Package org.apache.pdfbox.filter

Class RunLengthDecodeFilter

java.lang.Object
org.apache.pdfbox.filter.RunLengthDecodeFilter
All Implemented Interfaces:
Filter
public class RunLengthDecodeFilter extends Object implements Filter
This is a filter for the RunLength Decoder. From the PDF Reference 
 The RunLengthDecode filter decodes data that has been encoded in a simple
 byte-oriented format based on run length. The encoded data is a sequence of
 runs, where each run consists of a length byte followed by 1 to 128 bytes of data. If
 the length byte is in the range 0 to 127, the following length + 1 (1 to 128) bytes
 are copied literally during decompression. If length is in the range 129 to 255, the
 following single byte is to be copied 257 ? length (2 to 128) times during decompression.
 A length value of 128 denotes EOD.

 The compression achieved by run-length encoding depends on the input data. In
 the best case (all zeros), a compression of approximately 64:1 is achieved for long
 files. The worst case (the hexadecimal sequence 00 alternating with FF) results in
 an expansion of 127:128.
Version:
$Revision: 1.6 $
Author:
Ben Litchfield

  • Constructor Details

    • RunLengthDecodeFilter

      public RunLengthDecodeFilter()
      Constructor.

  • Method Details

    • decode

      public void decode(InputStream compressedData, OutputStream result, COSDictionary options, int filterIndex) throws IOException
      This will decode some compressed data.
      Specified by:
      decode in interface Filter
      Parameters:
      compressedData - The compressed byte stream.
      result - The place to write the uncompressed byte stream.
      options - The options to use to encode the data.
      filterIndex - The index to the filter being decoded.
      Throws:
      IOException - If there is an error decompressing the stream.

    • encode

      public void encode(InputStream rawData, OutputStream result, COSDictionary options, int filterIndex) throws IOException
      This will encode some data.
      Specified by:
      encode in interface Filter
      Parameters:
      rawData - The raw data to encode.
      result - The place to write to encoded results to.
      options - The options to use to encode the data.
      filterIndex - The index to the filter being encoded.
      Throws:
      IOException - If there is an error compressing the stream.