It's a bit of drudgery. The sharpest focus vid frame may be at a poor spot in the zooms & pans we normally don't notice.
I was surprised at how much thumbnails created by using a constant scaling factor vary... It's irregular enough that scripted editing isn't much help.
I may just pick a constant thumbnail aspect ratio and size for HTML table uniformity -- and let some thumbnails be a bit distorted (but recognizable).
Fortunately, my HTML editor ("BBEdit") has a good, live preview, so I can instantly see how things look as I "tweak" them...
I'm considering a separate thread to keep related comments together -- and using my FRProfile page for archival purposes --- and, maybe for revealing "drafts" that I can then remove or edit (without asking for "help" from the mods)... '-)
Still have a lot of frame image / thumbnail file pairs to create; I'll just keep trudging along -- and should have something for review before long.
Thanks for spending your time on this, I am anxious to see what emerges!
ThankQ for your amazing work on these clips, TXnMA!