I just got the following error trying to upload an image that was 2000 pixels wide:
“Post-processing of the image failed likely because the server is busy or does not have enough resources. Uploading a smaller image may help. Suggested maximum size is 2500 pixels.”
This was confusing because the image was clearly smaller than the maximum size in the error message.
Web search for the error reveals a million different possible causes – this page has a few of the obvious ones, but none of them were my problem.
I tried increasingly slightly smaller versions of the file, then quickly realised what the issue was when it started working once the file size got below 1MB – upload limit in PHP was set to 8MB, and this was being reported in WordPress, but it was not set properly in nginx.
If I’d thought to check the nginx error log sooner I would have seen the following error:
... client intended to send too large body: 1191539 bytes
The fix is of course to just add the appropriate directive in nginx config file to align the upload size with what you have in PHP. Something like: