I agree, it is thankfully somewhat difficult. One thing the US Copyright office pointed out to me on a request a number of years ago was that any changes need to be themselves copyrightable to have any influence on the status of the final work. Little snippets of text/titles are for the moment still not copyrightable, changing hue or saturation etc would probably not pass the smell test, nor would any batch processing, purely technical changes like resolution or file type, etc. Unfortunately the larger players with standing are unlikely to push for these rulings so it is hard to find established case law.