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Parse the font file to determine the correct type/subtype, rather than relying on the (often incorrect) data in the font dictionary #9961

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merged 3 commits into from
Aug 5, 2018
Merged

Parse the font file to determine the correct type/subtype, rather than relying on the (often incorrect) data in the font dictionary #9961

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f4db38a
Update the TrueType font file detection to also recognize the Mac spe…
Snuffleupagus Aug 5, 2018
9bbca04
Add a (basic) `isCFFFile` helper function to detect CFF font files
Snuffleupagus Aug 5, 2018
3177f6a
Parse the font file to determine the correct type/subtype, rather tha…
Snuffleupagus Aug 5, 2018
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97 changes: 66 additions & 31 deletions src/core/fonts.js
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Original file line number Diff line number Diff line change
Expand Up @@ -550,36 +550,14 @@ var Font = (function FontClosure() {
return;
}

// Some fonts might use wrong font types for Type1C or CIDFontType0C
if (subtype === 'Type1C') {
if (type !== 'Type1' && type !== 'MMType1') {
// Some TrueType fonts by mistake claim Type1C
if (isTrueTypeFile(file)) {
subtype = 'TrueType';
} else {
type = 'Type1';
}
} else if (isOpenTypeFile(file)) {
// Sometimes the type/subtype can be a complete lie (see issue7598.pdf).
subtype = 'OpenType';
}
}
if (subtype === 'CIDFontType0C' && type !== 'CIDFontType0') {
type = 'CIDFontType0';
}
// Some CIDFontType0C fonts by mistake claim CIDFontType0.
if (type === 'CIDFontType0') {
if (isType1File(file)) {
subtype = 'CIDFontType0';
} else if (isOpenTypeFile(file)) {
// Sometimes the type/subtype can be a complete lie (see issue6782.pdf).
subtype = 'OpenType';
} else {
subtype = 'CIDFontType0C';
}
}
if (subtype === 'OpenType' && type !== 'OpenType') {
type = 'OpenType';
// Parse the font file to determine the correct type/subtype, rather than
// relying on the (often incorrect) data in the font dictionary; (see e.g.
// issue6782.pdf, issue7598.pdf, and issue9949.pdf).
[type, subtype] = getFontFileType(file, properties);

if (type !== this.type || subtype !== this.subtype) {
info('Inconsistent font file Type/SubType, expected: ' +
`${this.type}/${this.subtype} but found: ${type}/${subtype}.`);
}

try {
Expand Down Expand Up @@ -680,7 +658,8 @@ var Font = (function FontClosure() {

function isTrueTypeFile(file) {
var header = file.peekBytes(4);
return readUint32(header, 0) === 0x00010000;
return (readUint32(header, 0) === 0x00010000 ||
bytesToString(header) === 'true');
}

function isTrueTypeCollectionFile(file) {
Expand All @@ -707,6 +686,62 @@ var Font = (function FontClosure() {
return false;
}

/**
* Compared to other font formats, the header in CFF files is not constant
* but contains version numbers. To reduce the possibility of misclassifying
* font files as CFF, it's recommended to check for other font formats first.
*/
function isCFFFile(file) {
const header = file.peekBytes(4);
if (/* major version, [1, 255] */ header[0] >= 1 &&
/* minor version, [0, 255]; header[1] */
/* header size, [0, 255]; header[2] */
/* offset(0) size, [1, 4] */ (header[3] >= 1 && header[3] <= 4)) {
return true;
}
return false;
}

function getFontFileType(file, { type, subtype, composite, }) {
let fileType, fileSubtype;

if (isTrueTypeFile(file) || isTrueTypeCollectionFile(file)) {
if (composite) {
fileType = 'CIDFontType2';
} else {
fileType = 'TrueType';
}
} else if (isOpenTypeFile(file)) {
if (composite) {
fileType = 'CIDFontType2';
} else {
fileType = 'OpenType';
}
} else if (isType1File(file)) {
if (composite) {
fileType = 'CIDFontType0';
} else if (type === 'MMType1') {
fileType = 'MMType1';
} else {
fileType = 'Type1';
}
} else if (isCFFFile(file)) {
if (composite) {
fileType = 'CIDFontType0';
fileSubtype = 'CIDFontType0C';
} else {
fileType = 'Type1';
fileSubtype = 'Type1C';
}
} else {
warn('getFontFileType: Unable to detect correct font file Type/Subtype.');
fileType = type;
fileSubtype = subtype;
}

return [fileType, fileSubtype];
}

function buildToFontChar(encoding, glyphsUnicodeMap, differences) {
var toFontChar = [], unicode;
for (var i = 0, ii = encoding.length; i < ii; i++) {
Expand Down