Create your own! This tool will produce much better results if the images are much larger than the intended size (e.g. 1400 x 800 at least) since it needs to downsize the original to fit the different dimensions.
Alan, I took a swing at trying out the live Comparator SPLOT today. It’s very cool looking! Sadly I kept getting an error in the WP upload interface simply saying “An error occurred in the upload. Please try again later.”
I was uploading a simple .jpg of about the same size and dimensions as those recommended and already in the repository. I tried a few different photo sizes and types with the same result, so I’m not sure what the underlying issue may be. Unless something has changed dramatically, my one guess would be to check the storage limits on the hosting account. I’ve seen that sort of failure before when running out of physical space on a host.
Incidentally, from a security standpoint, I’ll mention that it appears one has the ability within that interface to delete others’ previously uploaded photos. (May want to look at that as a potential future improvement.)
Hope you’re holding up!
That one’s not been attended to much since 2014; some of the other sites linked did it better. Will see if I can bring in line with more current SPLOTs, have been doing uploads w/o media library interface.