LUT‐Based Transforms in ICC Profiles
Phil Green · 2010
Look-up table (LUT)-based transforms in ICC profiles are used to define a mapping between two color encodings. They can be used when the transform cannot be defined through the curve and matrix elements provided in the matrix/TRC type of profile. In an LUT-based transform a sample of known outputs of a function is stored, allowing unknown values to be found by interpolation. The ICC profile defines a lutAToBType and lutBToAType in Versions 4.0 and above. The procedure for populating the BToAx table is similar to that for the AToBx table described above, with the additional step of gamut mapping to provide in-gamut output values for all the values in the CIELAB encoding domain. The curves are used in conjunction with the CLUT to provide a transform. Profiles using these v2 LUTs will interoperate with v4 profiles and current CMMs. Controlled Vocabulary Terms image colour analysis; table lookup