Patent ID: 8248430

Claim:
A method of converting an input image signal into a drive signal for driving sub-pixels of a display device comprising display pixels having at least two sub-pixel groups being able to contribute to luminance information displayed, the conversion comprising: a multi-primary conversion for receiving the input image signal and being performed under a constraint, and first determining the constraint by substantially matching local display luminances associated with the at least two sub-pixel groups with corresponding local input luminances of input pixels of the input image signal, thereby obtaining a display luminance pattern defined by the display pixels corresponding to an input luminance pattern defined by the input pixels associated with the display pixels; and, wherein the first determining the constraint comprises: selecting a first display area comprising a first sub-pixel group and a second sub-pixel group of the at least two sub-pixel groups, and a second display area comprising the first sub-pixel group and being a sub-area of the first display area, computing a first input luminance for input pixels associated with the first display area, computing a second input luminance for input pixels associated with the second display area, and second determining the constraint to obtain a substantially matching ratio or difference between on the one hand the first input luminance and the second input luminance and on the other hand a first display luminance being the luminance of the sub-pixels covered by the first display area and a second display luminance being the luminance of the sub-pixels covered by the second display area.