如何创建存储在 Google Cloud Storage 中的图像 PDF？

Question

如果这是一个愚蠢的问题，我很抱歉。我对 GCP 很陌生。

对于网络应用，我需要从存储在 Cloud Storage 中的图像创建 PDF。

首先，我尝试将 python 包 fpdf 与存储在 Cloud Storage 中的文件一起使用，看看这是否可行。 因为图片是在线存储的，所以我使用urllib2来获取图片。

代码：

from fpdf import FPDF
import urllib2
import os

imagelist = ["https://storage.googleapis.com/seventh-terrain-179700.appspot.com/excuses.jpg", "https://storage.googleapis.com/seventh-terrain-179700.appspot.com/excuses2.jpg"]

pdf = FPDF()
i = 0
for image in imagelist:
    image = urllib2.urlopen(image)

    # writing image files in current folder
    with open('image'+str(i)+'.jpg','wb') as output:
        output.write(image.read())

    pdf.add_page()
    pdf.image('image'+str(i)+'.jpg', 10, 10, 100, 100) # pdf.image(image,x,y,w,h)

    # removing images
    os.remove('image'+str(i)+'.jpg')
    i += 1

# Creating PDF in current folder
pdf.output("yourfile.pdf", "F")

这句话很好。

然后我尝试在本地服务器中部署相同的代码：

import webapp2
from fpdf import FPDF
import urllib2
import os

pdf = FPDF()

class MainPage(webapp2.RequestHandler):
    def get(self):
        imagelist = ["https://storage.googleapis.com/seventh-terrain-179700.appspot.com/excuses.jpg", "https://storage.googleapis.com/seventh-terrain-179700.appspot.com/excuses2.jpg"]

        pdf = FPDF()
        i = 0
        for image in imagelist:
            image = urllib2.urlopen(image)

            with open('image'+str(i)+'.jpg','wb') as output:
                output.write(image.read())

            pdf.add_page()
            pdf.image('image'+str(i)+'.jpg', 10, 10, 100, 100) # pdf.image(image,x,y,w,h)

            os.remove('image'+str(i)+'.jpg')
            i += 1

        pdf.output("yourfile.pdf", "F")

application = webapp2.WSGIApplication([('/', MainPage)],
                                      debug=True)

但是，我遇到了错误：

WARNING  2017-12-08 19:21:56,184 sandbox.py:1082] The module _winreg is whitelisted for local dev only. If your application relies on _winreg, it is likely that it will not function properly in production.
WARNING  2017-12-08 14:21:56,190 urlfetch_stub.py:551] Stripped prohibited headers from URLFetch request: ['Host']
ERROR    2017-12-08 19:21:57,332 webapp2.py:1528] [Errno 30] Read-only file system: 'image0.jpg'
Traceback (most recent call last):
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 1511, in __call__
    rv = self.handle_exception(request, response, e)
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 1505, in __call__
    rv = self.router.dispatch(request, response)
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 1253, in default_dispatcher
    return route.handler_adapter(request, response)
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 1077, in __call__
    return handler.dispatch()
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 547, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 545, in dispatch
    return method(*args, **kwargs)
  File "C:\MyMiniGCPProjects\FPDF\main.py", line 23, in get
    with open('image'+str(i)+'.jpg','wb') as output:
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\google\appengine\tools\devappserver2\python\runtime\stubs.py", line 278, in __init__
    raise IOError(errno.EROFS, 'Read-only file system', filename)
IOError: [Errno 30] Read-only file system: 'image0.jpg'
ERROR    2017-12-08 19:21:57,339 wsgi.py:279]
Traceback (most recent call last):
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\google\appengine\runtime\wsgi.py", line 267, in Handle
    result = handler(dict(self._environ), self._StartResponse)
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 1519, in __call__
    response = self._internal_error(e)
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 1511, in __call__
    rv = self.handle_exception(request, response, e)
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 1505, in __call__
    rv = self.router.dispatch(request, response)
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 1253, in default_dispatcher
    return route.handler_adapter(request, response)
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 1077, in __call__
    return handler.dispatch()
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 547, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\lib\webapp2-2.3\webapp2.py", line 545, in dispatch
    return method(*args, **kwargs)
  File "C:\MyMiniGCPProjects\FPDF\main.py", line 23, in get
    with open('image'+str(i)+'.jpg','wb') as output:
  File "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\platform\google_appengine\google\appengine\tools\devappserver2\python\runtime\stubs.py", line 278, in __init__
    raise IOError(errno.EROFS, 'Read-only file system', filename)
IOError: [Errno 30] Read-only file system: 'image0.jpg'

我找不到任何可行的解决方案。 有没有办法直接使用 Cloud Storage 中的文件并将 PDF 保存在 Cloud Storage 中？

Answer 1

您遇到了沙盒限制之一。来自The sandbox：

App Engine 应用程序不能：

• 写入文件系统。应用程序必须使用Cloud Datastore 来存储持久数据。允许从文件系统读取， 并且所有随应用上传的应用文件都可用。

好吧，关于数据存储的说明实际上是一种误导，有几种存储选项，最适合您的情况是恕我直言云存储 (GCS)。

但是您不能使用常规的open() 将文件写入 GCS，您需要为此使用 GCS 客户端库。你可以在这里找到一个例子：Write a CSV to store in Google Cloud Storage