Field Detail

• TAG_NUMBER_OF_TABLES

  public static final int TAG_NUMBER_OF_TABLES

  See Also:

  Constant Field Values

• TYPICAL_LUMINANCE_DC_LENGTHS

  final byte[] TYPICAL_LUMINANCE_DC_LENGTHS

• TYPICAL_LUMINANCE_DC_VALUES

  final byte[] TYPICAL_LUMINANCE_DC_VALUES

• TYPICAL_CHROMINANCE_DC_LENGTHS

  final byte[] TYPICAL_CHROMINANCE_DC_LENGTHS

• TYPICAL_CHROMINANCE_DC_VALUES

  final byte[] TYPICAL_CHROMINANCE_DC_VALUES

• TYPICAL_LUMINANCE_AC_LENGTHS

  final byte[] TYPICAL_LUMINANCE_AC_LENGTHS

• TYPICAL_LUMINANCE_AC_VALUES

  final byte[] TYPICAL_LUMINANCE_AC_VALUES

• TYPICAL_CHROMINANCE_AC_LENGTHS

  final byte[] TYPICAL_CHROMINANCE_AC_LENGTHS

• TYPICAL_CHROMINANCE_AC_VALUES

  final byte[] TYPICAL_CHROMINANCE_AC_VALUES

• tables

  protected final java.util.List<MetadataExtractor.HuffmanTablesDirectory.HuffmanTable> tables

• _tagNameMap

  private final java.util.HashMap<java.lang.Integer,​java.lang.String> _tagNameMap

Constructor Detail

• HuffmanTablesDirectory

  public HuffmanTablesDirectory()

Method Detail

• getName

  public java.lang.String getName()

  Description copied from class: MetadataExtractor.Directory
  Provides the name of the directory, for display purposes. E.g. Exif

  Specified by:

  getName in class MetadataExtractor.Directory

  Returns:

  the name of the directory

• getTagNameMap

  protected java.util.HashMap<java.lang.Integer,​java.lang.String> getTagNameMap()

  Description copied from class: MetadataExtractor.Directory
  Provides the map of tag names, hashed by tag type identifier.

  Specified by:

  getTagNameMap in class MetadataExtractor.Directory

  Returns:

  the map of tag names

• getTable

  public MetadataExtractor.HuffmanTablesDirectory.HuffmanTable getTable​(int tableNumber)

  Parameters:

  tableNumber - The zero-based index of the table. This number is normally between 0 and 3. Use getNumberOfTables() for bounds-checking.

  Returns:

  The MetadataExtractor.HuffmanTablesDirectory.HuffmanTable having the specified number.

• getNumberOfTables

  public int getNumberOfTables()
                        throws MetadataExtractor.MetadataException

  Returns:

  The number of Huffman tables held by this MetadataExtractor.HuffmanTablesDirectory instance.

  Throws:

  MetadataExtractor.MetadataException

• getTables

  protected java.util.List<MetadataExtractor.HuffmanTablesDirectory.HuffmanTable> getTables()

  Returns:

  The List of MetadataExtractor.HuffmanTablesDirectory.HuffmanTables in this MetadataExtractor.Directory.

• isTypical

  public boolean isTypical()

  Evaluates whether all the tables in this MetadataExtractor.HuffmanTablesDirectory are "typical" Huffman tables.

  "Typical" has a special meaning in this context as the JPEG standard (ISO/IEC 10918 or ITU-T T.81) defines 4 Huffman tables that has been developed from the average statistics of a large set of images with 8-bit precision. Using these instead of calculating the optimal Huffman tables for a given image is faster, and is preferred by many hardware encoders and some hardware decoders.

  Even though the JPEG standard doesn't define these as "standard tables" and requires a decoder to be able to read any valid Huffman tables, some are in reality limited decoding images using these "typical" tables. Standards like DCF (Design rule for Camera File system) and DLNA (Digital Living Network Alliance) actually requires any compliant JPEG to use only the "typical" Huffman tables.

  This is also related to the term "optimized" JPEG. An "optimized" JPEG is a JPEG that doesn't use the "typical" Huffman tables.

  Returns:

  Whether or not all the tables in this MetadataExtractor.HuffmanTablesDirectory are the predefined "typical" Huffman tables.

• isOptimized

  public boolean isOptimized()

  The opposite of isTypical().

  Returns:

  Whether or not the tables in this MetadataExtractor.HuffmanTablesDirectory are "optimized" - which means that at least one of them aren't one of the "typical" Huffman tables.