PDF 加水印

复制from reportlab.lib.pagesizes import letter
from reportlab.pdfgen import canvas
from reportlab.lib.units import inch
import io

# 生成一个示例 PDF 并添加文字水印
def add_text_watermark(input_pdf_path, output_pdf_path, watermark_text="CONFIDENTIAL"):
    # 创建水印层
    packet = io.BytesIO()
    c = canvas.Canvas(packet, pagesize=letter)
    c.setFont("Helvetica", 60)
    c.setFillAlpha(0.2)  # 透明度
    c.saveState()
    c.translate(letter[0]/2, letter[1]/2)
    c.rotate(45)
    c.drawCentredString(0, 0, watermark_text)
    c.restoreState()
    c.save()
    packet.seek(0)
    
    # 合并到原 PDF
    from PyPDF2 import PdfReader, PdfWriter
    reader = PdfReader(input_pdf_path)
    watermark = PdfReader(packet)
    writer = PdfWriter()
    
    for page in reader.pages:
        page.merge_page(watermark.pages[0])
        writer.add_page(page)
    
    with open(output_pdf_path, "wb") as f:
        writer.write(f)

# 使用示例（假设已有 input.pdf）
# add_text_watermark("input.pdf", "output.pdf", "SAMPLE")

复制package main

import (
	"github.com/unidoc/unipdf/v3/common/license"
	"github.com/unidoc/unipdf/v3/creator"
	"github.com/unidoc/unipdf/v3/model"
	"log"
)

func addWatermark(inputPath, outputPath, text string) {
	// 初始化许可证（生产环境需设置有效 key）
	license.SetMeteredKey("")

	// 读取源 PDF
	reader, err := model.NewPdfReaderFromFile(inputPath, nil)
	if err != nil {
		log.Fatal(err)
	}

	// 创建新 PDF
	c := creator.New()
	numPages, _ := reader.GetNumPages()

	for i := 1; i <= numPages; i++ {
		page, _ := reader.GetPage(i)
		c.AddPage(page)

		// 添加水印
		wm := c.NewText(text)
		wm.SetFontSize(48)
		wm.SetColor(creator.ColorRGBFromHex("#cccccc"))
		wm.SetOpacity(0.3)
		wm.SetAngle(45)
		wm.SetPos(200, 400)
		c.Draw(wm)
	}

	c.WriteToFile(outputPath)
}

func main() {
	addWatermark("input.pdf", "output.pdf", "DRAFT")
}

复制const { PDFDocument, rgb, degrees } = require('pdf-lib');
const fs = require('fs');

async function addWatermark(inputPath, outputPath, text = 'WATERMARK') {
  const pdfDoc = await PDFDocument.load(fs.readFileSync(inputPath));
  const pages = pdfDoc.getPages();
  
  pages.forEach((page) => {
    const { width, height } = page.getSize();
    page.drawText(text, {
      x: width / 2 - 100,
      y: height / 2,
      size: 50,
      opacity: 0.2,
      rotate: degrees(-45),
      color: rgb(0.8, 0.8, 0.8),
    });
  });

  const pdfBytes = await pdfDoc.save();
  fs.writeFileSync(outputPath, pdfBytes);
}

// 使用示例
// addWatermark('input.pdf', 'output.pdf', 'CONFIDENTIAL');