问题
I'm trying to automate merging several PDF files and have two requirements: a) existing bookmarks AND b) pagelabels (custom page numbering) need to be retained.
Retaining bookmarks when merging happens by default with PyPDF2 and pdftk, but not with pdfrw. Pagelabels are consistently not retained in PyPDF2, pdftk or pdfrw.
I am guessing, after having searched a lot, that there is no straightforward approach to doing what I want. If I'm wrong then I hope someone can point to this easy solution. But, if there is no easy solution, any tips on how to get this going in python will be much appreciated!
Some example code:
1) With PyPDF2
from PyPDF2 import PdfFileWriter, PdfFileMerger, PdfFileReader
tmp1 = PdfFileReader('file1.pdf', 'rb')
tmp2 = PdfFileReader('file2.pdf', 'rb')
#extracting pagelabels is easy
pl1 = tmp1.trailer['/Root']['/PageLabels']
pl2 = tmp2.trailer['/Root']['/PageLabels']
#but PdfFileWriter or PdfFileMerger does not support writing from what I understand
So I dont know how to proceed from here
2) With pdfrw (has more promise)
from pdfrw import PdfReader, PdfWriter
writer = PdfWriter()
#read 1st file
tmp1 = PdfReader('file1')
#add the pages
writer.addpages(tmp1.pages)
#copy bookmarks to writer
writer.trailer.Root.Outlines = tmp1.Root.Outlines
#copy pagelabels to writer
writer.trailer.Root.PageLabels = tmp1.Root.PageLabels
#read second file
tmp2 = PdfReader('file2')
#append pages
writer.addpages(tmp2.pages)
# so far so good
Page numbers of bookmarks from 2nd file need to be offset before adding them, but when reading outlines I almost always get (IndirectObject, XXX) instead of page numbers. Its unclear how to get page numbers for each label and bookmark using pdfrw. So, I'm stuck again
zp
回答1:
You need to iterate through the existing PageLabels and add them to the merged output, taking care to add an offset to the page index entry, based on the number of pages already added.
This solution also requires PyPDF4, since PyPDF2 produces a weird error (see bottom).
from PyPDF4 import PdfFileWriter, PdfFileMerger, PdfFileReader
# To manipulate the PDF dictionary
import PyPDF4.pdf as PDF
import logging
def add_nums(num_entry, page_offset, nums_array):
for num in num_entry['/Nums']:
if isinstance(num, (int)):
logging.debug("Found page number %s, offset %s: ", num, page_offset)
# Add the physical page information
nums_array.append(PDF.NumberObject(num+page_offset))
else:
# {'/S': '/r'}, or {'/S': '/D', '/St': 489}
keys = num.keys()
logging.debug("Found page label, keys: %s", keys)
number_type = PDF.DictionaryObject()
# Always copy the /S entry
s_entry = num['/S']
number_type.update({PDF.NameObject("/S"): PDF.NameObject(s_entry)})
logging.debug("Adding /S entry: %s", s_entry)
if '/St' in keys:
# If there is an /St entry, fetch it
pdf_label_offset = num['/St']
# and add the new offset to it
logging.debug("Found /St %s", pdf_label_offset)
number_type.update({PDF.NameObject("/St"): PDF.NumberObject(pdf_label_offset)})
# Add the label information
nums_array.append(number_type)
return nums_array
def write_merged(pdf_readers):
# Output
merger = PdfFileMerger()
# For PageLabels information
page_labels = []
page_offset = 0
nums_array = PDF.ArrayObject()
# Iterate through all the inputs
for pdf_reader in pdf_readers:
try:
# Merge the content
merger.append(pdf_reader)
# Handle the PageLabels
# Fetch page information
old_page_labels = pdf_reader.trailer['/Root']['/PageLabels']
page_count = pdf_reader.getNumPages()
# Add PageLabel information
add_nums(old_page_labels, page_offset, nums_array)
page_offset = page_offset + page_count
except Exception as err:
print("ERROR: %s" % err)
# Add PageLabels
page_numbers = PDF.DictionaryObject()
page_numbers.update({PDF.NameObject("/Nums"): nums_array})
page_labels = PDF.DictionaryObject()
page_labels.update({PDF.NameObject("/PageLabels"): page_numbers})
root_obj = merger.output._root_object
root_obj.update(page_labels)
# Write output
merger.write('merged.pdf')
pdf_readers = []
tmp1 = PdfFileReader('file1.pdf', 'rb')
tmp2 = PdfFileReader('file2.pdf', 'rb')
pdf_readers.append(tmp1)
pdf_readers.append(tmp2)
write_merged(pdf_readers)
Note: PyPDF2 produces this weird error:
...
...
File "/usr/lib/python3/dist-packages/PyPDF2/pdf.py", line 552, in _sweepIndirectReferences
data[key] = value
File "/usr/lib/python3/dist-packages/PyPDF2/generic.py", line 507, in __setitem__
raise ValueError("key must be PdfObject")
ValueError: key must be PdfObject
回答2:
As mentioned in my comment, I'm posting a generic solution to merge several pdfs that works in PyPDF2. Dont know what is different to make this work in PyPDF2 other than initializing pls as ArrayObject()
from PyPDF2 import PdfFileWriter, PdfFileMerger, PdfFileReader
import PyPDF2.pdf as PDF
# pls holds all the pagelabels as we iterate through multiple pdfs
pls = PDF.ArrayObject()
# used to offset bookmarks
pageCount = 0
cpdf = PdfFileMerger()
# pdffiles is a list of all files to be merged
for i in range(len(pdffiles)):
tmppdf = PdfFileReader(pdffiles[i], 'rb')
cpdf.append(tmppdf)
# copy all the pagelabels which I assume is present in all files
# you could use 'try' in case no pagelabels are present
plstmp = tmppdf.trailer['/Root']['/PageLabels']['/Nums']
# sometimes keys are indirect objects
# so, iterate through each pagelabel and...
for j in range(len(plstmp)):
# ... get the actual values
plstmp[j] = plstmp[j].getObject()
# offset pagenumbers by current count of pages
if isinstance(plstmp[j], int):
plstmp[j] = PDF.NumberObject(plstmp[j] + pageCount)
# once all the pagelabels are processed I append to pls
pls += plstmp
#increment pageCount
pageCount += tmppdf.getNumPages()
# rest follows KevinM's answer
pagenums = PDF.DictionaryObject()
pagenums.update({PDF.NameObject('/Nums') : pls})
pagelabels = PDF.DictionaryObject()
pagelabels.update({PDF.NameObject('/PageLabels') : pagenums})
cpdf.output._root_object.update(pagelabels)
cpdf.write("filename.pdf")
来源：https://stackoverflow.com/questions/61740267/merging-pdfs-while-retaining-custom-page-numbers-aka-pagelabels-and-bookmarks