使用数据uri的html中的已编码图像不适用于xhtml2pdf

Question

我正在尝试使用Google App Engine上的xhtml2pdf生成PDF。 我已经完成了大多数工作，包括将图像嵌入模板。 但是，这仅适用于可公开访问的图像（xhtml2pdf对该图像进行蚀刻以嵌入它们。）我需要能够将某些图像保持私有状态。 因此，我希望能够使用数据uri方案将一些图像直接嵌入html中。 可悲的是，当我这样做时，我得到一个错误：

有问题的html标签是：

<img src='data:image/png;base64,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%2BTl5ufo6erx8vP09fb3%2BPn6/8QAHwEAAwEBAQEBAQEBAQAAAAAAAAECAwQFBgcICQoL/8QAtREAAgECBAQDBAcFBAQAAQJ3AAECAxEEBSExBhJBUQdhcRMiMoEIFEKRobHBCSMzUvAVYnLRChYkNOEl8RcYGRomJygpKjU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ2hpanN0dXZ3eHl6goOEhYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExcbHyMnK0tPU1dbX2Nna4uPk5ebn6Onq8vP09fb3%2BPn6/9oADAMBAAIRAxEAPwD3%2BiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAoopGZUUszBQOpJoAWiuY1f4geHNFYrdahHvHVVOa4jVPj9oFqxW0hknI70AevUV8%2BXf7Rcm7/RtOUD3NVh%2B0VfZ50%2BOgD6Morw/Rf2hLG4lCalZmIH%2BJa9S0LxjoniGNWsL2N2P8BODQBvUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFAHN%2BMPGWn%2BD9NN1dtlj9xPU183%2BLvjHrniCV47WU2tseAqHBxXq/wAaPBup%2BJLaGWwBcx9U9a4XwV8Db7UJ1n1smCAH7nc0AeTRwalq9wdiTXEjH0JrpdM%2BF3inU2Hl6dIgPdxivqvQvBeh%2BH4VjsrGMMB99lyTW%2BqqowqgfQUAfLdp8A/EkxHmtHGPc1dP7POt44u4s19MUUAfH%2Bv/AAi8TaErSG1M0a/xR81ydhqepeH9QWWCWWCaNuRnFfdbIrqVZQwPUEV85/HvwnY6bNb6raRrE0xIdVGOaAPTPhb4%2BTxhowjnIF7CMOPWvQa%2BT/gdqMtp43jhUnZKMMK%2BsKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigBCARgjNAAAwBilooAKKKKACiiigBGYIpZjgAZJr5U%2BNXjH%2B3/ERsYGzb2p2jHc1738SvEsfhrwjdTbws0qlIxnnNfH0aTatqyry8s8n6k0AesfAPw7Ld%2BIH1R0IhhGAxHevpquX8A%2BG4fDXha1tkQLKyBpD3JrqKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACo55o7eF5pWCogySe1JcXEVrbvPM4SNBlmPavnf4ofGFr4TaPozFYclXlB60Acv8XvHD%2BJ9fe1gcm0tztUA8E1q/BLwQ%2Br60urXUX%2BjW5yuR1NefeF/Dl74p1yK0gRn3sN7Y6Cvsjwv4ft/Deh29hboBsUbiO5oA2AAoAHAFLRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABUVxcQ2sLTTyLHGoyWY4FZeveKNL8O2T3N9dRrtHC7uTXzV8Qvi5f%2BJpXtLF2gsgcfKcFqAOm%2BLnxXS9jfRtGl/d9JJFPWvKfCfha%2B8W6zHZ2ysdzfO%2BOgpPDPhPVPFepJBaQuwY/NIRwK%2BrvAXgOy8G6WqIga6YfvJMc0AP8E%2BAtN8HWCpBGr3JHzyEc5rrqKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAqO4njtoHmlYKiDJJqSszxDYSanoV3aRMVeSMgEUAeV%2BI/j7p%2Bm3slrp9qbgoSC5PFcDrnx41/UVMdoq2yn%2B71rkdd8AeItL1CZJNPmkUMcOqkg1hSaJqcWd9jOuPVDQBJqWu6prUxe8upZmJ6E11fgX4czeJbtJLyeO2tAcsXYAmuK%2By3cZ/1Mo/4Camjv9St%2BEnnT2BIoA%2Bz/AAxoOieHNPS207yOBy4Iya6AMGGQQR7V8Nw%2BKtdt%2BI9RuF/4Ea3dN%2BK3irTV2pqDuP8Aa5oA%2ByKK%2BSP%2BF2eLc/8AH0PyqK4%2BM3i2eMp9s257igD64aeJPvSoPqwrKv8AxXoem5%2B1ajAhHbcK%2BOrnxt4iu2Jk1Oc59GNZjS6lqMmS08zH3JoA%2Btrr4u%2BErViDfhyP7taHh74haF4knMNjcAv/AHT1r5Eg8L65dn91p9w3/ADXq/wj%2BHmuWevJqN5E9vEnY8ZoA%2Bj6KQDAApaACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAY8Mcn341b6iqz6Tp8gIezgbPqgq5RQBkN4X0N87tMtzn/AGBVCb4f%2BGJyS%2BlQZPoK6aigDhLn4Q%2BErkkmwCZ/u1zN7%2Bz9oU8pa3uJIlPavYaKAPE/%2BGd9Lz/x/v8AlTo/2eNJVwXvpCPTFe1UUAecWPwU8KWkSq9u0rDuxrptN8EeHtKAFtpsII7sua6GigCCOztohiO3iUeyipgAowAB9KWigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKAP//Z' width='230' height='143' >

我得到的错误是：

Traceback (most recent call last):
  File "/Users/hamish/dev/kp3/src/libs/xhtml2pdf/tags.py", line 332, in start
    height=None)
  File "/Users/hamish/dev/kp3/src/libs/xhtml2pdf/xhtml2pdf_reportlab.py", line 476, in __init__
    img = self.getImage()
  File "/Users/hamish/dev/kp3/src/libs/xhtml2pdf/xhtml2pdf_reportlab.py", line 497, in getImage
    img = PmlImageReader(StringIO.StringIO(self._imgdata))
  File "/Users/hamish/dev/kp3/src/libs/xhtml2pdf/xhtml2pdf_reportlab.py", line 343, in __init__
    self._image = self._read_image(self.fp)
  File "/Users/hamish/dev/kp3/src/libs/xhtml2pdf/xhtml2pdf_reportlab.py", line 373, in _read_image
    return PILImage.open(fp)
  File "/Library/Python/2.7/site-packages/PIL/Image.py", line 1980, in open
    raise IOError("cannot identify image file")
IOError: cannot identify image file fileName=<StringIO.StringIO instance at 0x10503ca70>

Answer 1

您可以查看/Library/Python/2.7/site-packages/PIL/Image.py，甚至可以对其进行一些修改，以了解到底是什么原因导致了不高兴：

文件“ /Library/Python/2.7/site-packages/PIL/Image.py”，行1980，以开放式方式出现IOError（“无法识别图像文件”）

假设这是私有文件与公共文件的访问权限问题，请检查这两种访问类型之间的区别。

如果您的应用程序同时静态地提供这两种文件，并且您允许通过app.yaml文件中的application_read：true标志进行公共访问，则您需要对私有文件执行相同的操作，并可能使用login：required或login：admin保护它们。

如果私有保护是动态地来自您的应用程序，请检查您的实现方式，并在可能的情况下相应地调整xhtml2pdf访问。