thumbnailLength = get16Bits(inTagValueOffset);
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410 extractThumbnail(inMetadata);
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412 else if (inTagType == TAG_ORIENTATION) {
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413 if (inMetadata.getOrientationCode() < 1) {
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414 inMetadata.setOrientationCode(get16Bits(inTagValueOffset));
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420 * Attempt to extract the thumbnail image
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422 private void extractThumbnail(JpegData inMetadata)
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424 if (_thumbnailOffset > 0 && _thumbnailLength > 0 && inMetadata.getThumbnailImage() == null)
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426 byte[] thumbnailBytes = new byte[_thumbnailLength];
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427 System.arraycopy(_data, _thumbnailOffset, thumbnailBytes, 0, _thumbnailLength);
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428 inMetadata.setThumbnailImage(thumbnailBytes);
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434 * Calculate the tag value offset
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435 * @param inByteCount
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436 * @param inDirEntryOffset
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437 * @param inTiffHeaderOffset
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438 * @return new offset
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440 private int calculateTagValueOffset(int inByteCount, int inDirEntryOffset, int inTiffHeaderOffset)
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442 if (inByteCount > 4)
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444 // If it's bigger than 4 bytes, the dir entry contains an offset.
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445 // dirEntryOffset must be passed, as some makers (e.g. FujiFilm) incorrectly use an
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446 // offset relative to the start of the makernote itself, not the TIFF segment.
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447 final int offsetVal = get32Bits(inDirEntryOffset + 8);
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448 if (offsetVal + inByteCount > _data.length)
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450 // Bogus pointer offset and / or bytecount value
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451 return -1; // signal error
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453 return inTiffHeaderOffset + offsetVal;
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457 // 4 bytes or less and value is in the dir entry itself
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458 return inDirEntryOffset + 8;
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464 * Creates a String from the _data buffer starting at the specified offset,
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465 * and ending where byte=='\0' or where length==maxLength.
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466 * @param inOffset start offset
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467 * @param inFormatCode format code - should be string
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468 * @param inMaxLength max length of string
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469 * @return contents of tag, or null if format incorrect
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471 private String readString(int inOffset, int inFormatCode, int inMaxLength)
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473 if (inFormatCode != FMT_STRING) return null;
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474 // Calculate length
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476 while ((inOffset + length)<_data.length
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477 && _data[inOffset + length]!='\0'
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478 && length < inMaxLength)
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482 return new String(_data, inOffset, length);
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486 * Creates a Rational from the _data buffer starting at the specified offset
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487 * @param inOffset start offset
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488 * @param inFormatCode format code - should be srational or urational
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489 * @param inCount component count - should be 1
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490 * @return contents of tag as a Rational object
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492 private Rational readRational(int inOffset, int inFormatCode, int inCount)
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494 // Check the format is a single rational as expected
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495 if (inFormatCode != FMT_SRATIONAL && inFormatCode != FMT_URATIONAL
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496 || inCount != 1) return null;
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497 return new Rational(get32Bits(inOffset), get32Bits(inOffset + 4));
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502 * Creates a Rational array from the _data buffer starting at the specified offset
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503 * @param inOffset start offset
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504 * @param inFormatCode format code - should be srational or urational
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505 * @param inCount component count - number of components
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506 * @return contents of tag as an array of Rational objects
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508 private Rational[] readRationalArray(int inOffset, int inFormatCode, int inCount)
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510 // Check the format is rational as expected
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511 if (inFormatCode != FMT_SRATIONAL && inFormatCode != FMT_URATIONAL)
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513 // Build array of Rationals
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514 Rational[] answer = new Rational[inCount];
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515 for (int i=0; i<inCount; i++)
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516 answer[i] = new Rational(get32Bits(inOffset + (8 * i)), get32Bits(inOffset + 4 + (8 * i)));
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522 * Determine the offset at which a given InteropArray entry begins within the specified IFD.
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523 * @param dirStartOffset the offset at which the IFD starts
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524 * @param entryNumber the zero-based entry number
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526 private int calculateTagOffset(int dirStartOffset, int entryNumber)
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528 // add 2 bytes for the tag count
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529 // each entry is 12 bytes, so we skip 12 * the number seen so far
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530 return dirStartOffset + 2 + (12 * entryNumber);
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535 * Get a 16 bit value from file's native byte order. Between 0x0000 and 0xFFFF.
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537 private int get16Bits(int offset)
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539 if (offset<0 || offset+2>_data.length)
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540 throw new ArrayIndexOutOfBoundsException("attempt to read data outside of exif segment (index "
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541 + offset + " where max index is " + (_data.length - 1) + ")");
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543 if (_isMotorolaByteOrder) {
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544 // Motorola - MSB first
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545 return (_data[offset] << 8 & 0xFF00) | (_data[offset + 1] & 0xFF);
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547 // Intel ordering - LSB first
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548 return (_data[offset + 1] << 8 & 0xFF00) | (_data[offset] & 0xFF);
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554 * Get a 32 bit value from file's native byte order.
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556 private int get32Bits(int offset)
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558 if (offset < 0 || offset+4 > _data.length)
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559 throw new ArrayIndexOutOfBoundsException("attempt to read data outside of exif segment (index "
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560 + offset + " where max index is " + (_data.length - 1) + ")");
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562 if (_isMotorolaByteOrder)
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564 // Motorola - MSB first
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565 return (_data[offset] << 24 & 0xFF000000) |
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566 (_data[offset + 1] << 16 & 0xFF0000) |
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567 (_data[offset + 2] << 8 & 0xFF00) |
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568 (_data[offset + 3] & 0xFF);
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572 // Intel ordering - LSB first
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573 return (_data[offset + 3] << 24 & 0xFF000000) |
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574 (_data[offset + 2] << 16 & 0xFF0000) |
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575 (_data[offset + 1] << 8 & 0xFF00) |
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576 (_data[offset] & 0xFF);
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