wehub-skill-sync
613 lines
16 KiB
Markdown
613 lines
16 KiB
Markdown
# PDF 处理高级参考
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本文档包含主要技能说明中未涵盖的高级 PDF 处理功能、详细示例和附加库。
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## pypdfium2 库（Apache/BSD 许可证）
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### 概述
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pypdfium2 是 PDFium（Chromium 的 PDF 库）的 Python 绑定。它非常适合快速 PDF 渲染、图片生成，并且可以作为 PyMuPDF 的替代方案。
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### 将 PDF 渲染为图片
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```python
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import pypdfium2 as pdfium
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from PIL import Image
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# 加载 PDF
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pdf = pdfium.PdfDocument("document.pdf")
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# 将页面渲染为图片
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page = pdf[0] # 第一页
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bitmap = page.render(
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scale=2.0, # 更高分辨率
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rotation=0 # 不旋转
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)
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# 转换为 PIL Image
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img = bitmap.to_pil()
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img.save("page_1.png", "PNG")
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# 处理多个页面
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for i, page in enumerate(pdf):
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bitmap = page.render(scale=1.5)
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img = bitmap.to_pil()
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img.save(f"page_{i+1}.jpg", "JPEG", quality=90)
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```
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### 使用 pypdfium2 提取文本
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```python
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import pypdfium2 as pdfium
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pdf = pdfium.PdfDocument("document.pdf")
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for i, page in enumerate(pdf):
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text = page.get_text()
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print(f"第 {i+1} 页文本长度：{len(text)} 个字符")
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```
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## JavaScript 库
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### pdf-lib（MIT 许可证）
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pdf-lib 是一个功能强大的 JavaScript 库，用于在任何 JavaScript 环境中创建和修改 PDF 文档。
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#### 加载和操作现有 PDF
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```javascript
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import { PDFDocument } from 'pdf-lib';
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import fs from 'fs';
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async function manipulatePDF() {
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// 加载现有 PDF
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const existingPdfBytes = fs.readFileSync('input.pdf');
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const pdfDoc = await PDFDocument.load(existingPdfBytes);
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// 获取页数
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const pageCount = pdfDoc.getPageCount();
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console.log(`文档共有 ${pageCount} 页`);
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// 添加新页面
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const newPage = pdfDoc.addPage([600, 400]);
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newPage.drawText('由 pdf-lib 添加', {
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x: 100,
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y: 300,
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size: 16
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});
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// 保存修改后的 PDF
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const pdfBytes = await pdfDoc.save();
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fs.writeFileSync('modified.pdf', pdfBytes);
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}
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```
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#### 从零开始创建复杂 PDF
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```javascript
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import { PDFDocument, rgb, StandardFonts } from 'pdf-lib';
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import fs from 'fs';
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async function createPDF() {
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const pdfDoc = await PDFDocument.create();
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// 添加字体
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const helveticaFont = await pdfDoc.embedFont(StandardFonts.Helvetica);
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const helveticaBold = await pdfDoc.embedFont(StandardFonts.HelveticaBold);
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// 添加页面
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const page = pdfDoc.addPage([595, 842]); // A4 尺寸
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const { width, height } = page.getSize();
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// 添加带样式的文本
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page.drawText('发票 #12345', {
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x: 50,
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y: height - 50,
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size: 18,
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font: helveticaBold,
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color: rgb(0.2, 0.2, 0.8)
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});
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// 添加矩形（页眉背景）
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page.drawRectangle({
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x: 40,
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y: height - 100,
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width: width - 80,
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height: 30,
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color: rgb(0.9, 0.9, 0.9)
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});
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// 添加表格类内容
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const items = [
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['项目', '数量', '单价', '合计'],
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['小工具', '2', '$50', '$100'],
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['小装置', '1', '$75', '$75']
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];
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let yPos = height - 150;
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items.forEach(row => {
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let xPos = 50;
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row.forEach(cell => {
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page.drawText(cell, {
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x: xPos,
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y: yPos,
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size: 12,
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font: helveticaFont
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});
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xPos += 120;
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});
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yPos -= 25;
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});
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const pdfBytes = await pdfDoc.save();
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fs.writeFileSync('created.pdf', pdfBytes);
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}
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```
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#### 高级合并与拆分操作
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```javascript
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import { PDFDocument } from 'pdf-lib';
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import fs from 'fs';
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async function mergePDFs() {
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// 创建新文档
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const mergedPdf = await PDFDocument.create();
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// 加载源 PDF
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const pdf1Bytes = fs.readFileSync('doc1.pdf');
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const pdf2Bytes = fs.readFileSync('doc2.pdf');
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const pdf1 = await PDFDocument.load(pdf1Bytes);
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const pdf2 = await PDFDocument.load(pdf2Bytes);
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// 从第一个 PDF 复制页面
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const pdf1Pages = await mergedPdf.copyPages(pdf1, pdf1.getPageIndices());
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pdf1Pages.forEach(page => mergedPdf.addPage(page));
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// 从第二个 PDF 复制特定页面（第 0、2、4 页）
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const pdf2Pages = await mergedPdf.copyPages(pdf2, [0, 2, 4]);
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pdf2Pages.forEach(page => mergedPdf.addPage(page));
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const mergedPdfBytes = await mergedPdf.save();
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fs.writeFileSync('merged.pdf', mergedPdfBytes);
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}
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```
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### pdfjs-dist（Apache 许可证）
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PDF.js 是 Mozilla 的 JavaScript 库，用于在浏览器中渲染 PDF。
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#### 基本的 PDF 加载与渲染
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```javascript
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import * as pdfjsLib from 'pdfjs-dist';
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// 配置 worker（对性能很重要）
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pdfjsLib.GlobalWorkerOptions.workerSrc = './pdf.worker.js';
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async function renderPDF() {
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// 加载 PDF
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const loadingTask = pdfjsLib.getDocument('document.pdf');
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const pdf = await loadingTask.promise;
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console.log(`已加载 PDF，共 ${pdf.numPages} 页`);
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// 获取第一页
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const page = await pdf.getPage(1);
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const viewport = page.getViewport({ scale: 1.5 });
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// 渲染到 canvas
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const canvas = document.createElement('canvas');
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const context = canvas.getContext('2d');
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canvas.height = viewport.height;
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canvas.width = viewport.width;
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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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await page.render(renderContext).promise;
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document.body.appendChild(canvas);
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}
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```
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#### 提取带坐标的文本
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```javascript
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import * as pdfjsLib from 'pdfjs-dist';
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async function extractText() {
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const loadingTask = pdfjsLib.getDocument('document.pdf');
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const pdf = await loadingTask.promise;
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let fullText = '';
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// 从所有页面提取文本
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for (let i = 1; i <= pdf.numPages; i++) {
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const page = await pdf.getPage(i);
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const textContent = await page.getTextContent();
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const pageText = textContent.items
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.map(item => item.str)
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.join(' ');
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fullText += `\n--- 第 ${i} 页 ---\n${pageText}`;
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// 获取带坐标的文本以供高级处理
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const textWithCoords = textContent.items.map(item => ({
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text: item.str,
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x: item.transform[4],
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y: item.transform[5],
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width: item.width,
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height: item.height
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}));
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}
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console.log(fullText);
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return fullText;
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}
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```
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#### 提取注释和表单
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```javascript
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import * as pdfjsLib from 'pdfjs-dist';
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async function extractAnnotations() {
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const loadingTask = pdfjsLib.getDocument('annotated.pdf');
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const pdf = await loadingTask.promise;
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for (let i = 1; i <= pdf.numPages; i++) {
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const page = await pdf.getPage(i);
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const annotations = await page.getAnnotations();
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annotations.forEach(annotation => {
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console.log(`注释类型：${annotation.subtype}`);
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console.log(`内容：${annotation.contents}`);
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console.log(`坐标：${JSON.stringify(annotation.rect)}`);
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});
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}
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}
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```
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## 高级命令行操作
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### poppler-utils 高级功能
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#### 提取带边界框坐标的文本
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```bash
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# 提取带边界框坐标的文本（对结构化数据至关重要）
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pdftotext -bbox-layout document.pdf output.xml
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# XML 输出中包含每个文本元素的精确坐标
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```
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#### 高级图片转换
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```bash
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# 转换为指定分辨率的 PNG 图片
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pdftoppm -png -r 300 document.pdf output_prefix
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# 以高分辨率转换指定页面范围
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pdftoppm -png -r 600 -f 1 -l 3 document.pdf high_res_pages
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# 转换为 JPEG 并设置质量
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pdftoppm -jpeg -jpegopt quality=85 -r 200 document.pdf jpeg_output
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```
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#### 提取嵌入图片
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```bash
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# 提取所有嵌入图片及元数据
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pdfimages -j -p document.pdf page_images
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# 列出图片信息（不提取）
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pdfimages -list document.pdf
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# 以原始格式提取图片
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pdfimages -all document.pdf images/img
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```
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### qpdf 高级功能
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#### 复杂页面操作
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```bash
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# 将 PDF 拆分为多组页面
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qpdf --split-pages=3 input.pdf output_group_%02d.pdf
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# 使用复杂页码范围提取特定页面
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qpdf input.pdf --pages input.pdf 1,3-5,8,10-end -- extracted.pdf
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# 合并来自多个 PDF 的特定页面
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qpdf --empty --pages doc1.pdf 1-3 doc2.pdf 5-7 doc3.pdf 2,4 -- combined.pdf
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```
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#### PDF 优化与修复
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```bash
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# 优化 PDF 以便网络传输（线性化以实现流式传输）
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qpdf --linearize input.pdf optimized.pdf
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# 移除未使用对象并压缩
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qpdf --optimize-level=all input.pdf compressed.pdf
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# 尝试修复损坏的 PDF 结构
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qpdf --check input.pdf
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qpdf --fix-qdf damaged.pdf repaired.pdf
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# 显示详细 PDF 结构以进行调试
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qpdf --show-all-pages input.pdf > structure.txt
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```
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#### 高级加密
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```bash
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# 添加带特定权限的密码保护
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qpdf --encrypt user_pass owner_pass 256 --print=none --modify=none -- input.pdf encrypted.pdf
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# 检查加密状态
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qpdf --show-encryption encrypted.pdf
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# 移除密码保护（需要密码）
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qpdf --password=secret123 --decrypt encrypted.pdf decrypted.pdf
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```
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## 高级 Python 技术
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### pdfplumber 高级功能
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#### 提取带精确坐标的文本
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```python
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import pdfplumber
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with pdfplumber.open("document.pdf") as pdf:
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page = pdf.pages[0]
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# 提取所有文本及坐标
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chars = page.chars
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for char in chars[:10]: # 前 10 个字符
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print(f"字符：'{char['text']}' 位置 x:{char['x0']:.1f} y:{char['y0']:.1f}")
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# 按边界框提取文本（左、上、右、下）
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bbox_text = page.within_bbox((100, 100, 400, 200)).extract_text()
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```
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#### 自定义设置的高级表格提取
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```python
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import pdfplumber
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import pandas as pd
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with pdfplumber.open("complex_table.pdf") as pdf:
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page = pdf.pages[0]
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# 使用自定义设置提取复杂布局的表格
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table_settings = {
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"vertical_strategy": "lines",
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"horizontal_strategy": "lines",
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"snap_tolerance": 3,
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"intersection_tolerance": 15
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}
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tables = page.extract_tables(table_settings)
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# 表格提取的可视化调试
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img = page.to_image(resolution=150)
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img.save("debug_layout.png")
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```
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### reportlab 高级功能
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#### 创建带表格的专业报告
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```python
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from reportlab.platypus import SimpleDocTemplate, Table, TableStyle, Paragraph
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from reportlab.lib.styles import getSampleStyleSheet
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from reportlab.lib import colors
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# 示例数据
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data = [
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['产品', 'Q1', 'Q2', 'Q3', 'Q4'],
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['小工具', '120', '135', '142', '158'],
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['小装置', '85', '92', '98', '105']
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]
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# 创建带表格的 PDF
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doc = SimpleDocTemplate("report.pdf")
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elements = []
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# 添加标题
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styles = getSampleStyleSheet()
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title = Paragraph("季度销售报告", styles['Title'])
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elements.append(title)
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# 添加带高级样式的表格
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table = Table(data)
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table.setStyle(TableStyle([
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('BACKGROUND', (0, 0), (-1, 0), colors.grey),
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('TEXTCOLOR', (0, 0), (-1, 0), colors.whitesmoke),
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('ALIGN', (0, 0), (-1, -1), 'CENTER'),
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('FONTNAME', (0, 0), (-1, 0), 'Helvetica-Bold'),
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('FONTSIZE', (0, 0), (-1, 0), 14),
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('BOTTOMPADDING', (0, 0), (-1, 0), 12),
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('BACKGROUND', (0, 1), (-1, -1), colors.beige),
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('GRID', (0, 0), (-1, -1), 1, colors.black)
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]))
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elements.append(table)
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doc.build(elements)
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```
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## 复杂工作流
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### 从 PDF 提取图形/图片
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#### 方法一：使用 pdfimages（最快）
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```bash
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# 以原始质量提取所有图片
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pdfimages -all document.pdf images/img
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```
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#### 方法二：使用 pypdfium2 + 图片处理
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```python
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import pypdfium2 as pdfium
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from PIL import Image
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import numpy as np
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def extract_figures(pdf_path, output_dir):
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pdf = pdfium.PdfDocument(pdf_path)
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for page_num, page in enumerate(pdf):
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# 渲染高分辨率页面
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bitmap = page.render(scale=3.0)
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img = bitmap.to_pil()
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# 转换为 numpy 以进行处理
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img_array = np.array(img)
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# 简单的图形检测（非白色区域）
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mask = np.any(img_array != [255, 255, 255], axis=2)
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# 查找轮廓并提取边界框
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# （此处已简化——实际实现需要更复杂的检测）
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# 保存检测到的图形
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# ……具体实现取决于实际需求
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```
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### 带错误处理的批量 PDF 处理
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```python
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import os
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import glob
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from pypdf import PdfReader, PdfWriter
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import logging
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logging.basicConfig(level=logging.INFO)
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logger = logging.getLogger(__name__)
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def batch_process_pdfs(input_dir, operation='merge'):
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pdf_files = glob.glob(os.path.join(input_dir, "*.pdf"))
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if operation == 'merge':
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writer = PdfWriter()
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for pdf_file in pdf_files:
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try:
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reader = PdfReader(pdf_file)
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for page in reader.pages:
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writer.add_page(page)
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logger.info(f"已处理：{pdf_file}")
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except Exception as e:
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logger.error(f"处理 {pdf_file} 失败：{e}")
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continue
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with open("batch_merged.pdf", "wb") as output:
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writer.write(output)
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elif operation == 'extract_text':
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for pdf_file in pdf_files:
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try:
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reader = PdfReader(pdf_file)
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text = ""
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for page in reader.pages:
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text += page.extract_text()
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output_file = pdf_file.replace('.pdf', '.txt')
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with open(output_file, 'w', encoding='utf-8') as f:
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f.write(text)
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logger.info(f"已从以下文件提取文本：{pdf_file}")
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except Exception as e:
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logger.error(f"从 {pdf_file} 提取文本失败：{e}")
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continue
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```
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||
### 高级 PDF 裁剪
|
||
```python
|
||
from pypdf import PdfWriter, PdfReader
|
||
|
||
reader = PdfReader("input.pdf")
|
||
writer = PdfWriter()
|
||
|
||
# 裁剪页面（左、下、右、上，单位：点）
|
||
page = reader.pages[0]
|
||
page.mediabox.left = 50
|
||
page.mediabox.bottom = 50
|
||
page.mediabox.right = 550
|
||
page.mediabox.top = 750
|
||
|
||
writer.add_page(page)
|
||
with open("cropped.pdf", "wb") as output:
|
||
writer.write(output)
|
||
```
|
||
|
||
## 性能优化技巧
|
||
|
||
### 1. 处理大型 PDF
|
||
- 使用流式方法而非将整个 PDF 加载到内存
|
||
- 使用 `qpdf --split-pages` 拆分大文件
|
||
- 使用 pypdfium2 逐页处理
|
||
|
||
### 2. 文本提取
|
||
- `pdftotext -bbox-layout` 是纯文本提取最快的方案
|
||
- 使用 pdfplumber 处理结构化数据和表格
|
||
- 对于非常大的文档，避免使用 `pypdf.extract_text()`
|
||
|
||
### 3. 图片提取
|
||
- `pdfimages` 比渲染页面快得多
|
||
- 预览使用低分辨率，最终输出使用高分辨率
|
||
|
||
### 4. 表单填写
|
||
- pdf-lib 比大多数替代方案更好地保留表单结构
|
||
- 处理前预先验证表单字段
|
||
|
||
### 5. 内存管理
|
||
```python
|
||
# 分块处理 PDF
|
||
def process_large_pdf(pdf_path, chunk_size=10):
|
||
reader = PdfReader(pdf_path)
|
||
total_pages = len(reader.pages)
|
||
|
||
for start_idx in range(0, total_pages, chunk_size):
|
||
end_idx = min(start_idx + chunk_size, total_pages)
|
||
writer = PdfWriter()
|
||
|
||
for i in range(start_idx, end_idx):
|
||
writer.add_page(reader.pages[i])
|
||
|
||
# 处理块
|
||
with open(f"chunk_{start_idx//chunk_size}.pdf", "wb") as output:
|
||
writer.write(output)
|
||
```
|
||
|
||
## 常见问题排查
|
||
|
||
### 加密的 PDF
|
||
```python
|
||
# 处理密码保护的 PDF
|
||
from pypdf import PdfReader
|
||
|
||
try:
|
||
reader = PdfReader("encrypted.pdf")
|
||
if reader.is_encrypted:
|
||
reader.decrypt("password")
|
||
except Exception as e:
|
||
print(f"解密失败：{e}")
|
||
```
|
||
|
||
### 损坏的 PDF
|
||
```bash
|
||
# 使用 qpdf 修复
|
||
qpdf --check corrupted.pdf
|
||
qpdf --replace-input corrupted.pdf
|
||
```
|
||
|
||
### 文本提取问题
|
||
```python
|
||
# 对扫描件回退到 OCR
|
||
import pytesseract
|
||
from pdf2image import convert_from_path
|
||
|
||
def extract_text_with_ocr(pdf_path):
|
||
images = convert_from_path(pdf_path)
|
||
text = ""
|
||
for i, image in enumerate(images):
|
||
text += pytesseract.image_to_string(image)
|
||
return text
|
||
```
|
||
|
||
## 许可证信息
|
||
|
||
- **pypdf**：BSD 许可证
|
||
- **pdfplumber**：MIT 许可证
|
||
- **pypdfium2**：Apache/BSD 许可证
|
||
- **reportlab**：BSD 许可证
|
||
- **poppler-utils**：GPL-2 许可证
|
||
- **qpdf**：Apache 许可证
|
||
- **pdf-lib**：MIT 许可证
|
||
- **pdfjs-dist**：Apache 许可证
|