1. A controller comprising: input logic configured to receive an input image frame; subfield derivation logic configured to: derive a plurality of initial color subfields based on the received image frame, wherein each of the initial color subfields includes a respective intensity value for each pixel of the display for a corresponding color; apply a vector dithering process across the initial color subfields by: deriving a plurality of quantized color subfields, each quantized color subfield corresponding to one of the initial color subfields, wherein for at least one of the quantized color subfields, the controller quantizes the intensity values to an unevenly spaced set of available intensity values; and deriving a plurality of final color subfields based on the quantized color subfields, the uneven spacing of available intensity values in the at least one quantized color subfield, and a dither map; and output logic configured to cause the final color subfields to be output on a display.