PdfProcessing/drag_signature.py

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

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


def download_image_from_url(url, output_path):
    """从URL下载图片到本地"""
    response = requests.get(url, stream=True)
    response.raise_for_status()
    
    # 判断文件类型
    content_type = response.headers.get('content-type', '').lower()
    if 'image' in content_type:
        with open(output_path, 'wb') as f:
            for chunk in response.iter_content(chunk_size=8192):
                f.write(chunk)
        return output_path
    else:
        raise Exception(f"不支持的图片类型: {content_type}")


def add_signature_at_position(input_pdf, output_pdf, signature_url, page_num, x, y, width=None, height=None):
    """
    在PDF的指定位置添加签名或电子章
    
    参数:
    - input_pdf: 输入PDF文件路径
    - output_pdf: 输出PDF文件路径
    - signature_url: 签名/电子章的URL（可以是图片）
    - page_num: 页码（从0开始）
    - x: X坐标（相对于PDF页面左下角，单位：点）
    - y: Y坐标（相对于PDF页面左下角，单位：点）
    - width: 签名宽度（可选，单位：点，默认43mm）
    - height: 签名高度（可选，单位：点，默认按比例）
    """
    try:
        # 下载签名图片
        temp_signature = os.path.join(tempfile.gettempdir(), f"temp_signature_{os.urandom(8).hex()}")
        try:
            # 尝试下载为图片
            download_image_from_url(signature_url, temp_signature)
            signature_path = temp_signature
        except Exception as e:
            logger.error(f"下载签名失败: {e}")
            raise Exception(f"无法下载签名图片: {e}")
        
        # 读取PDF
        reader = PdfReader(input_pdf)
        writer = PdfWriter()
        a4_width, a4_height = A4  # (595.2, 841.68)
        
        # 确保页码有效
        if page_num >= len(reader.pages):
            raise Exception(f"页码超出范围，PDF共有{len(reader.pages)}页")
        
        # 处理每一页
        for page_index in range(len(reader.pages)):
            page = reader.pages[page_index]
            
            # 只在指定页面添加签名
            if page_index == page_num:
                # 创建覆盖层
                packet = io.BytesIO()
                can = canvas.Canvas(packet, pagesize=A4)
                
                # 打开图片并获取尺寸
                try:
                    img = Image.open(signature_path)
                    img_width, img_height = img.size
                    aspect_ratio = img_height / img_width
                    
                    # 设置签名尺寸
                    if width is None:
                        new_width = 43 * (72 / 25.4)  # 43mm转换为点
                    else:
                        new_width = width
                    
                    if height is None:
                        new_height = new_width * aspect_ratio
                    else:
                        new_height = height
                    
                    # 转换坐标：前端传入的坐标通常是相对于页面左上角，需要转换为左下角
                    # y坐标需要从页面顶部翻转到底部
                    pdf_x = x
                    pdf_y = a4_height - y - new_height  # 翻转Y坐标
                    
                    # 确保坐标在页面范围内
                    pdf_x = max(0, min(pdf_x, a4_width - new_width))
                    pdf_y = max(0, min(pdf_y, a4_height - new_height))
                    
                    # 绘制图片
                    can.drawImage(signature_path, pdf_x, pdf_y, width=new_width, height=new_height, mask='auto')
                    can.save()
                    
                    # 合并覆盖层到PDF页面
                    packet.seek(0)
                    overlay_pdf = PdfReader(packet)
                    page.merge_page(overlay_pdf.pages[0])
                except Exception as e:
                    logger.error(f"处理图片失败: {e}")
                    raise Exception(f"处理签名图片失败: {e}")
            
            writer.add_page(page)
        
        # 保存PDF
        with open(output_pdf, "wb") as f:
            writer.write(f)
        
        # 清理临时文件
        try:
            if os.path.exists(signature_path):
                os.remove(signature_path)
        except:
            pass
        
        logger.info(f"成功添加签名到PDF: {output_pdf}")
        return True
        
    except Exception as e:
        logger.error(f"添加签名失败: {e}")
        # 清理临时文件
        try:
            if 'signature_path' in locals() and os.path.exists(signature_path):
                os.remove(signature_path)
        except:
            pass
        raise


def add_multiple_signatures(input_pdf, output_pdf, signatures):
    """
    在PDF的多个位置添加签名
    
    参数:
    - input_pdf: 输入PDF文件路径
    - output_pdf: 输出PDF文件路径
    - signatures: 签名列表，每个元素为字典：
        {
            'signature_url': '签名URL',
            'page_num': 页码（从0开始）,
            'x': X坐标,
            'y': Y坐标,
            'width': 宽度（可选）,
            'height': 高度（可选）
        }
    """
    try:
        # 读取PDF
        reader = PdfReader(input_pdf)
        writer = PdfWriter()
        
        # 按页码分组签名
        signatures_by_page = {}
        for sig in signatures:
            page_num = sig['page_num']
            if page_num not in signatures_by_page:
                signatures_by_page[page_num] = []
            signatures_by_page[page_num].append(sig)
        
        # 处理每一页
        for page_index in range(len(reader.pages)):
            page = reader.pages[page_index]
            
            # 如果这一页有签名，添加所有签名
            if page_index in signatures_by_page:
                # 获取PDF页面实际尺寸（单位：点）
                page_box = page.mediabox
                page_width = float(page_box.width)
                page_height = float(page_box.height)
                
                # 创建覆盖层，使用PDF页面实际尺寸
                packet = io.BytesIO()
                can = canvas.Canvas(packet, pagesize=(page_width, page_height))
                
                for sig in signatures_by_page[page_index]:
                    try:
                        # 下载签名图片
                        temp_signature = os.path.join(tempfile.gettempdir(), f"temp_sig_{os.urandom(8).hex()}")
                        download_image_from_url(sig['signature_url'], temp_signature)
                        
                        # 打开图片并获取尺寸
                        img = Image.open(temp_signature)
                        img_width, img_height = img.size
                        aspect_ratio = img_height / img_width
                        
                        # 设置签名尺寸（前端传入的已经是点坐标）
                        new_width = sig.get('width', 43 * (72 / 25.4))
                        new_height = sig.get('height', new_width * aspect_ratio)
                        
                        # 转换坐标：前端传入的y坐标是相对于页面左上角，需要转换为左下角
                        # PDF坐标系：左下角为原点，y向上
                        pdf_x = sig['x']
                        pdf_y = page_height - sig['y'] - new_height
                        
                        # 确保坐标在页面范围内
                        pdf_x = max(0, min(pdf_x, page_width - new_width))
                        pdf_y = max(0, min(pdf_y, page_height - new_height))
                        
                        # 绘制图片
                        can.drawImage(temp_signature, pdf_x, pdf_y, width=new_width, height=new_height, mask='auto')
                        
                        # 清理临时文件
                        os.remove(temp_signature)
                    except Exception as e:
                        logger.error(f"添加签名失败: {e}")
                        if os.path.exists(temp_signature):
                            try:
                                os.remove(temp_signature)
                            except:
                                pass
                        continue
                
                can.save()
                packet.seek(0)
                overlay_pdf = PdfReader(packet)
                page.merge_page(overlay_pdf.pages[0])
            
            writer.add_page(page)
        
        # 保存PDF
        with open(output_pdf, "wb") as f:
            writer.write(f)
        
        logger.info(f"成功添加多个签名到PDF: {output_pdf}")
        return True
        
    except Exception as e:
        logger.error(f"添加多个签名失败: {e}")
        raise