feat: 新增PDF转图片工具的前端实现
添加了完整的PDF转图片工具的前端实现，包括HTML、CSS、JavaScript代码。该工具允许用户在浏览器中安全地将PDF文件转换为图片，支持单页导出或合并为单张长图，并提供了实时预览功能。所有处理均在本地完成，无需上传文件到服务器，确保用户数据安全。
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376
cssjs/js/main.js
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376
cssjs/js/main.js
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// 设置PDF.js worker路径
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pdfjsLib.GlobalWorkerOptions.workerSrc = 'cssjs/js/pdf.worker.js';
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// 全局变量
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let pdfDocument = null;
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let pdfFile = null;
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let renderedPages = [];
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// DOM元素
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const uploadArea = document.getElementById('upload-area');
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const pdfFileInput = document.getElementById('pdf-file-input');
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const selectFileBtn = document.getElementById('select-file-btn');
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const loadingContainer = document.getElementById('loading-container');
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const pdfInfoContainer = document.getElementById('pdf-info-container');
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const previewContainer = document.getElementById('preview-container');
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const previewItems = document.getElementById('preview-items');
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const exportBtn = document.getElementById('export-btn');
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const combinePagesSwitch = document.getElementById('combine-pages-switch');
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const highQualitySwitch = document.getElementById('high-quality-switch');
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// PDF信息显示元素
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const pdfNameValue = document.getElementById('pdf-name-value');
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const pdfSizeValue = document.getElementById('pdf-size-value');
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const pdfPagesValue = document.getElementById('pdf-pages-value');
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// 事件监听器
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document.addEventListener('DOMContentLoaded', function() {
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// 检查PDF.js是否正确加载
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if (typeof pdfjsLib === 'undefined') {
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alert('PDF.js库加载失败，请确保pdf.js文件已正确放置');
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return;
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}
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// 初始化事件监听
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initEventListeners();
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});
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// 初始化事件监听器
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function initEventListeners() {
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selectFileBtn.addEventListener('click', () => pdfFileInput.click());
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pdfFileInput.addEventListener('change', handleFileSelect);
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exportBtn.addEventListener('click', exportImages);
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// 拖放功能
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uploadArea.addEventListener('dragover', (e) => {
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e.preventDefault();
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uploadArea.classList.add('dragover');
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});
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uploadArea.addEventListener('dragleave', () => {
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uploadArea.classList.remove('dragover');
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});
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uploadArea.addEventListener('drop', (e) => {
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e.preventDefault();
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uploadArea.classList.remove('dragover');
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if (e.dataTransfer.files.length > 0) {
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const file = e.dataTransfer.files[0];
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if (file.type === 'application/pdf') {
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pdfFileInput.files = e.dataTransfer.files;
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handleFileSelect(e);
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} else {
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showError('请选择PDF文件');
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}
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}
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});
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}
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// 处理文件选择
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function handleFileSelect(e) {
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const file = pdfFileInput.files[0];
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if (!file) return;
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if (file.type !== 'application/pdf') {
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showError('请选择PDF文件');
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return;
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}
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if (file.size > 20 * 1024 * 1024) { // 20MB
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showError('文件大小不能超过20MB');
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return;
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}
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pdfFile = file;
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// 显示加载状态
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uploadArea.style.display = 'none';
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loadingContainer.style.display = 'block';
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previewContainer.style.display = 'none';
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pdfInfoContainer.style.display = 'none';
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previewItems.innerHTML = '';
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renderedPages = [];
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// 读取PDF文件
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const reader = new FileReader();
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reader.onload = function(event) {
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const typedArray = new Uint8Array(event.target.result);
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loadPdfFromData(typedArray);
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};
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reader.readAsArrayBuffer(file);
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}
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// 从ArrayBuffer加载PDF
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function loadPdfFromData(data) {
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pdfjsLib.getDocument({ data }).promise
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.then(pdf => {
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pdfDocument = pdf;
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// 更新PDF信息
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pdfNameValue.textContent = pdfFile.name;
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pdfSizeValue.textContent = formatFileSize(pdfFile.size);
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pdfPagesValue.textContent = pdf.numPages;
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// 渲染预览
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renderPdfPreview(pdf);
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})
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.catch(error => {
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console.error('PDF加载错误:', error);
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showError('无法加载PDF文件，请确保文件未损坏');
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resetUI();
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});
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}
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// 渲染PDF预览
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function renderPdfPreview(pdf) {
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const totalPages = pdf.numPages;
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let renderedCount = 0;
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// 更新加载文本
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document.getElementById('loading-text').textContent = `正在渲染预览 (0/${totalPages})`;
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// 为每一页创建预览
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for (let pageNumber = 1; pageNumber <= totalPages; pageNumber++) {
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pdf.getPage(pageNumber).then(page => {
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const scale = 0.5; // 预览缩放比例
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const viewport = page.getViewport({ scale });
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// 创建canvas元素
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const canvas = document.createElement('canvas');
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const context = canvas.getContext('2d');
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canvas.width = viewport.width;
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canvas.height = viewport.height;
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// 渲染PDF页面到canvas
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const renderContext = {
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canvasContext: context,
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viewport: viewport
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};
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page.render(renderContext).promise.then(() => {
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renderedCount++;
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document.getElementById('loading-text').textContent = `正在渲染预览 (${renderedCount}/${totalPages})`;
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// 存储渲染的页面
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renderedPages[pageNumber - 1] = {
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pageNumber: pageNumber,
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canvas: canvas,
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width: viewport.width,
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height: viewport.height
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};
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// 如果所有页面都已渲染，显示预览
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if (renderedCount === totalPages) {
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displayPreviews();
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}
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});
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});
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}
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}
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// 显示预览
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function displayPreviews() {
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// 按页码排序
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renderedPages.sort((a, b) => a.pageNumber - b.pageNumber);
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// 清空预览容器
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previewItems.innerHTML = '';
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// 添加每一页的预览
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renderedPages.forEach(page => {
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const colDiv = document.createElement('div');
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colDiv.className = 'col-md-6 col-lg-4 preview-item';
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const pageNumberDiv = document.createElement('div');
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pageNumberDiv.className = 'page-number';
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pageNumberDiv.textContent = `第 ${page.pageNumber} 页`;
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// 克隆canvas以避免原始canvas被修改
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const displayCanvas = document.createElement('canvas');
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displayCanvas.width = page.canvas.width;
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displayCanvas.height = page.canvas.height;
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const displayContext = displayCanvas.getContext('2d');
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displayContext.drawImage(page.canvas, 0, 0);
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colDiv.appendChild(displayCanvas);
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colDiv.appendChild(pageNumberDiv);
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previewItems.appendChild(colDiv);
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});
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// 显示预览和控制面板
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loadingContainer.style.display = 'none';
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pdfInfoContainer.style.display = 'block';
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previewContainer.style.display = 'block';
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}
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// 导出图片
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function exportImages() {
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if (!pdfDocument || renderedPages.length === 0) {
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showError('没有可导出的内容');
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return;
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}
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const combinePages = combinePagesSwitch.checked;
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const highQuality = highQualitySwitch.checked;
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const scale = highQuality ? 2.0 : 1.0;
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// 显示加载状态
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loadingContainer.style.display = 'block';
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document.getElementById('loading-text').textContent = '正在准备导出...';
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if (combinePages) {
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// 合并为单张图片
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exportCombinedImage(scale);
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} else {
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// 导出为多张图片
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exportMultipleImages(scale);
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}
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}
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// 导出合并的单张图片
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function exportCombinedImage(scale) {
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// 计算合并后的图片尺寸
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let totalHeight = 0;
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let maxWidth = 0;
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renderedPages.forEach(page => {
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totalHeight += page.height * (scale / 0.5);
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maxWidth = Math.max(maxWidth, page.width * (scale / 0.5));
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});
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// 创建合并的canvas
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const combinedCanvas = document.createElement('canvas');
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combinedCanvas.width = maxWidth;
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combinedCanvas.height = totalHeight;
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const combinedContext = combinedCanvas.getContext('2d');
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// 填充白色背景
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combinedContext.fillStyle = '#FFFFFF';
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combinedContext.fillRect(0, 0, combinedCanvas.width, combinedCanvas.height);
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// 重新渲染每一页到合并的canvas
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let currentY = 0;
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let renderedCount = 0;
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const renderNextPage = (index) => {
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if (index >= renderedPages.length) {
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// 所有页面都已渲染，导出图片
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combinedCanvas.toBlob(blob => {
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saveAs(blob, `${pdfFile.name.replace('.pdf', '')}_combined.png`);
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loadingContainer.style.display = 'none';
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}, 'image/png');
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return;
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}
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const page = renderedPages[index];
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// 更新加载文本
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document.getElementById('loading-text').textContent = `正在合并页面 (${index + 1}/${renderedPages.length})`;
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// 获取原始页面
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pdfDocument.getPage(page.pageNumber).then(pdfPage => {
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const viewport = pdfPage.getViewport({ scale });
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// 创建临时canvas
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const tempCanvas = document.createElement('canvas');
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tempCanvas.width = viewport.width;
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tempCanvas.height = viewport.height;
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const tempContext = tempCanvas.getContext('2d');
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// 渲染到临时canvas
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const renderContext = {
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canvasContext: tempContext,
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viewport: viewport
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};
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pdfPage.render(renderContext).promise.then(() => {
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// 将临时canvas的内容绘制到合并的canvas
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const x = (maxWidth - viewport.width) / 2; // 居中
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combinedContext.drawImage(tempCanvas, x, currentY);
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// 更新Y坐标
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currentY += viewport.height;
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// 渲染下一页
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renderNextPage(index + 1);
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});
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});
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};
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// 开始渲染第一页
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renderNextPage(0);
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}
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// 导出多张图片
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function exportMultipleImages(scale) {
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const zip = new JSZip();
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const folder = zip.folder("images");
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let processedCount = 0;
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// 更新加载文本
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document.getElementById('loading-text').textContent = `正在导出图片 (0/${renderedPages.length})`;
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// 处理每一页
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renderedPages.forEach((page, index) => {
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// 获取原始页面
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pdfDocument.getPage(page.pageNumber).then(pdfPage => {
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const viewport = pdfPage.getViewport({ scale });
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// 创建canvas
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const canvas = document.createElement('canvas');
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canvas.width = viewport.width;
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canvas.height = viewport.height;
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const context = canvas.getContext('2d');
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// 填充白色背景
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context.fillStyle = '#FFFFFF';
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context.fillRect(0, 0, canvas.width, canvas.height);
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// 渲染PDF页面到canvas
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const renderContext = {
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canvasContext: context,
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viewport: viewport
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};
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pdfPage.render(renderContext).promise.then(() => {
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// 将canvas转换为blob
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canvas.toBlob(blob => {
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// 添加到zip
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folder.file(`page_${page.pageNumber}.png`, blob);
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processedCount++;
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document.getElementById('loading-text').textContent = `正在导出图片 (${processedCount}/${renderedPages.length})`;
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// 如果所有页面都已处理，生成并下载zip
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if (processedCount === renderedPages.length) {
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zip.generateAsync({ type: 'blob' }).then(content => {
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saveAs(content, `${pdfFile.name.replace('.pdf', '')}_images.zip`);
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loadingContainer.style.display = 'none';
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});
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}
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}, 'image/png');
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});
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});
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});
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}
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// 辅助函数
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function formatFileSize(bytes) {
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if (bytes < 1024) return bytes + ' B';
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else if (bytes < 1048576) return (bytes / 1024).toFixed(2) + ' KB';
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else return (bytes / 1048576).toFixed(2) + ' MB';
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}
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function showError(message) {
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alert(message);
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}
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function resetUI() {
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uploadArea.style.display = 'block';
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loadingContainer.style.display = 'none';
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pdfInfoContainer.style.display = 'none';
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previewContainer.style.display = 'none';
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pdfFileInput.value = '';
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}
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