PIL open()方法不适用于BytesIO

问题描述

由于某些原因，当我尝试从BytesIO流制作图像时，它无法识别该图像.这是我的代码:

For some reason, when I try to make an image from a BytesIO steam, it can't identify the image. Here is my code:

from PIL import Image, ImageGrab
from io import BytesIO

i = ImageGrab.grab()
i.resize((1280, 720))
output = BytesIO()
i.save(output, format = "JPEG")
output.flush()
print(isinstance(Image.open(output), Image.Image))

及其引发的错误的堆栈跟踪:

And the stack trace of the error it throws:

Traceback (most recent call last):
  File "C:/Users/Natecat/PycharmProjects/Python/test.py", line 9, in <module>
    print(isinstance(Image.open(output), Image.Image))
  File "C:\Python27\lib\site-packages\PIL\Image.py", line 2126, in open
    % (filename if filename else fp))
IOError: cannot identify image file <_io.BytesIO object at 0x02394DB0>

我正在使用PIL的Pillow实现.

I am using the Pillow implementation of PIL.

推荐答案

将BytesIO视为文件对象，完成写入图像后，文件的光标位于文件的末尾，因此当Image.open()尝试执行以下操作时:调用output.read()，它会立即获得EOF.

Think of BytesIO as a file object, after you finish writing the image, the file's cursor is at the end of the file, so when Image.open() tries to call output.read(), it immediately gets an EOF.

在将output传递到Image.open()之前，您需要添加output.seek(0).

You need to add a output.seek(0) before passing output to Image.open().

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