tim/prune/jpeg/drew/JpegSegmentReader.java

   1 package tim.prune.jpeg.drew;\r
   2 \r
   3 import java.io.*;\r
   4 \r
   5 /**\r
   6  * Class to perform read functions of Jpeg files, returning specific file segments\r
   7  * Based on Drew Noakes' Metadata extractor at http://drewnoakes.com\r
   8  */\r
   9 public class JpegSegmentReader\r
  10 {\r
  11         /** Start of scan marker */\r
  12         private static final byte SEGMENT_SOS = (byte)0xDA;\r
  13 \r
  14         /** End of image marker */\r
  15         private static final byte MARKER_EOI = (byte)0xD9;\r
  16 \r
  17         /** APP0 Jpeg segment identifier -- Jfif data. */\r
  18         public static final byte SEGMENT_APP0 = (byte)0xE0;\r
  19         /** APP1 Jpeg segment identifier -- where Exif data is kept. */\r
  20         public static final byte SEGMENT_APP1 = (byte)0xE1;\r
  21         /** APP2 Jpeg segment identifier. */\r
  22         public static final byte SEGMENT_APP2 = (byte)0xE2;\r
  23         /** APP3 Jpeg segment identifier. */\r
  24         public static final byte SEGMENT_APP3 = (byte)0xE3;\r
  25         /** APP4 Jpeg segment identifier. */\r
  26         public static final byte SEGMENT_APP4 = (byte)0xE4;\r
  27         /** APP5 Jpeg segment identifier. */\r
  28         public static final byte SEGMENT_APP5 = (byte)0xE5;\r
  29         /** APP6 Jpeg segment identifier. */\r
  30         public static final byte SEGMENT_APP6 = (byte)0xE6;\r
  31         /** APP7 Jpeg segment identifier. */\r
  32         public static final byte SEGMENT_APP7 = (byte)0xE7;\r
  33         /** APP8 Jpeg segment identifier. */\r
  34         public static final byte SEGMENT_APP8 = (byte)0xE8;\r
  35         /** APP9 Jpeg segment identifier. */\r
  36         public static final byte SEGMENT_APP9 = (byte)0xE9;\r
  37         /** APPA Jpeg segment identifier -- can hold Unicode comments. */\r
  38         public static final byte SEGMENT_APPA = (byte)0xEA;\r
  39         /** APPB Jpeg segment identifier. */\r
  40         public static final byte SEGMENT_APPB = (byte)0xEB;\r
  41         /** APPC Jpeg segment identifier. */\r
  42         public static final byte SEGMENT_APPC = (byte)0xEC;\r
  43         /** APPD Jpeg segment identifier -- IPTC data in here. */\r
  44         public static final byte SEGMENT_APPD = (byte)0xED;\r
  45         /** APPE Jpeg segment identifier. */\r
  46         public static final byte SEGMENT_APPE = (byte)0xEE;\r
  47         /** APPF Jpeg segment identifier. */\r
  48         public static final byte SEGMENT_APPF = (byte)0xEF;\r
  49         /** Start Of Image segment identifier. */\r
  50         public static final byte SEGMENT_SOI = (byte)0xD8;\r
  51         /** Define Quantization Table segment identifier. */\r
  52         public static final byte SEGMENT_DQT = (byte)0xDB;\r
  53         /** Define Huffman Table segment identifier. */\r
  54         public static final byte SEGMENT_DHT = (byte)0xC4;\r
  55         /** Start-of-Frame Zero segment identifier. */\r
  56         public static final byte SEGMENT_SOF0 = (byte)0xC0;\r
  57         /** Jpeg comment segment identifier. */\r
  58         public static final byte SEGMENT_COM = (byte)0xFE;\r
  59 \r
  60         /** Magic numbers to mark the beginning of all Jpegs */\r
  61         private static final int MAGIC_JPEG_BYTE_1 = 0xFF;\r
  62         private static final int MAGIC_JPEG_BYTE_2 = 0xD8;\r
  63 \r
  64 \r
  65         /**\r
  66          * Obtain the Jpeg segment data from the specified file\r
  67          * @param inFile File to read\r
  68          * @return Jpeg segment data from file\r
  69          * @throws JpegException on file read errors or exif data errors\r
  70          */\r
  71         public static JpegSegmentData readSegments(File inFile) throws JpegException\r
  72         {\r
  73                 JpegSegmentData segmentData = new JpegSegmentData();\r
  74 \r
  75                 BufferedInputStream bStream = null;\r
  76 \r
  77                 try\r
  78                 {\r
  79                         bStream = new BufferedInputStream(new FileInputStream(inFile));\r
  80                         int offset = 0;\r
  81                         // first two bytes should be jpeg magic number\r
  82                         int magic1 = bStream.read() & 0xFF;\r
  83                         int magic2 = bStream.read() & 0xFF;\r
  84                         checkMagicNumbers(magic1, magic2);\r
  85 \r
  86                         offset += 2;\r
  87                         // Loop around segments found\r
  88                         do\r
  89                         {\r
  90                                 // next byte is 0xFF\r
  91                                 byte segmentIdentifier = (byte) (bStream.read() & 0xFF);\r
  92                                 if ((segmentIdentifier & 0xFF) != 0xFF)\r
  93                                 {\r
  94                                         throw new JpegException("expected jpeg segment start identifier 0xFF at offset "\r
  95                                                 + offset + ", not 0x" + Integer.toHexString(segmentIdentifier & 0xFF));\r
  96                                 }\r
  97                                 offset++;\r
  98                                 // next byte is <segment-marker>\r
  99                                 byte thisSegmentMarker = (byte) (bStream.read() & 0xFF);\r
 100                                 offset++;\r
 101                                 // next 2-bytes are <segment-size>: [high-byte] [low-byte]\r
 102                                 byte[] segmentLengthBytes = new byte[2];\r
 103                                 bStream.read(segmentLengthBytes, 0, 2);\r
 104                                 offset += 2;\r
 105                                 int segmentLength = ((segmentLengthBytes[0] << 8) & 0xFF00) | (segmentLengthBytes[1] & 0xFF);\r
 106                                 // segment length includes size bytes, so subtract two\r
 107                                 segmentLength -= 2;\r
 108                                 if (segmentLength > bStream.available())\r
 109                                         throw new JpegException("segment size would extend beyond file stream length");\r
 110                                 else if (segmentLength < 0)\r
 111                                         throw new JpegException("segment size would be less than zero");\r
 112                                 byte[] segmentBytes = new byte[segmentLength];\r
 113                                 bStream.read(segmentBytes, 0, segmentLength);\r
 114                                 offset += segmentLength;\r
 115                                 if ((thisSegmentMarker & 0xFF) == (SEGMENT_SOS & 0xFF))\r
 116                                 {\r
 117                                         // The 'Start-Of-Scan' segment comes last so break out of loop\r
 118                                         break;\r
 119                                 }\r
 120                                 else if ((thisSegmentMarker & 0xFF) == (MARKER_EOI & 0xFF))\r
 121                                 {\r
 122                                         // the 'End-Of-Image' segment - should already have exited by now\r
 123                                         break;\r
 124                                 }\r
 125                                 else\r
 126                                 {\r
 127                                         segmentData.addSegment(thisSegmentMarker, segmentBytes);\r
 128                                 }\r
 129                                 // loop through to the next segment\r
 130                         }\r
 131                         while (true);\r
 132                 }\r
 133                 catch (FileNotFoundException fnfe)\r
 134                 {\r
 135                         throw new JpegException("Jpeg file not found");\r
 136                 }\r
 137                 catch (IOException ioe)\r
 138                 {\r
 139                         throw new JpegException("IOException processing Jpeg file: " + ioe.getMessage(), ioe);\r
 140                 }\r
 141                 finally\r
 142                 {\r
 143                         try\r
 144                         {\r
 145                                 if (bStream != null) {\r
 146                                         bStream.close();\r
 147                                 }\r
 148                         }\r
 149                         catch (IOException ioe) {\r
 150                                 throw new JpegException("IOException processing Jpeg file: " + ioe.getMessage(), ioe);\r
 151                         }\r
 152                 }\r
 153                 // Return the result\r
 154                 return segmentData;\r
 155         }\r
 156 \r
 157 \r
 158         /**\r
 159          * Helper method that validates the Jpeg file's magic number.\r
 160          * @param inMagic1 first half of magic number\r
 161          * @param inMagic2 second half of magic number\r
 162          * @throws JpegException if numbers do not match magic numbers expected\r
 163          */\r
 164         private static void checkMagicNumbers(int inMagic1, int inMagic2) throws JpegException\r
 165         {\r
 166                 if (inMagic1 != MAGIC_JPEG_BYTE_1 || inMagic2 != MAGIC_JPEG_BYTE_2)\r
 167                 {\r
 168                         throw new JpegException("not a jpeg file");\r
 169                 }\r
 170         }\r
 171 }