How can I find a 512*512 icon

[xiasummer]

I’ve updated discourse to 2.2.0.beta8.

But it always reports a problem:

Your site is missing a 512 × 512 icon, which allows users to add a home screen 
shortcut to this site on Android devices. 
Go to the Site Settings and upload a 512 × 512 icon.

I tried a random picture which is not 512 * 512, the problem remains.
I tried to download a 512 * 512 picture, but the problem still remains.

So, how can I solve the problem?

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Fine, I see the picture is not exactly 512 * 512.

[fhe (Florian)]

I tried a 512 512 picture, but the problem still remains.

It must be exactly 512 x 512 pixels in size, see Discourse 2.2.0.beta8 - PWA Error for background discussion.

Are you sure it displays the same warning after you click refresh? On some installations it then also gives a warning about the short title not set or being too long, which can give the impression that the original problem remains, while in fact it’s a different one.

[xiasummer]

You are right, the picture have to be exactly 512 * 512;

Now it works, seems I have to cut my picture as exactly this size.