Monty's PNG compression
side-by-side comparison

Before	After
Original PNG: 180454 bytes	Reduced PNG: 23399 bytes

So Monty's approach gives a file 13% the size of the original. And while it's clear looking at them side-by-side that something has been lost, it's not all that significant a loss. Certainly my reaction to either, coming across it on a random page, would be the same: Nice bobbins. I might be a little frustrated by a slight sense that the bobbins are out of focus if I encountered the compressed image in the wild — but absent the original to compare it too, I also might not notice.

There is one way in which I'm fairly sure my reaction to the two images would differ: With the original, I find myself wondering if the background the bobbins are resting on is someone's skin. I don't think that would have crossed my mind if I had only seen the compressed image, in which the background very much looks like a woven material.