IANAL, but from my understanding of the points at issue, I think a court might be likely to find that a) sucking the image into RAM is a copy in the first place

IANAL, but from my understanding of the points at issue, I think a court might be likely to find that a) sucking the image into RAM is a copy in the first place; b) the FFT/etc. would be a (first) derivative work; c) using a form of the original image sufficient to communicate to the alteration processes what it should be altering would constitute a copy; and/or d) identifying something as a de-copyrighted work will undercut any defenses. Here's an interesting answer apropos to all this: https://opensource.stackexchange.com/questions/7250/could-i-remove-gplv2-from-this-algorithm-implementation https://opensource.stackexchange.com/questions/7250/could-i-...