u201d in the description of embodiments all numbers have been normalized in other words if the colors are encoded with n bits the components lt r g b gt with r g and b in the interval 0 1 are obtained by dividing the numbers encoded as n bit digits by 2 n u2212 1 the invention will make use of the following results by subtracting from a vector lt r g b gt a fraction of the same vector lt r g b gt a color can be shifted toward black and still remain collinear to the vector lt r g b gt by multiplying the components of a vector lt r g b gt by a value greater than 1 0 the color r g b can be brightened and still remain collinear to the ray the brightness of a color r g b can be determined as follows as shown on fig1 the straight line determined by the points 0 0 0 and r g b intersects the cube at a point r g b the point r g b being on the surface of the color cube at least one of the components of r g b is equal to 1 in the example of fig1 it is the green component g that is equal to 1 to project r g b on the cube we just have to divide the components of r g b by max r g b the maximum value of the.