tools/python/add_watermark.py

#!/usr/bin/env python3
"""Add text watermark to PDF pages."""
import argparse, json, sys, io
from pathlib import Path

def add_watermark(input_path, output_path, text='CONFIDENTIAL', opacity=0.3, angle=45, font_size=48):
    from PyPDF2 import PdfReader, PdfWriter
    from reportlab.pdfgen import canvas
    
    reader = PdfReader(input_path)
    writer = PdfWriter()
    
    for page in reader.pages:
        media = page.mediabox
        pw = float(media.width)
        ph = float(media.height)
        
        packet = io.BytesIO()
        c = canvas.Canvas(packet, pagesize=(pw, ph))
        c.saveState()
        c.setFont("Helvetica-Bold", font_size)
        c.setFillAlpha(opacity)
        c.setFillColorRGB(0.5, 0.5, 0.5)
        c.translate(pw / 2, ph / 2)
        c.rotate(angle)
        c.drawCentredString(0, 0, text)
        c.restoreState()
        c.save()
        
        packet.seek(0)
        overlay = PdfReader(packet)
        page.merge_page(overlay.pages[0])
        writer.add_page(page)
    
    if not output_path:
        output_path = str(Path(input_path).with_stem(Path(input_path).stem + '_watermarked'))
    
    with open(output_path, 'wb') as f:
        writer.write(f)
    return output_path

def main():
    parser = argparse.ArgumentParser(description='Add watermark to PDF')
    parser.add_argument('--input', required=True)
    parser.add_argument('--output', required=True)
    parser.add_argument('--text', default='CONFIDENTIAL')
    parser.add_argument('--opacity', type=float, default=0.3)
    parser.add_argument('--angle', type=float, default=45)
    parser.add_argument('--font-size', type=int, default=48)
    args = parser.parse_args()
    try:
        result = add_watermark(args.input, args.output, args.text, args.opacity, args.angle, args.font_size)
        print(json.dumps({"success": True, "output": result, "message": "Watermark added successfully"}))
    except Exception as e:
        print(json.dumps({"success": False, "output": "", "message": str(e)}))
        sys.exit(1)

if __name__ == '__main__':
    main()