It's bad dithering, but it's still dithering. Random noise gives poor but fast results. Error diffusion is great but slow (pixels are processed sequentially).

It's bad dithering, but it's still dithering. Random noise gives poor but fast results. Error diffusion is great but slow (pixels are processed sequentially). My favorite technique is using a blue-noise matrix because it gives great results quickly. Creating the matrix is tricky, but you can do it offline and reuse it.