. // // See LICENSE.TXT file for more information. // ------------------------------------------------------------------- // // Description : This is a PHP class for decoding common PDF filters (PDF 32000-2008 - 7.4 Filters). // //============================================================+ /** * @file * This is a PHP class for decoding common PDF filters (PDF 32000-2008 - 7.4 Filters).
* @package com.tecnick.tcpdf * @author Nicola Asuni * @version 1.0.001 */ /** * @class TCPDF_FILTERS * This is a PHP class for decoding common PDF filters (PDF 32000-2008 - 7.4 Filters).
* @package com.tecnick.tcpdf * @brief This is a PHP class for decoding common PDF filters. * @version 1.0.001 * @author Nicola Asuni - info@tecnick.com */ class TCPDF_FILTERS { /** * Define a list of available filter decoders. * @private static */ private static $available_filters = array('ASCIIHexDecode', 'ASCII85Decode', 'LZWDecode', 'FlateDecode', 'RunLengthDecode'); // ----------------------------------------------------------------------------- /** * Get a list of available decoding filters. * @return array Array of available filter decoders. * @since 1.0.000 (2011-05-23) * @public static */ public static function getAvailableFilters() { return self::$available_filters; } /** * Decode data using the specified filter type. * @param string $filter Filter name. * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilter($filter, $data) { switch ($filter) { case 'ASCIIHexDecode': { return self::decodeFilterASCIIHexDecode($data); break; } case 'ASCII85Decode': { return self::decodeFilterASCII85Decode($data); break; } case 'LZWDecode': { return self::decodeFilterLZWDecode($data); break; } case 'FlateDecode': { return self::decodeFilterFlateDecode($data); break; } case 'RunLengthDecode': { return self::decodeFilterRunLengthDecode($data); break; } case 'CCITTFaxDecode': { return self::decodeFilterCCITTFaxDecode($data); break; } case 'JBIG2Decode': { return self::decodeFilterJBIG2Decode($data); break; } case 'DCTDecode': { return self::decodeFilterDCTDecode($data); break; } case 'JPXDecode': { return self::decodeFilterJPXDecode($data); break; } case 'Crypt': { return self::decodeFilterCrypt($data); break; } default: { return self::decodeFilterStandard($data); break; } } } // --- FILTERS (PDF 32000-2008 - 7.4 Filters) ------------------------------ /** * Standard * Default decoding filter (leaves data unchanged). * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterStandard($data) { return $data; } /** * ASCIIHexDecode * Decodes data encoded in an ASCII hexadecimal representation, reproducing the original binary data. * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterASCIIHexDecode($data) { // initialize string to return $decoded = ''; // all white-space characters shall be ignored $data = preg_replace('/[\s]/', '', $data); // check for EOD character: GREATER-THAN SIGN (3Eh) $eod = strpos($data, '>'); if ($eod !== false) { // remove EOD and extra data (if any) $data = substr($data, 0, $eod); $eod = true; } // get data length $data_length = strlen($data); if (($data_length % 2) != 0) { // odd number of hexadecimal digits if ($eod) { // EOD shall behave as if a 0 (zero) followed the last digit $data = substr($data, 0, -1).'0'.substr($data, -1); } else { self::Error('decodeFilterASCIIHexDecode: invalid code'); } } // check for invalid characters if (preg_match('/[^a-fA-F\d]/', $data) > 0) { self::Error('decodeFilterASCIIHexDecode: invalid code'); } // get one byte of binary data for each pair of ASCII hexadecimal digits $decoded = pack('H*', $data); return $decoded; } /** * ASCII85Decode * Decodes data encoded in an ASCII base-85 representation, reproducing the original binary data. * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterASCII85Decode($data) { // initialize string to return $decoded = ''; // all white-space characters shall be ignored $data = preg_replace('/[\s]/', '', $data); // remove start sequence 2-character sequence <~ (3Ch)(7Eh) if (strpos($data, '<~') !== false) { // remove EOD and extra data (if any) $data = substr($data, 2); } // check for EOD: 2-character sequence ~> (7Eh)(3Eh) $eod = strpos($data, '~>'); if ($eod !== false) { // remove EOD and extra data (if any) $data = substr($data, 0, $eod); } // data length $data_length = strlen($data); // check for invalid characters if (preg_match('/[^\x21-\x75,\x74]/', $data) > 0) { self::Error('decodeFilterASCII85Decode: invalid code'); } // z sequence $zseq = chr(0).chr(0).chr(0).chr(0); // position inside a group of 4 bytes (0-3) $group_pos = 0; $tuple = 0; $pow85 = array((85*85*85*85), (85*85*85), (85*85), 85, 1); $last_pos = ($data_length - 1); // for each byte for ($i = 0; $i < $data_length; ++$i) { // get char value $char = ord($data[$i]); if ($char == 122) { // 'z' if ($group_pos == 0) { $decoded .= $zseq; } else { self::Error('decodeFilterASCII85Decode: invalid code'); } } else { // the value represented by a group of 5 characters should never be greater than 2^32 - 1 $tuple += (($char - 33) * $pow85[$group_pos]); if ($group_pos == 4) { $decoded .= chr($tuple >> 24).chr($tuple >> 16).chr($tuple >> 8).chr($tuple); $tuple = 0; $group_pos = 0; } else { ++$group_pos; } } } if ($group_pos > 1) { $tuple += $pow85[($group_pos - 1)]; } // last tuple (if any) switch ($group_pos) { case 4: { $decoded .= chr($tuple >> 24).chr($tuple >> 16).chr($tuple >> 8); break; } case 3: { $decoded .= chr($tuple >> 24).chr($tuple >> 16); break; } case 2: { $decoded .= chr($tuple >> 24); break; } case 1: { self::Error('decodeFilterASCII85Decode: invalid code'); break; } } return $decoded; } /** * LZWDecode * Decompresses data encoded using the LZW (Lempel-Ziv-Welch) adaptive compression method, reproducing the original text or binary data. * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterLZWDecode($data) { // initialize string to return $decoded = ''; // data length $data_length = strlen($data); // convert string to binary string $bitstring = ''; for ($i = 0; $i < $data_length; ++$i) { $bitstring .= sprintf('%08b', ord($data[$i])); } // get the number of bits $data_length = strlen($bitstring); // initialize code length in bits $bitlen = 9; // initialize dictionary index $dix = 258; // initialize the dictionary (with the first 256 entries). $dictionary = array(); for ($i = 0; $i < 256; ++$i) { $dictionary[$i] = chr($i); } // previous val $prev_index = 0; // while we encounter EOD marker (257), read code_length bits while (($data_length > 0) AND (($index = bindec(substr($bitstring, 0, $bitlen))) != 257)) { // remove read bits from string $bitstring = substr($bitstring, $bitlen); // update number of bits $data_length -= $bitlen; if ($index == 256) { // clear-table marker // reset code length in bits $bitlen = 9; // reset dictionary index $dix = 258; $prev_index = 256; // reset the dictionary (with the first 256 entries). $dictionary = array(); for ($i = 0; $i < 256; ++$i) { $dictionary[$i] = chr($i); } } elseif ($prev_index == 256) { // first entry $decoded .= $dictionary[$index]; $prev_index = $index; } else { // check if index exist in the dictionary if ($index < $dix) { // index exist on dictionary $decoded .= $dictionary[$index]; $dic_val = $dictionary[$prev_index].$dictionary[$index][0]; // store current index $prev_index = $index; } else { // index do not exist on dictionary $dic_val = $dictionary[$prev_index].$dictionary[$prev_index][0]; $decoded .= $dic_val; } // update dictionary $dictionary[$dix] = $dic_val; ++$dix; // change bit length by case if ($dix == 2047) { $bitlen = 12; } elseif ($dix == 1023) { $bitlen = 11; } elseif ($dix == 511) { $bitlen = 10; } } } return $decoded; } /** * FlateDecode * Decompresses data encoded using the zlib/deflate compression method, reproducing the original text or binary data. * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterFlateDecode($data) { // initialize string to return $decoded = @gzuncompress($data); if ($decoded === false) { self::Error('decodeFilterFlateDecode: invalid code'); } return $decoded; } /** * RunLengthDecode * Decompresses data encoded using a byte-oriented run-length encoding algorithm. * @param string $data Data to decode. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterRunLengthDecode($data) { // initialize string to return $decoded = ''; // data length $data_length = strlen($data); $i = 0; while($i < $data_length) { // get current byte value $byte = ord($data[$i]); if ($byte == 128) { // a length value of 128 denote EOD break; } elseif ($byte < 128) { // if the length byte is in the range 0 to 127 // the following length + 1 (1 to 128) bytes shall be copied literally during decompression $decoded .= substr($data, ($i + 1), ($byte + 1)); // move to next block $i += ($byte + 2); } else { // if length is in the range 129 to 255, // the following single byte shall be copied 257 - length (2 to 128) times during decompression $decoded .= str_repeat($data[($i + 1)], (257 - $byte)); // move to next block $i += 2; } } return $decoded; } /** * CCITTFaxDecode (NOT IMPLEMETED - RETURN AN EXCEPTION) * Decompresses data encoded using the CCITT facsimile standard, reproducing the original data (typically monochrome image data at 1 bit per pixel). * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterCCITTFaxDecode($data) { self::Error('~decodeFilterCCITTFaxDecode: this method has not been yet implemented'); //return $data; } /** * JBIG2Decode (NOT IMPLEMETED - RETURN AN EXCEPTION) * Decompresses data encoded using the JBIG2 standard, reproducing the original monochrome (1 bit per pixel) image data (or an approximation of that data). * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterJBIG2Decode($data) { self::Error('~decodeFilterJBIG2Decode: this method has not been yet implemented'); //return $data; } /** * DCTDecode (NOT IMPLEMETED - RETURN AN EXCEPTION) * Decompresses data encoded using a DCT (discrete cosine transform) technique based on the JPEG standard, reproducing image sample data that approximates the original data. * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterDCTDecode($data) { self::Error('~decodeFilterDCTDecode: this method has not been yet implemented'); //return $data; } /** * JPXDecode (NOT IMPLEMETED - RETURN AN EXCEPTION) * Decompresses data encoded using the wavelet-based JPEG2000 standard, reproducing the original image data. * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterJPXDecode($data) { self::Error('~decodeFilterJPXDecode: this method has not been yet implemented'); //return $data; } /** * Crypt (NOT IMPLEMETED - RETURN AN EXCEPTION) * Decrypts data encrypted by a security handler, reproducing the data as it was before encryption. * @param string $data Data to decode. * @return string Decoded data string. * @since 1.0.000 (2011-05-23) * @public static */ public static function decodeFilterCrypt($data) { self::Error('~decodeFilterCrypt: this method has not been yet implemented'); //return $data; } // --- END FILTERS SECTION ------------------------------------------------- /** * Throw an exception. * @param string $msg The error message * @since 1.0.000 (2011-05-23) * @public static */ public static function Error($msg) { throw new Exception('TCPDF_PARSER ERROR: '.$msg); } } // END OF TCPDF_FILTERS CLASS //============================================================+ // END OF FILE //============================================================+