That last one is talked about in the article -- it sucks!
replyI think if you were going to "downsample" for the purpose of creating a color set you could just scan through the picture and randomly select 10% (or whatever) of the pixels and apply k-means to that and not do any averaging which costs resources and makes your colors muddy.
Random sampling makes a lot of intuitive sense, but unfortunately doesn't work well. I just answered over at lobsters: https://lobste.rs/s/t43mh5/okmain_you_have_image_you_want_co...
replyI should probably add this nuance to the post itself.
Edit: added a footnote
How about sampling more from the more "prominent" areas of the image[0] and less from less "prominent" areas?
reply[0]: https://dgroshev.com/blog/okmain/img/distance_mask.png?hash=...
