[wp-hackers] Reject uploaded image

[scribu]

I'm trying to do something like this:

A user uploads an image. If the image resolution is lower than 640x480px
(for example), then an error message is sent to the user and the image is
deleted.

I've tried using *add_action('media_upload_image', 'my_function')*, but that
doesn't help.

Maybe using *add_filter('async_upload_image', 'my_function')* ?

Any ideas?

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