Python 图像库和 KeyError：'JPG'

Question

This works:

from PIL import Image, ImageFont, ImageDraw

def create_image_file(name='test.jpeg', ext='jpeg', size=(500, 500), color=(5, 179, 200)):
    file_obj = open(name, 'w')
    image = Image.new("RGBA", size=size, color=color)
    usr_font = ImageFont.truetype(
        "/Users/myuser/ENV/lib/python3.5/site-packages/matplotlib/mpl-data/fonts/ttf/Vera.ttf", 59)
    d_usr = ImageDraw.Draw(image)
    d_usr = d_usr.text((105, 280), "Test Image", (0, 0, 0), font=usr_font)
    image.save(file_obj, ext)
    file_obj.close()

if __name__ == '__main__':
    f = create_image_file()

But if I change the arguments to:

def create_image_file(name='test.jpg', ext='jpg', ...)

An exception is raised:

File "/Users/myuser/project/venv/lib/python2.7/site-packages/PIL/Image.py", line 1681, in save
    save_handler = SAVE[format.upper()]
KeyError: 'JPG'

And I need to work with user uploaded images that have .jpg as the extension. Is this a Mac specific problem? Is there something I can do to add the format data to the Image lib?

Answer 1

The second argument of save is not the extension, it is the format argument as specified in image file formats and the format specifier for JPEG files is JPEG , not JPG .

If you want PIL to decide which format to save, you can ignore the second argument, such as:

image.save(name)

Note that in this case you can only use a file name and not a file object.

See the documentation of .save() method for details:

format – Optional format override. If omitted, the format to use is determined from the filename extension. If a file object was used instead of a filename, this parameter should always be used.

Alternatively, you can check the extension and decide the format manually. For example:

def create_image_file(name='test.jpeg', ext='jpeg', size=(500, 500), color=(5, 179, 200)):
    format = 'JPEG' if ext.lower() == 'jpg' else ext.upper()
    # ...
    image.save(file_obj, format)