Patent ID: 8194288

Claim:
A computer implemented method for changing a neutral behavior of a color marking device, the method comprising: receiving a gray balance aim curve specified in L*a*b* space of a color gamut of a target color device, said gray balance aim curve being defined by three functions, L*(aim)=f 1 (L*), a*(aim)=f 2 (L*), and b*(aim)=f 3 (L*), where, L*(aim), a*(aim) and b*(aim) are aimed curves for L*a*b* respectively, and L* is neutral axis input of L*; displaying said received gray balance aim curve on a user interface for a visual review by a user thereof; physically changing a shape of said gray balance aim curve in which L*(aim), b*(aim) and a*(aim) is a new function of L* along the neutral line to produce a desired neutral behavior in said target color device, said modifying said shape of said gray balance curve comprising a user using said user interface to perform any of: physically manipulating said neutral line and entering a new value for points along said neutral line, wherein a change in said shape of said gray balance aim curve is limited to a range>max(f 2 ′(L*), f 3 ′(L*))×√{square root over (2)}×exp(−0.5), where f 2 ′, and f 3 ′ are functions with respect to L* that define said modified gray balance curve, said range preventing color reversals; generating a pre-LUT reflecting neutral line changes specified by said modified gray balance aim curve, said pre-LUT being defined by a 3-D N×N×N L*a*b* to L*a*b* conversion lookup table which transforms a neutral axis input of L*, a*=0 and b*=0 to L*(aim), a*(aim) and b*(aim); updating a color LUT of said target color device with values of said pre-LUT to produce an updated color LUT for said device, said updated color LUT being generated by concatenating said pre-LUT with said color LUT.