Why is the Floyd-Steinberg error diffusion kernel so uneven? What's the output like if the error is distributed equally among the bottom-right pixels?
And this is a naive question, but could one construct a kernel that diffuses the error across all surrounding pixels, not just the bottom+right? I get that this will cause recursion difficulties as error bounces back-and-forth between neighboring pixels, but is that resolvable?
Bottom+right is purely a performance optimization, when processing top-to-bottom, left-to-right. You only ever push the error terms to pixels you haven't processed yet, so the whole algorithm remains a single linear pass. That was the standard approach for handling images at the time. Everything was stored as lines of raster data, rather than the blocks modern compressed formats prefer, and there wasn't parallel processing available to speed things up in ways that make linear data dependency awkward.
Instead of top/bottom left/right scan, you can perform a serpentine scan that goes top/bottom, but alternates left/and right/left each row, zig zagging as it goes down the page.
That way the errors get spread out more evenly, and you don't get 45 degree diagonal flowing artifacts down and to the right.
The In-Laws (1979): Getting off the plane in Tijuara:
And this is a naive question, but could one construct a kernel that diffuses the error across all surrounding pixels, not just the bottom+right? I get that this will cause recursion difficulties as error bounces back-and-forth between neighboring pixels, but is that resolvable?