Python的PIL裁剪问题：裁剪图像的颜色搞砸了

Question

I have a probably very basic problem with PIL's crop function: The cropped image's colors are totally screwed. Here's the code:

>>> from PIL import Image
>>> img = Image.open('football.jpg')
>>> img
<PIL.JpegImagePlugin.JpegImageFile instance at 0x00
>>> img.format
'JPEG'
>>> img.mode
'RGB'
>>> box = (120,190,400,415)
>>> area = img.crop(box)
>>> area
<PIL.Image._ImageCrop instance at 0x00D56328>
>>> area.format
>>> area.mode
'RGB'
>>> output = open('cropped_football.jpg', 'w')
>>> area.save(output)
>>> output.close()

The original image:

and the output .

As you can see, the output's colors are totally messed up...

Thanks in advance for any help!

-Hoff

Answer 1

output应该是文件名，而不是处理程序。

Answer 2

instead of

output = open('cropped_football.jpg', 'w')
area.save(output)
output.close()

just do

area.save('cropped_football.jpg')

Answer 3

Since the call to save actually produced output, I have to assume that PIL is able to use either a filename or an open file interchangeably. The problem is in the file mode, which by default will try to convert based on text conventions - a '\\n' will be replaced by '\\r\\n' on Windows. You need to open the file in binary mode:

output = open('cropped_football.jpg', 'wb')

PS I tested this and it works: