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//
// 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 1.0.000
*/
/**
* @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 1.0.000
* @author Nicola Asuni - info@tecnick.com
*/
class TCPDF_FILTERS {
/**
Define a list of available filter decoders.
@private
/
private $available_filters = array('ASCIIHexDecode', 'ASCII85Decode', 'LZWDecode', 'FlateDecode', 'RunLengthDecode');
// -----------------------------------------------------------------------------
/**
Get a list of available decoding filters.
@return (array) Array of available filter decoders.
@public
@since 1.0.000 (2011-05-23)
/
public function getAvailableFilters() {
return $this->available_filters;
}
/**
Decode data using the specified filter type.
@param $filter (string) Filter name.
@param $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilter($filter, $data) {
switch ($filter) {
case 'ASCIIHexDecode': {
return $this->decodeFilterASCIIHexDecode($data);
break;
}
case 'ASCII85Decode': {
return $this->decodeFilterASCII85Decode($data);
break;
}
case 'LZWDecode': {
return $this->decodeFilterLZWDecode($data);
break;
}
case 'FlateDecode': {
return $this->decodeFilterFlateDecode($data);
break;
}
case 'RunLengthDecode': {
return $this->decodeFilterRunLengthDecode($data);
break;
}
case 'CCITTFaxDecode': {
return $this->decodeFilterCCITTFaxDecode($data);
break;
}
case 'JBIG2Decode': {
return $this->decodeFilterJBIG2Decode($data);
break;
}
case 'DCTDecode': {
return $this->decodeFilterDCTDecode($data);
break;
}
case 'JPXDecode': {
return $this->decodeFilterJPXDecode($data);
break;
}
case 'Crypt': {
return $this->decodeFilterCrypt($data);
break;
}
default: {
return decodeFilterStandard($data);
break;
}
}
}
// --- FILTERS (PDF 32000-2008 - 7.4 Filters) ------------------------------
/**
Standard
Default decoding filter (leaves data unchanged).
@param $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterStandard($data) {
return $data;
}
/**
ASCIIHexDecode
Decodes data encoded in an ASCII hexadecimal representation, reproducing the original binary data.
@param $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterASCIIHexDecode($data) {
// intialize 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 {
$this->Error('decodeASCIIHex: invalid code');
}
}
// check for invalid characters
if (preg_match('/[^a-fA-F\d]/', $data) > 0) {
$this->Error('decodeASCIIHex: 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 $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterASCII85Decode($data) {
// intialize 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) {
$this->Error('decodeASCII85: 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 {
$this->Error('decodeASCII85: 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: {
$this->Error('decodeASCII85: 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 $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterLZWDecode($data) {
// intialize 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 $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterFlateDecode($data) {
// intialize string to return
$decoded = gzuncompress($data);
if ($decoded === false) {
$this->Error('decodeFlate: invalid code');
}
return $decoded;
}
/**
RunLengthDecode
Decompresses data encoded using a byte-oriented run-length encoding algorithm.
@param $data (string) Data to decode.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterRunLengthDecode($data) {
// intialize 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)
Decompresses data encoded using the CCITT facsimile standard, reproducing the original data (typically monochrome image data at 1 bit per pixel).
@param $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterCCITTFaxDecode($data) {
return $data;
}
/**
JBIG2Decode (NOT IMPLEMETED)
Decompresses data encoded using the JBIG2 standard, reproducing the original monochrome (1 bit per pixel) image data (or an approximation of that data).
@param $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterJBIG2Decode($data) {
return $data;
}
/**
DCTDecode (NOT IMPLEMETED)
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 $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterDCTDecode($data) {
return $data;
}
/**
JPXDecode (NOT IMPLEMETED)
Decompresses data encoded using the wavelet-based JPEG2000 standard, reproducing the original image data.
@param $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterJPXDecode($data) {
return $data;
}
/**
Crypt (NOT IMPLEMETED)
Decrypts data encrypted by a security handler, reproducing the data as it was before encryption.
@param $data (string) Data to decode.
@return Decoded data string.
@public
@since 1.0.000 (2011-05-23)
/
public function decodeFilterCrypt($data) {
return $data;
}
// --- END FILTERS SECTION -------------------------------------------------
/**
This method is automatically called in case of fatal error; it simply outputs the message and halts the execution.
@param $msg (string) The error message
@public
@since 1.0.000 (2011-05-23)
/
public function Error($msg) {
// exit program and print error
die('TCPDF_FILTERS ERROR: '.$msg);
}
} // END OF TCPDF_FILTERS CLASS
//============================================================+
// END OF FILE
//============================================================+