Twenty Eleven screenshot is a jpeg

[pross]

In Twenty Twelve the screenshot is a PNG and in the codex for themes we have the following:
Theme is required to include, at a minimum:

quote from codex...
index.php
comments.php
Must be included using comments_template()
screenshot.png
Recommended 4:3 W:H ratio, size 300x225px. Maximum size: 320:240px
Should be a "reasonable facsimile" of the Theme after it is initially activated with default options

Theme-Check plugin checks for a screenshot.png and fails if not found. Not sure what the main theme uploader checks for, assuming the same (otto?), Surely it should be consistent,

[dd32]

You'll be running an old version of TwentyEleven due to a bug in the core updater (#17816)

The latest TwentyEleven has a jpg screenshot.

[nacin]

screenshot.png, jpg, jpeg, and gif are all valid for WordPress themes.

[MattyRob]

Pross,

I do hope you'll post more issue on this trac and I'll offer you an apology even though it's not really mine to offer.

​18054 shows that you were indeed quite right - too bad this trac is apparently so dismissive.

[nacin]

MattyRob: Relax. What the ticket didn't highlight is that the theme directory itself (not just any guidelines) expects PNG. Neither dd32 nor I -- two core committers -- caught the distinction. We don't need the attitude and backhandedness.

[MattyRob]

Nacin: I am totally relax - really. And I'm sorry if you feel I have an attitude - I really don't. My motive is to keep trac reporters and contributors feeling valued - something that I believe could be done much better. This will keep them contributing rather than risk pushing them away. Happy to discuss in a more appropriate arena if you wish.