python - Wand 无法打开现有文件

Question

我想打开一个 pdf 文件，只获取第一页并将其另存为图像。我用过 this solution它工作完美。它在我的本地环境中仍然有效，但最近在 Travis 中无法正常工作。

是的，这段代码来 self 的unittest，我正试图在 Travis 中运行它。我有一个测试 pdf 文件，我想打开它:

import os
from wand.image import Image

root_path = 'some/correct/path'
filename = 'two_page_pdf.pdf'
full_path = os.path.join(root_parg, filename)
Image(file=open(full_path, mode='rb'), resolution=300) # Error!!!

-----------------------------------------------
DelegateError                             
Traceback (most recent call last)
<ipython-input-2-1b1fd9537a14> in <module>()
----> 1 Image(file=open(full_path, mode='rb'), resolution=300)

~/virtualenv/python3.5.3/lib/python3.5/site-packages/wand/image.py in __init__(self, image, blob, file, filename, format, width, height, depth, background, resolution)
   2738                                                   b'buffer.' + format)
   2739                 if file is not None:
-> 2740                     self.read(file=file, resolution=resolution)
   2741                 elif blob is not None:
   2742                     self.read(blob=blob, resolution=resolution)

~/virtualenv/python3.5.3/lib/python3.5/site-packages/wand/image.py in read(self, file, filename, blob, resolution)
   2820             r = library.MagickReadImage(self.wand, filename)
   2821         if not r:
-> 2822             self.raise_exception()
   2823 
   2824     def close(self):

~/virtualenv/python3.5.3/lib/python3.5/site-packages/wand/resource.py in raise_exception(self, stacklevel)
    220             warnings.warn(e, stacklevel=stacklevel + 1)
    221         elif isinstance(e, Exception):
--> 222             raise e
    223 
    224     def __enter__(self):

DelegateError: Postscript delegate failed `/tmp/magick-5ypXvY6l': No such file or directory @ error/pdf.c/ReadPDFImage/677

检查文件:

os.path.isfile(full_path) == True 
len(open(full_path, mode='rb').read()) == 18386

环境:

• python 3.5.3
• 魔杖0.4.4

怎么了？我卡住了。请帮忙

更新 1:

Imagemagick pack 似乎与此有关!上次测试在 8:6.6.9.7-5ubuntu3.9 版本时通过，更新到 8:6.7.7.10-6ubuntu3.9 后停止工作p>

更新 2:

.travis.yml 文件。

language: python
sudo: false
cache: pip
python: "3.5"
services:
  - rabbitmq
addons:
  apt:
    packages:
    - imagemagick
    - python-enchant

Answer 1

此错误的原因是缺少 PDF 委托(delegate) (ghostscript)。我刚刚将此应用添加到 addons > apt > packages travis.yml 部分