The present invention relates to a processing device and a method of providing privacy for a display device comprising a display panel arranged to display a first image signal (405), the display panel having an off-axis tonal reproduction curve that is different from the on-axis tonal reproduction curve of the display panel, and the display panel comprising a group of adjacent subpixels, wherein subpixels of the group of adjacent subpixels contribute at least a common primary color component, and wherein the group of adjacent subpixels associated with at least one pixel; the method comprising modulating control signals of individual subpixels of the group of adjacent subpixels, using a second image signal (425), the control signals arranged to generate tonal values for at least two of the individual subpixels of the group of adjacent subpixels that are at least in part decorrelated from the first image signal when viewed off-axis, and to generate tonal values for the group of adjacent subpixels that on average correspond to the first image signal when viewed on-axis.