tc-lib-pdf-filter

Decoder library for standard PDF stream filters.

💖 Part of the tc-lib-pdf / TCPDF ecosystem (100M+ installs). Sponsor its maintenance →

tc-lib-pdf-filter decodes the stream filters defined by the PDF specification (PDF 32000-1:2008 §7.4), one at a time or as a chain, with the DecodeParms of each filter.

• FlateDecode, LZWDecode, RunLengthDecode
• ASCIIHexDecode, ASCII85Decode
• CCITTFaxDecode, DCTDecode, JPXDecode, JBIG2Decode
• Crypt (Identity and None)

• Decode one filter, or a chain of filters applied in order
• DecodeParms as a single dictionary or as an array parallel to Filter
• Predictor (TIFF and PNG) for FlateDecode and LZWDecode
• Filter names as the full name, the inline-image abbreviation, or a FilterType enum case
• A single exception class for unknown filters and malformed streams

• PHP 8.2 or later
• Extensions: zlib, pcre
• Composer

Optional:

• Extension imagick: required by CCITTFaxDecode and JPXDecode
• CLI tool jbig2dec: required by JBIG2Decode

Without them those three filters throw; the others are unaffected.

DecodeParms entries are passed to decode() and decodeAll() as an array. Beyond the parameters defined by the PDF specification, three filters accept one more:

FlateDecode reaches compression ratios above 1000:1, so callers decoding untrusted documents should set MaxOutputSize to bound decompression bombs.

CCITTFaxDecode derives the image height from Rows. When Rows is absent the height is estimated from the encoded length, which under-estimates it and truncates the image, so pass Rows (the image dictionary /Height).

composer require tecnickcom/tc-lib-pdf-filter

<?php

require_once __DIR__ . '/vendor/autoload.php';

$filter = new \Com\Tecnick\Pdf\Filter\Filter();
$decoded = $filter->decodeAll(['ASCIIHexDecode', 'FlateDecode'], $data);

make deps
make help
make qa

make rpm
make deb

For system packages, bootstrap with:

require_once '/usr/share/php/Com/Tecnick/Pdf/Filter/autoload.php';

Contributions are welcome. Please review CONTRIBUTING.md, CODE_OF_CONDUCT.md, and SECURITY.md.