pdf2img/cssjs/js/main.js

// 设置PDF.js worker路径
pdfjsLib.GlobalWorkerOptions.workerSrc = 'cssjs/js/pdf.worker.js';

// 全局变量
let pdfDocument = null;
let pdfFile = null;
let renderedPages = [];

// DOM元素
const uploadArea = document.getElementById('upload-area');
const pdfFileInput = document.getElementById('pdf-file-input');
const selectFileBtn = document.getElementById('select-file-btn');
const loadingContainer = document.getElementById('loading-container');
const pdfInfoContainer = document.getElementById('pdf-info-container');
const previewContainer = document.getElementById('preview-container');
const previewItems = document.getElementById('preview-items');
const exportBtn = document.getElementById('export-btn');
const combinePagesSwitch = document.getElementById('combine-pages-switch');
const highQualitySwitch = document.getElementById('high-quality-switch');

// PDF信息显示元素
const pdfNameValue = document.getElementById('pdf-name-value');
const pdfSizeValue = document.getElementById('pdf-size-value');
const pdfPagesValue = document.getElementById('pdf-pages-value');

// 事件监听器
document.addEventListener('DOMContentLoaded', function() {
  // 检查PDF.js是否正确加载
  if (typeof pdfjsLib === 'undefined') {
    alert('PDF.js库加载失败，请确保pdf.js文件已正确放置');
    return;
  }
  
  // 初始化事件监听
  initEventListeners();
});

// 初始化事件监听器
function initEventListeners() {
  selectFileBtn.addEventListener('click', () => pdfFileInput.click());
  pdfFileInput.addEventListener('change', handleFileSelect);
  exportBtn.addEventListener('click', exportImages);
  
  // 拖放功能
  uploadArea.addEventListener('dragover', (e) => {
    e.preventDefault();
    uploadArea.classList.add('dragover');
  });
  
  uploadArea.addEventListener('dragleave', () => {
    uploadArea.classList.remove('dragover');
  });
  
  uploadArea.addEventListener('drop', (e) => {
    e.preventDefault();
    uploadArea.classList.remove('dragover');
    
    if (e.dataTransfer.files.length > 0) {
      const file = e.dataTransfer.files[0];
      if (file.type === 'application/pdf') {
        pdfFileInput.files = e.dataTransfer.files;
        handleFileSelect(e);
      } else {
        showError('请选择PDF文件');
      }
    }
  });
}

// 处理文件选择
function handleFileSelect(e) {
  const file = pdfFileInput.files[0];
  
  if (!file) return;
  
  if (file.type !== 'application/pdf') {
    showError('请选择PDF文件');
    return;
  }
  
  if (file.size > 20 * 1024 * 1024) { // 20MB
    showError('文件大小不能超过20MB');
    return;
  }
  
  pdfFile = file;
  
  // 显示加载状态
  uploadArea.style.display = 'none';
  loadingContainer.style.display = 'block';
  previewContainer.style.display = 'none';
  pdfInfoContainer.style.display = 'none';
  previewItems.innerHTML = '';
  renderedPages = [];
  
  // 读取PDF文件
  const reader = new FileReader();
  reader.onload = function(event) {
    const typedArray = new Uint8Array(event.target.result);
    loadPdfFromData(typedArray);
  };
  reader.readAsArrayBuffer(file);
}

// 从ArrayBuffer加载PDF
function loadPdfFromData(data) {
  pdfjsLib.getDocument({ data }).promise
    .then(pdf => {
      pdfDocument = pdf;
      
      // 更新PDF信息
      pdfNameValue.textContent = pdfFile.name;
      pdfSizeValue.textContent = formatFileSize(pdfFile.size);
      pdfPagesValue.textContent = pdf.numPages;
      
      // 渲染预览
      renderPdfPreview(pdf);
    })
    .catch(error => {
      console.error('PDF加载错误:', error);
      showError('无法加载PDF文件，请确保文件未损坏');
      resetUI();
    });
}

// 渲染PDF预览
function renderPdfPreview(pdf) {
  const totalPages = pdf.numPages;
  let renderedCount = 0;
  
  // 更新加载文本
  document.getElementById('loading-text').textContent = `正在渲染预览 (0/${totalPages})`;
  
  // 为每一页创建预览
  for (let pageNumber = 1; pageNumber <= totalPages; pageNumber++) {
    pdf.getPage(pageNumber).then(page => {
      const scale = 0.5; // 预览缩放比例
      const viewport = page.getViewport({ scale });
      
      // 创建canvas元素
      const canvas = document.createElement('canvas');
      const context = canvas.getContext('2d');
      canvas.width = viewport.width;
      canvas.height = viewport.height;
      
      // 渲染PDF页面到canvas
      const renderContext = {
        canvasContext: context,
        viewport: viewport
      };
      
      page.render(renderContext).promise.then(() => {
        renderedCount++;
        document.getElementById('loading-text').textContent = `正在渲染预览 (${renderedCount}/${totalPages})`;
        
        // 存储渲染的页面
        renderedPages[pageNumber - 1] = {
          pageNumber: pageNumber,
          canvas: canvas,
          width: viewport.width,
          height: viewport.height
        };
        
        // 如果所有页面都已渲染，显示预览
        if (renderedCount === totalPages) {
          displayPreviews();
        }
      });
    });
  }
}

// 显示预览
function displayPreviews() {
  // 按页码排序
  renderedPages.sort((a, b) => a.pageNumber - b.pageNumber);
  
  // 清空预览容器
  previewItems.innerHTML = '';
  
  // 添加每一页的预览
  renderedPages.forEach(page => {
    const colDiv = document.createElement('div');
    colDiv.className = 'col-md-6 col-lg-4 preview-item';
    
    const pageNumberDiv = document.createElement('div');
    pageNumberDiv.className = 'page-number';
    pageNumberDiv.textContent = `第 ${page.pageNumber} 页`;
    
    // 克隆canvas以避免原始canvas被修改
    const displayCanvas = document.createElement('canvas');
    displayCanvas.width = page.canvas.width;
    displayCanvas.height = page.canvas.height;
    const displayContext = displayCanvas.getContext('2d');
    displayContext.drawImage(page.canvas, 0, 0);
    
    colDiv.appendChild(displayCanvas);
    colDiv.appendChild(pageNumberDiv);
    previewItems.appendChild(colDiv);
  });
  
  // 显示预览和控制面板
  loadingContainer.style.display = 'none';
  pdfInfoContainer.style.display = 'block';
  previewContainer.style.display = 'block';
}

// 导出图片
function exportImages() {
  if (!pdfDocument || renderedPages.length === 0) {
    showError('没有可导出的内容');
    return;
  }
  
  const combinePages = combinePagesSwitch.checked;
  const highQuality = highQualitySwitch.checked;
  const scale = highQuality ? 2.0 : 1.0;
  
  // 显示加载状态
  loadingContainer.style.display = 'block';
  document.getElementById('loading-text').textContent = '正在准备导出...';
  
  if (combinePages) {
    // 合并为单张图片
    exportCombinedImage(scale);
  } else {
    // 导出为多张图片
    exportMultipleImages(scale);
  }
}

// 导出合并的单张图片
function exportCombinedImage(scale) {
  // 计算合并后的图片尺寸
  let totalHeight = 0;
  let maxWidth = 0;
  
  renderedPages.forEach(page => {
    totalHeight += page.height * (scale / 0.5);
    maxWidth = Math.max(maxWidth, page.width * (scale / 0.5));
  });
  
  // 创建合并的canvas
  const combinedCanvas = document.createElement('canvas');
  combinedCanvas.width = maxWidth;
  combinedCanvas.height = totalHeight;
  const combinedContext = combinedCanvas.getContext('2d');
  
  // 填充白色背景
  combinedContext.fillStyle = '#FFFFFF';
  combinedContext.fillRect(0, 0, combinedCanvas.width, combinedCanvas.height);
  
  // 重新渲染每一页到合并的canvas
  let currentY = 0;
  let renderedCount = 0;
  
  const renderNextPage = (index) => {
    if (index >= renderedPages.length) {
      // 所有页面都已渲染，导出图片
      combinedCanvas.toBlob(blob => {
        saveAs(blob, `${pdfFile.name.replace('.pdf', '')}_combined.png`);
        loadingContainer.style.display = 'none';
      }, 'image/png');
      return;
    }
    
    const page = renderedPages[index];
    
    // 更新加载文本
    document.getElementById('loading-text').textContent = `正在合并页面 (${index + 1}/${renderedPages.length})`;
    
    // 获取原始页面
    pdfDocument.getPage(page.pageNumber).then(pdfPage => {
      const viewport = pdfPage.getViewport({ scale });
      
      // 创建临时canvas
      const tempCanvas = document.createElement('canvas');
      tempCanvas.width = viewport.width;
      tempCanvas.height = viewport.height;
      const tempContext = tempCanvas.getContext('2d');
      
      // 渲染到临时canvas
      const renderContext = {
        canvasContext: tempContext,
        viewport: viewport
      };
      
      pdfPage.render(renderContext).promise.then(() => {
        // 将临时canvas的内容绘制到合并的canvas
        const x = (maxWidth - viewport.width) / 2; // 居中
        combinedContext.drawImage(tempCanvas, x, currentY);
        
        // 更新Y坐标
        currentY += viewport.height;
        
        // 渲染下一页
        renderNextPage(index + 1);
      });
    });
  };
  
  // 开始渲染第一页
  renderNextPage(0);
}

// 导出多张图片
function exportMultipleImages(scale) {
  const zip = new JSZip();
  const folder = zip.folder("images");
  let processedCount = 0;
  
  // 更新加载文本
  document.getElementById('loading-text').textContent = `正在导出图片 (0/${renderedPages.length})`;
  
  // 处理每一页
  renderedPages.forEach((page, index) => {
    // 获取原始页面
    pdfDocument.getPage(page.pageNumber).then(pdfPage => {
      const viewport = pdfPage.getViewport({ scale });
      
      // 创建canvas
      const canvas = document.createElement('canvas');
      canvas.width = viewport.width;
      canvas.height = viewport.height;
      const context = canvas.getContext('2d');
      
      // 填充白色背景
      context.fillStyle = '#FFFFFF';
      context.fillRect(0, 0, canvas.width, canvas.height);
      
      // 渲染PDF页面到canvas
      const renderContext = {
        canvasContext: context,
        viewport: viewport
      };
      
      pdfPage.render(renderContext).promise.then(() => {
        // 将canvas转换为blob
        canvas.toBlob(blob => {
          // 添加到zip
          folder.file(`page_${page.pageNumber}.png`, blob);
          
          processedCount++;
          document.getElementById('loading-text').textContent = `正在导出图片 (${processedCount}/${renderedPages.length})`;
          
          // 如果所有页面都已处理，生成并下载zip
          if (processedCount === renderedPages.length) {
            zip.generateAsync({ type: 'blob' }).then(content => {
              saveAs(content, `${pdfFile.name.replace('.pdf', '')}_images.zip`);
              loadingContainer.style.display = 'none';
            });
          }
        }, 'image/png');
      });
    });
  });
}

// 辅助函数
function formatFileSize(bytes) {
  if (bytes < 1024) return bytes + ' B';
  else if (bytes < 1048576) return (bytes / 1024).toFixed(2) + ' KB';
  else return (bytes / 1048576).toFixed(2) + ' MB';
}

function showError(message) {
  alert(message);
}

function resetUI() {
  uploadArea.style.display = 'block';
  loadingContainer.style.display = 'none';
  pdfInfoContainer.style.display = 'none';
  previewContainer.style.display = 'none';
  pdfFileInput.value = '';
}