Method of computing drive currents for a plurality of leds in a pixel of a signboard to achieve a desired color at a desired luminous intensity

A method of computing control currents for a plurality of LEDs (101, 102, 103, 104 and 105) in a pixel (700) of a sign in order to achieve a desired color with a desired light intensity, the plurality being 5 LEDs (101, 102, 103, 104 and 105) of more than three basic colors that define a range of colors (120), and comprising: the selection of different LED combinations; for each LED combination, the computation of the control currents for the LEDs in the combination required to provide (a) the desired color, when the desired color is within the color range (120), or (b) a substitute color, when the desired color is outside the range of colors, so that the light intensity resulting from the desired color or substitute is the maximum; the substitute color is a color along a line of constant hue perceived in a boundary of the range (120) between the desired color and an achromatic point within the range; and the use of the computed control currents, scaling the control currents to reach the desired light intensity in the desired color, in which the control currents for each selected color are computed in a uniform color space.