PIL open()方法不能与BytesIO一起使用

Question

出于某种原因,当我尝试从BytesIO蒸汽制作图像时,它无法识别图像.这是我的代码:

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))

它抛出的错误的堆栈跟踪:

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.

Answer 1

将BytesIO视为文件对象,在完成图像写入后,文件的光标位于文件的末尾,因此在Image.open()尝试调用时output.read(),它会立即获得EOF.

您需要添加一个output.seek(0)经过之前output到Image.open().