以JSON序列化base64编码的数据

问题描述

我正在编写一个脚本来自动生成演示数据，我需要在JSON中序列化一些数据.这些数据的一部分是图像，因此我在base64中对其进行了编码，但是当我尝试运行脚本时，我得到了:

I'm writing a script to automate data generation for a demo and I need to serialize in a JSON some data. Part of this data is an image, so I encoded it in base64, but when I try to run my script I get:

Traceback (most recent call last):
  File "lazyAutomationScript.py", line 113, in <module>
    json.dump(out_dict, outfile)
  File "/usr/lib/python3.4/json/__init__.py", line 178, in dump
    for chunk in iterable:
  File "/usr/lib/python3.4/json/encoder.py", line 422, in _iterencode
    yield from _iterencode_dict(o, _current_indent_level)
  File "/usr/lib/python3.4/json/encoder.py", line 396, in _iterencode_dict
    yield from chunks
  File "/usr/lib/python3.4/json/encoder.py", line 396, in _iterencode_dict
    yield from chunks
  File "/usr/lib/python3.4/json/encoder.py", line 429, in _iterencode
    o = _default(o)
  File "/usr/lib/python3.4/json/encoder.py", line 173, in default
    raise TypeError(repr(o) + " is not JSON serializable")
  TypeError: b'iVBORw0KGgoAAAANSUhEUgAADWcAABRACAYAAABf7ZytAAAABGdB...
     ...
   BF2jhLaJNmRwAAAAAElFTkSuQmCC' is not JSON serializable

据我所知，任何以base64编码的内容(在这种情况下为PNG图像)只是一个字符串，因此它应该给序列化带来问题.我想念什么?

As far as I know, a base64-encoded-whatever (a PNG image, in this case) is just a string, so it should pose to problem to serializating. What am I missing?

推荐答案

您必须注意数据类型.

如果读取二进制图像，则会得到字节.如果将这些字节编码为base64，则将再次获得...字节！ (请参见 b64encode 上的文档)

If you read a binary image, you get bytes.If you encode these bytes in base64, you get ... bytes again! (see documentation on b64encode)

json无法处理原始字节，这就是您收到错误的原因.

json can't handle raw bytes, that's why you get the error.

我刚刚写了一些带有注释的示例，希望对您有所帮助:

I have just written some example, with comments, I hope it helps:

from base64 import b64encode
from json import dumps

ENCODING = 'utf-8'
IMAGE_NAME = 'spam.jpg'
JSON_NAME = 'output.json'

# first: reading the binary stuff
# note the 'rb' flag
# result: bytes
with open(IMAGE_NAME, 'rb') as open_file:
    byte_content = open_file.read()

# second: base64 encode read data
# result: bytes (again)
base64_bytes = b64encode(byte_content)

# third: decode these bytes to text
# result: string (in utf-8)
base64_string = base64_bytes.decode(ENCODING)

# optional: doing stuff with the data
# result here: some dict
raw_data = {IMAGE_NAME: base64_string}

# now: encoding the data to json
# result: string
json_data = dumps(raw_data, indent=2)

# finally: writing the json string to disk
# note the 'w' flag, no 'b' needed as we deal with text here
with open(JSON_NAME, 'w') as another_open_file:
    another_open_file.write(json_data)

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