… because this is just stupid. Yesterday I needed to generate pairs of thumbnails - images consisting of scaled-down versions of two other images - and the quickest, least fiddly way I came up with was to lay the images out on a web page, screenshot each pair and trim the shots in Preview.
I did spend a while flailing in Gimp, where creating just the first pair took me about as long as the whole convoluted solution I used above. I used to be better at Gimp, I think. Or perhaps I was just more tolerant of all its quirks.
I am pretty sure what I should do is invest in Pixelmator or Acorn or something similar. And perhaps learn some more command line/scripting magic. Preview is great for batch resizes, and Imageoptim does size crunching, but when it comes to basic building and laying out of new images I think I need something more.