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Add support for CID-keyed fonts.
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This adds support for the special CID processing, indicated by the ROS
operator.

This is almost entirely based on the work by @tshinnic.
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@fdb
fdb committed Apr 25, 2017
1 parent 2b8c07a commit 106039d
Showing 1 changed file with 188 additions and 32 deletions.
220 changes: 188 additions & 32 deletions src/tables/cff.js
100644 → 100755
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,21 @@ function equals(a, b) {
}
}

// Subroutines are encoded using the negative half of the number space.
// See type 2 chapter 4.7 "Subroutine operators".
function calcCFFSubroutineBias(subrs) {
var bias;
if (subrs.length < 1240) {
bias = 107;
} else if (subrs.length < 33900) {
bias = 1131;
} else {
bias = 32768;
}

return bias;
}

// Parse a `CFF` INDEX array.
// An index array consists of a list of offsets, then a list of objects at those offsets.
function parseCFFIndex(data, start, conversionFn) {
Expand Down Expand Up @@ -208,21 +223,38 @@ function getCFFString(strings, index) {
// This function takes `meta` which is a list of objects containing `operand`, `name` and `default`.
function interpretDict(dict, meta, strings) {
var newDict = {};
var value;

// Because we also want to include missing values, we start out from the meta list
// and lookup values in the dict.
for (var i = 0; i < meta.length; i += 1) {
var m = meta[i];
var value = dict[m.op];
if (value === undefined) {
value = m.value !== undefined ? m.value : null;
}

if (m.type === 'SID') {
value = getCFFString(strings, value);
}
if (Array.isArray(m.type)) {
var values = [];
values.length = m.type.length;
for (var j = 0; j < m.type.length; j++) {
value = dict[m.op] !== undefined ? dict[m.op][j] : undefined;
if (value === undefined) {
value = m.value !== undefined && m.value[j] !== undefined ? m.value[j] : null;
}
if (m.type[j] === 'SID') {
value = getCFFString(strings, value);
}
values[j] = value;
}
newDict[m.name] = values;
} else {
value = dict[m.op];
if (value === undefined) {
value = m.value !== undefined ? m.value : null;
}

newDict[m.name] = value;
if (m.type === 'SID') {
value = getCFFString(strings, value);
}
newDict[m.name] = value;
}
}

return newDict;
Expand Down Expand Up @@ -261,7 +293,16 @@ var TOP_DICT_META = [
{name: 'charset', op: 15, type: 'offset', value: 0},
{name: 'encoding', op: 16, type: 'offset', value: 0},
{name: 'charStrings', op: 17, type: 'offset', value: 0},
{name: 'private', op: 18, type: ['number', 'offset'], value: [0, 0]}
{name: 'private', op: 18, type: ['number', 'offset'], value: [0, 0]},
{name: 'ros', op: 1230, type: ['SID', 'SID', 'number']},
{name: 'cidFontVersion', op: 1231, type: 'number', value: 0},
{name: 'cidFontRevision', op: 1232, type: 'number', value: 0},
{name: 'cidFontType', op: 1233, type: 'number', value: 0},
{name: 'cidCount', op: 1234, type: 'number', value: 8720},
{name: 'uidBase', op: 1235, type: 'number'},
{name: 'fdArray', op: 1236, type: 'offset'},
{name: 'fdSelect', op: 1237, type: 'offset'},
{name: 'fontName', op: 1238, type: 'SID'}
];

var PRIVATE_DICT_META = [
Expand All @@ -283,6 +324,47 @@ function parseCFFPrivateDict(data, start, size, strings) {
return interpretDict(dict, PRIVATE_DICT_META, strings);
}

// Returns a list of "Top DICT"s found using an INDEX list.
// Used to read both the usual high-level Top DICTs and also the FDArray
// discovered inside CID-keyed fonts. When a Top DICT has a reference to
// a Private DICT that is read and saved into the Top DICT.
//
// In addition to the expected/optional values as outlined in TOP_DICT_META
// the following values might be saved into the Top DICT.
//
// _subrs [] array of local CFF subroutines from Private DICT
// _subrsBias bias value computed from number of subroutines
// (see calcCFFSubroutineBias() and parseCFFCharstring())
// _defaultWidthX default widths for CFF characters
// _nominalWidthX bias added to width embedded within glyph description
//
// _privateDict saved copy of parsed Private DICT from Top DICT
function gatherCFFTopDicts(data, start, cffIndex, strings) {
var topDictArray = [];
for (var iTopDict = 0; iTopDict < cffIndex.length; iTopDict += 1) {
var topDictData = new DataView(new Uint8Array(cffIndex[iTopDict]).buffer);
var topDict = parseCFFTopDict(topDictData, strings);
topDict._subrs = [];
topDict._subrsBias = 0;
var privateSize = topDict.private[0];
var privateOffset = topDict.private[1];
if (privateSize !== 0 && privateOffset !== 0) {
var privateDict = parseCFFPrivateDict(data, privateOffset + start, privateSize, strings);
topDict._defaultWidthX = privateDict.defaultWidthX;
topDict._nominalWidthX = privateDict.nominalWidthX;
if (privateDict.subrs !== 0) {
var subrOffset = privateOffset + privateDict.subrs;
var subrIndex = parseCFFIndex(data, subrOffset + start);
topDict._subrs = subrIndex.objects;
topDict._subrsBias = calcCFFSubroutineBias(topDict._subrs);
}
topDict._privateDict = privateDict;
}
topDictArray.push(topDict);
}
return topDictArray;
}

// Parse the CFF charset table, which contains internal names for all the glyphs.
// This function will return a list of glyph names.
// See Adobe TN #5176 chapter 13, "Charsets".
Expand Down Expand Up @@ -371,10 +453,27 @@ function parseCFFCharstring(font, glyph, code) {
var stack = [];
var nStems = 0;
var haveWidth = false;
var width = font.defaultWidthX;
var open = false;
var x = 0;
var y = 0;
var subrs;
var subrsBias;
var defaultWidthX;
var nominalWidthX;
if (font.isCIDFont) {
var fdIndex = font.tables.cff.topDict._fdSelect[glyph.index];
var fdDict = font.tables.cff.topDict._fdArray[fdIndex];
subrs = fdDict._subrs;
subrsBias = fdDict._subrsBias;
defaultWidthX = fdDict._defaultWidthX;
nominalWidthX = fdDict._nominalWidthX;
} else {
subrs = font.tables.cff.topDict._subrs;
subrsBias = font.tables.cff.topDict._subrsBias;
defaultWidthX = font.tables.cff.topDict._defaultWidthX;
nominalWidthX = font.tables.cff.topDict._nominalWidthX;
}
var width = defaultWidthX;

function newContour(x, y) {
if (open) {
Expand All @@ -392,7 +491,7 @@ function parseCFFCharstring(font, glyph, code) {
// If the value is uneven, that means a width is specified.
hasWidthArg = stack.length % 2 !== 0;
if (hasWidthArg && !haveWidth) {
width = stack.shift() + font.nominalWidthX;
width = stack.shift() + nominalWidthX;
}

nStems += stack.length >> 1;
Expand Down Expand Up @@ -427,7 +526,7 @@ function parseCFFCharstring(font, glyph, code) {
break;
case 4: // vmoveto
if (stack.length > 1 && !haveWidth) {
width = stack.shift() + font.nominalWidthX;
width = stack.shift() + nominalWidthX;
haveWidth = true;
}

Expand Down Expand Up @@ -481,8 +580,8 @@ function parseCFFCharstring(font, glyph, code) {

break;
case 10: // callsubr
codeIndex = stack.pop() + font.subrsBias;
subrCode = font.subrs[codeIndex];
codeIndex = stack.pop() + subrsBias;
subrCode = subrs[codeIndex];
if (subrCode) {
parse(subrCode);
}
Expand All @@ -506,8 +605,8 @@ function parseCFFCharstring(font, glyph, code) {
c3y = jpy + stack.shift(); // dy4
c4x = c3x + stack.shift(); // dx5
c4y = c3y + stack.shift(); // dy5
x = c4x + stack.shift(); // dx6
y = c4y + stack.shift(); // dy6
x = c4x + stack.shift(); // dx6
y = c4y + stack.shift(); // dy6
stack.shift(); // flex depth
p.curveTo(c1x, c1y, c2x, c2y, jpx, jpy);
p.curveTo(c3x, c3y, c4x, c4y, x, y);
Expand Down Expand Up @@ -572,7 +671,7 @@ function parseCFFCharstring(font, glyph, code) {
break;
case 14: // endchar
if (stack.length > 0 && !haveWidth) {
width = stack.shift() + font.nominalWidthX;
width = stack.shift() + nominalWidthX;
haveWidth = true;
}

Expand All @@ -592,7 +691,7 @@ function parseCFFCharstring(font, glyph, code) {
break;
case 21: // rmoveto
if (stack.length > 2 && !haveWidth) {
width = stack.shift() + font.nominalWidthX;
width = stack.shift() + nominalWidthX;
haveWidth = true;
}

Expand All @@ -602,7 +701,7 @@ function parseCFFCharstring(font, glyph, code) {
break;
case 22: // hmoveto
if (stack.length > 1 && !haveWidth) {
width = stack.shift() + font.nominalWidthX;
width = stack.shift() + nominalWidthX;
haveWidth = true;
}

Expand Down Expand Up @@ -765,19 +864,49 @@ function parseCFFCharstring(font, glyph, code) {
return p;
}

// Subroutines are encoded using the negative half of the number space.
// See type 2 chapter 4.7 "Subroutine operators".
function calcCFFSubroutineBias(subrs) {
var bias;
if (subrs.length < 1240) {
bias = 107;
} else if (subrs.length < 33900) {
bias = 1131;
function parseCFFFDSelect(data, start, nGlyphs, fdArrayCount) {
var fdSelect = [];
var fdIndex;
var parser = new parse.Parser(data, start);
var format = parser.parseCard8();
if (format === 0) {
// Simple list of nGlyphs elements
for (var iGid = 0; iGid < nGlyphs; iGid++) {
fdIndex = parser.parseCard8();
if (fdIndex >= fdArrayCount) {
throw new Error('CFF table CID Font FDSelect has bad FD index value ' + fdIndex + ' (FD count ' + fdArrayCount + ')');
}
fdSelect.push(fdIndex);
}
} else if (format === 3) {
// Ranges
var nRanges = parser.parseCard16();
var first = parser.parseCard16();
if (first !== 0) {
throw new Error('CFF Table CID Font FDSelect format 3 range has bad initial GID ' + first);
}
var next;
for (var iRange = 0; iRange < nRanges; iRange++) {
fdIndex = parser.parseCard8();
next = parser.parseCard16();
if (fdIndex >= fdArrayCount) {
throw new Error('CFF table CID Font FDSelect has bad FD index value ' + fdIndex + ' (FD count ' + fdArrayCount + ')');
}
if (next > nGlyphs) {
throw new Error('CFF Table CID Font FDSelect format 3 range has bad GID ' + next);
}
for (; first < next; first++) {
fdSelect.push(fdIndex);
}
first = next;
}
if (next !== nGlyphs) {
throw new Error('CFF Table CID Font FDSelect format 3 range has bad final GID ' + next);
}
} else {
bias = 32768;
throw new Error('CFF Table CID Font FDSelect table has unsupported format ' + format);
}

return bias;
return fdSelect;
}

// Parse the `CFF` table, which contains the glyph outlines in PostScript format.
Expand All @@ -791,10 +920,37 @@ function parseCFFTable(data, start, font) {
font.gsubrs = globalSubrIndex.objects;
font.gsubrsBias = calcCFFSubroutineBias(font.gsubrs);

var topDictData = new DataView(new Uint8Array(topDictIndex.objects[0]).buffer);
var topDict = parseCFFTopDict(topDictData, stringIndex.objects);
var topDictArray = gatherCFFTopDicts(data, start, topDictIndex.objects, stringIndex.objects);
if (topDictArray.length !== 1) {
throw new Error('CFF table has too many fonts in \'FontSet\' - ' + 'count of fonts NameIndex.length = ' + topDictArray.length);
}

var topDict = topDictArray[0];
font.tables.cff.topDict = topDict;

if (topDict._privateDict) {
font.defaultWidthX = topDict._privateDict.defaultWidthX;
font.nominalWidthX = topDict._privateDict.nominalWidthX;
}

if (topDict.ros[0] !== undefined && topDict.ros[1] !== undefined) {
font.isCIDFont = true;
}

if (font.isCIDFont) {
var fdArrayOffset = topDict.fdArray;
var fdSelectOffset = topDict.fdSelect;
if (fdArrayOffset === 0 || fdSelectOffset === 0) {
throw new Error('Font is marked as a CID font, but FDArray and/or FDSelect information is missing');
}
fdArrayOffset += start;
var fdArrayIndex = parseCFFIndex(data, fdArrayOffset);
var fdArray = gatherCFFTopDicts(data, start, fdArrayIndex.objects, stringIndex.objects);
topDict._fdArray = fdArray;
fdSelectOffset += start;
topDict._fdSelect = parseCFFFDSelect(data, fdSelectOffset, font.numGlyphs, fdArray.length);
}

var privateDictOffset = start + topDict['private'][1];
var privateDict = parseCFFPrivateDict(data, privateDictOffset, topDict['private'][0], stringIndex.objects);
font.defaultWidthX = privateDict.defaultWidthX;
Expand Down

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