what is the best way to save PIL image in json

问题

I'm trying to send json dict that should contain Pillow image as one of his fields, to do that I have to convert the image to string. I tried to use pillow function: image.toString() but still got it as bytes, so I tried to encode it:

buff = BytesIO()
image.save(buff, format="JPEG")
img_str = base64.b64encode(buff.getvalue())

but still got it as bytes. How can I convert Pillow images to format that can be saved in json file?

回答1:

In the comments, Mark Setchell suggests calling .decode('ascii') on the result of your b64encode call. I agree that this will work, but I think base64encoding to begin with is introducing an unnecessary extra step that complicates your code.*

Instead, I suggest directly decoding the bytes returned by image.tostring. The only complication is that the bytes object can contain values larger than 128, so you can't decode it with ascii. Try using an encoding that can handle values up to 256, such as latin1.

from PIL import Image
import json

#create sample file. You don't have to do this in your real code.
img = Image.new("RGB", (10,10), "red")

#decode.
s = img.tobytes().decode("latin1")

#serialize.
with open("outputfile.json", "w") as file:
    json.dump(s, file)

(*but, to my surprise, the resulting json file is still smaller than one made with a latin1 encoding, at least for my sample file. Use your own judgement to determine whether file size or program clarity is more important.)

回答2:

I use the following to exchange Pillow images via json.

import json
from PIL import Image
import numpy as np

filename = "filename.jpeg"
image = Image.open(filename)
json_data = json.dumps(np.array(image).tolist())
new_image = Image.fromarray(np.array(json.loads(json_data), dtype='uint8'))

来源：https://stackoverflow.com/questions/56428037/what-is-the-best-way-to-save-pil-image-in-json