Pillow: is_animated should be defined for all images

[uri-rodberg]

What did you do?

I have a user with a photo. I want to check if the photo is animated. I ran the code:
```python
from PIL import Image

if (Image.open(user.photo.file).is_animated):
````

What did you expect to happen?

I expect is_animated to be defined for all images.
https://stackoverflow.com/a/50808096/1412564
https://github.com/python-pillow/Pillow/pull/1319

What actually happened?

If the image if not a GIF, I got an exception:

'JpegImageFile' object has no attribute 'is_animated'

What are your OS, Python and Pillow versions?

• OS: Ubuntu 18.04
• Python: 3.6
• Pillow: 7.1.2

[radarhere]

With the current version of Pillow, you could run

if (getattr(Image.open(user.photo.file), "is_animated", False):

I should also point out that opening an image like that won't close the file resource - https://pillow.readthedocs.io/en/stable/deprecations.html#image-del

[uri-rodberg]

Hi,

1. I would like "is_animated" to be defined also for images of non-animated formats (such as PNG, JPEG). Just define it to False.

2. So it's not recommended to use if (Image.open(user.photo.file).is_animated) because the image is not closed? What is the recommended method to use which the image will also be closed?

[radarhere]

1. To close the file, you could either use a context manager

from PIL import Image
with Image.open(user.photo.file) as im:
    im_is_animated = im.is_animated
if im_is_animated:
    pass

or you could use .close()

from PIL import Image
im = Image.open(user.photo.file)
im_is_animated = im.is_animated
im.close()
if im_is_animated:
    pass

[uri-rodberg]

Thank you.

[uri-rodberg]

Now, I would like the following code to work for any image:

with Image.open(user.photo.file) as image:
    if (image.is_animated):

[radarhere]

I'm kind of reluctant about this.

If we implemented is_animated for all images, then why not n_frames? Why not tell() and seek()? Doesn't this have the potential to confuse a user into thinking that JPEG images, for example, can be animated?

[uri-rodberg]

I think is_animated should just return true or false whether the image is animated or not. It doesn't have to do with the file format. I don't think it will confuse users - if they check is_animated, and get false, then the image is not animated.

[uri-rodberg]

Why do I have to check if (getattr(image, "is_animated", False)): if I can just check if (image.is_animated): and it works?

[hugovk]

We'd need to implement is_animated for each of the file formats:

• https://pillow.readthedocs.io/en/stable/handbook/image-file-formats.html

Are there any in there which _can_ be animated but don't currently have is_animated?

For example, (getattr(image, "is_animated", False) could be returning False for an animated format when we just haven't implemented support. There's some old and obscure ones in there.

[radarhere]

I've realised that seek() and tell() are already defined on the base Image class. I've created PR #4628 to add in is_animated and n_frames as well.

Regarding the different image formats, that's an interesting point. For example, for FitsStubImagePlugin, the wiki page for FITS says that

normal image data are usually 2-D or 3-D, with the third dimension representing for example time

So it could have animated images.

[uri-rodberg]

Thank you.

[radarhere]

Discussion in that PR raised a point that by adding a universal is_animated, it would mean that for images without Pillow animation support, we could be claiming that an image is not animated, when it is, just without Pillow support yet.

Instead, #4739 has documented the current situation.