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Add a (basic) isCFFFile helper function to detect CFF font files

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Compared to most other font formats, the CFF doesn't have a constant header which makes is slightly more difficult to detect such font files.

Please refer to the Compact Font Format specification: https://www.adobe.com/content/dam/acom/en/devnet/font/pdfs/5176.CFF.pdf#G3.32094
This commit is contained in:
Jonas Jenwald 2018-08-05 10:34:06 +02:00
parent f4db38aadf
commit 9bbca04579
1 changed files with 16 additions and 0 deletions
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16
src/core/fonts.js
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@ -708,6 +708,22 @@ 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 buildToFontChar(encoding, glyphsUnicodeMap, differences) {
var toFontChar = [], unicode;
for (var i = 0, ii = encoding.length; i < ii; i++) {