You're thinking of error diffusion, not the dithering itself, they are two separate things. Error diffusion is what spreads samples out spatially.
Audio and image dithering are the same thing, they only become different when you add error diffusion.
The modern image dithering that you use when going from an HDR image down to an 8-bits per pixel PNG or JPG uses exactly the same (very simple) algorithm you'd use to dither an audio file during mastering.
Fair enough. I forgot about noise dithering, which only preserves error information statistically rather than exactly.
I don't understand your point about audio and image dithering being different when error diffusion is present. You can use error diffusion on both; in delta-sigma audio modulation, the error is diffused in only one dimension but it's still error diffusion.
Yes, absolutely right. Just making clear the distinction between dither and diffuse. Dither is always a local operation on a sample, diffuse is the spatial spreading to make the neighborhood more pleasant for humans.
I was reacting to the statement "images and audio usually use dithering in opposite ways". The article here is about error diffusion, but it's pretty hard to say whether adding error diffusion to the dither process is the 'usual' choice, for either images or audio. It's very very common to not use error diffusion in both cases.
Diffuse is more much important when the destination resolution is well above human perceptible just-noticeable differences. For example, going from 8 bits per channel to 1 bit per pixel, or for audio when going from 16 bit samples down to 8 bit samples.
Audio and image dithering are the same thing, they only become different when you add error diffusion.
The modern image dithering that you use when going from an HDR image down to an 8-bits per pixel PNG or JPG uses exactly the same (very simple) algorithm you'd use to dither an audio file during mastering.