244 lines
6.8 KiB
Plaintext
244 lines
6.8 KiB
Plaintext
/**
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* @file ttf写入器
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* @author mengke01(kekee000@gmail.com)
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*/
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import Writer from './writer';
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import Directory from './table/directory';
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import supportTables from './table/support';
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import checkSum from './util/checkSum';
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import error from './error';
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// 支持写的表, 注意表顺序
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const SUPPORT_TABLES = [
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'OS/2',
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'cmap',
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'glyf',
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'head',
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'hhea',
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'hmtx',
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'loca',
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'maxp',
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'name',
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'post'
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];
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export default class TTFWriter {
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constructor(options = {}) {
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this.options = {
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writeZeroContoursGlyfData: options.writeZeroContoursGlyfData || false, // 不写入空 glyf 数据
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hinting: options.hinting || false, // 默认不保留hints信息
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kerning: options.kerning || false, // 默认不保留 kernings space 信息
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support: options.support // 自定义的导出表结构，可以自己修改某些表项目
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};
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}
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/**
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* 处理ttf结构，以便于写
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*
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* @param {ttfObject} ttf ttf数据结构
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*/
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resolveTTF(ttf) {
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// 头部信息
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ttf.version = ttf.version || 0x1;
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ttf.numTables = ttf.writeOptions.tables.length;
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ttf.entrySelector = Math.floor(Math.log(ttf.numTables) / Math.LN2);
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ttf.searchRange = Math.pow(2, ttf.entrySelector) * 16;
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ttf.rangeShift = ttf.numTables * 16 - ttf.searchRange;
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// 重置校验码
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ttf.head.checkSumAdjustment = 0;
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ttf.head.magickNumber = 0x5F0F3CF5;
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if (typeof ttf.head.created === 'string') {
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ttf.head.created = /^\d+$/.test(ttf.head.created)
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? +ttf.head.created : Date.parse(ttf.head.created);
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}
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if (typeof ttf.head.modified === 'string') {
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ttf.head.modified = /^\d+$/.test(ttf.head.modified)
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? +ttf.head.modified : Date.parse(ttf.head.modified);
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}
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// 重置日期
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if (!ttf.head.created) {
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ttf.head.created = Date.now();
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}
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if (!ttf.head.modified) {
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ttf.head.modified = ttf.head.created;
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}
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const checkUnicodeRepeat = {}; // 检查是否有重复代码点
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// 将glyf的代码点按小到大排序
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ttf.glyf.forEach((glyf, index) => {
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if (glyf.unicode) {
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glyf.unicode = glyf.unicode.sort();
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glyf.unicode.forEach((u) => {
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if (checkUnicodeRepeat[u]) {
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error.raise({
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number: 10200,
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data: index
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}, index);
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}
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else {
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checkUnicodeRepeat[u] = true;
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}
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});
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}
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});
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}
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/**
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* 写ttf文件
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*
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* @param {ttfObject} ttf ttf数据结构
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* @return {ArrayBuffer} 字节流
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*/
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dump(ttf) {
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// 用来做写入缓存的对象，用完后删掉
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ttf.support = Object.assign({}, this.options.support);
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// head + directory
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let ttfSize = 12 + ttf.numTables * 16;
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let ttfHeadOffset = 0; // 记录head的偏移
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// 构造tables
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ttf.support.tables = [];
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ttf.writeOptions.tables.forEach((tableName) => {
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const offset = ttfSize;
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const TableClass = supportTables[tableName];
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const tableSize = new TableClass().size(ttf); // 原始的表大小
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let size = tableSize; // 对齐后的表大小
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if (tableName === 'head') {
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ttfHeadOffset = offset;
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}
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// 4字节对齐
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if (size % 4) {
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size += 4 - size % 4;
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}
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ttf.support.tables.push({
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name: tableName,
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checkSum: 0,
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offset,
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length: tableSize,
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size
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});
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ttfSize += size;
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});
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const writer = new Writer(new ArrayBuffer(ttfSize));
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// 写头部
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writer.writeFixed(ttf.version);
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writer.writeUint16(ttf.numTables);
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writer.writeUint16(ttf.searchRange);
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writer.writeUint16(ttf.entrySelector);
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writer.writeUint16(ttf.rangeShift);
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// 写表偏移
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new Directory().write(writer, ttf);
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// 写支持的表数据
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ttf.support.tables.forEach((table) => {
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const tableStart = writer.offset;
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const TableClass = supportTables[table.name];
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new TableClass().write(writer, ttf);
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if (table.length % 4) {
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// 对齐字节
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writer.writeEmpty(4 - table.length % 4);
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}
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// 计算校验和
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table.checkSum = checkSum(writer.getBuffer(), tableStart, table.size);
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});
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// 重新写入每个表校验和
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ttf.support.tables.forEach((table, index) => {
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const offset = 12 + index * 16 + 4;
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writer.writeUint32(table.checkSum, offset);
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});
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// 写入总校验和
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const ttfCheckSum = (0xB1B0AFBA - checkSum(writer.getBuffer()) + 0x100000000) % 0x100000000;
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writer.writeUint32(ttfCheckSum, ttfHeadOffset + 8);
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delete ttf.writeOptions;
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delete ttf.support;
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const buffer = writer.getBuffer();
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writer.dispose();
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return buffer;
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}
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/**
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* 对ttf的表进行评估，标记需要处理的表
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*
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* @param {Object} ttf ttf对象
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*/
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prepareDump(ttf) {
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if (!ttf.glyf || ttf.glyf.length === 0) {
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error.raise(10201);
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}
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if (!ttf['OS/2'] || !ttf.head || !ttf.name) {
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error.raise(10204);
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}
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const tables = SUPPORT_TABLES.slice(0);
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ttf.writeOptions = {};
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// hinting tables direct copy
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if (this.options.hinting) {
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['cvt', 'fpgm', 'prep', 'gasp', 'GPOS', 'kern', 'kerx'].forEach((table) => {
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if (ttf[table]) {
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tables.push(table);
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}
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});
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}
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// copy kerning space table
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if (this.options.kerning) {
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['GPOS', 'kern', 'kerx'].forEach((table) => {
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if (ttf[table]) {
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tables.push(table);
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}
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});
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}
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ttf.writeOptions.writeZeroContoursGlyfData = !!this.options.writeZeroContoursGlyfData;
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ttf.writeOptions.hinting = !!this.options.hinting;
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ttf.writeOptions.kerning = !!this.options.kerning;
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ttf.writeOptions.tables = tables.sort();
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}
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/**
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* 写一个ttf字体结构
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*
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* @param {Object} ttf ttf数据结构
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* @return {ArrayBuffer} 缓冲数组
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*/
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write(ttf) {
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this.prepareDump(ttf);
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this.resolveTTF(ttf);
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const buffer = this.dump(ttf);
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return buffer;
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}
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/**
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* 注销
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*/
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dispose() {
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delete this.options;
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}
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}
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