Cyrus Draegur

Probably because it’s been downscaled from its full resolution.

Also rotated for some reason from the original? Or perhaps just rendered from the same mathematical sequence with some parameters swapped. Here’s an uncompressed one:

https://allrgb.com/hilbert

there are a lot of pieces that use one pixel per color too! you might really dig what people can do with it: it’s honestly astonishing the kinds of arrangements they can make just by mixing the colors.

https://allrgb.com/

this fails to capture the grades of saturation.

Here is every color in the RGB (#000000-#FFFFFF) color space arranged sequentially on a Hilbert curve (but scaled down to 512x512)