ZlibCompressionOptions

interface ZlibCompressionOptions

• level?: 0 | 2 | 1 | 5 | 3 | 4 | -1 | 6 | 7 | 8 | 9

  The compression level to use. Must be between -1 and 9.

  • -1 uses the default compression level (6)
  • 0 gives no compression
  • 1 gives least compression, fastest speed
  • 9 gives best compression, slowest speed
• library?: 'zlib'
• memLevel?: 2 | 1 | 5 | 3 | 4 | 6 | 7 | 8 | 9

  How much memory to allocate for the internal compression state.

  A value of 1 uses minimum memory but is slow and reduces compression ratio.

  A value of 9 uses maximum memory for optimal speed. The default is 8.

• strategy?: number

  Tunes the compression algorithm.

  • Z_DEFAULT_STRATEGY: For normal data (Default)
  • Z_FILTERED: For data produced by a filter or predictor
  • Z_HUFFMAN_ONLY: Force Huffman encoding only (no string match)
  • Z_RLE: Limit match distances to one (run-length encoding)
  • Z_FIXED prevents the use of dynamic Huffman codes

  Z_RLE is designed to be almost as fast as Z_HUFFMAN_ONLY, but give better compression for PNG image data.

  Z_FILTERED forces more Huffman coding and less string matching; it is somewhat intermediate between Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY. Filtered data consists mostly of small values with a somewhat random distribution.

• windowBits?: 25 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 28 | -9 | -10 | -11 | -12 | -13 | -14 | -15 | 26 | 27 | 29 | 30 | 31

  The base 2 logarithm of the window size (the size of the history buffer).

  Larger values of this parameter result in better compression at the expense of memory usage.

  The following value ranges are supported:

  • 9..15: The output has a zlib header and footer (Deflate)
  • -9..-15: The output does not have a zlib header or footer (Raw Deflate)
  • 25..31 (16+9..15): The output has a gzip header and footer (gzip)

  The gzip header has no file name, no extra data, no comment, no modification time (set to zero) and no header CRC.