Dithering algorithms

Retro Graphics Toolkit strives to offer flexibility and choices. Dithering is no exception.
You have some choices for dithering and I plan to add even more at some point.

## Floyd Steinberg Very common error diffusion algorithm. It is the default option. ## Riemersma Claims to combine the advantages of ordered dithering with the advantages of error diffusion. ## Nearest color Does not do dithering of any sort, it just picks the nearest color. ## Vertical dithering Kind of like ordered dithering but only with vertical lines. ## Yliluoma 1 Not very good try Yliluoma 2 or Yliluoma 3 ## Yliluoma 2 Better but not as good as Yliluoma 3 also slower than Yliluoma 3 ## Yliluoma 3 Good ordered dithering algorithm.