Question

我正在尝试使用Ghostscript重新保存PDF（以纠正PyPDF2无法处理的错误）。我用subprocess.check_output调用Ghostscript，我想将原始PDF作为STDIN传递，并将新的PDF作为STDOUT导出。

当我将PDF保存到文件并将其重新读入时，它可以正常工作。当我尝试从STDOUT传递文件时，它不起作用。我想也许这可能是一个编码问题，但我不想对文本进行任何编码，我只想要二进制数据。也许有一些我不理解的编码。

如何使STDOUT数据像文件数据一样工作？

import subprocess
from PyPDF2 import PdfFileReader
from io import BytesIO
import traceback

input_file_name = "SKMBT_42116071215160 (1).pdf"
output_file_name = 'saved2.pdf'
# input_file = open(input_file_name, "rb") # Moved below.

# Write to a file, then read the file back in. This works.
try:
    ps1 = subprocess.check_output(
        ('gs', '-o', output_file_name, '-sDEVICE=pdfwrite', '-dPDFSETTINGS=/prepress', input_file_name),
        # stdin=input_file # [edit] We pass in the file name, so this only confuses things.
    )
    # I use BytesIO() in this example only to make the examples parallel.
    # In the other example, I use BytesIO() because I can't pass a string to PdfFileReader().
    fakeFile1 = BytesIO()
    fakeFile1.write(open(output_file_name, "rb").read())
    inputpdf = PdfFileReader(fakeFile1)
    print inputpdf
except:
    traceback.print_exc()

print "---------"
# input_file.seek(0) # Added to address one comment. Removed while addressing another.
input_file = open(input_file_name, "rb")

# Export to STDOUT. This doesn't work.
try:
    ps2 = subprocess.check_output(
        ('gs', '-o', '-', '-sDEVICE=pdfwrite', '-dPDFSETTINGS=/prepress', '-'),
        stdin=input_file,
        # shell=True # Using shell produces the same error.
    )
    fakeFile2 = BytesIO()
    fakeFile2.write(ps2)
    inputpdf = PdfFileReader(fakeFile2)
    print inputpdf
except:
    traceback.print_exc()

输出：

   **** The file was produced by:
   **** >>>> KONICA MINOLTA bizhub 421 <<<<
<PyPDF2.pdf.PdfFileReader object at 0x101d1d550>
---------
   **** The file was produced by:
   **** >>>> KONICA MINOLTA bizhub 421 <<<<
Traceback (most recent call last):
  File "pdf_file_reader_test2.py", line 34, in <module>
    inputpdf = PdfFileReader(fakeFile2)
  File "/Library/Python/2.7/site-packages/PyPDF2/pdf.py", line 1065, in __init__
    self.read(stream)
  File "/Library/Python/2.7/site-packages/PyPDF2/pdf.py", line 1774, in read
    idnum, generation = self.readObjectHeader(stream)
  File "/Library/Python/2.7/site-packages/PyPDF2/pdf.py", line 1638, in readObjectHeader
    return int(idnum), int(generation)
ValueError: invalid literal for int() with base 10: "7-8138-11f1-0000-59be60c931e0'"

Answer 1

事实证明，这与Python无关。这是一个Ghostscript错误。正如本文中所指出的：Prevent Ghostscript from writing errors to standard output，Ghostscript将错误写入stdout，这会破坏管道传输的文件。

感谢@ Jean-FrançoisFabre，他建议我查看二进制文件。

如何通过STDOUT从Python子进程命令导出二进制数据？

1 个答案: