LzwFilter
in package
implements
FilterInterface
FinalYes
LZW filter — decode/encode per ISO 32000-2 §7.4.4.2.
PDF LZW uses MSB-first bit packing, variable code widths from 9 to 12 bits, clear code = 256, EOD code = 257.
The "early change" convention is used: code width increases immediately after the entry that causes nextCode to reach 2^codeSize, so the NEXT code read/written uses the wider width.
Table of Contents
Interfaces
- FilterInterface
- Symmetric encode/decode contract for PDF stream filters (ISO 32000-2 §7.4).
Methods
- __construct() : mixed
- decode() : string
- encode() : string
Methods
__construct()
public
__construct([int $earlyChange = 1 ]) : mixed
Parameters
- $earlyChange : int = 1
-
When 1 (default), code-size transition uses "early change" convention per PDF spec. When 0, the transition happens one code later.
decode()
public
decode(string $data) : string
Parameters
- $data : string
Return values
stringencode()
public
encode(string $data) : string
Parameters
- $data : string