Exemplo n.º 1
0
  /**
   * Utility method for decoding an LZW-compressed image strip. Adapted from the TIFF 6.0
   * Specification: http://partners.adobe.com/asn/developer/pdfs/tn/TIFF6.pdf (page 61) Author:
   * Curtis Rueden (ctrueden at wisc.edu)
   */
  public byte[] lzwUncompress(byte[] input) {
    if (input == null || input.length == 0) return input;
    byte[][] symbolTable = new byte[4096][1];
    int bitsToRead = 9;
    int nextSymbol = 258;
    int code;
    int oldCode = -1;
    ByteVector out = new ByteVector(8192);
    BitBuffer bb = new BitBuffer(input);
    byte[] byteBuffer1 = new byte[16];
    byte[] byteBuffer2 = new byte[16];

    while (out.size() < byteCount) {
      code = bb.getBits(bitsToRead);
      if (code == EOI_CODE || code == -1) break;
      if (code == CLEAR_CODE) {
        // initialize symbol table
        for (int i = 0; i < 256; i++) symbolTable[i][0] = (byte) i;
        nextSymbol = 258;
        bitsToRead = 9;
        code = bb.getBits(bitsToRead);
        if (code == EOI_CODE || code == -1) break;
        out.add(symbolTable[code]);
        oldCode = code;
      } else {
        if (code < nextSymbol) {
          // code is in table
          out.add(symbolTable[code]);
          // add string to table
          ByteVector symbol = new ByteVector(byteBuffer1);
          symbol.add(symbolTable[oldCode]);
          symbol.add(symbolTable[code][0]);
          symbolTable[nextSymbol] = symbol.toByteArray(); // **
          oldCode = code;
          nextSymbol++;
        } else {
          // out of table
          ByteVector symbol = new ByteVector(byteBuffer2);
          symbol.add(symbolTable[oldCode]);
          symbol.add(symbolTable[oldCode][0]);
          byte[] outString = symbol.toByteArray();
          out.add(outString);
          symbolTable[nextSymbol] = outString; // **
          oldCode = code;
          nextSymbol++;
        }
        if (nextSymbol == 511) {
          bitsToRead = 10;
        }
        if (nextSymbol == 1023) {
          bitsToRead = 11;
        }
        if (nextSymbol == 2047) {
          bitsToRead = 12;
        }
      }
    }
    return out.toByteArray();
  }
Exemplo n.º 2
0
 /** Based on the Bio-Formats PackbitsCodec written by Melissa Linkert. */
 public byte[] packBitsUncompress(byte[] input, int expected) {
   if (expected == 0) expected = Integer.MAX_VALUE;
   ByteVector output = new ByteVector(1024);
   int index = 0;
   while (output.size() < expected && index < input.length) {
     byte n = input[index++];
     if (n >= 0) { // 0 <= n <= 127
       byte[] b = new byte[n + 1];
       for (int i = 0; i < n + 1; i++) b[i] = input[index++];
       output.add(b);
       b = null;
     } else if (n != -128) { // -127 <= n <= -1
       int len = -n + 1;
       byte inp = input[index++];
       for (int i = 0; i < len; i++) output.add(inp);
     }
   }
   return output.toByteArray();
 }