PdfProcessing/add_signature.py

import io
import tempfile
from reportlab.lib.pagesizes import A4
import pdfplumber
from PyPDF2 import PdfReader, PdfWriter
from reportlab.pdfgen import canvas
from PIL import Image
import logging

# 配置日志
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)


def find_signature_positions(pdf_path, target_texts=["签字或盖章", "技术支持单位（盖章）"]):
    """查找所有签名位置"""
    positions = []
    with pdfplumber.open(pdf_path) as pdf:
        for i, page in enumerate(pdf.pages):
            for word in page.extract_words():
                for target in target_texts:
                    if target in word["text"]:
                        x, y = word["x0"], word["top"]
                        positions.append((i, x, y, target))
                        logger.info(f"找到签名位置: 第{i}页, {target} at ({x}, {y})")

    # 返回结果：所有"签字或盖章"和"技术支持单位（盖章）"的位置
    if len(positions) == 0 or positions == []:
        return None
        # 返回结果：第二个"签字或盖章"和技术支持单位位置
    result = []
    if len(positions) >= 2:
        result.append(positions[1])
        # 第二个出现的位置（索引1）
    else:
        result.append(positions[0])

    return result




def add_signature_to_pdf(input_pdf, output_pdf, signature_img, positions, offset_x=30, offset_y=-10):
    """添加签名到PDF"""
    reader = PdfReader(input_pdf)
    writer = PdfWriter()
    a4_width, a4_height = A4  # (595.2, 841.68)
    for page_index in range(len(reader.pages)):
        page = reader.pages[page_index]
        for pos in positions:
            if pos[0] == page_index:
                packet = io.BytesIO()
                can = canvas.Canvas(packet, pagesize=A4)
                img = Image.open(signature_img)
                img_width, img_height = img.size
                aspect_ratio = img_height / img_width
                new_width = 43 * (72 / 25.4)  # 40mm ≈ 113.39点
                new_height = new_width * aspect_ratio
                x, y = pos[1], a4_height - pos[2]
                if pos[3] == "技术支持单位（盖章）":
                    y = y - new_height / 2
                else:
                    y = y - new_height / 3 * 2
                x = max(0, min(x, a4_width - new_width))
                y = max(0, min(y, a4_height - new_height))
                can.drawImage(signature_img, x, y, width=new_width, height=new_height, mask='auto')
                can.save()
                packet.seek(0)
                overlay_pdf = PdfReader(packet)
                page.merge_page(overlay_pdf.pages[0])
        writer.add_page(page)

    with open(output_pdf, "wb") as f:
        writer.write(f)