[amelius]

This makes me wonder: what if instead of converting everything to grayscale, you swap color channels. I'm sure that would make images less appealing (e.g. human skin color would become something completely different), but still you'd be able to distinguish colors, so functionality isn't lost. Also, black and white, and grayscale stays the same, so text remains readable.

[John_KZ]

This is easily done, you can create an index for each color or color range.

Additionally, you can mess with the typical B&W conversion weights for each channel.

However this got me thinking, what do we want when we convert an image to bw? It's a pretty hard problem, because we want both semantic segmentation and preserving lightness. Also you clearly can't have a one-to-one mapping when you lose 2 dimensions. Of course in the case of a simple UI that's not a problem, but with photography it is.