在函数计算中给 PDF 添加水印,可以使用 Python 的第三方库,如 PyPDF2 和 reportlab。以下是一个简单的示例代码:
from PyPDF2 import PdfFileReader, PdfFileWriter
from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import letter
def add_watermark(input_pdf_path, output_pdf_path, watermark_text):
# Read input PDF file
with open(input_pdf_path, 'rb') as f:
reader = PdfFileReader(f)
# Create output PDF writer
writer = PdfFileWriter()
# Add watermark to each page
for i in range(reader.getNumPages()):
# Get page and create canvas for watermark
page = reader.getPage(i)
c = canvas.Canvas(page, pagesize=letter)
# Draw watermark text
c.setFont('Helvetica', 80)
c.setFillColorRGB(0.5, 0.5, 0.5)
c.saveState()
c.translate(0, letter[1] / 2)
c.rotate(45)
c.drawCentredString(0, 0, watermark_text)
c.restoreState()
# Merge page and watermark
c.showPage()
c.save()
# Add page to output PDF
writer.addPage(page)
# Write output PDF file
with open(output_pdf_path, 'wb') as f:
writer.write(f)
在你的函数代码中调用这个函数,并传入输入 PDF 文件路径、输出 PDF 文件路径和水印文本即可。
在阿里云函数计算(Function Compute,FC)中实现给PDF文件添加水印的步骤大致如下:
创建函数:
安装依赖:
PyPDF2
和reportlab
库,对于Node.js可以使用pdf-lib
库。编写代码:
from PyPDF2 import PdfFileReader, PdfFileWriter
from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import letter
def add_watermark(input_pdf_path, output_pdf_path, watermark_text):
# Read the input PDF
with open(input_pdf_path, 'rb') as f:
pdf_reader = PdfFileReader(f)
# Create a new PDF writer object
pdf_writer = PdfFileWriter()
for page_num in range(pdf_reader.getNumPages()):
# Add the page to the writer object
page = pdf_reader.getPage(page_num)
pdf_writer.addPage(page)
# Create a canvas to draw the watermark
c = canvas.Canvas(output_pdf_path, pagesize=letter)
# Draw the watermark text
c.setFillColorRGB(0.5, 0.5, 0.5) # Set the color (gray in this case)
c.setFont('Helvetica', 80) # Set the font and size
text_width, text_height = c.textExtent(watermark_text)
c.saveState()
c.translate(279.5 - text_width / 2, 421 - text_height / 2) # Position the text in the center of the page
c.rotate(45) # Rotate the text
c.drawString(0, 0, watermark_text)
c.restoreState()
# Save the changes to the output PDF
c.showPage()
c.save()
# Write the modified PDF to a new file
with open(output_pdf_path, 'wb') as f:
pdf_writer.write(f)
# Call the function with your input and output paths, and the watermark text
add_watermark('/path/to/input.pdf', '/path/to/output.pdf', 'Watermark Text')
配置触发器:
测试函数:
验证结果:
在阿里云函数计算(FC)中给PDF文件添加水印,你可以按照以下步骤进行:
准备环境和工具:
pdfbox
、PyPDF2
或 PDFtk
等。PyPDF2
,你可以在函数的初始化或构建脚本中运行 pip install PyPDF2
命令来安装这个库。编写加水印的函数代码:
以下是一个使用Python和PyPDF2
库添加文本水印的简单示例:
from PyPDF2 import PdfFileReader, PdfFileWriter
def add_watermark(input_pdf_path, output_pdf_path, watermark_text):
# 读取PDF文件
with open(input_pdf_path, 'rb') as f:
pdf_reader = PdfFileReader(f)
# 创建PDF写入对象
pdf_writer = PdfFileWriter()
for page_num in range(pdf_reader.getNumPages()):
# 获取页面
page = pdf_reader.getPage(page_num)
# 添加水印
page.mergePage(_add_text_watermark(page, watermark_text))
# 将修改后的页面写入新的PDF
pdf_writer.addPage(page)
# 保存结果到输出文件
with open(output_pdf_path, 'wb') as f:
pdf_writer.write(f)
def _add_text_watermark(page, text):
# 创建一个新的页面用于添加水印
watermarked_page = PdfFileWriter()
# 获取页面的媒体盒以确定水印的位置和大小
media_box = page.mediaBox
# 创建水印内容
watermark_content = "<< /Type /XObject /Subtype /Form /Resources << /Font << /F1 << /Type /Font /Subtype /Type1 /Name /F1 /BaseFont /Helvetica /Encoding /MacRomanEncoding >> >> >> /BBox [0 0 %.2f %.2f] /Matrix [1 0 0 1 0 0] /Length 0 >>" % (media_box.getWidth(), media_box.getHeight())
watermark_stream = "q BT /F1 36 Tf 1 0 0 1 50 50 Tm (%s) Tj ET Q" % (text)
# 创建PDF操作器
pdf_operation = PyPDF2.pdf.PdfOperation(PyPDF2.pdf.ContentStream.uncompressContent([watermark_content, watermark_stream]))
# 在新页面上应用水印操作
watermarked_page.addPage(page)
watermarked_page.operations.append(pdf_operation)
# 创建一个内存中的PDF文件来保存带有水印的页面
with BytesIO() as output:
watermarked_page.write(output)
watermarked_page_data = output.getvalue()
# 从内存中的PDF文件中读取带有水印的页面
watermarked_pdf = PdfFileReader(BytesIO(watermarked_page_data))
return watermarked_pdf.getPage(0)
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