Methods of reducing contouring in images display by a linear display device, such as a spatial light modulator. The methods operate on a high resolution signal, which represents a stream of pixel values. The per pixel resolution of this signal is greater than the per pixel display resolution, and its less significant bits are treated as an error component. Random values are added to the error component either in conjunction with error diffusion values (FIG. 1) or to provide a dither that is directly proportional to the error (FIG. 4), or to provide a dither that has both spatial and temporal contributions (FIG. 5).