/**
* Returns a subset of the TrueType font data without the unused glyphs.
* @param $font (string) TrueType font data.
* @param $subsetchars (array) Array of used characters (the glyphs to keep).
* @return (string) A subset of TrueType font data without the unused glyphs.
* @author Nicola Asuni
* @since 5.2.000 (2010-06-02)
* @public static
*/
public static function _getTrueTypeFontSubset($font, $subsetchars)
{
ksort($subsetchars);
$offset = 0;
// offset position of the font data
if (TcpdfStatic::_getULONG($font, $offset) != 0x10000) {
// sfnt version must be 0x00010000 for TrueType version 1.0.
return $font;
}
$offset += 4;
// get number of tables
$numTables = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
// skip searchRange, entrySelector and rangeShift
$offset += 6;
// tables array
$table = array();
// for each table
for ($i = 0; $i < $numTables; ++$i) {
// get table info
$tag = substr($font, $offset, 4);
$offset += 4;
$table[$tag] = array();
$table[$tag]['checkSum'] = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
$table[$tag]['offset'] = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
$table[$tag]['length'] = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
}
// check magicNumber
$offset = $table['head']['offset'] + 12;
if (TcpdfStatic::_getULONG($font, $offset) != 0x5f0f3cf5) {
// magicNumber must be 0x5F0F3CF5
return $font;
}
$offset += 4;
// get offset mode (indexToLocFormat : 0 = short, 1 = long)
$offset = $table['head']['offset'] + 50;
$short_offset = TcpdfStatic::_getSHORT($font, $offset) == 0;
$offset += 2;
// get the offsets to the locations of the glyphs in the font, relative to the beginning of the glyphData table
$indexToLoc = array();
$offset = $table['loca']['offset'];
if ($short_offset) {
// short version
$tot_num_glyphs = floor($table['loca']['length'] / 2);
// numGlyphs + 1
for ($i = 0; $i < $tot_num_glyphs; ++$i) {
$indexToLoc[$i] = TcpdfStatic::_getUSHORT($font, $offset) * 2;
$offset += 2;
}
} else {
// long version
$tot_num_glyphs = $table['loca']['length'] / 4;
// numGlyphs + 1
for ($i = 0; $i < $tot_num_glyphs; ++$i) {
$indexToLoc[$i] = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
}
}
// get glyphs indexes of chars from cmap table
$subsetglyphs = array();
// glyph IDs on key
$subsetglyphs[0] = true;
// character codes that do not correspond to any glyph in the font should be mapped to glyph index 0
$offset = $table['cmap']['offset'] + 2;
$numEncodingTables = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
$encodingTables = array();
for ($i = 0; $i < $numEncodingTables; ++$i) {
$encodingTables[$i]['platformID'] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
$encodingTables[$i]['encodingID'] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
$encodingTables[$i]['offset'] = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
}
foreach ($encodingTables as $enctable) {
// get all platforms and encodings
$offset = $table['cmap']['offset'] + $enctable['offset'];
$format = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
switch ($format) {
case 0:
// Format 0: Byte encoding table
$offset += 4;
// skip length and version/language
for ($c = 0; $c < 256; ++$c) {
if (isset($subsetchars[$c])) {
$g = TcpdfStatic::_getBYTE($font, $offset);
$subsetglyphs[$g] = true;
}
++$offset;
}
break;
case 2:
// Format 2: High-byte mapping through table
$offset += 4;
// skip length and version/language
$numSubHeaders = 0;
for ($i = 0; $i < 256; ++$i) {
// Array that maps high bytes to subHeaders: value is subHeader index * 8.
$subHeaderKeys[$i] = TcpdfStatic::_getUSHORT($font, $offset) / 8;
$offset += 2;
if ($numSubHeaders < $subHeaderKeys[$i]) {
$numSubHeaders = $subHeaderKeys[$i];
}
}
// the number of subHeaders is equal to the max of subHeaderKeys + 1
++$numSubHeaders;
// read subHeader structures
$subHeaders = array();
$numGlyphIndexArray = 0;
for ($k = 0; $k < $numSubHeaders; ++$k) {
$subHeaders[$k]['firstCode'] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
$subHeaders[$k]['entryCount'] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
$subHeaders[$k]['idDelta'] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
$subHeaders[$k]['idRangeOffset'] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
$subHeaders[$k]['idRangeOffset'] -= 2 + ($numSubHeaders - $k - 1) * 8;
$subHeaders[$k]['idRangeOffset'] /= 2;
$numGlyphIndexArray += $subHeaders[$k]['entryCount'];
}
for ($k = 0; $k < $numGlyphIndexArray; ++$k) {
$glyphIndexArray[$k] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
}
for ($i = 0; $i < 256; ++$i) {
$k = $subHeaderKeys[$i];
if ($k == 0) {
// one byte code
$c = $i;
if (isset($subsetchars[$c])) {
$g = $glyphIndexArray[0];
$subsetglyphs[$g] = true;
}
} else {
// two bytes code
$start_byte = $subHeaders[$k]['firstCode'];
$end_byte = $start_byte + $subHeaders[$k]['entryCount'];
for ($j = $start_byte; $j < $end_byte; ++$j) {
// combine high and low bytes
$c = ($i << 8) + $j;
if (isset($subsetchars[$c])) {
$idRangeOffset = $subHeaders[$k]['idRangeOffset'] + $j - $subHeaders[$k]['firstCode'];
$g = ($glyphIndexArray[$idRangeOffset] + $idDelta[$k]) % 65536;
if ($g < 0) {
$g = 0;
}
$subsetglyphs[$g] = true;
}
}
}
}
break;
case 4:
// Format 4: Segment mapping to delta values
$length = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
$offset += 2;
// skip version/language
$segCount = floor(TcpdfStatic::_getUSHORT($font, $offset) / 2);
$offset += 2;
$offset += 6;
// skip searchRange, entrySelector, rangeShift
$endCount = array();
// array of end character codes for each segment
for ($k = 0; $k < $segCount; ++$k) {
$endCount[$k] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
}
$offset += 2;
// skip reservedPad
$startCount = array();
// array of start character codes for each segment
for ($k = 0; $k < $segCount; ++$k) {
$startCount[$k] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
}
$idDelta = array();
// delta for all character codes in segment
for ($k = 0; $k < $segCount; ++$k) {
$idDelta[$k] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
}
$idRangeOffset = array();
// Offsets into glyphIdArray or 0
for ($k = 0; $k < $segCount; ++$k) {
$idRangeOffset[$k] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
}
$gidlen = floor($length / 2) - 8 - 4 * $segCount;
$glyphIdArray = array();
// glyph index array
for ($k = 0; $k < $gidlen; ++$k) {
$glyphIdArray[$k] = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
}
for ($k = 0; $k < $segCount; ++$k) {
for ($c = $startCount[$k]; $c <= $endCount[$k]; ++$c) {
if (isset($subsetchars[$c])) {
if ($idRangeOffset[$k] == 0) {
$g = ($idDelta[$k] + $c) % 65536;
} else {
$gid = floor($idRangeOffset[$k] / 2) + ($c - $startCount[$k]) - ($segCount - $k);
$g = ($glyphIdArray[$gid] + $idDelta[$k]) % 65536;
}
if ($g < 0) {
$g = 0;
}
$subsetglyphs[$g] = true;
}
}
}
break;
case 6:
// Format 6: Trimmed table mapping
$offset += 4;
// skip length and version/language
$firstCode = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
$entryCount = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
for ($k = 0; $k < $entryCount; ++$k) {
$c = $k + $firstCode;
if (isset($subsetchars[$c])) {
$g = TcpdfStatic::_getUSHORT($font, $offset);
$subsetglyphs[$g] = true;
}
$offset += 2;
}
break;
case 8:
// Format 8: Mixed 16-bit and 32-bit coverage
$offset += 10;
// skip reserved, length and version/language
for ($k = 0; $k < 8192; ++$k) {
$is32[$k] = TcpdfStatic::_getBYTE($font, $offset);
++$offset;
}
$nGroups = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
for ($i = 0; $i < $nGroups; ++$i) {
$startCharCode = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
$endCharCode = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
$startGlyphID = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
for ($k = $startCharCode; $k <= $endCharCode; ++$k) {
$is32idx = floor($c / 8);
if (isset($is32[$is32idx]) and ($is32[$is32idx] & 1 << 7 - $c % 8) == 0) {
$c = $k;
} else {
// 32 bit format
// convert to decimal (http://www.unicode.org/faq//utf_bom.html#utf16-4)
//LEAD_OFFSET = (0xD800 - (0x10000 >> 10)) = 55232
//SURROGATE_OFFSET = (0x10000 - (0xD800 << 10) - 0xDC00) = -56613888
$c = (55232 + ($k >> 10) << 10) + (0xdc00 + ($k & 0x3ff)) - 56613888;
}
if (isset($subsetchars[$c])) {
$subsetglyphs[$startGlyphID] = true;
}
++$startGlyphID;
}
}
break;
case 10:
// Format 10: Trimmed array
$offset += 10;
// skip reserved, length and version/language
$startCharCode = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
$numChars = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
for ($k = 0; $k < $numChars; ++$k) {
$c = $k + $startCharCode;
if (isset($subsetchars[$c])) {
$g = TcpdfStatic::_getUSHORT($font, $offset);
$subsetglyphs[$g] = true;
}
$offset += 2;
}
break;
case 12:
// Format 12: Segmented coverage
$offset += 10;
// skip length and version/language
$nGroups = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
for ($k = 0; $k < $nGroups; ++$k) {
$startCharCode = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
$endCharCode = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
$startGlyphCode = TcpdfStatic::_getULONG($font, $offset);
$offset += 4;
for ($c = $startCharCode; $c <= $endCharCode; ++$c) {
if (isset($subsetchars[$c])) {
$subsetglyphs[$startGlyphCode] = true;
}
++$startGlyphCode;
}
}
break;
case 13:
// Format 13: Many-to-one range mappings
// to be implemented ...
break;
case 14:
// Format 14: Unicode Variation Sequences
// to be implemented ...
break;
}
}
// include all parts of composite glyphs
$new_sga = $subsetglyphs;
while (!empty($new_sga)) {
$sga = $new_sga;
$new_sga = array();
foreach ($sga as $key => $val) {
if (isset($indexToLoc[$key])) {
$offset = $table['glyf']['offset'] + $indexToLoc[$key];
$numberOfContours = TcpdfStatic::_getSHORT($font, $offset);
$offset += 2;
if ($numberOfContours < 0) {
// composite glyph
$offset += 8;
// skip xMin, yMin, xMax, yMax
do {
$flags = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
$glyphIndex = TcpdfStatic::_getUSHORT($font, $offset);
$offset += 2;
if (!isset($subsetglyphs[$glyphIndex])) {
// add missing glyphs
$new_sga[$glyphIndex] = true;
}
// skip some bytes by case
if ($flags & 1) {
$offset += 4;
} else {
$offset += 2;
}
if ($flags & 8) {
$offset += 2;
} elseif ($flags & 64) {
$offset += 4;
} elseif ($flags & 128) {
$offset += 8;
}
} while ($flags & 32);
}
}
}
$subsetglyphs += $new_sga;
}
// sort glyphs by key (and remove duplicates)
ksort($subsetglyphs);
// build new glyf and loca tables
$glyf = '';
$loca = '';
$offset = 0;
$glyf_offset = $table['glyf']['offset'];
for ($i = 0; $i < $tot_num_glyphs; ++$i) {
if (isset($subsetglyphs[$i])) {
$length = $indexToLoc[$i + 1] - $indexToLoc[$i];
$glyf .= substr($font, $glyf_offset + $indexToLoc[$i], $length);
} else {
$length = 0;
}
if ($short_offset) {
$loca .= pack('n', floor($offset / 2));
} else {
$loca .= pack('N', $offset);
}
$offset += $length;
}
// array of table names to preserve (loca and glyf tables will be added later)
// the cmap table is not needed and shall not be present, since the mapping from character codes to glyph descriptions is provided separately
$table_names = array('head', 'hhea', 'hmtx', 'maxp', 'cvt ', 'fpgm', 'prep');
// minimum required table names
// get the tables to preserve
$offset = 12;
foreach ($table as $tag => $val) {
if (in_array($tag, $table_names)) {
$table[$tag]['data'] = substr($font, $table[$tag]['offset'], $table[$tag]['length']);
if ($tag == 'head') {
// set the checkSumAdjustment to 0
$table[$tag]['data'] = substr($table[$tag]['data'], 0, 8) . "" . substr($table[$tag]['data'], 12);
}
$pad = 4 - $table[$tag]['length'] % 4;
if ($pad != 4) {
// the length of a table must be a multiple of four bytes
$table[$tag]['length'] += $pad;
$table[$tag]['data'] .= str_repeat("", $pad);
}
$table[$tag]['offset'] = $offset;
$offset += $table[$tag]['length'];
// check sum is not changed (so keep the following line commented)
//$table[$tag]['checkSum'] = self::_getTTFtableChecksum($table[$tag]['data'], $table[$tag]['length']);
} else {
unset($table[$tag]);
}
}
// add loca
$table['loca']['data'] = $loca;
$table['loca']['length'] = strlen($loca);
$pad = 4 - $table['loca']['length'] % 4;
if ($pad != 4) {
// the length of a table must be a multiple of four bytes
$table['loca']['length'] += $pad;
$table['loca']['data'] .= str_repeat("", $pad);
}
$table['loca']['offset'] = $offset;
$table['loca']['checkSum'] = self::_getTTFtableChecksum($table['loca']['data'], $table['loca']['length']);
$offset += $table['loca']['length'];
// add glyf
$table['glyf']['data'] = $glyf;
$table['glyf']['length'] = strlen($glyf);
$pad = 4 - $table['glyf']['length'] % 4;
if ($pad != 4) {
// the length of a table must be a multiple of four bytes
$table['glyf']['length'] += $pad;
$table['glyf']['data'] .= str_repeat("", $pad);
}
$table['glyf']['offset'] = $offset;
$table['glyf']['checkSum'] = self::_getTTFtableChecksum($table['glyf']['data'], $table['glyf']['length']);
// rebuild font
$font = '';
$font .= pack('N', 0x10000);
// sfnt version
$numTables = count($table);
$font .= pack('n', $numTables);
// numTables
$entrySelector = floor(log($numTables, 2));
$searchRange = pow(2, $entrySelector) * 16;
$rangeShift = $numTables * 16 - $searchRange;
$font .= pack('n', $searchRange);
// searchRange
$font .= pack('n', $entrySelector);
// entrySelector
$font .= pack('n', $rangeShift);
// rangeShift
$offset = $numTables * 16;
foreach ($table as $tag => $data) {
$font .= $tag;
// tag
$font .= pack('N', $data['checkSum']);
// checkSum
$font .= pack('N', $data['offset'] + $offset);
// offset
$font .= pack('N', $data['length']);
// length
}
foreach ($table as $data) {
$font .= $data['data'];
}
// set checkSumAdjustment on head table
$checkSumAdjustment = 0xb1b0afba - self::_getTTFtableChecksum($font, strlen($font));
$font = substr($font, 0, $table['head']['offset'] + 8) . pack('N', $checkSumAdjustment) . substr($font, $table['head']['offset'] + 12);
return $font;
}
