Python處理PDF及生成多層PDF

Python提供了眾多的PDF支持庫，本文是在Python3環境下，試用了兩個庫來完成PDF的生成的功能。PyPDF對於讀取PDF支持較好，但是沒找到生成多層PDF的方法。Reportlab看起來更成熟，能夠利用Canvas很方便的生成多層PDF，這樣就能夠實現圖片掃描上來的內容也可以進行內容搜索的目標。

Reportlab

生成雙層PDF

雙層PDF應用PDF中的Canvas概念，先畫文字，最后將圖片畫上去，這樣就是兩層的PDF。

import os
# import urllib2
import time
from reportlab import platypus
from reportlab.lib.pagesizes import letter
from reportlab.lib.units import inch
from reportlab.platypus import SimpleDocTemplate, Image
from reportlab.pdfgen import canvas

image_file = "./42.png"

# Use Canvas to generate pdf
c = canvas.Canvas('reportlab_canvas.pdf', pagesize=letter)
width, height = letter

c.setFillColorRGB(0,0.77,0.77)
# say hello (note after rotate the y coord needs to be negative!)
c.drawString( 3*inch, 3*inch, "Hello World")
c.drawImage(image_file, 0 , 0)
c.showPage()
c.save()

PyPDF2

讀取PDF

from PyPDF2 import PdfFileWriter, PdfFileReader

output = PdfFileWriter()
input1 = PdfFileReader(open("jquery.pdf", "rb"))

# print document info
print(input1.getDocumentInfo())

# print how many pages input1 has:
print ("pdf_document.pdf has %d pages." % input1.getNumPages())

# print page content
page_content = input1.getPage(0).extractText()
print( page_content )

# add page 1 from input1 to output document, unchanged
output.addPage(input1.getPage(0))

# add page 2 from input1, but rotated clockwise 90 degrees
output.addPage(input1.getPage(1).rotateClockwise(90))

# finally, write "output" to document-output.pdf
outputStream = open("PyPDF2-output.pdf", "wb")
output.write(outputStream)

但是PyPDF獲取PDF內容有很多問題，可以看這個問題列表。文檔中也有說明。

| extractText(self) | ## | # Locate all text drawing commands, in the order they are provided in the | # content stream, and extract the text. This works well for some PDF | # files, but poorly for others, depending on the generator used. This will | # be refined in the future. Do not rely on the order of text coming out of | # this function, as it will change if this function is made more | # sophisticated. | #
| # Stability: Added in v1.7, will exist for all future v1.x releases. May | # be overhauled to provide more ordered text in the future. | # @return a unicode string object

參考資料：
1、PDF 1.0
2、PyPDF 2
3、PyPDF2 Homepage
4、PyPDF2 Documentation
5、python name 'file' is not defined的解決辦法
6、ReportLab
7、用Python/reportlab生成PDF
8、Writing Pdf with Python: Add image