Port image types detections from PIL to the imghdr module

[serhiy-storchaka]

BPO	21574
Nosy	@vstinner, @PCManticore, @serhiy-storchaka, @iritkatriel
Files	issue21574.patch: Port 10 new formats; some improvements issue21574.zip: Test images

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2022-03-13.17:15:04.729>
created_at = <Date 2014-05-25.09:37:01.012>
labels = ['type-feature', 'library']
title = 'Port image types detections from PIL to the imghdr module'
updated_at = <Date 2022-03-13.17:15:04.728>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2022-03-13.17:15:04.728>
actor = 'iritkatriel'
assignee = 'none'
closed = True
closed_date = <Date 2022-03-13.17:15:04.729>
closer = 'iritkatriel'
components = ['Library (Lib)']
creation = <Date 2014-05-25.09:37:01.012>
creator = 'serhiy.storchaka'
dependencies = []
files = ['36785', '36786']
hgrepos = []
issue_num = 21574
keywords = ['patch']
message_count = 11.0
messages = ['219078', '219079', '224002', '224005', '228063', '228255', '237663', '237768', '238079', '348629', '415046']
nosy_count = 7.0
nosy_names = ['effbot', 'vstinner', 'pythonhacker', 'Claudiu.Popa', 'serhiy.storchaka', 'coldmind', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = 'wont fix'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue21574'
versions = ['Python 3.5']

[serhiy-storchaka]

It would be good to add support of all image types which are supported in PIL to the imghdr module.

[PCManticore]

Sounds good, I'll create a patch.

[serhiy-storchaka]

Claudiu, are you working on this issue? If not, I'll start writing a patch.

[PCManticore]

No, I didn't start any work on this and right now, with EuroPython, I don't have that much time to start, so feel free to take it and write a patch.

[coldmind]

I'll try to do this issue.
https://mail.python.org/mailman/private/core-mentorship/2014-October/002766.html

[coldmind]

Hi! Here is first version of patch. What I've done:

• Ported 10 new image formats from PIL (tests included)
• Improved existing file detections like PIL does.
• Add some byte manipulation routines

One more thing - I removed ord() calls, because python3 expects unicode symbol,
but bytes was provided, and I'm not sure is that right. Will these changes be included to python 3.5 only?

Here are some other image formats in PIL, that I didn't port, because they are so excotic, that I didn't find
even file examples. I can do this blindly, but I think without tests files this is useless.
What community think about this?

[PCManticore]

In general, the patch looks good, I left a couple of comments on Rietvld. It should be applied to 3.5 only. Also, there are some image test files which aren't included in this patch, could you update it to include them? Thanks.

[coldmind]

@Claudiu Popa, IIRC I did not add 1-2 test images because I not found how to make image or how to convert image to this format.
So, if there will no chance to add them, should we remove these formats from the patch?

[PCManticore]

Well, we should have test files for each format imghdr supports. Doesn't PIL have test files for them?

[vstinner]

This issue is 5 years old and has patches: it is no newcomer friendly, I remove the "easy" keyword.

[iritkatriel]

imghdr is deprecated as per PEP-594, so there won't be further enhancements to it.