474 lines
14 KiB
JavaScript
474 lines
14 KiB
JavaScript
// utils/text-fitting.js
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// 文本自适应算法 - 为 PDF 保留格式翻译优化
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/**
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* 文本自适应引擎
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*
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* 核心功能：
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* 1. 自动计算最优字体大小，让翻译文本完美适配原始 bbox
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* 2. 智能换行和行距控制
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* 3. CJK 和西文混排优化
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* 4. 空间不足时自动缩放或扩展容器
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*
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* 设计原则：
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* - 渐进式缩放搜索（从 100% 开始逐步缩小）
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* - 全局一致性（使用统计方法统一字体大小）
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* - 智能空间扩展（优先向下，次选向右）
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*/
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class TextFittingEngine {
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constructor(options = {}) {
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// 核心参数
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this.INITIAL_SCALE = options.initialScale || 1.0;
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this.MIN_SCALE = options.minScale || 0.1;
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this.SCALE_STEP_HIGH = options.scaleStepHigh || 0.05; // >0.6 时的步长
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this.SCALE_STEP_LOW = options.scaleStepLow || 0.1; // <0.6 时的步长
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this.EXPAND_THRESHOLD = options.expandThreshold || 0.7; // 触发空间扩展的阈值
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// 行距配置（根据排版规范优化）
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this.LINE_SKIP_CJK = options.lineSkipCJK || 1.30; // 降低中文行距，更紧凑
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this.LINE_SKIP_WESTERN = options.lineSkipWestern || 1.20; // 降低西文行距
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this.MIN_LINE_HEIGHT = options.minLineHeight || 1.05;
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// 间距配置
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this.CJK_SPACE_WIDTH_RATIO = options.cjkSpaceRatio || 0.5;
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this.MIXED_LANG_SPACE_RATIO = options.mixedLangSpaceRatio || 0.5;
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this.FIRST_LINE_INDENT_SPACES = options.firstLineIndent || 4;
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// 扩展边距
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this.BOTTOM_EXPAND_MARGIN = options.bottomExpandMargin || 2;
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this.RIGHT_EXPAND_MARGIN = options.rightExpandMargin || -5;
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// Canvas 上下文（用于精确测量文本宽度）
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this._measureCanvas = null;
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this._measureContext = null;
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}
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/**
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* 为单个段落计算最优缩放因子
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*
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* @param {string} text - 翻译后的文本
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* @param {Object} bbox - 边界框 [x0, y0, x1, y1]
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* @param {number} originalFontSize - 原始字体大小
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* @param {string} fontFamily - 字体族
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* @param {boolean} isCJK - 是否为 CJK 语言
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* @param {Object} options - 额外选项
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* @returns {Object} { scale, reason, fitsWithoutExpansion }
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*/
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calculateOptimalScale(text, bbox, originalFontSize, fontFamily = 'Arial', isCJK = false, options = {}) {
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if (!text || !bbox || bbox.length < 4) {
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return { scale: 1.0, reason: 'invalid_input', fitsWithoutExpansion: true };
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}
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const [x0, y0, x1, y1] = bbox;
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const availableWidth = x1 - x0;
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const availableHeight = y1 - y0;
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if (availableWidth <= 0 || availableHeight <= 0) {
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return { scale: 1.0, reason: 'invalid_bbox', fitsWithoutExpansion: true };
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}
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// 获取行距倍数
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const lineSkip = isCJK ? this.LINE_SKIP_CJK : this.LINE_SKIP_WESTERN;
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let currentScale = this.INITIAL_SCALE;
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// 渐进式搜索最优缩放
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while (currentScale >= this.MIN_SCALE) {
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const scaledFontSize = originalFontSize * currentScale;
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const layout = this._layoutText(
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text,
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availableWidth,
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availableHeight,
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scaledFontSize,
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fontFamily,
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lineSkip,
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isCJK,
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options
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);
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// 如果所有文本都放得下
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if (layout.fitsCompletely) {
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return {
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scale: currentScale,
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reason: 'fits_perfectly',
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fitsWithoutExpansion: true,
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lineCount: layout.lineCount,
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actualHeight: layout.actualHeight
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};
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}
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// 减小缩放因子
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if (currentScale > 0.6) {
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currentScale -= this.SCALE_STEP_HIGH;
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} else {
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currentScale -= this.SCALE_STEP_LOW;
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}
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}
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// 无法适配，返回最小缩放
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return {
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scale: this.MIN_SCALE,
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reason: 'requires_expansion',
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fitsWithoutExpansion: false,
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requiresExpansion: true
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};
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}
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/**
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* 布局文本（模拟排版）
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*
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* @private
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* @param {string} text
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* @param {number} maxWidth
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* @param {number} maxHeight
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* @param {number} fontSize
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* @param {string} fontFamily
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* @param {number} lineSkip
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* @param {boolean} isCJK
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* @param {Object} options
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* @returns {Object} { fitsCompletely, lineCount, actualHeight }
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*/
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_layoutText(text, maxWidth, maxHeight, fontSize, fontFamily, lineSkip, isCJK, options = {}) {
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const lines = [];
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const words = this._tokenizeText(text, isCJK);
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let currentLine = '';
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let currentWidth = 0;
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const spaceWidth = this._measureTextWidth(' ', fontSize, fontFamily);
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const cjkSpaceWidth = fontSize * this.CJK_SPACE_WIDTH_RATIO;
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// 首行缩进
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if (options.firstLineIndent) {
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currentWidth = cjkSpaceWidth * this.FIRST_LINE_INDENT_SPACES;
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}
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for (let i = 0; i < words.length; i++) {
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const word = words[i];
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// 处理换行符：强制换行（和 wrapText 保持一致）
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if (word === '\n') {
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if (currentLine) {
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lines.push(currentLine);
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currentLine = '';
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currentWidth = 0;
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}
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continue;
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}
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const wordWidth = this._measureTextWidth(word, fontSize, fontFamily);
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// 标点符号：直接加到当前行（和 wrapText 保持一致）
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if (isCJK && /^[。？！，、；：]$/.test(word)) {
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currentLine += word;
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currentWidth += wordWidth;
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continue;
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}
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// 中英文混排：添加间距
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const lastChar = currentLine.slice(-1);
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const needsMixedSpace = lastChar &&
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this._isCJKChar(lastChar) !== this._isCJKChar(word[0]);
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const mixedSpaceWidth = needsMixedSpace ? (spaceWidth * this.MIXED_LANG_SPACE_RATIO) : 0;
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// 检查是否需要换行
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const totalWidth = currentWidth + mixedSpaceWidth + wordWidth;
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if (totalWidth > maxWidth && currentLine.length > 0) {
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lines.push(currentLine);
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currentLine = word;
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currentWidth = wordWidth;
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} else {
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if (needsMixedSpace) {
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currentWidth += mixedSpaceWidth;
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}
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currentLine += word;
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currentWidth += wordWidth;
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}
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}
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// 添加最后一行
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if (currentLine) {
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lines.push(currentLine);
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}
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// 计算总高度
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const lineHeight = fontSize * lineSkip;
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const actualHeight = lines.length * lineHeight;
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return {
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fitsCompletely: actualHeight <= maxHeight,
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lineCount: lines.length,
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actualHeight: actualHeight,
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lines: lines
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};
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}
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/**
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* 分词（支持 CJK 和西文）
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*
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* 重要：这个方法的分词逻辑必须和 history_pdf_compare.js 中的 wrapText() 保持一致！
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*
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* @private
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* @param {string} text
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* @param {boolean} isCJK
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* @returns {Array<string>}
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*/
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_tokenizeText(text, isCJK) {
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if (!text) return [];
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if (isCJK) {
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// CJK：按标点符号分段，然后每个字符作为一个单元
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// 这和 wrapText() 的逻辑保持一致
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const tokens = [];
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const segments = text.split(/([。？！，、；：\n])/);
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for (let segment of segments) {
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if (!segment) continue;
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// 标点符号作为独立 token
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if (/^[。？！，、；：]$/.test(segment)) {
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tokens.push(segment);
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} else if (segment === '\n') {
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tokens.push('\n'); // 换行符作为独立 token
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} else {
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// 其他字符逐个分割
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tokens.push(...segment.split(''));
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}
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}
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return tokens;
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} else {
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// 西文：按空格和标点分词
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return text.match(/\S+|\s+/g) || [];
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}
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}
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/**
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* 判断是否为 CJK 字符
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*
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* @private
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* @param {string} char
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* @returns {boolean}
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*/
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_isCJKChar(char) {
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if (!char || char.length === 0) return false;
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const code = char.charCodeAt(0);
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return (
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(code >= 0x4E00 && code <= 0x9FFF) || // CJK Unified Ideographs
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(code >= 0x3400 && code <= 0x4DBF) || // CJK Extension A
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(code >= 0x20000 && code <= 0x2A6DF) || // CJK Extension B
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(code >= 0x3000 && code <= 0x303F) || // CJK Symbols and Punctuation
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(code >= 0xFF00 && code <= 0xFFEF) || // Fullwidth Forms
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(code >= 0xAC00 && code <= 0xD7AF) || // Hangul Syllables
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(code >= 0x3040 && code <= 0x309F) || // Hiragana
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(code >= 0x30A0 && code <= 0x30FF) // Katakana
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);
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}
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/**
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* 测量文本宽度（使用 Canvas）
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*
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* @private
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* @param {string} text
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* @param {number} fontSize
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* @param {string} fontFamily
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* @returns {number}
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*/
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_measureTextWidth(text, fontSize, fontFamily) {
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if (!this._measureContext) {
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this._measureCanvas = document.createElement('canvas');
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this._measureContext = this._measureCanvas.getContext('2d');
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}
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this._measureContext.font = `${fontSize}px ${fontFamily}`;
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return this._measureContext.measureText(text).width;
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}
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/**
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* 批量计算最优缩放（全局一致性）
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*
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* 实现策略：
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* 1. 计算每个段落的最优缩放
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* 2. 使用众数作为全局缩放
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* 3. 统一所有段落的缩放
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*
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* @param {Array<Object>} items - content_list.json 的项数组
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* @param {string} fontFamily
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* @param {string} targetLang
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* @returns {Object} { globalScale, itemScales }
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*/
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calculateGlobalScale(items, fontFamily = 'Arial', targetLang = 'zh-CN') {
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const isCJK = this._isTargetLangCJK(targetLang);
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const scales = [];
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const itemScales = [];
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for (const item of items) {
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if (item.type !== 'text' || !item.text || !item.bbox) {
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itemScales.push(null);
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continue;
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}
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// 估算原始字体大小（基于 bbox 高度）
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const bboxHeight = item.bbox[3] - item.bbox[1];
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const estimatedFontSize = bboxHeight * 0.8; // 经验值：bbox 高度的 80%
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const result = this.calculateOptimalScale(
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item.text,
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item.bbox,
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estimatedFontSize,
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fontFamily,
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isCJK
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);
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scales.push(result.scale);
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itemScales.push(result);
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}
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// 计算众数（最常见的缩放因子）
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const globalScale = this._calculateMode(scales);
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// 统一所有段落的缩放（大于众数的降为众数）
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for (let i = 0; i < itemScales.length; i++) {
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if (itemScales[i] && itemScales[i].scale > globalScale) {
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itemScales[i].scale = globalScale;
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itemScales[i].reason = 'global_consistency';
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}
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}
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return { globalScale, itemScales };
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}
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/**
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* 计算众数
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*
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* @private
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* @param {Array<number>} values
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* @returns {number}
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*/
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_calculateMode(values) {
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if (!values || values.length === 0) return 1.0;
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const frequency = {};
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let maxFreq = 0;
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let mode = values[0];
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for (const value of values) {
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if (value == null) continue;
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const rounded = Math.round(value * 100) / 100; // 保留两位小数
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frequency[rounded] = (frequency[rounded] || 0) + 1;
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if (frequency[rounded] > maxFreq) {
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maxFreq = frequency[rounded];
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mode = rounded;
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}
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}
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return mode;
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}
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/**
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* 判断目标语言是否为 CJK
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*
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* @private
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* @param {string} targetLang
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* @returns {boolean}
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*/
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_isTargetLangCJK(targetLang) {
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if (!targetLang) return false;
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const upper = targetLang.toUpperCase();
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return upper.includes('ZH') ||
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upper.includes('JA') ||
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upper.includes('JP') ||
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upper.includes('KO') ||
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upper.includes('KR');
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}
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/**
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* 智能扩展 bbox（当缩放无法解决时）
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*
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* @param {Array} bbox - [x0, y0, x1, y1]
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* @param {Array<Object>} allItems - 所有段落项（用于检测障碍物）
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* @param {number} pageWidth
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* @param {number} pageHeight
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* @returns {Array} 扩展后的 bbox
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*/
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expandBbox(bbox, allItems, pageWidth, pageHeight) {
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const [x0, y0, x1, y1] = bbox;
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let expandedBbox = [...bbox];
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let expanded = false;
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// 策略1：向下扩展
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const bottomSpace = this._getMaxBottomSpace(bbox, allItems, pageHeight);
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if (bottomSpace > y0) {
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expandedBbox[1] = bottomSpace + this.BOTTOM_EXPAND_MARGIN;
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expanded = true;
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console.log(`[TextFitting] 向下扩展: ${y0} -> ${expandedBbox[1]}`);
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}
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// 策略2：向右扩展（如果向下不够）
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if (!expanded) {
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const rightSpace = this._getMaxRightSpace(bbox, allItems, pageWidth);
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if (rightSpace > x1) {
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expandedBbox[2] = rightSpace + this.RIGHT_EXPAND_MARGIN;
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expanded = true;
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console.log(`[TextFitting] 向右扩展: ${x1} -> ${expandedBbox[2]}`);
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}
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}
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return expandedBbox;
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}
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/**
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* 获取下方最大可用空间
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*
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* @private
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*/
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_getMaxBottomSpace(bbox, allItems, pageHeight) {
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const [x0, y0, x1, y1] = bbox;
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let minY = pageHeight * 0.1; // 页面底部 10% 作为最小限制
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for (const item of allItems) {
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if (!item.bbox || item.bbox === bbox) continue;
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const [ix0, iy0, ix1, iy1] = item.bbox;
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// 检查是否在当前 bbox 下方且有水平重叠
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const hasHorizontalOverlap = !(ix1 <= x0 || ix0 >= x1);
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if (iy1 < y0 && hasHorizontalOverlap) {
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minY = Math.max(minY, iy1);
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}
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}
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return minY;
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}
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/**
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* 获取右侧最大可用空间
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*
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* @private
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*/
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_getMaxRightSpace(bbox, allItems, pageWidth) {
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const [x0, y0, x1, y1] = bbox;
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let maxX = pageWidth * 0.9; // 页面右侧 10% 作为最大限制
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for (const item of allItems) {
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if (!item.bbox || item.bbox === bbox) continue;
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const [ix0, iy0, ix1, iy1] = item.bbox;
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// 检查是否在当前 bbox 右侧且有垂直重叠
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const hasVerticalOverlap = !(iy1 <= y0 || iy0 >= y1);
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if (ix0 > x0 && hasVerticalOverlap) {
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maxX = Math.min(maxX, ix0);
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}
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}
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return maxX;
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}
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}
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// 导出到全局
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if (typeof window !== 'undefined') {
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window.TextFittingEngine = TextFittingEngine;
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}
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// 模块化导出
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if (typeof module !== 'undefined' && module.exports) {
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module.exports = TextFittingEngine;
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}
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