Could this error message be more concise and friendly? How about splitting the two checks so that instead of a bounding check, you check the minimum and maximum separately. That way one does not depend on the other (so you could specify a maximum but no minimum) and the error messages can be made more concise, e.g. `must be at least 50px wide and 50px tall` and `must be at most 960x wide and 640px tall`. Obviously they'd get two error messages if they manage to upload an image that is say too narrow but also too tall, but I don't think that's too much of a problem and a fairly unlikely edge case.