Class HuffmanTablesDirectory.HuffmanTable

  • Enclosing class:

    public static class HuffmanTablesDirectory.HuffmanTable
    extends Object
    An instance of this class holds a JPEG Huffman table.
    • Method Detail

      • getTableLength

        public int getTableLength()
        The table length in bytes.
      • getTableDestinationId

        public int getTableDestinationId()
        the the destination identifier for this table.
      • getLengthBytes

        public byte[] getLengthBytes()
        A byte array with the L values for this table.
      • getValueBytes

        public byte[] getValueBytes()
        A byte array with the V values for this table.
      • isTypical

        public boolean isTypical()
        Evaluates whether this table is a "typical" Huffman table.

        "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.

        Whether or not this table is one of the predefined "typical" Huffman tables.
      • isOptimized

        public boolean isOptimized()
        The opposite of isTypical().
        Whether or not this table is "optimized" - which means that it isn't one of the "typical" Huffman tables.