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162 lines
5.1 KiB
162 lines
5.1 KiB
2 years ago
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'use strict';
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var _ = require('lodash');
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var ByteBuffer = require('microbuffer');
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var createGSUBTable = require('./ttf/tables/gsub');
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var createOS2Table = require('./ttf/tables/os2');
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var createCMapTable = require('./ttf/tables/cmap');
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var createGlyfTable = require('./ttf/tables/glyf');
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var createHeadTable = require('./ttf/tables/head');
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var createHHeadTable = require('./ttf/tables/hhea');
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var createHtmxTable = require('./ttf/tables/hmtx');
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var createLocaTable = require('./ttf/tables/loca');
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var createMaxpTable = require('./ttf/tables/maxp');
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var createNameTable = require('./ttf/tables/name');
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var createPostTable = require('./ttf/tables/post');
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var utils = require('./ttf/utils');
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// Tables
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var TABLES = [
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{ innerName: 'GSUB', order: 4, create: createGSUBTable }, // GSUB
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{ innerName: 'OS/2', order: 4, create: createOS2Table }, // OS/2
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{ innerName: 'cmap', order: 6, create: createCMapTable }, // cmap
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{ innerName: 'glyf', order: 8, create: createGlyfTable }, // glyf
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{ innerName: 'head', order: 2, create: createHeadTable }, // head
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{ innerName: 'hhea', order: 1, create: createHHeadTable }, // hhea
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{ innerName: 'hmtx', order: 5, create: createHtmxTable }, // hmtx
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{ innerName: 'loca', order: 7, create: createLocaTable }, // loca
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{ innerName: 'maxp', order: 3, create: createMaxpTable }, // maxp
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{ innerName: 'name', order: 9, create: createNameTable }, // name
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{ innerName: 'post', order: 10, create: createPostTable } // post
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];
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// Various constants
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var CONST = {
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VERSION: 0x10000,
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CHECKSUM_ADJUSTMENT: 0xB1B0AFBA
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};
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function ulong(t) {
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t &= 0xffffffff;
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if (t < 0) {
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t += 0x100000000;
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}
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return t;
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}
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function calc_checksum(buf) {
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var sum = 0;
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var nlongs = Math.floor(buf.length / 4);
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var i;
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for (i = 0; i < nlongs; ++i) {
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var t = buf.getUint32(i * 4);
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sum = ulong(sum + t);
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}
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var leftBytes = buf.length - nlongs * 4; //extra 1..3 bytes found, because table is not aligned. Need to include them in checksum too.
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if (leftBytes > 0) {
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var leftRes = 0;
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for (i = 0; i < 4; i++) {
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leftRes = (leftRes << 8) + ((i < leftBytes) ? buf.getUint8(nlongs * 4 + i) : 0);
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}
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sum = ulong(sum + leftRes);
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}
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return sum;
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}
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function generateTTF(font) {
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// Prepare TTF contours objects. Note, that while sfnt countours are classes,
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// ttf contours are just plain arrays of points
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_.forEach(font.glyphs, function (glyph) {
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glyph.ttfContours = _.map(glyph.contours, function (contour) {
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return contour.points;
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});
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});
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// Process ttf contours data
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_.forEach(font.glyphs, function (glyph) {
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// 0.3px accuracy is ok. fo 1000x1000.
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glyph.ttfContours = utils.simplify(glyph.ttfContours, 0.3);
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glyph.ttfContours = utils.simplify(glyph.ttfContours, 0.3); // one pass is not enougth
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// Interpolated points can be removed. 1.1px is acceptable
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// measure - it will give us 1px error after coordinates rounding.
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glyph.ttfContours = utils.interpolate(glyph.ttfContours, 1.1);
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glyph.ttfContours = utils.roundPoints(glyph.ttfContours);
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glyph.ttfContours = utils.removeClosingReturnPoints(glyph.ttfContours);
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glyph.ttfContours = utils.toRelative(glyph.ttfContours);
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});
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// Add tables
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var headerSize = 12 + 16 * TABLES.length; // TTF header plus table headers
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var bufSize = headerSize;
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_.forEach(TABLES, function (table) {
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//store each table in its own buffer
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table.buffer = table.create(font);
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table.length = table.buffer.length;
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table.corLength = table.length + (4 - table.length % 4) % 4; // table size should be divisible to 4
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table.checkSum = calc_checksum(table.buffer);
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bufSize += table.corLength;
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});
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//calculate offsets
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var offset = headerSize;
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_.forEach(_.sortBy(TABLES, 'order'), function (table) {
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table.offset = offset;
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offset += table.corLength;
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});
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//create TTF buffer
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var buf = new ByteBuffer(bufSize);
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//special constants
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var entrySelector = Math.floor(Math.log(TABLES.length) / Math.LN2);
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var searchRange = Math.pow(2, entrySelector) * 16;
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var rangeShift = TABLES.length * 16 - searchRange;
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// Add TTF header
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buf.writeUint32(CONST.VERSION);
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buf.writeUint16(TABLES.length);
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buf.writeUint16(searchRange);
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buf.writeUint16(entrySelector);
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buf.writeUint16(rangeShift);
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_.forEach(TABLES, function (table) {
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buf.writeUint32(utils.identifier(table.innerName)); //inner name
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buf.writeUint32(table.checkSum); //checksum
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buf.writeUint32(table.offset); //offset
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buf.writeUint32(table.length); //length
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});
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var headOffset = 0;
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_.forEach(_.sortBy(TABLES, 'order'), function (table) {
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if (table.innerName === 'head') { //we must store head offset to write font checksum
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headOffset = buf.tell();
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}
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buf.writeBytes(table.buffer.buffer);
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for (var i = table.length; i < table.corLength; i++) { //align table to be divisible to 4
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buf.writeUint8(0);
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}
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});
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// Write font checksum (corrected by magic value) into HEAD table
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buf.setUint32(headOffset + 8, ulong(CONST.CHECKSUM_ADJUSTMENT - calc_checksum(buf)));
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return buf;
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}
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module.exports = generateTTF;
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