Figure A-4Correcting Native Display Characteristics
It can be shown that the required transform (T) may be implemented as a pair of appropriately-sized look-up tables (LUTs), on either side of a 3 x 3 matrix multiplication. The LUT preceding the matrix multiplication (the “pre-LUT”) implements the desired standard transfer function or gamma response curve, such that input values are correctly mapped per that standard into a “linear light” space. The required matrix for the color remapping (which is referred to as R) is a combination of the matrix that transforms R′G′B′ to X′Y′Z′ values under the target standard (AS), and the inverse of the corresponding matrix for the existing display device (AD). In other words,
R= AD-1AS
This stage must then be followed by a second look-up table (the “post-LUT”), which linearizes the existing display device; specifically, it contains the inverse of the display’s transfer functions γD(R,G,B). The complete transform block (plus the LCD module) as implemented in the LP2480zx monitor is then:
Figure A-5Color Space Conversion Hardware in the LP2480zx
36 Appendix A Advanced Color Management Features and Usage